Fracture and Structural Integrity: The Podcast

Effect of corrosion damage on the fatigue behavior of S460NL High-Strength Steel under cyclic loading

Sun, 05 Apr 2026 04:14:00 +0000

https://doi.org/10.3221/IGF-ESIS.77.05

The present study investigates the influence of corrosion exposure on the fatigue behavior of S460NL high-strength structural steel, a material that is frequently utilized in offshore and civil engineering structures. Accelerated corrosion was simulated under controlled laboratory conditions for exposure periods of 3 days, 6 days, and 6 + 3 days, in addition to specimens subjected to natural atmospheric corrosion. To this end, fatigue tests were performed to obtain S–N curves, and the results were evaluated using Basquin’s law and the probabilistic Castillo–Canteli model. The findings indicate that corrosion has a substantial impact on fatigue resistance. The endurance limit exhibited a decline from 214 MPa for the reference specimens to 176 MPa following three days of corrosion, 135 MPa after six days, and approximately 92 MPa after combined corrosion exposure, signifying a reduction of up to 57%. Fractographic observations revealed that corrosion pits act as stress concentrators, thereby promoting early crack initiation. A discernible correlation was identified between corrosion mass loss and normalized endurance limit. These findings highlight the importance of considering corrosion effects in fatigue life assessment and structural design of high-strength steel components.

On the relationship between crack initiation angle and loading equivalent angle for asymmetric ...

Sat, 04 Apr 2026 04:23:00 +0000

In this work, the prediction of crack initiation angle (θo) under mixed mode (I/II) load is estimated from the generalized minimum plastic zone radius (GMPZR) criterion. The paper presents a detailed study on the crack-tip plastic core for asymmetric three-point bend (TPB) specimens of different crack-to-width (a/W) = 0.4-0.7 ratios and loading equivalent angle (βeq) using elastic finite element (FE) analyses. The θo estimated from the FE analysis is compared with the GMPZR criterion, other fracture criteria, and available experimental results. It is found that the θo evaluated from the FE analysis provides the best correlation with the GMPZR criterion among other fracture criteria. The FE results are used to propose an analytical relation between θo and βeq. This proposed relationship can be used to quickly estimate the crack initiation direction/angle for TPB specimens with only βeq available. Finally, the effect of T-stress on θo, will be assessed using as estimated from the GMPZR criterion.

Effect of specimen size and type on real-mode-I fracture toughness of hooked-end steel fiber-reinforced concrete

Fri, 03 Apr 2026 15:39:00 +0000

This paper studied the effects of specimen size and type on the real-mode-I fracture toughness (KIC )of steel fiber-reinforced concrete (SFRC) specimens. Mode I KIC tests were performed using semicircular bend (SCB) and center-cracked circular disk (CCCD) specimens with different sizes and crack-to-depth ratios, (a/R). SCB Specimens were tested under three-point bending, and CCCD specimens were tested under indirect tension test conditions to achieve pure Mode I crack growth. Moreover, KIC was analyzed as a function of specimen type (SCB and CCCD), specimen size (R values of 50, 75, 100, and 125 mm), and a/R ratios of 0.2, 0.3, 0.4, and 0.5. The results clearly show that the KIC of SFRC exhibits a distinct size effect: it increases with specimen radius up to a critical range of 75-100 mm, after which it levels off. The a/R ratio is an important parameter affecting the toughness; higher values of a/R result in increased KIC values, with increases of 12.9% for CCCD specimens and 22.7% for SCB specimens when a/R is raised from 0.2 to 0.5 at R=75 mm. In addition, the failure mode shifts from ductile fiber pull-out at shallow a/R to brittle fiber rupture at highera/R. The results also emphasize the importance of using geometry-adjusted models, such as Bazant's size effect law (SEL), especially when dealing with SFRC, since fiber distribution and crack-bridging efficiency depend on both size and geometry.

Effect of continuous carbon fiber layup architecture on tensile performance of hybrid FDM composites

Fri, 03 Apr 2026 14:10:00 +0000

Hybrid continuous fiber–reinforced composites produced by fused deposition modeling (FDM) offer a promising solution for lightweight load-bearing structures. However, their mechanical performance is strongly governed by internal reinforcement architecture. This study experimentally investigates the effect of continuous carbon fiber layup orientation on the tensile behavior of hybrid FDM composites based on three short-fiber-reinforced thermoplastic matrices: ABS, PA12, and PET-G. Specimens were fabricated using continuous fiber co-extrusion technology with controlled constant and combined fiber layup schemes. Uniaxial tensile tests with non-contact strain measurement were performed to evaluate Young’s modulus, ultimate tensile strength, and strain-to-failure. Results show that fiber alignment with the load direction is essential for maximizing stiffness and strength, while the polymer matrix primarily controls ductility and failure strain. Combined layups with axially oriented and off-axis layers offer a balance between strength and damage tolerance. Fractographic observations indicate mixed Mode I/Mode II failure governed by structural anisotropy and matrix plasticity. These findings establish the design basics for optimizing hybrid continuous-fiber-reinforced FDM composites and provide a practical framework for the development of additively manufactured structural components.

Multimodal residual stress evaluation following one-sided dimpling in a Ti-6Al-4V alloy plate

Fri, 03 Apr 2026 13:53:00 +0000

Residual stress significantly influences the mechanical performance, fatigue resistance, and structural reliability of titanium alloys used in engineering applications. This study investigates the residual stress distribution induced by one-sided dimpling in Ti-6Al-4V alloy using a combined experimental–numerical approach. Localized plastic deformation produced by spherical indentation generates stress fields that are difficult to characterize with a single technique. Residual stresses in the plane were evaluated using Focused Ion Beam–Digital Image Correlation (FIB-DIC) and Electronic Speckle Pattern Interferometry (ESPI). To evaluate the residual stress through the sample thickness, the cross-section warp method was used, that analyze the warping (deplanation) of the cross-section after cutting and provides an alternative way to infer the internal stress distributions and complements existing measurement techniques. The results reveal compressive residual stresses near the dimpled surface and tensile stresses developing at greater depths due to elastic recovery and equilibrium constraints. Finite element simulations match the experimentally observed stress distributions and confirm the reliability of the proposed methodology. The validated finite element model provides a predictive framework for future studies, enabling systematic analysis of how indentation depth and the indenter diameter affect the magnitude and distribution of compressive residual stresses, and supporting the optimization of dimpling parameters for improved structural performance.

Predicting fatigue limits of defective A356-T6 and A357-T6 cast aluminum alloys using a hybrid empirical–machine learning approa

Wed, 18 Mar 2026 05:42:00 +0000

The present study develops a knowledge-based machine learning framework for estimating the fatigue life of Al alloy using a combination of data-driven models and an empirical equation. Three different ML models were developed and tested, including Support Vector Regression, Random Forest and Gaussian Process Regression, to predict the fatigue limit for the spherical defective cast A356-T aluminum alloy, considering different Second Dendrite Army spacing (SDAS) values and different defect sizes. The effectiveness of the models is assessed using standard analytical metrics, like Root Mean Squared Error (RMSE) and R-squared ( ). With R² value 0.99, the SVR model outperformed the others.

Numerical and experimental study of the behavior of a polyamide during the ECAE process using a 105° die

Fri, 13 Mar 2026 04:00:00 +0000

Among the various severe plastic deformation techniques, Equal Channel Angular Extrusion (ECAE) is a widely used method that introduces significant plastic deformation into a sample by forcing it through two intersecting channels, without substantially altering its overall dimensions. In this work, the behavior of polyamide (PA 6.6) under single-turn and double-turn ECAE (1-ECAE and 2-ECAE) was investigated using finite element analysis with a 105° die. Experimental results on PA 6.6 are also presented. The analysis focused on the influence of the channel angle, the intermediate channel length, and friction on equivalent plastic strain distribution and pressing force. The results indicate that using adequate intermediate channel length enhances strain homogeneity, while friction exerts a moderate effect but can lead to localized strain concentration near the die walls. Therefore, proper lubrication is recommended to stabilize material flow, reduce tool wear, and improve process reliability. These findings provide optimized processing parameters for PA 6.6 extrusion and open up new perspectives for enhancing its mechanical performance and expanding its industrial applications.

Influence of hybrid nano Al2O3–ZrO2 reinforcements on microstructure ...

Wed, 04 Mar 2026 05:29:00 +0000

A present study reveals the influence of nano Al2O3 and ZrO2 reinforcements on the fracture toughness of Hybrid Metal matrix Composites (HMMCs) made of Al6061 alloy. Composites are synthesized by varying weight fraction of alumina and Zirconia oxide using ultrasonic stir casing technique. Microstructural characterization of the synthesized composites for different weight fractions are carried out by using Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and X-ray Diffraction (XRD) which shows the uniform dissemination of the reinforced particulates, elemental composition and formation of phases. As per ASTM E399 fracture toughness was investigated which indicates the addition of nano sized reinforced particulates into the matrix alloy enhances the crack propagation resistance. Among the produced nano composites, Al6061-1 wt. % of Al2O3p+ ZrO2p shows maximum fracture toughness (47.39%) due to uniform dissemination of the nano reinforced particulates and load bearing capacity. The fractographic examination revealed a transition from ductile to mixed-mode fracture, with nanoparticles adequately disseminated to impede crack propagation and improve energy absorption. Meanwhile, further increase in the weight fraction of the reinforcing particulates leads to agglomeration there by reduces the fracture toughness. The results show that optimized nano hybrid reinforcement improves fracture toughness of Al6061 alloy and making it suitable for structural applications.

Effect of external operational damage on the mechanical behavior of GFRP under quasi-static and fatigue loading

Sun, 01 Mar 2026 05:36:00 +0000

An experimental study was conducted to investigate the influence of operational defects, such as surface scratches and dents, on the residual mechanical properties of glass fiber-reinforced plastic (GFRP) during quasi-static tensile and fatigue tests. Based on the results of static tests, the types of simulated defects and loading parameters for cyclic testing were determined. Fatigue tests were performed on groups of samples without defects, with a 10 kN dent, a 15 kN dent, and a scratch. The results of these tests allowed the identification of the most critical type of external damage. The failure of GFRP samples with operational defects was analyzed after both quasi-static tension and fatigue testing. Examination of the fracture surfaces of the fatigue-tested samples revealed that failure occurs primarily at the site of the applied defect due to fiber fracture.

Numerical assessment of the seismic vulnerability of the historical earthen remains ...

Sun, 15 Feb 2026 10:57:00 +0000

This work primarily aims to carry out a numerical assessment of the seismic vulnerability of the historical Rammed Earth (RE) remains of the enclosure of Mansourah, a small town in the Wilaya (Province) of Tlemcen, in northwestern Algeria. For the purpose of successfully conducting this work, it was deemed appropriate to consider six geometric configurations, which were analyzed using three-dimensional finite element models developed in ANSYS with elastoplastic behavior based on the Drucker-Prager criterion. Two seismic excitations were applied successively along the two orthogonal horizontal directions X and Y. In addition, the analysis essentially focused on five major physical indicators, i.e. the principal tensile and compressive stresses, equivalent stress, equivalent plastic deformation, and maximum displacement. The results showed a spatial coherence of the critical zones that are most exposed to damage, for all the cases studied. These zones are located mainly at the base of the intermediate walls, at the ends of the free walls, and in the thickness transition zones of the walls constituting the towers. The vulnerability classification, from the most critical to the most stable case, was found to be as follows: Structure 05, 04, 01, 03, 02, 06. These findings facilitate the orientation and prioritization of strategies for the reinforcement and preservation of historic monuments built with RE.

Effects of machining methods on uniaxial tensile properties of 75μm thick 304L stainless steel foil

Fri, 13 Feb 2026 03:49:00 +0000

Considering the fragility of ultra-thin foil material, the machining methods might bring in undesired and non-neglectable damage, which would affect the uniaxial tensile properties of such material. This presented work systematically investigates the effect of five machining methods on the tensile performance of 75μm thick 304L stainless steel foil across four different gage width through uniaxial tension test. The yield stress and ultimate strength are found insensitive to the machining methods and gage widths. Full-field digital image correlation analysis confirmed that the fabrication method dictates the failure mode. Laser cutting and photochemical etched specimens failed in the gage central portion due to intrinsic plastic instability, while specimens fabricated by electrical discharge machining, mechanical milling, and waterjet cutting failed prematurely from process-induced edge defects. Thus, the uniform and fracture elongations were dependent on the process. Geometric size effect on material ductility was also observed for samples with good or moderate edge qualities.

The influence of temperature on the deformation behavior, strength and fracture mechanism of the heat-resistant Nickel-based all

Thu, 05 Feb 2026 14:47:00 +0000

A detailed investigation was conducted into the fracture mechanisms of cylindrical specimens made of a polycrystalline heat-resistant nickel-based alloy XH73MBTU-VD (EI698-VD), under uniaxial tension in the temperature range of 25–700°C. The presence of both surface and internal defects was identified and subsequently described. The alloy microstructure was observed using scanning electron microscopy and energy-dispersive X-ray spectroscopy methods. In the temperature range of 650 to 700°C, it has been observed that the onset of crack formation occurs at surface defects. Conversely, at lower temperatures, failure was attributed to the process of ductile growth and the coalescence of pores, leading to the formation of an internal crack. At a test temperature of 400°C and above, the Porteven-Le Chatelier effect (serrated flow) was identified. At temperatures of 25, 400 and 550°C, fracture was accompanied by deformation in different slip planes. An increase in the test temperature was found to result in a change in the slope angle of the slip planes. It was observed that at higher temperatures, there was a significant decrease in plasticity. An excess of 90 times the nominal mass composition of Pb content was detected. A possible cause and mechanism of the steep loss of alloy plasticity with increasing temperature is explained.

Seismic performance of steel frames with a hybrid bracing system combining concentric steel bracing and friction dampers

Sat, 31 Jan 2026 07:36:00 +0000

This paper assesses a hybrid bracing system involving concentric steel bracing in combination with friction dampers to improve seismic performance in steel moment frame buildings. Three prototype (5, 10, and 15 stories) steel moment frame configurations were analyzed under a nonlinear time history and pushover sequences as per performance-based design procedure, to examine the effects of the without, brace-only, damper-only, and hybrid systems. The hybrid system is most effective in decreasing roof displacement and story drift for all height configurations, with the maximum drift reductions of approximately 59% for the base brace system in the 5-story frame, while maintaining the optimal reductions of 15% - 31% (displacement) and 40% - 48% (drift) in 10- and 15-story frames. The hybrid method, unlike a brace-only solution, which can intensify the response of a tall structure through shortening of the periods of the oscillation and resonance, and damper-only solution, which lacks a stiffness control, is composed of both: initial stiffness and stable frictional energy dissipation. For taller frames, damping due to the vertical difference in load and slip should be taken into account, and then the suspension distribution should be adjusted to account for these higher mode effects.

Effects of Ni-P + DLC multilayer coating on cavitation erosion behavior of AlSi10Mg produced by laser powder bed fusion

Fri, 23 Jan 2026 14:17:00 +0000

Additive manufacturing (AM) technologies are currently contributing to significant progress in the design of lightweight metal components. Al alloys constitute the most studied light metal, particularly the Al-Si ones, due to their high specific properties. However, surface-driven damage mechanisms represent a limitation in the lifespan of such components. In the present work, different coatings are studied to enhance the cavitation erosion resistance of AlSi10Mg alloy manufactured via laser powder bed fusion (L-PBF). In detail, a Ni-P single layer and a Ni-P + DLC (diamond like carbon) multilayer were considered. Erosion resistance was examined by means of ultrasonic cavitation erosion tests with periodic interruptions to monitor mass loss and damage evolution. The damaged surfaces were inspected through a field emission scanning electron microscopy (FEG-SEM) to determine the damage mechanism, with the aim of evaluating the performances of the different proposed coatings.

The damping influence in monitoring the tension of cable using the vibration method

Thu, 22 Jan 2026 15:48:00 +0000

In the maintenance work of cable configurations, which have limitations such as cables in cable-stayed bridges, suspenders in suspension bridges, and hangers in arch bridges, tension on the cables is required. The safety of the cable is confirmed by checking whether the tensile force on the cable is within the allowable value. In the current widespread practice, cable tension is estimated using the vibration method by measuring the natural frequencies of the cable. However, this method is affected by several factors, including flexural rigidity, sag, and damper. The main difference is that natural frequencies (ωn) are the theoretical frequency of vibration without any energy loss, while damped natural frequencies (ωd) are of the actual system where damping (energy loss) is present. The undamped frequency is a system's inherent property based on its mass and stiffness, while the damped frequency is a practical measurement that is always less than the undamped frequency. This paper proposes a novel method for estimating tensile force that considers global damping. To model the cable as a Rayleigh beam, a theoretical equation for a viscoelastic system has been developed to estimate the natural frequency. The solution method calculates the cable tension and the material damping simultaneously from the natural frequencies. Previous studies verified the validity of the method. The maximum error in the tension is in the range of 4.71% in all valid tests. The evidence confirms the effectiveness of the proposed methods in tension estimation. In this research, the influence of damping on the evaluation of tension is investigated through analytical model, in which the natural frequencies, determined by the damping levels and the damped natural frequencies (measured frequencies). Then, the Hierarchical Bayes model was used to find stable estimates while preserving partial pooling, under sparse data, to stabilize estimates and fully quantify uncertainty. The results show that neglecting damping can cause noticeable errors, especially in low-tension or short cables. The study emphasizes the importance of considering damping in vibration-based tensile force assessments to enhance accuracy and reliability.

Experimental study on the mechanical and tribological characteristics of pineapple leaf fiber reinforced polymer composites for

Sat, 17 Jan 2026 05:34:00 +0000

New biomedical supportive and lightweight structures require the creation of sustainable polymer composites of high strength and wear resistance. This research explores the use of alkali-treated pineapple leaf fiber (PALF) reinforced epoxy composites and determines complete structure property wear relationships using combined mechanical, tribological, and microstructural analysis. The novelty of the work is based on the correlation of fiber content with the stiffness increment, the damage tolerance, and degradation behavior under friction conditions at controlled fabrication conditions. A hand lay-up method was used to manufacture composite laminates with 5-25 wt.% PALF. The tensile strength rose to 78 MPa and Youngs modulus rose to 3.5 GPa. Flexural strength increased to 112 MPa and flexural modulus to 3.7 GPa. The energy impact decreased by 12 and dropped to 20 kJ/m2 and Shore D hardness rose by 72 and 76, respectively, which means the increase in deformation and surface damage resistance. Tribological testing revealed that coefficient of friction and wear rate decreased to 0.51 and 3.7 x 10-6 mm 3/N-m respectively by fiber-supported load distribution and establishment of protective transfer films. The scanning electron microscopy showed that there was consistent fiber dispersion, good bonding of fiber matrix, and predominance of crack-bridging and pull-out processes involving the fracture resistance. The best mechanical tribological behavior was observed with a concentration of 10-15 wt.% PALF. A further study will involve biocompatibility studies, long-lasting stability, and surface functionalization to permit biomedical assistance elements like orthotic braces, prosthetic frames, and non-load-bearing auxiliary medical components.

Effect of B4C variation on the mechanical, fractographic and tribological performance of hybrid composites Al7075/Gr/ZrO₂

Sat, 10 Jan 2026 06:52:00 +0000

The current study focuses on the influence of varying levels of boron-carbide (B4C) particles on mechanical and tribological characteristics of Al7075 hybrid composites that are strengthened by fixed percentages of graphite (Gr) and zirconia (ZrO2). Hybrid composites were made by stir casting the 2 and 4 wt.% of B4C to Al7075-Gr-ZrO2 matrix in two-steps. The reinforcements were evenly spread throughout the matrix was confirmed by analysis through electron microscopy SEM together with elemental mapping through energy dispersive spectroscopy was utilized. Microstructural properties, tensile, hardness, and wear behaviour of the resulting hybrid composites were tested. The findings suggest that the adding of 4 wt.% B4C shall improve the hardness of Al7075 hybrid reinforced composites to 87 BHN, the UTS by 37% (214 MPa to 293 MPa) and vice versa slight decrease in ductility was attributed due to the addition of B4C. The tribological study revealed that the resistance to wear increased with additions of B4C as the hard ceramic particles served as load bearing phases. These results demonstrate the importance of B4C variation in improving mechanical and tribological behaviour of Al7075-Gr-ZrO2 hybrid reinforced composites in potential structural and aerospace application.

Hybrid feedforward neural network for pressure vessel internal corrosion prediction: integrating chemical models with inspection

Tue, 06 Jan 2026 15:45:00 +0000

This study presents a hybrid framework integrating a physics-based corrosion model with a feedforward neural network (FNN) to predict corrosion rates and estimate the remaining useful life (RUL) of industrial pressure vessels for condition-based maintenance. Using non-destructive evaluation (NDE) wall thickness measurements from 24 inspection points over multiple years (2002–2008) and physics-based training data, a three-layer FNN with Monte Carlo dropout predicts localized corrosion rates, while exponential and linear degradation models project future wall thickness. The FNN achieved a coefficient of determination (R²) of 0.975 for corrosion rate prediction and a mean absolute error (MAE) of 0.1204 mm/year. For thickness prediction, the exponential model achieved R² = 0.99 with MAE = 0.0389 mm, outperforming the linear model (MAE) = 0.1350 mm. The framework was integrated with Fitness-for-Service (FFS) assessment based on API 579-1/ASME FFS-1 standards, enabling classification of vessel components and identification of sections requiring maintenance. This hybrid approach translates predictive analytics into standards-compliant engineering decisions for structural integrity management.

Experimental calibration of a virtual raster section for high-accuracy FDM simulation in Abaqus

Fri, 02 Jan 2026 05:43:00 +0000

This study presents an experimentally calibrated methodology to enhance the predictive accuracy of finite element simulations for Fused Deposition Modeling (FDM) parts in Abaqus by replacing idealized filament geometry with a physically accurate “corrected virtual raster section.” A Box-Behnken Design of Experiments (DoE) across 27 ABS specimens systematically quantifies how key printing parameters, layer thickness, raster width, extrusion temperature, and print speed, influence the true cross-sectional geometry of deposited filaments, as measured via Scanning Electron Microscopy (SEM). These data inform a predictive mathematical model that transforms the conventional circular filament shape into an experimentally grounded oval-rectangular profile, accurately capturing extrusion-induced flattening and lateral spreading. The calibrated virtual section is integrated into a custom Python-based tool that parses G-code toolpaths and sweeps the corrected geometry along deposition trajectories to generate high-fidelity, mesh-ready Abaqus models. The workflow is validated through tensile testing of ASTM D638 specimens printed at 0°, 45°, and 90° raster orientations (n=3 per orientation). Error analysis against the experimental mean demonstrates that the corrected model reduces simulation errors from catastrophic levels in the non-corrected approach (7–92% relative error, 2.5–19 MPa absolute) to engineering-grade precision (0.03–7% relative error, ≤1.3 MPa absolute). This workflow bridges G-code to physical behavior, enabling reliable simulation of FDM anisotropy.

Guided waves with machine learning for structural health monitoring: transparent features and Monte Carlo confidence

Fri, 02 Jan 2026 05:12:00 +0000

Reliable discrimination of small damage states under operational variability requires uncertainty aware Structural Health Monitoring. A pipeline is presented that couples guided wave physics with supervised machine learning to classify damage severity in a metallic panel. The experimental platform is a 310 × 190 × 1 mm aluminum plate with one central piezoelectric actuator and three receivers, interrogated by five cycle tone bursts at 20 kHz and sampled at 250 kHz. Signals are reduced to vectors of 20 physics informed features including root mean square, peak measures, analytic envelope statistics in fundamental and second harmonic bands, band limited energies, a spectral peak near 20 kHz, inter channel correlation, and a second harmonic index that captures weak interface nonlinearity. Uncertainty is propagated with Monte Carlo waveform perturbations, 5 000 realizations per condition, using amplitude scaling around 5 percent, time of flight jitter around 20 µs, and broadband noise near 2 percent of peak. These perturbations yield prediction bands and calibrated decision scores. The method is benchmarked across four learners: random forest, support vector machine with radial basis function kernel, additive boosting, and a hierarchical screener that first detects any mass and then separates severities. A finite element model provides a physics baseline for feature design. The study is a laboratory proof of concept on one specimen and three conditions, practical implications for aerospace deployment are outlined, including transfer to composite skins and links to certification metrics such as probability of detection. Calibration against the pristine response verified timing and mode content.

Mechanical and morphological evaluation of jute fiber reinforced epoxy composites for sustainable structural and automotive appl

Fri, 02 Jan 2026 04:10:00 +0000

This study investigates jute fibre reinforced epoxy composites fabricated using a controlled vacuum bag moulding process, with emphasis on establishing reliable structure property relationships relevant to sustainable engineering applications. To address limitations in earlier jute/epoxy studies such as generic claims, limited processing transparency, and weak correlation between impact behaviour and fracture mechanisms laminates containing 5, 10, 15, 20, and 25 wt.% jute fibre were produced and systematically characterized. Tensile strength and modulus increased with fibre content, reaching peak values of 95 MPa and 4.5 GPa at 20 wt.%, while reduced elongation at break indicated enhanced stiffness. Flexural strength and modulus exhibited similar trends, attaining maximum values of 150 MPa and 4.8 GPa, respectively, consistent with improved load transfer and crack-bridging mechanisms. Hardness and low-velocity impact energy absorption were also optimized at 20 wt.% fibre loading due to strengthened fibre matrix interfacial bonding and more uniform stress distribution. A decline in mechanical performance at 25 wt.% was attributed to fibre agglomeration, micro-void formation, and localized interfacial debonding. Scanning electron microscopy revealed matrix-dominated fracture at low fibre contents 5 to 10 wt.%, optimal dispersion and interfacial integrity at intermediate contents 15 to 20 wt.%, and severe clustering at higher loading. These findings identify 15 to 20 wt.% jute fibre as the optimal range for achieving a balanced combination of stiffness, strength, and impact resistance, supporting potential application in lightweight, non-critical structural and automotive components.

Modified elastic-plastic model: implementation algorithm and comparison of computational efficiency with the elastic-viscoplasti

Tue, 16 Dec 2025 18:01:00 +0000

The most important element of mathematical models of thermomechanical processing of metals and alloys is the constitutive model. In recent decades, multilevel physically-oriented constitutive models (CMs) have found widespread application. The first two-level model was the rigid-plastic theory of J. Taylor,a rigorous mathematical justification of which was developed by J. Bishop and R. Hill (TBH type models). The main disadvantage of this model is the uncertainty of the choice of active slip systems when more than 5 systems are activated. Despite this, the TBH models have become widespread, and its basic provisions have been preserved in many later developments. It seems that limiting the number of active slip systems to 5 has no physical justification and is determined only by the numerical procedure for implementing the model. Since the 1970s, elastic-viscoplastic models have emerged; it has been shown that as the velocity sensitivity parameter tends to zero, the macroparameters determined in the modeling converge to a solution using an elastic-plastic model. However, the system of equations becomes rigid, requiring the use of implicit schemes and extremely small time steps, which significantly reduces the computational efficiency. The paper proposes a modification of elastic-plastic model of the TBH type, in which a procedure for overcoming the above-mentioned drawback is proposed. To compare the computational efficiency of the elastic-plastic and elastic-viscoplastic models, a series of numerical experiments was carried out.

Utilizing cylindrical and cubical specimens with edge notch to determine size-independent fracture quantities of rock materials

Thu, 11 Dec 2025 17:16:00 +0000

The compliance method was first applied to short rod specimens to determine the nonlinear fracture toughness of rock materials by ISRM (International Society for Rock Mechanics) in the 1980s. In this study, utilizing the techniques of the J-integral and the crack closure integral (CCI), crucial linear elastic fracture mechanics expressions for straight-notched disk bending (SNDB) specimens, whose tests are simpler than those for short bar specimens, and single-notch cube bending (SNCB) specimens are initially derived to estimate crack propagation states in rock samples. Andesite-based SNDB specimens from the literature are examined using the compliance approach, and a strong correlation is observed between the compliance approach and the nonlinear approach reported in the literature. Subsequently, limestone-based SNCB specimens and beams containing cracks are produced and tested under bending. The fracture test data are estimated using the peak load approach, and the results of the comparative analysis are found to be satisfactorily consistent for both beams and SNCB specimens. The findings of this study reveal that the non-Hookean fracture quantities of rocks can be adequately determined using SNDB and SNCB specimens of a single size.

Reduction of cracks in concrete slabs through the incorporation of polypropylene synthetic fiber

Thu, 11 Dec 2025 04:34:00 +0000

In Peru, research on cracking in concrete slabs has been limited, partly due to the perception that cracks do not pose an immediate problem. However, their cumulative effect over the long term can compromise structural durability, highlighting the need for further study. This research was conducted according to the recommendations of ASTM C1579, which establishes procedures for evaluating shrinkage cracking in concrete mixes with and without fiber reinforcement. The main objective was to determine the optimal proportion of polypropylene synthetic fiber that maximizes the reduction in the appearance and formation of cracks. Three dosages were evaluated: DM-01 (500 g/m³), DM-02 (1000 g/m³), and DM-03 (2000 g/m³), compared to a reference concrete (MP) during a 35-day curing period. The results indicated that dosage DM-02 (1000 g/m³) exhibited the best performance, with reductions of 18.41% in average crack thickness, 11.46% in total crack length, and 32.43% in the number of cracks compared to the control concrete. Furthermore, the Mann-Whitney U test applied to DM-02 and MP showed that the average crack thickness at 28 days (p = 0.073) showed a trend toward statistical significance, suggesting a possible reduction in crack thickness with the addition of fibers. In contrast, mixes DM-01 and DM-03 showed heterogeneous results, without substantial improvements in any of the variables; in particular, DM-03 registered an increase in crack thickness. It is concluded that a moderate fiber dosage (DM-02) is the most suitable option, since both a deficiency and an excess of fiber can compromise the material's effectiveness against cracking.

Application of the thermography method for determining the fatigue limit of a nickel alloy produced by wire‑arc additive manufac

Mon, 08 Dec 2025 10:23:00 +0000

The development of additive technologies for manufacturing safety‑critical components operating under vibration must be accompanied by a careful analysis of the material’s resistance to high‑cycle fatigue (HCF). This paper presents a technique for the rapid assessment of the fatigue limit of nickel alloys fabricated by wire‑and‑arc additive manufacturing (WAAM). The technique grounded in infrared thermography (IRT), utilizes the self‑heating effect during cyclic loading. The technique realisation involves choosing specimen design, test equipment, the number and parameters of loading blocks, self‑heating indicators, and result‑processing procedures that account for material specifics. It is shown that the rate of temperature rise at the specimen surface at the start of each loading block can serve as an indicator of self‑heating. Experimental data on the fatigue limit of specimens made from the heat‑resistant alloy Inconel 625 produced by WAAM are obtained. Validation of the developed method is performed by comparing the fatigue limit derived from IRT with the results of conventional fatigue testing and the corresponding S–N curve. For additive nickel alloys, the proposed accelerated fatigue‑limit assessment allows a substantial reduction in the number of specimens and the time required to select technological parameters and refine additive manufacturing processes compared with traditional fatigue testing.

Coupling crystal plasticity and microstructure in SLM manufactured 316L parts: model development and experimental assessment

Sun, 23 Nov 2025 15:33:00 +0000

Additive manufacturing is extensively used for the production of complex-shaped parts from metals and polymers. Because of the influence of various physical factors, the structure of materials processed under different processing conditions may vary considerably, altering their properties. Application of a multi-level crystal plasticity approach helps explicitly describe the structure of materials at different scale levels. It makes possible the evaluation of basic mechanical properties of the samples fabricated by layer-wise laser melting. In this work, a two-level statistical constitutive model is suggested for calculation the main mechanical characteristics (elastic modulus, offset yield stress) of the AISI 316L stainless steel samples produced by selective laser melting. The model explicitly considers the grain structure and texture of metal parts, twinning defects, and residual stresses in the as-build structure of materials. Under predefined loading conditions, the primary mechanism of inelastic deformation is through intra-granular slips of edge dislocations. Thus, the mechanism of material hardening has been described by a modified form of the Hall-Petch law, where the boundaries of grains and original twins are counted as effective barriers to dislocations. All model parameters are properly identified based on own experimental data and the data found in literature. The elastic moduli and yield stresses are calculated at different residual deformations and are found to be in fair agreement with experiments.

Machine learning-assisted fracture prediction: Integrating synthetic and experimental data for quasi-static notch failure analys

Sun, 23 Nov 2025 10:40:00 +0000

Machine learning has emerged as a powerful tool in various scientific fields for developing data-driven models, reducing the need for extensive physical testing. In this study, the fracture load was first predicted using Theory of Critical Distances (TCD) for experimental data. Further, this study presents a machine learning-based framework for the prediction of quasi-static fracture loads of U-notched polycarbonate specimens using a combination of experimental and synthetic data. Experimental data was obtained for eleven notch configurations, while synthetic data was generated through fracture mechanics-based simulations using PYMAPDL. XGBoost was trained on experimental and synthetic training datasets, evaluated against a fixed randomly selected experimental test set. Model performance was evaluated using MAPE, MAE, RMSE values as R2 varied significantly with test set sampling and random state selection. This study systematically evaluates how varying the proportion of synthetic data influences model performance, offering a scalable strategy to minimize experimental dependence without compromising accuracy. Experiment-only dataset provided the highest accuracy, while hybrid models performed reasonably well. The full dataset model combining all experimental and synthetic data, achieved the most robust and accurate predictions, with errors ranging within ±5% and yielding the lowest MAPE of 1.18% and MAE of 78.73 N. It is suggested that synthetic data can significantly enhance the training of machine learning models, but cannot completely replace the experimental data, especially in critical applications.

Modified multi-scale constitutive model of Aluminum: complex loading with variable thermal conditions

Wed, 19 Nov 2025 14:14:00 +0000

During manufacturing of parts from metals and alloys through forming and subsequent thermal and mechanical treatments the materials are often subjected to complex loading. In such cases materials significantly change their structure, which determines the operational characteristics of a finished product. Therefore, for digital design of technological processes aimed at improving the functional characteristics of products, it is promising to develop mathematical models that adequately describe the material structure evolution during forming, thermal and mechanical processes including complex loading. This work considers the previously developed two-level constitutive models of aluminum under complex loading accompanied by temperature variations. The model parameters were calibrated to the experimental data of simple shear loading of aluminum specimens. The resulting deformation curves for aluminum subjected to simulated reversed simple shear loading with temperature variations, as well as loading involving strain-path changes, correspond well to the experimental data. The observed effects arising under the considered complex loading conditions are explained through analysis of the obtained description of the intragranular dislocation slip mechanisms. The study results demonstrate the applicability of multilevel constitutive models for comprehensive descriptions of the effects observed in the material during thermal and mechanical treatments.

Diagnostics and experimental analysis of 3D printed concrete structural elements

Fri, 14 Nov 2025 14:57:00 +0000

This study investigates the structural behaviour of elements produced by extrusion-based 3D concrete printing (3DCP). Six full-scale columns with intentional imperfections were tested in three-point bending and subsequently analysed through fragment testing. Compressive strength (16.6–32.2 MPa), flexural tensile strength (1.96 MPa parallel vs. 1.27 MPa perpendicular), ultrasonic pulse velocity, bulk density, and water absorption were measured. The results confirmed pronounced anisotropy and strong correlations between physical and mechanical properties. A simplified FEM model, calibrated with fragment data, reproduced global stiffness but not brittle delamination. The combined methodology offers a basis for diagnostics and quality control of 3DCP elements.

Study on mechanical, wear, corrosion and fracture characteristics of Al7075 by modifying nano sized Magnesium (n-Mg) element

Thu, 13 Nov 2025 03:49:00 +0000

Aluminum alloys are widely used in the automobile industry because of their excellent mechanical strength, low weight, and remarkable resistance to corrosion and wear. The purpose of this study is to investigate how the microstructure, mechanical properties, and corrosion resistance of the Al7075 alloy are affected by the addition of nano sized magnesium (n-Mg) particulates. Stir casting was used to fabricate the alloy samples, which had varied wt. % of n-Mg (0, 1, 1.5, 2, and 2.5 wt. %). By studying corrosion, wear, microstructural, and mechanical characteristics, the impact of n-Mg dispersion was assessed. The findings provided crucial information on magnesium's function in fortifying aluminum by demonstrating that optical micrographs depicted a homogeneous distribution of n-Mg particles within the Al7075 matrix. Magnesium at the nanoscale improved the alloy's strength, reduced dislocation motion, and refined the grain structure. However, as evidenced by a decrease in impact energy, the addition of magnesium also resulted in decreased toughness and ductility. Tensile strength, hardness, wear resistance, as well as corrosion resistance all improved by roughly 9.21%, 15.73%, 18.82%, and 23.80%, respectively, in the modified Al7075 alloy.

The effect of energy director on ultrasonic consolidation of multilayered composites (laminates) made from unidirectional PEEK/C

Wed, 12 Nov 2025 18:43:00 +0000

The study aims at assessing the effects of the ultrasonic consolidation parameters and the insertion of energy directors from the commercially available polyetheretherketone film ~250 µm thick on the structure and mechanical properties of the layered composites (laminates). Commercially available polyetheretherketone-based prepregs reinforced with tapes of unidirectional carbon fibers were ultrasonically consolidated with and without energy directors from neat polyetheretherketone film using an ‘UZPS-7’ ultrasonic welding machine. The laminates without the energy directors consisted of 16 prepreg layers, while 7 and 6 layers of the prepregs and the energy directors, respectively, included the other ones to ensure similar thicknesses during subsequent interlaminar shear strength tests. In the laminates with the energy directors, prolonging the ultrasonic duration allowed for the prepreg interfaces to be virtually blurred, increasing the interlaminar shear strength value up to the maximum level of 60 MPa. With the energy directors, excessive melting and spreading of the polymer occurred at the prolonged ultrasonic durations, increasing the number of discontinuities at the layer interfaces, including delamination and the impregnation of the prepregs with the excessive binder. The ultrasonic duration of 800 ms was the most rational, as it enabled to reduce the damaging effect of applied ultrasonic vibrations on the joined layers (prepregs), increasing the interlaminar shear strength value above 50 MPa.

Fatigue properties of a spring element for mounts with tunable stiffness made of C85S+QT sheet steel

Wed, 12 Nov 2025 08:47:00 +0000

Mounting stiffness has an important impact on a system’s structural dynamics and also on the durability of many structures. Mounts with tunable stiffness allow adapting a system’s structural dynamic behavior. Furthermore, they can be used to emulate elastic behavior of adjacent structures in test benches for components and substructures, e.g. for designing simplified, but accurate fatigue tests. For these applications, the tunable mounts themselves need to have sufficient fatigue strength. In this paper, results of experimental fatigue tests with such mounts are reported, providing material and geometry related fatigue data for four different configurations. Based on these experimental results, numerical parameter studies and analytical correlations, fatigue strength and stiffness approxima-tions are proposed for a wider range of geometries. This enables efficient pre-dimensioning of the tunable mounts starting from basic requirements.

Effect of pearlite nanoclay reinforcements on the mechanical and tribological behaviour of AA7076 metal nanocomposites

Thu, 06 Nov 2025 08:32:00 +0000

Aluminium alloy composites are extensively utilised in the aerospace, automobile, and marine industries due to their lightweight structure and high strength-to-density ratio. However, there remains significant potential to further improve these composites for advanced applications by enhancing their strength-to-weight ratio, corrosion resistance, wear resistance, and temperature performance. This study investigates the mechanical and tribological properties of AA7076 alloy reinforced with varying concentrations (1.0 and 1.5 wt.%) of perlite nanoclay. These composites were synthesized using a motorised stir casting process and characterised through tensile, wear, and hardness tests. Results showed that 1.5 wt. % perlite nanoclay composite exhibited the most significant improvements, with hardness, tensile strength, and wear resistance increasing by 32%, 38%, and 59%, respectively, compared to the base AA7076 alloy. Finite element simulations in ANSYS Workbench predicted tensile strengths in close agreement (within 5 – 8%) with experimental results, validating the strengthening effects of nanoclay. The enhancements are attributed to the homogeneous dispersion of nanoclay particles, strong interfacial bonding, and their role in restricting dislocation motion. These findings establish perlite nanoclay as a cost-effective and sustainable reinforcement for aluminium alloy, well-suited for demanding applications in automotive, aerospace, and marine industries, offering a promising combination of lightweight design and superior performance.

Experimental and 3D numerical analysis on the effect of specimen thickness on fracture toughness of Al6061-SiC-cenosphere hybrid

Wed, 05 Nov 2025 05:04:00 +0000

This study examines the fracture toughness of Al6061 alloy-based hybrid composites reinforced with silicon carbide particles and cenosphere microspheres. Aluminum alloy Al6061 is widely utilized in structural applications due to its balanced mechanical properties, and its hybridization with SiC and cenosphere reinforcements enhances its performance under critical loading conditions. The effect of specimen thickness on fracture toughness was examined by fabricating compact tension specimens in accordance with ASTM E399 standards, with thickness-to-width ratios ranging from 0.2 to 0.7. Controlled fatigue cracks were introduced, and both experimental testing and finite element simulations were conducted to assess the critical stress intensity factor and crack propagation behaviour across different thicknesses. Results show that the fracture toughness is constant after the B/W ratio of 0.5 and above, states as plane strain fracture toughness. The 3wt% SiC and 6wt% cenosphere in Al6061 shows the highest fracture toughness up to 15.56 MPa√m, due to the effective stress distribution and interfacial bonding. The fractography using the scanning electron microscopy reveals that particle debonding is major failure mechanism, with microcracking in 3wt% cenosphere composites and crack deflection and stress transfer at high reinforcement contents. Experimental results were well matched with the simulation model with ±10% differences, proving its validity.

Consecutive shock waves and fatigue loads: action invariants as optimization parameters under Laser Shock Peening

Sat, 01 Nov 2025 16:31:00 +0000

The criteria for optimizing shock-wave modes to increase the fatigue life of aircraft engine alloys are discussed with reference to laser shock peening (LSP). They are based on the self-similarity of plastic wave fronts and the kinetics of fatigue cracks related to the Swegle-Grady power law of structured plastic wave fronts and the Paris power law of fatigue crack advance. It is shown that the self-similar patterns and the power-law relationships of structured wave fronts at shock pulse amplitudes of 1-10 GPa and strain rates of 105-109 s-1 correspond to “action invariants” that determine the dissipative properties (stored energy) of materials caused by multiscale defect development. The relationship between the “action invariants” of structured plastic waves, the fatigue crack kinetics and the structural scaling invariants is shown using the 3D data of qualitative fracture surface profilometry. The methodological principles for studying material behavior under successive shock-wave and fatigue loads have been developed to optimize LSP processes and thus to ensure maximum fatigue life.

Experimental field analysis of damage-failure transition in composite material with a stress concentrator under cyclic loading (

Sat, 01 Nov 2025 15:58:00 +0000

Predicting the failure of carbon fiber composites remains a challenge due to the complex evolution of damage, where the collective behavior of defects like pores and microcracks dictates material strength. The objective of this work is to elucidate the transition from damage accumulation to final failure under cyclic loading by analyzing the integral structural characteristics of the material. A methodology combining microtomography and digital image correlation (DIC) was employed to monitor damage evolution in situ. The analysis of DIC-derived strain fields during block cyclic loading pinpointed the critical transition stage to failure. Furthermore, Bayesian Gaussian Mixture models were used for threshold segmentation and cluster analysis, revealing that mechanical loading induces distinct populations of small and large pores. The main results show that while the overall pore orientation distribution remains consistent, the clustering and ordering of pores evolve differently under cyclic loads compared to quasi-static conditions. Specifically, unloaded samples exhibit three distinct pore clusters based on orientation, a structure that is altered by cyclic loading through pore expansion and coalescence, which ultimately reduces specimen strength. These insights advance the understanding of damage criticality in composites and provide a foundation for developing more accurate predictive models.

Effect of the stress state on ultimate strain energy density in the failure of reinforced epoxy resin

Sat, 01 Nov 2025 10:04:00 +0000

Epoxy resin reinforced with 10% of TiO2 and pure epoxy resin are taken to exemplify the possibility of constructing a fracture locus for engineering organic polymers as a dependence of ultimate strain energy density in cohesive failure on the stress triaxiality factor in the range and the Lode–Nadai coefficient . The fracture loci are based on the results of compressive testing of cylindrical specimens, tensile and compressive testing of bell-shaped specimens, dishing of thick-walled cup-shaped specimens, shearing of oblique dog-bone-shaped specimens. The tests were performed at 25 and −50 °C. The obtained dependences are approximated by interpolation formulas, and they can be used to predict the failure of structural components made of organic polymer materials mechanically affected under conditions of a complex stress state.

Certain issues in the analytical integration of the Boussinesq problem

Sat, 01 Nov 2025 04:21:00 +0000

The Boussinesq solution, one of the fundamental problems in the theory of elasticity, enables an analysis of stresses and strains (displacements) in a semi-elastic space subject to surface loads. This solution has a form of formulas for displacements evoked by a concentrated force; these formulas can be treated as Green functions for calculation of displacements (and then – stresses) in a half-space loaded in any way at its surface z = 0. The study presents difficulties met during the analytical integration of the Green functions in the Mathematica environment as well as methods of coping with these difficulties. The authors are going to present particular issues which can be quite surprising and confusing, for example a failure to obtain a close result for definite integrals in Wolfram Mathematica or differences between results of calculations of the sum of integrals and the integral of the sums. The results of the study can help in establishing more exact benchmarks for the numerical methods applied in the analysis of settlement under foundations as well as other contact issues of the theory of elasticity based on the Boussinesq solution.

A novel procedure for accurately measuring the Mode II fracture toughness of steel fiber reinforced self-compacting concrete

Fri, 31 Oct 2025 04:37:00 +0000

Most research on the mode II fracture toughness of fiber-reinforced concrete (FRC) has intentionally avoided bridging fibers at pre-notch surfaces by using a through-thickness crack (TTC) that cuts the entire thickness, including fibers in this region. The objective of the present research is to accurately measure mode II fracture toughness (KIIC) using double-notched cube (DNC) specimens on steel fiber reinforced self-compacting concrete (SFRSCC). The effects of precrack-to-specimen width ratios (a/w), i.e., a/w = 0.3, 0.4, and 0.5, and fiber volume fraction percentage (Vf%), i.e., Vf% = 1% and 1.5% were investigated. A comparison between KIIC measured through specimens having the TTC concept, i.e., the absence of fiber bridging on the surfaces of the pre-notch, and those with the presence of fiber bridging on the surfaces of the pre-notch, i.e., the matrix crack (MC) concept. For greater clarity, the SCC specimens were cast without fibers with (MC/C) or without fiber bridging on the pre-crack surfaces to determine the unique effect of the presence of fiber bridging on the pre-crack surfaces on enhancing KIIC. The results showed that DNC specimens with MC consistently obtained the highest mode KIIC for all values of a/w, indicating the greatest resistance to crack growth. KIIC increased as the a/w ratio increased. MC/C method, i.e., the presence of fibers behind the crack front only, showed more effectiveness on the KIIC than the TTC, i.e., the presence of fibers ahead of the crack front only. In general, the MC is an accurate method for measuring KIIC of FRC.

Optimization of austenitic and ferritic steels for deep drawing.Part 2: FEM analyses with damage development

Sat, 25 Oct 2025 05:25:00 +0000

Deep drawing of sheet metal is a crucial industrial process due to its high productivity and low cost per unit produced. Stainless steels are ideal for this process, given their high deformability compared to other steels. Despite its apparent simplicity, understanding how the material deforms during deep drawing is essential to predict the final result. From this point of view, simulation via finite element modelling (FEM) represents a rapid and cost-effective alternative to experimental testing. When properly calibrated, FEM models allow for analysing stress and strain distribution, identifying areas at risk of failure, calculating final wall thickness, and optimizing die geometry. This research led to the development of a FEM model capable of simulating deep drawing under different operating conditions, steel types (AISI 304 and AISI 430) and lubrication. The model was calibrated and validated by comparing the numerical results with those obtained from a series of Erichsen tests. To ensure the accuracy of the true stress-strain curves, the steels were thoroughly characterized through tensile tests, Erichsen tests, and metallographic analyses. A specific method was also developed to represent the true stress-strain curve beyond necking, up to physical failure of the steel. The experiment was conducted according to the principles of DoE (Design of Experiments), combined with statistical analysis using the ANOVA technique.

Fatigue experimental characterisation of brazed joints in aluminium microchannel heat exchangers

Fri, 24 Oct 2025 04:07:00 +0000

Brazing is a widely employed joining technique for aluminium components due to its cost-effectiveness and compatibility with complex geometries. However, the structural integrity of brazed joints under cyclic loading remains a scarcely addressed scientific and engineering concern. This study investigates the tensile and fatigue behaviour of aluminium 3xxx-series alloy components employed in microchannel heat exchangers—headers and multi-port extruded tubes—both in the as-received and heat-treated (brazing cycle) conditions. Tensile tests were performed on parent materials using a microtensile equipped with a Digital Image Correlation (DIC) system for accurate strain evaluation during testing. On the other hand, uniaxial fatigue tests were performed on specimens containing a representative brazed joint. Finite element analyses were used to design the fatigue specimen geometry based on stress concentrations observed in simplified heat exchanger models. Fatigue test data were employed to determine fatigue behaviour both in the finite life region of high-cycle fatigue and to characterise the fatigue endurance limit at 107 cycles. Experimental testing unveiled crack initiation consistently occurring at the brazed fillet toe near the tube lateral edge. SEM observations revealed surface-initiated cracking, ratchet marks, sub-surface inclusions and final ductile failure. Results underline the need for fatigue-based design criteria for brazed aluminium structures.

Three points bending ultrasonic fatigue resistance and vickers hardness of Tlalpujahua clay thermally treated

Wed, 22 Oct 2025 17:47:00 +0000

Ultrasonic fatigue at an operating frequency of 20 kHz was conducted on thermally treated clay bricks at 500, 750, and 1000 °C with a holding time of 5 h, using a three-point bending setup to assess their fatigue endurance. A Vickers hardness test was also performed on small clay squares thermally treated at the same temperatures, showing increased hardness values. X-ray diffraction (XRD) analysis was also performed, revealing temperature-induced changes in the clay chemical composition. Specifically, the illite transformation into spinel at 1000 °C contributed to a significant increase in hardness and, consequently, a diminution in fatigue life. A finite element simulation under different applied loads was performed to evaluate the von Mises stress behavior of the clay brick. Considering the change in mechanical properties, such as bulk density, at various temperatures. The simulation results show a corresponding behavior with the values of the Vickers hardness. This study provides a perspective on the relationship between ultrasonic fatigue, Vickers hardness, and thermal treatment.

Elasto-plastic truss optimization under geometric nonlinearity using a genetic algorithm

Tue, 21 Oct 2025 12:19:00 +0000

This paper presents an advanced optimization methodology for truss structures, addressing both elasto-plastic design cases—where plastic deformations are controlled within predefined limits—and purely elastic scenarios, in which inelastic behavior is entirely prevented. Plastic deformations are characterized and quantified using the complementary strain energy of residual forces, providing a reliable measure of inelastic response. Additional design constraints related to load-bearing capacity and structural stability are incorporated through penalization terms, while the objective function focuses on minimizing structural weight. Serviceability restrictions are also applied to enhance the robustness of the design. Building on these considerations, the framework integrates material and geometric nonlinear finite element analysis (FEA) with a genetic algorithm (GA), enabling the automated determination of optimal cross-sectional areas for individual bar members within a predefined design domain. To further enhance safety, geometric imperfections are introduced through an integrated automatic strategy. The effectiveness of the proposed technique was validated using two benchmark numerical examples: a 37-bar planar truss and a 25-bar space truss, evaluated under multiple design scenarios. The results highlight the flexibility and reliability of the optimization framework, demonstrating substantial weight savings while fully meeting all structural performance criteria.

Optimization of austenitic and ferritic steels for deep drawing. Part 1: metallurgical and mechanical analyses

Sat, 18 Oct 2025 05:25:00 +0000

Deep drawing of stainless steels thin sheets is a cold forming process used to produce components with complex geometries at limited costs. Although it seems a simple shaping technique, this technology requires a high level of know-how, essential to optimize parameters and limit production scraps. The choice of stainless steel type also plays a fundamental role, since there are austenitic and ferritic grades with improved chemical composition which should be characterized by a superior deformability when compared to the more common ones. This study investigates the formability of two austenitic and two ferritic stainless steels, AISI 304, 304 mod., AISI 430 and AISI 441, using tensile tests and Erichsen tests. From the former, the mechanical properties and anisotropy coefficients were determined along three sampling directions in respect to the rolling direction. Since the deep drawing is influenced also by some technological parameters such as the lubrication, the punch speed, and the blank-holder pressure, Erichsen tests were performed varying the deformation conditions and an Erichsen index (IE) was determined. The Erichsen samples were also subjected to metallographic and HV0.2 microhardness analyses to study the modification of the microstructure and the consequent impact on the local mechanical properties.

J-integral evaluation and structural integrity assessment using FAD for SA 312 Type 304 LN steel welded pipes with notch under m

Fri, 17 Oct 2025 04:17:00 +0000

In the present study, structural integrity of SA312 Type 304 LN steel welded pipes with through-wall crack under monotonic loading has been assessed using failure assessment diagram (FAD). Plastic capacity utilization and fracture capacity utilization are compared simultaneously using a FAD. Material’s initiation fracture toughness and J-integral evaluated using load-CMOD method were used for evaluating fracture resistance were used for generation of failure assessment diagrams. Various analytical expressions proposed by Zahoor (1989) and Takahashi (2002) were used to evaluate limit load moment (plastic capacity). Various approaches for deriving the failure assessment line were considered in this study viz, BS 7910 2A, BS 7910 2B, and SINTAP. The failure assessment lines constructed using SINTAP, BS 7910 2A level and BS 7910 2B level for SA312 Type 304 LN steel procedures yielded similar results. Limit load moment values from Takahashi were lower and hence resulted in assessment points closer to the failure assessment lines. Structural integrity assessment is very significant in deciding the safety of operation of the piping components.

Realization of introducing a non-woven veil on the interlaminar radial strength of glass-epoxy L-bend composites

Thu, 16 Oct 2025 04:16:00 +0000

This study investigates the effect of interleaving non-woven veils and their surface areal density on the curved beam strength (CBS) and interlaminar radial stress (ILRS) of glass/epoxy L-bend composite laminates. Carbon veils with areal densities of 15, 20, and 30 g/m2 , and glass veils with 25 and 30 g/m2 were used as interleaving materials. The L-bend laminates, both interleaved and non-interleaved, were fabricated using the compression moulding technique. A four-point bending test was employed to evaluate the influence of veil interleaving and areal density on CBS and ILRS. The experimental results demonstrated that interleaving with carbon and glass non-woven veils significantly affects the performance of curved laminates. Notably, the CBS of the glass/epoxy laminate improved by 88% and 17% for specimens interleaved with 15 g/m2 carbon and 30 g/m2 glass veils, respectively. Furthermore, the ILRS of carbon veil-interleaved laminates showed a strong dependence on the veil’s areal density. In contrast, interleaving with glass veils did not exhibit a significant effect on ILRS. Finally, the fracture surfaces of the tested laminates were examined using scanning electron microscopy (SEM) to identify the various failure modes in the curved region and to understand the underlying fracture mechanisms.

Prediction of crack length in thin-walled plates under different fracture mode conditions using machine learning algorithms

Thu, 16 Oct 2025 03:21:00 +0000

This study uses theoretical stress intensity factor data to assess how well machine learning models predict crack length. Thin-walled damage plate under various modes was evaluated based on the theoretical relation. Using theoretical data, this study implemented various ML algorithms to determine the most accurate model for thin-walled crack length prediction. The prediction/true class was used to assess each algorithm using an evaluation matrix, and each class was divided into four levels of crack length for testing and training data. According to theoretical results, SIF increases as the crack length increases, which shows that higher crack lengths cause the structures. The ability of ML algorithms trained on theoretical data to predict crack length using SIF values is investigated in this work. To estimate crack length in thin-walled structures under Mode I, Mode II, and Mode III conditions, the current work successfully evaluated the accuracy in predicting the crack length using ML algorithms. By eliminating the need for experimental/theoretical trials, the suggested ML algorithms not only simplify the process of identifying important input parameters but also provide cost-effective approaches. Finally, the results demonstrate the algorithms’ ability to yield accurate predictions.

Experimental investigation of the influence of internal defects (voids, wrinkles) on the shear properties of CFRP

Thu, 16 Oct 2025 03:19:00 +0000

The study focuses on examining the impact of internal manufacturing defects (voids and wrinkles) on the mechanical behavior of structural carbon fiber reinforced polymers (CFRP) under shear loading. Specimens of VKU/VSE1212 material with a [0/90]10 layup were artificially embedded with defects: circular voids (Ø 20 mm) and square voids (20×20 mm) at a concentration (area fraction) of 5.3%, as well as wrinkles increasing thickness by 10%. In-plane shear tests were conducted according to ASTM D7078 using a Vic-3D system for digital image correlation (DIC) to record strain fields. Results revealed that voids at 5.3% concentration (area fraction) reduced shear strength by 2.2% (from 72.1 MPa to 70.5–70.6 MPa, regardless of geometry, indicating that the defect area, rather than its shape, governs the failure response. The shear modulus of void-containing specimens (~4.48 GPa) did not differ from defect-free specimens (~4.49 GPa). Wrinkles increased the shear modulus to 5.39 GPa due to added layers but reduced strength by ~3% (to 69.9 MPa). DIC analysis confirmed the method’s efficacy for tracking strain localization in defect zones. Failure modes across all specimens involved vertical crack formation between V-notches. These results help systematize knowledge on of manufacturing defects on CFRP shear properties and hold practical significance for refining design tolerances in critical components, developing non-destructive testing methods, optimizing manufacturing processes.

Influence of laser shock peening on the residual strains and stresses in additively manufactured TC4

Thu, 16 Oct 2025 02:48:00 +0000

Additively manufactured materials possess significant heterogeneities and anisotropies of stiffness and strength properties between the growth and transverse directions. Residual stresses induced by the fabrication and processing stages are critical to the service life of these materials. In this work, an experimental study of the residual stress fields was conducted in samples cut from additively manufactured titanium alloy TC4. The depth profiles of residual elastic strains for various regimes of laser impact treatment were obtained on elementary samples in the form of rectangular plates of 100´20´5 mm. Five treatment regimes were studied by varying the laser power density, the spot shape, and the percentage of overlap. The dependence of relief strains and residual stress levels on the laser energy density was obtained for two laser spot shapes: a 1´1 mm square and a 2 mm diameter circle. The numerical model, validated against experimental data for both as-built and laser-peened states, provides a reliable tool for analyzing the residual stresses and strain in additively manufactured components.

Studies on influence of seashell-based filler on water absorption behaviour of bamboo-epoxy composite: mechanical and fractured

Sun, 12 Oct 2025 15:50:00 +0000

The hydrophilic nature of bamboo fiber makes them prone to moisture uptake and subsequent property degradation. In this study, bamboo fiber–epoxy composites were hybridized with clamshell-derived particulate fillers to mitigate the adverse effect of moisture absorption and enhance performance. Composites with 0, 3, 6, and 9 wt% filler were fabricated via compression molding technique. Moisture absorption and its influence on tensile and flexural strength were evaluated following ASTM standards. Results revealed that unfilled composites exhibited highest water uptake and severe strength loss upon moisture exposure, whereas filler addition reduced water uptake and improved strength retention. The 6 wt% filler showed optimal performance with 30.4% reduction in water uptake, 67.5% retention of tensile strength, and 70% retention of flexural strength. Fractography analysis confirmed the role of filler acting as a barrier against moisture ingress and restricting interfacial degradation.

Numerical simulation of crack propagation in clinch joints

Sat, 11 Oct 2025 14:48:00 +0000

The mechanical clinching process can be used for the load-bearing structures of thin-walled steel frame halls. Numerical simulation of crack propagation in a clinching joint using finite element method (FEM) software is an important tool for the analysis and prediction of the behavior of materials under load. This study focuses on clinch joints that must withstand high loads and repeated load cycles. Crack propagation in these joints can lead to failure of the entire structure, therefore it is important to understand the mechanisms of crack propagation and predict their behavior. Using specialized software, a numerical simulation of crack propagation was prepared, including modelling of joint geometry, definition of material properties and application of loads. The simulation provides valuable information on the crack propagation process, which allows optimization of the behavior of the whole structure and the reliability of the clinch joints.

Impact of tool rotational speed on friction stir welded joints of AA2014-T6/AA5052-H32: synthesis, microstructural, mechanical a

Sat, 11 Oct 2025 14:16:00 +0000

This study examines the changes in microstructure and mechanical properties of friction stir-welded (FSW) dissimilar joints between AA2014-T6 and AA5052-H32 aluminium alloys, with an emphasis on optimizing tool rotation speed for enhanced joint quality. FSW is performed at three different tool rotation speeds (860, 1160, and 1460 rpm) while maintaining a constant welding speed and tool tilt angle of 40 mm/min and 1°, respectively. The joint created at an optimal rotation speed of 860 rpm exhibits outstanding mechanical properties, with an ultimate tensile strength (UTS) of 211 ± 1.0 MPa, a yield strength of 181 ± 1.5 MPa, and an elongation of 16.1%. The joint efficiency, in comparison to the aluminium alloy AA5052-H32, is 93.8%, indicating minimal strength loss relative to the parent material. Vickers hardness tests across the weld cross-section reveal a maximum hardness of 156 ± 1.5 HV in the stir zone, closely matching the hardness of the stronger AA2014-T6 base metal. Fractographic analysis of the FSW joint made at 860 rpm indicates a predominantly ductile failure mode with micro-dimple fracture surfaces, whereas higher tool rotation speeds exhibit brittle characteristics with circular voids and tear ridges.

ENLO-SED: an innovative method for large-scale Strain Energy Density (SED) estimation in welded ...

Mon, 22 Sep 2025 13:00:00 +0000

Welded joints have always been critical elements of industrial mechanical structures, often being the source of failures related to the presence of fatigue loads. Although the academic world has presented advanced methodologies for the assessment of local fatigue, such as the Strain Energy Density (SED) approach, which offers high accuracy, their high computational requirements hinder their adoption by the industrial world. This paper introduces a new hybrid methodology, called ENLO-SED, which integrates the SED approach by calculating the Strain Energy Density using the element Nodal load approach (ENLO), with the aim of maintaining high accuracy while significantly reducing the computational effort. The proposed method is validated on a complex case study, representative of a real industrial case, demonstrating a prediction error within 8% compared to the application of the classic SED method. Furthermore, the innovative ENLO-SED approach reduces the meshing and solution times by 15 and 5 times, respectively. These results confirm the robustness, efficiency, and scalability of the method, making it suitable for large-scale industrial applications.

Assessment of mechanical, fracture and thermal properties of epoxy nanocomposites reinforced with low-concentration nano Boron C

Sun, 21 Sep 2025 09:43:00 +0000

This study investigates the effects of low concentration (0.1-0.4 wt.%) nano-boron carbide (B4C) reinforcement on the mechanical, thermal and fracture properties of epoxy nanocomposites. The nanocomposites were prepared via solution casting using ultrasonication to ensure proper dispersion of the nanofiller. The characterisation included Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), tensile, flexural, impact and fracture tests. Results showed significant enhancements in mechanical properties. Tensile strength peaked at 31.2 MPa (71% improvement) for 0.3 wt. % B4C, while modulus increased steadily to 1400 MPa (33% improvement). Flexural tests showed a progressive enhancement in bending strength, exhibiting 70.46 MPa (50% improvement) at 0.4 wt. % B4C. Impact strength surged by 62% at 0.4 wt. % and fracture toughness increased steadily, exhibiting 70% improvement. Thermal analysis revealed a higher glass transition temperature (Tg) and improved stability with B4C addition, attributed to restricted polymer chain mobility. SEM images showed improved fracture resistance, with rougher surfaces and smaller cleavage planes indicating effective energy absorption. Finite element (FE) simulations validated experimental tensile and flexural results, with variations within 15%. Statistical analysis confirmed all improvements were significant (p < 0.05).

Numerical and experimental analysis of mechanical and fatigue properties of special shaped 3D printed sample

Sun, 21 Sep 2025 08:59:00 +0000

Research in the field of property analysis of 3D printed structural elements raises many new questions. A major challenge is to understand the behavior of the material, as the raw material and the resulting printed sample cannot be considered the same in this respect. In 3D printing, the properties of the sample change due to high temperatures, changes in the state of the raw material and different setups. Currently, there is no standard for determining certain properties, which leads to the need for appropriate use of experimental and numerical tools. This study highlights the results of tensile testing and numerical analysis of a special 3D printed shape. Different material settings were used to allow a complete inverse analysis of the specimen behavior and calibration between experiment and model. The model was created in Ansys software and was prepared in several variations to be as close as possible to the real specimen. Subsequently, the numerical model was subjected to a simplified fatigue analysis with respect to the S-N curves and the predicted fatigue life of the specimen was determined.

Very High Cycle Fatigue (VHCF) of notched specimens: a review

Sat, 13 Sep 2025 04:21:00 +0000

A large number of mechanical components are subjected to fatigue loading beyond 106 cycles. The VHCF behaviour of smooth specimens has been extensively investigated in the recent years, even if more efforts are necessary to reveal the mecahnism governing failures. On the other hand, the influence of notches in the VHCF regime remains relatively unexplored. In the present review, the available studies on the VHCF behaviour of notched components have been analysed and compared. The review highlights that multiple approaches for accounting for the stress concentration introduced by notches are available in the literature and that notches alter the failure mechanisms compared to smooth specimens. In general, a model for the design of complex structures against VHCF failures and with notches/geometric discontinuities is missing, and more experimental data for different materials are to be obtained to prove the validity of the approaches already available in the literature or employed for the High Cycle Fatigue (HCF) life range. Moreover, since the ultrasonic fatigue testing machines are mainly used for the tests, different definitions for the stress concentration factors have been found in the literature, since, with these types of tests, the stress distribution within the specimen depends on the wave propagation and on the resonance condition.

Studies on mechanical, fractured surface, wear, and thermal characteristics of TiC reinforced structural grade Al6061 MMCs

Fri, 12 Sep 2025 12:41:00 +0000

Stir casting technique has been used in the current study to process Al6061 reinforced with TiC particles of different concentrations. The processed compounds' composition of TiC and Al6061 has been verified by Energy Dispersive X-Ray Spectroscopy (EDS) tests. TiC has been added to Al6061 in a range of weight concentrations, including 0, 3, 6, 9, and 12%. To determine the composite material's structure, an optical microscope research was used. It is endeavored to investigate the microstructure, mechanical, wear, and thermal performance of TiC-reinforced composites with varying weight fractions in this study. It was observed that, the strength of the developed composites increased by 51.89% in hardness, 18.47% in tensile strength and 40% in wear rate with the addition of TiC. Also, when compared to the alloy material, TiC particle reinforced Al6061 showed superior thermal characteristics.

A novel approach to estimation of residual strength of laminated polymer composites under compression after impact

Thu, 11 Sep 2025 13:26:00 +0000

This work is dedicated to the experimental study of the influence of preliminary dynamic loading on the residual strength of the laminated polymer composite under compression. A series of low-velocity transverse drop-weight impact tests in a wide range of energies was carried out, followed by quasi-static compression of composite specimens with two reinforcement schemes [0/90]n and [±45]n. Nonlinearity of the obtained dependences of residual static strength on the energy of preliminary dynamic loading has been discovered. It has been noted that there are three characteristic stages on the diagram of fiberglass laminate’s impact sensitivity: area of impact insensitivity; area of reduced bearing capacity; area of achieving the minimum bearing capacity. The identified patterns are consistent with the data on the response of specimens during impact, as well as with specimens’ surface damage after dynamic loading. An anisotropy of the composite's impact sensitivity has been discovered. A novel approach to estimation of residual strength of laminated polymer composites under compression after impact and determination of impact sensitivity thresholds based on the use of mathematical models has been proposed. A new model of residual strength has been developed and tested, its applicability for description of the mechanical behavior of composites with various reinforcement schemes has been demonstrated.

Strengthening of steel I-Section girder web with depth discontinuity against localized buckling

Thu, 11 Sep 2025 03:03:00 +0000

Stepped steel girders and beams with a jump in section depth are highly susceptible to local web buckling at the step location. Although tapered steel girders have been studied extensively by researchers, abruptly stepped steel girders have been very rarely investigated. This study uses the finite element method to investigate the local web buckling of stepped steel I-section girders. Firstly, linear buckling analysis is verified against experimental results and the AISC-360 and Eurocode 3 formulae. Then, a case study of stepped steel girder failure during construction is presented and discussed. Finally, the effect of step height, step location, boundary conditions, and adding stiffeners on the local web buckling of stepped girders was investigated. Stepping the girder section was found to cause local web buckling at significantly low loads, reaching only 27% of the original buckling capacity in some cases. Moving the step from the compression flange to the tension flange, or to lower moment locations in the girder, can mitigate the problem. When the step needs to be in the compression flange at high moment points, using a long enough horizontal stiffener was found to almost fully restore the web buckling capacity, while using a vertical one only restores about half of the original buckling capacity. Using both vertical and horizontal stiffeners almost doubles the buckling capacity at the step.

Dynamic damage analysis of carbon fiber reinforced polymer composite pressure vessels

Tue, 09 Sep 2025 04:41:00 +0000

This study investigates spall damage and failure in Carbon Fiber-Reinforced Polymer (CFRP) pressure vessels under explosive internal loading using stimulated electric discharge. Analytical modeling, validation with published experimental data, and explicit numerical simulations were employed. A Coupled Eulerian–Lagrangian (CEL) framework in Abaqus/Explicit captured the dynamic-impact shock propagation, using continuum shell (SC8R) elements for the vessel, solid (C3D8R) for the PMMA insert, and Eulerian (EC3D8R) for copper-wire vapor. Intralaminar failure was modeled using the Hashin criterion, while interlaminar damage was captured using the energy-release-rate-tuned Virtual Crack Closure Technique (VCCT). Results demonstrated high-accuracy agreement with experiments in terms of free surface velocity and failure stresses, with minor discrepancies attributed to wire alignment, material model limitations, and wave reverberations. These findings highlight the reliability of the integrated modeling framework and support improved design and risk-mitigation strategies for composite pressure vessels, advancing safety and cost-efficiency through refined material characterization and structural assessment.

Correlation between process parameters and mechanical properties of Ti6Al4V alloys processed by electron beam melting

Mon, 08 Sep 2025 03:39:00 +0000

The present study of Ti6Al4V alloy production via Electron Beam Melting (EBM) represents a cutting-edge research topic impacting different strategic engineering applications. This can be attributed to the widespread use of this alloy and by the unique characteristics of the EBM process. Operating under vacuum and with powder pre-heating, EBM enables the fabrication of components with higher density and reduced residual stress compared to other additive manufacturing techniques. The research reported in this paper analyses the effect of process parameters used in the manufacturing process on defect formation and then on mechanical properties. The results highlighted that the presence of lack of fusion defects leads to a markedly anisotropic behavior of the alloy. This is due to the different morphology of the defects in the different considered directions and to their effect in concentrating stresses.

Advanced algorithms for early detection of first damage during static tensile tests

Mon, 08 Sep 2025 03:10:00 +0000

The Static Thermographic Method (STM) involves analyzing the thermal behavior of a specimen subjected to a quasi-static tensile test. The temperature trend, measured by an infrared camera, follows three phases where the first and second are cooling phases, while the third a heating phase. A limit stress value can be determined, corresponding to the macroscopic stress level at the point of slope change between the first and second phase, indicating the occurrence of initial damage. The onset of plasticity is the reason of fatigue failure; thus, the limit stress can be adopted as a first indication of failure stress level for design purposes. This work aims to objectify the Static Thermographic Method, which currently relies on the operator's experience and skill in identifying the different thermal phases during the static tensile test. Three different algorithms have been developed to determine the best mathematical model for the temperature trend over time, eliminating the subjectivity of data observation.

An innovative analytical approach for predicting the fundamental time period of moment-resisting frames

Sun, 07 Sep 2025 03:11:00 +0000

Most seismic design codes provide formulas for estimating base shear and lateral loads. To determine lateral loads, the building's fundamental vibration period must be calculated, either theoretically or experimentally. However, there is no simplified equation that accurately calculates this parameter. This paper proposes a new simplified formula for computing the fundamental period of reinforced concrete moment-resisting frames (MRFs). The proposed formula is validated through eigenvalue analysis of the mathematical models of various building frames using finite element methods (FEM), with varying structural properties along their height. The proposed model achieved an average prediction error of around 4% and an R² (coefficient of determination) value of 0.999 when compared to FEM results, outperforming existing empirical formulas. A sensitivity analysis was conducted to identify the effect of each of the design parameters, accompanied by a comparative evaluation against some formulas from the literature. The novelty of the suggested method is that it can calculate the fundamental period more accurately and easily by considering the stiffness and seismic mass of the building.

Multidisciplinary characterisation, weathering patterns, and durability assessment of stone blocks for the conservation of Tamen

Thu, 04 Sep 2025 16:09:00 +0000

This study investigates the physico-mechanical properties, mineralogical composition, deterioration processes, weathering patterns, and durability of building materials in the Ottoman Fort of Tamentfoust, Algiers, to inform heritage conservation strategies. Stone block samples were taken from a highly damaged wall and, the mechanical and physical characterisation was carried out with through laboratory and on-site methods. These methods included destructive tests (compressive and flexural strength) and non-destructive techniques (Schmidt hammer rebound, ultrasonic pulse velocity, thermal imaging, density, porosity, and capillarity coefficients. Mineralogical and petrographical analyses were conducted using X-ray diffraction (XRD) and X-ray fluorescence (XRF), while durability was evaluated through sodium chloride crystallization and hydrogen chloride ageing tests, with scanning electron microscopy (SEM-EDX) analysing microstructural properties. Weathering forms were assessed and documented using 3D laser scanning, thus generating a weathering mapping for the most damaged facade. The results revealed two stone types: one with high porosity, low strength, and poor durability, and another with high compactness and excellent durability. These findings provide critical insights into material behaviour, enabling tailored preservation strategies for the fort and contributing to the broader field of heritage conservation.

The static and modal analysis of concrete tank filled with water

Thu, 04 Sep 2025 12:56:00 +0000

Tanks and reservoirs are structural systems designed for storing various liquids, gravels, granular or other bulk materials. Special attention is usually given to the potable water storage. Regarding the increasing scarcity of clean water and the recent lack of it in some regions worldwide, it is essential that these structures have to be carefully analysed and properly designed. Water tanks are significant architectonic works as well. They are typically constructed from steel or reinforced concrete, and most commonly, they adopt the cylindrical shape. Considering their future utilization and regarding other essential circumstances related to the site of their planned placement, they can be situated on the ground, above the ground, partially buried, or fully underground. Due to the expected static and dynamic effects, both static and modal analysis have to be carried out prior to building them up, even within the designing process. This paper provides the numerical analysis of a cylindrical surface-mounted water reservoir by using the Finite element method in Ansys Workbench. The hydrostatic pressure simulating the water acting to the wall was imposed. The static and modal analysis were carried out for empty and fully filled tank. Mutual comparison of various approaches is provided.

Implementation of interface damage model with friction to concrete-FRP shear connector

Thu, 04 Sep 2025 12:54:00 +0000

The study investigates the application of fibre-reinforced polymer (FRP) composites in constructions of bridges. It highlights the main advantages of using FRP as a building material and points out its suitability for various structural applications. A numerical analysis was performed on different shape modifications of a jigsaw-puzzle type continuous shear connector. For the interface between concrete and FRP, a bilinear cohesive zone model with friction within a variationally based formulation of interface damage has been chosen and tested. This model captures the load displacement relation accounting for a softening region and offering a continuous response of key variables of stress and damage. Findings illustrate reliability of the cohesive bilinear model as a tool for predicting failure and show a promise for applying it in material design, or in design of FRP composite structures, their members and specifications of their construction details.

Studying the strength and damageability of composite element in looped metal-composite joint under tensile loading

Thu, 28 Aug 2025 16:05:00 +0000

The article presents the results of computational and experimental studies of the strength and damageability of a connecting composite part in a metal-composite joint of isogrid and anisogrid structures made of polymer composite material under tension. The assessment of the minimal cross-sectional area of the connecting part was performed based on design calculations, taking into account strengthening during extrusion of the excess binder. The onset of failure in the contact zone with the steel element of the metal-composite joint was predicted based on experimental studies using model samples. A comparison was made between the calculation results for the tensile loading diagram, considering the physical nonlinear behavior of composite material in the joint zone, and the readings of strain gauges after testing the metal-composite joint. Damages and deformation of the connecting composite part under the tensile load was imaged using acoustic microscopy.

Behavior of steel columns with double curvature: a numerical simulation and design-oriented parametric study

Tue, 26 Aug 2025 15:08:00 +0000

This research present a novel investigation, which focuses on the numerical exploration of steel columns having a double curvature, built with both hollow square and circular cross-sections. A finite element model was initially created using ABAQUS software and was validated through a series of compression experiments conducted on square hollow specimens exhibiting double curvature. close agreement was observed in term of ultimate loads, load–displacement curves and deformed shapes corresponding to the failure modes. Based on validated numerical simulations, parametric analyses are carried out to investigate the effects of major geometric parameters on the axial bearing capacity of double curved steel columns. The study consists in a systematic variation of curvature angle (20°, 25°, 30°, and 35°), curvature radius (500 mm, 700 mm, 900 mm, and 1100 mm), square cross-section size (250 mm, 300 mm, 350 mm, and 400 mm), circular diameter (318 mm, 381 mm, 445 mm, and 509 mm) and end offset distance (400 mm, 600 mm, 800 mm, and 1000 mm). The findings highlighted the sensitivity of axial performance to angle curvature, section width and offset distance at column ends. The outcomes of this study provide valuable insights for the design and optimization of curved steel columns in structural engineering applications, particularly where stability and axial strength are critical.

Fatigue performance of flexible pavements with cement-bound granular material (CBGM)

Tue, 26 Aug 2025 13:15:00 +0000

The article analyzes the fatigue performance of flexible pavement structures incorporating cement-bound granular material (CBGM) as a subbase layer. In current Polish design methodologies, overly conservative and underestimated stiffness modulus values are often assumed for CBGM, neglecting the material’s behavior in the uncracked state. A mechanistic analysis was conducted using the theory of multilayer elastic half-space. Fatigue life was evaluated based on two criteria: Dempsey and De Beer. The results showed that, according to Dempsey’s criterion, only one selected layer configuration would not crack under construction traffic, whereas De Beer’s criterion indicated that none of the analyzed structures should fail. The findings demonstrate a significant reserve in the fatigue life of CBGM layers and highlight the need to revise existing design assumptions, particularly for mixtures of lower strength classes.

Parameters optimization for manufacturing advanced self-reinforced composites based on ultra-high molecular weight polyethylene

Tue, 19 Aug 2025 10:07:00 +0000

In this study, the relationships between processing, structure and properties of self-reinforced ultra-high molecular weight polyethylene (UHMWPE) composites fabricated via thermal pressing are investigated. By systematically varying processing temperatures (145, 155, 165, 170, 175,180 °C) and pressures (25 and 50 MPa), we demonstrate that mechanical performance is governed by the interplay between fiber consolidation and the preservation of the oriented crystalline phase. Scanning electron microscopy reveals the presence of residual voids that are independent of the processing parameters, and which lead to interfacial failure and fibrillar fracture morphologies. We identify a critical processing threshold at 165 °C (25 MPa), which yields peak interlayer shear strength (7.8–11.1 MPa), bending strength (102–130 MPa), elastic modulus (23–42 GPa), and Charpy impact resistance (72–95 kJ/m²). Beyond this threshold, however, mechanical performance deteriorates due to fiber remelting and loss of anisotropy, resulting in the composite transitioning to an isotropic UHMWPE matrix. Conversely, elevated pressures fail to improve properties due to insufficient macromolecular interdiffusion, which is the dominant bonding mechanism. These findings establish a processing-structure-property framework for UHMWPE-based self-reinforced composites that balances interfacial adhesion and crystalline alignment, while providing actionable guidelines for engineering high-performance single-polymer materials.

Fatigue behaviour of high-strength low-alloy steel sheets: influence of loading direction and microstructure on microcrack initi

Mon, 18 Aug 2025 04:43:00 +0000

This work presents an in-depth study of the low-cycle fatigue behaviour of ferritic-pearlitic HSLA-420 high-strength steel sheets, with emphasis on the influence of loading direction on fatigue life and damage mechanisms. Plastic strain-controlled fatigue tests were conducted along the rolling (RD), transverse (TD), and diagonal (DD) directions. Despite the nearly isotropic tensile response associated with weak crystallographic texture and similar microstructural characteristics, fatigue life varied depending on the loading orientation. RD specimens showed the highest fatigue life, nearly doubling TD at low strain and remaining over 25% at high strain. DD behaved similarly to RD at low strain but approached TD at higher strain levels. The Coffin–Manson relationship was linear in RD, while TD and DD showed bilinear trends with a slope change at Δεp/2 = 1 × 10⁻³. Transmission electron microscopy revealed that dislocation structure evolution during cycling was direction-dependent. In RD, intragranular slip bands within ferrite grains dominated and acted as primary crack initiation sites. In contrast, TD and DD exhibited subgrain structures near grain boundaries, promoting strain localization and intergranular crack nucleation. At higher strain amplitudes, compact subgrains reinforced by cementite particles favored intergranular crack propagation in TD and DD samples, contributing to reduced fatigue life.

An experimental study on the rehabilitation performance of CFRP-strengthened bubble deck slabs: effects of void size and preload

Sat, 16 Aug 2025 18:35:00 +0000

This study examines the rehabilitation performance of reinforced concrete bubble deck slabs (with 50 mm and 60 mm voids) strengthened with externally bonded CFRP sheets. Nine specimens were tested: eight bubble slabs (grouped by void size and preloading level) and one solid control slab. Three specimens of each void size were pre-damaged to 50%, 60%, and 75% of their ultimate load before being strengthened with CFRP and retested. One specimen per group remained unstrengthened for comparison. Results show that increasing void size reduces load capacity: the unstrengthened 50 mm and 60 mm void slabs achieved 96.2% and 86.5% of the solid slab’s strength, respectively. CFRP rehabilitation effectively restored structural performance, with 50 mm void slabs recovering up to 98.5% of the control slab’s capacity and exhibiting 25% lower deflection. In contrast, 60 mm void slabs showed lower recovery efficiency, particularly at higher preloading levels SB-6-75 recovered only 82.5% of the control strength. All strengthened specimens failed by CFRP debonding combined with flexural cracking, with no shear failures observed. The study demonstrates that CFRP retrofitting significantly enhances the strength and stiffness of damaged bubble deck slabs, especially those with smaller voids. Void size and pre-damage level are critical factors influencing rehabilitation success.

Experimental investigation of tensile and bond strength for a GFRP–SSWM hybrid wraps

Sun, 10 Aug 2025 17:17:00 +0000

This study experimentally investigates the tensile and bond performance of novel GFRP–SSWM hybrid wraps developed using two epoxy adhesives - Sikadur 30 LP and Sikadur 330. A total of 42 coupon specimens for tensile testing and 48 dumbbell specimens for bond testing are prepared using various two-layer and three-layer configurations of GFRP, SSWM, and their hybrids. Tensile tests are conducted as per ASTM D3039, and specimen performance are evaluated in terms of ultimate load capacity, displacement at peak load, stiffness, rupture strain, and failure modes. Fractographic assessment is also performed at the failure plane of coupon specimens. Study results of tensile and bond test, indicate that GFRP-only specimens exhibit high tensile strength and stiffness but fail in a brittle manner, while SSWM-only specimens show greater ductility with reduced strength. Hybrid configurations offer a balanced response between strength and ductility. Among hybrids, GS specimens bonded with Sikadur 30 LP show superior performance in two-layer systems. Fractographic observations confirm effective hybrid action between GFRP and SSWM without delamination or layer separation at the interface. The capacity utilization ratio further supports that Sikadur 30 LP performs better than Sikadur 330, especially in hybrid configurations involving SSWM. The study highlights the mechanical viability of GFRP-SSWM hybrid wraps for use in strengthening applications.

Study on B4C particulates size on mechanical behavior, fractured surface and optimization of the wear parameters of the Al7075 c

Sun, 10 Aug 2025 16:39:00 +0000

Aluminum composites with varied weight percentages of 0-2.5 B4C particles and micro- and nanoparticle sizes were fabricated by stir-casting. The material's mechanical and wear characteristics were evaluated. We used dry pin-on-disc wear testing to examine the wear behavior of both micro and nano composites. In the sliding wear trials, different particle sizes (micro and nano), sliding distances (1500 m and 3000 m), and sliding speeds (3 m/s and 6 m/s) were employed. Scanning Electron Microscope (SEM) was utilized in the experiment to examine the materials and microstructures of several composites. Uniform dispersion of the micro and nano particles was readily evident in the SEM image. B4C particle microhardness increased by 16.06 % in nano composites and 10.78 % in micro composites. In a similar way, B4C particles' tensile strength increased by 12.90% in nano composites and 8.78% in micro composites. Taguchi design for experimental technique was applied to a L8 orthogonal array in order to design and ascertain the effects of sliding distance, sliding speed, and particle size on dry sliding wear behavior. ANOVA study showed that the most significant influencing factor on wear resistance was particle size (61.29%), followed by sliding speed (17.27%) as well as sliding distance (14.20%). From the confirmatory tests, the Coefficient of Friction (COF) of the produced composites had a maximum error of 9.09 % and the error of 3.33 % was found in the wear rate which was within the acceptable limit. The wornout surface shows that the composite reinforced with nanoparticles has a smooth wear surface with a finer wear scar.

Numerical modeling of fracture processes of bodies with stress concentrators under conditions of proportional loading, taking in

Tue, 29 Jul 2025 13:01:00 +0000

This work is dedicated to the development of a fracture model for an elastic-brittle solid with statistically distributed strength characteristics of subregions and the application of this model to describe fracture processes of bodies with stress concentrators under biaxial loading. The methodology of numerical modeling of deformation and fracture processes is improved to take into account the partial loss of load bearing capacity and the appearance of local anisotropy. Based on the improved methodology, modified algorithm is developed. The influence of the biaxial loading mode and the dispersion of the ultimate strength distribution on the loading diagrams and the orientation of the macrodefect is considered. The realization of the gradual macrodefect development (localized type of damage accumulation) or its growth through the most weakened damaged areas (mixed type) is revealed. The applicability of the approach to assessing the type of damage accumulation based on the analysis of numerical solutions of boundary value problems within the elasticity theory is demonstrated. The efficiency of the usage of the modified approach to ensure the reliability and safety of critical structures under multiaxial loading is concluded.

Analyzing the effect of residual stresses on the fatigue life of cold-drawn steel wire specimens

Wed, 09 Jul 2025 13:35:00 +0000

An analytical model, based on Solid Mechanics, is developed based on a comprehensive analysis of the effect of residual stress on the fatigue performance of cold-drawn steel wires partially yielded specimens. In the experimental part, it was initially assumed that the specimens, taken from the manufacturer's wire spools, did not have appreciable residual stresses. Therefore, a residual stress pattern was imposed on the specimens before the fatigue testing. Nevertheless, it was realized that the number of cycles spent by the specimens up to failure was higher than those predicted by the fatigue/residual stress compound analytical model. Hence, the initial assumption was reviewed, and a prior superficial compressive residual stress was incorporated into the model, most likely generated by cold-rolling manufacturing. The “resistance increase” and the “stress reduction” approaches were suggested to encompass the number of cycles difference, with good results. In addition, the prior level of existing superficial compressive residual stresses was also estimated.

Optimizing different damaged reinforced concrete corbel characteristics utilizing CFRP sheets

Tue, 08 Jul 2025 15:32:00 +0000

Concrete corbels are short cantilever constructions that may lose their strength over time because of loads that happen over and over again. As an external bonding method for reinforcement, carbon fiber-reinforced polymer (CFRP) strips are utilized to improve performance. This study examines the influence of CFRP strips on the reinforcement and repair of conventional concrete corbels by concentrating on ultimate strength, performance under monotonic loads, and the effects of varying damage ratios during restoration. As part of a study project, nine double-concrete corbels with the same size and reinforcement had to be manufactured and tested. The samples were split into two groups: those with strip wrapping and those with side wrapping. Each group had three corbels that had already been damaged, one corbel that had been reinforced, and control specimens that had not been repaired. The results showed that side-wrapped corbels with CFRP reinforcement exhibited a 19.72% (SCS-0-1) improvement in strength and a 13.73% (RCS-50-1), 18.35% (RCS-60-1), and 4.15% (RCS-70-1) increase in ultimate load. Strip-wrapped corbels showed improvements of 9.86% (RCST-50-2), 5.44% (RCST-60-2), and 0.51% (RCST-70-2), whereas strengthening (SCST-0-2) showed an improvement of 19.72%. Also, specimens wrapped in CFRP showed less ultimate deflection than their un-strengthened counterparts at the same damage levels, which shows that they perform better and last longer.

Modeling of the transition from transgranular to intergranular fracture at elevated temperatures in EI698 nickel alloy

Thu, 03 Jul 2025 03:47:00 +0000

In this study, an efficient computational method for modeling the transition from transgranular to intergranular fracture mechanisms based on phase field fracture theory is discussed. Structural heterogeneity of the material is modeled on the basis of Voroni diagrams. Parameters characterizing the mechanical properties of the material for the intergranular and transgranular space are the same for models of continuum mechanics. The location of crack initiation and the crack path in the proposed method controlled by the difference in the values of the critical energy release rate for the intergranular and transgranular spaces for the phase field model. The source code of the created and used finite element is an open source project and available to download from https://github.com/Andrey-Fog/ANSYS-USERELEMENT-PHFLD. The obtained results correlate well with previously conducted fractographic studies.

Optimizing mechanical properties of AA7075 Metal Matrix Composites reinforced with TiB2 and ZrO2 particulates

Thu, 03 Jul 2025 03:01:00 +0000

Hybrid metal matrix composites (MMCs), recognized for their superior strength-to-weight ratios and synergistic property enhancements, are emerging as advanced materials capable of mitigating the inherent limitations observed in conventional monolithic composites. While traditional composites offer structural benefits, their susceptibility to creep deformation and abrasive wear restricts their broader applicability. In sectors such as aerospace, automotive, and marine engineering, aluminum-based hybrid MMCs reinforced with ceramic particulates like titanium diboride (TiB2) and zirconium dioxide (ZrO₂) have garnered considerable interest due to their enhanced mechanical integrity and tribological performance. This investigation is an extension of previous work by authors AA7075 MMCs. This work systematically examines the influence of TiB2 (fixed at 5 wt%) coupled with incremental ZrO₂ reinforcement levels (2, 4, and 6 wt%) on the microstructure, mechanical strength, hardness, and wear resistance of AA7075 alloys fabricated via the stir casting process. The study aims to elucidate the compositional optimization of hybrid reinforcements to tailor material properties for high-performance applications. Microstructural analysis revealed an equiaxed grain structure with uniform reinforcement distribution, particularly in AA7075/5% TiB2/4% ZrO2 composition. The addition of reinforcements improved hardness up to 85.45%, increasing from 55 Hv (base alloy) to 102.40 Hv. And, also the yield strength increased from 107 MPa (base alloy) to 123 MPa, an increase of 15%, attributed to the improved particle detachment resistance. Introducing TiB2 and ZrO2 particles remarkably enhanced wear resistance with a wear rate of 155 µm with 10N load due to reinforcements that act as the lubricating agent between the metal matrix and the rotating disc. Among the compositions studied, AA7075/5% TiB2/4% ZrO2 exhibited superior performance, highlighting the potential of tailored hybrid composites for advanced mechanical and tribological applications in automotive, aerospace and marine industries.

Integral bridge abutment with composite dowels: structural scheme and failure patterns

Thu, 19 Jun 2025 03:18:00 +0000

This paper presents a novel integral abutment design incorporating a composite dowel girder and H-shaped steel pile abutments to enhance load-bearing capacity and construction efficiency. Numerical analysis is conducted to investigate the failure modes, load-transfer mechanisms, and ultimate bearing capacity of the integrated abutment joint. A parametric study examines the influence of key factors, including steel girder web thickness and the reinforcement ratio of the deck and abutment, on structural performance. Results indicate that abutment failure is primarily attributed to concrete compression failure beneath the steel girder. Based on the findings, a formula for predicting the ultimate bearing capacity of the integrated abutment joint is proposed. Under the same steel girder depth and bottom plate width, the steel consumption of the integral abutment proposed in this work is reduced while the section has a slightly higher bearing capacity compared that of the traditional I-shaped steel girder.

An experimental study into the net cross-sectional failure of damaged plates with holes for different steel grades and temperatu

Sun, 15 Jun 2025 15:04:00 +0000

This study reports an experimental investigation on the applicability of the net cross-sectional resistance rules of Eurocode 3 for steel plates with different bolt-hole configurations and steel grades, when relatively small fatigue cracks are present at the edge(s) of the holes. Previous studies have confirmed that the considered design rule is on the safe side. Moreover, part of this safety margin accounts for the potential occurrence of relatively small fatigue cracks. Two steel grades are considered, namely S275JR and S700MC. Therefore, in addition to previous studies, a relatively high steel grade is considered. Moreover, some tests were carried out on cooled specimens to get an impression of the effect of low temperatures on the failure mechanism. The experimental results demonstrate that relatively small cracks (<1 mm) have a negligible practical influence on the measured ultimate resistance of the plates. Furthermore, the failure assessment diagram is found to be suitable to predict the critical condition in the presence of cracks with length and shape as found in the experiments, also for relatively high steel grades.

Damage of additively manufactured polymer materials: experimental and probabilistic analysis

Wed, 11 Jun 2025 04:23:00 +0000

This paper presents a study on the tensile, fracture, damage, and reliability properties of 3D printed polylactic acid (PLA), based on a series of experiments. The study focuses on polylactic acid (PLA) samples produced using fused filament manufacturing (FFF) technology, specifically examining unidirectional print orientations of 0°, 45°, and 90°. Tensile testing demonstrated significant anisotropy in mechanical behavior, The specimens oriented at 0° exhibited the highest tensile strength, while those at 90° showed the lowest. An increase in artificial crack length (a) resulted in a progressive decrease in the mechanical properties. Weibull analysis confirmed the presence of significant anisotropic behavior in 3D-printed PLA specimens, with ultimate stress (σu0) values ranging from 39.82 MPa for the 90° orientation to 44.69 MPa for the 0° orientation, and elastic stress (σe0) values from 35.49 MPa (90°) to 39.11 MPa (0°), indicating greater strength for the 0° oriented specimens. Damage evolution analysis showed accelerated damage, with the 90° orientation demonstrating the fastest rate of damage compared to the 0° and 45° orientations. This indicates that the 90° orientation is more vulnerable to crack propagation and has diminished structural integrity under stress.

Investigation on the tensile strength, hardness and wear properties in n-B4C reinforced Al7075 composites

Fri, 06 Jun 2025 04:13:00 +0000

The impact of n-B4C on the mechanical and tribological behavior of Al7075 particle reinforced composites were assessed by analyzing samples of the resultant nano-composites for micro-structure, hardness, tensile strength, and wear behavior using stircasting technology. According to microstructural research, nanoparticles were dispersed throughout the specimen space. Adding the wt. % of nano B4C resulted in a considerable improvement in hardness (17.89%) and tensile strength (13.75%). Because of the cleavage that forms on the fractured surfaces of Al+n-B4C nanocomposites, fractography analysis on the fractured tensile specimens revealed brittle fracture for the n-B4C reinforcement composites and ductile fracture for unreinforced aluminum. By adjusting the process conditions, the dry sliding wear characteristics of n-B4C reinforced aluminum alloys were investigated using Taguchi's Design of Experiment Methodology. The independent process factors were determined to be the applied load (7-21N), the sliding speed (750-1250 rpm), and the reinforcement composition (0-3 weight percent of n-B4C). The L27 orthogonal array by Taguchi was selected to react based on the coefficient of friction and wear rate. The following processing parameters were determined to be optimal for the highest wear rates: 750 rpm sliding speed, 7 N load, and 3 weight percent reinforcement. Similarly, the optimal processing parameters for assessing Coefficient of Friction (COF) were determined to be 3 wt. % reinforcement, 21 N load, and a sliding distance of 1250 rpm.

An investigation on the free vibration behaviors of additively manufactured PA6 layered plates: influences of stacking sequenc

Wed, 04 Jun 2025 16:26:00 +0000

This study investigates the free vibration behavior of 3D-printed PA6 layered plates by considering the effects of stacking sequence, infill ratio, and boundary conditions. Unlike previous works, this research provides a comprehensive analysis combining experimental pre-analyses and finite element simulations. Nine different plate configurations with infill ratios of 40%, 70%, and 100%, and aspect ratios (a/b = 1, 1.5, 2, and 2.5) were analyzed under clamped and simply supported boundary conditions. The mechanical properties of the printed material were determined through tensile testing, and these properties were used as input for the numerical model developed in ANSYS. Before the vibration analyses, the model was validated by comparing its results with existing literature, showing close agreement. Results showed that higher infill ratios in the outer layers increase natural frequencies due to improved stiffness, whereas a denser core can reduce them due to increased mass. Additionally, increasing the aspect ratio leads to higher natural frequencies. The findings offer valuable insights for improving the vibration performance of 3D-printed PA6 components used in functional parts such as gears, fan blades, and robotic arms.

Experimental test on 3D-printing components for Architectural Restoration

Wed, 04 Jun 2025 15:11:00 +0000

The paper investigates the use of 3D-printed components made from Polylactic Acid (PLA) for the restoration of architectural and ornamental elements, focusing on architectural/structural components. The material PLA was chosen for its potentiality in respecting the principles of restoration, recognizability, reversibility and minimum intervention, thanks its visual appearance, very different from typical construction materials, biodegradability and affordability. The paper represents an exploratory study aimed to derive the characteristics of 3D-printed PLA components thought tensile tests on dog-bone samples, and to analyze the behavior of structural components, thought tensile and bending tests on small truss beam samples. Unlike previous works mainly oriented towards aesthetic reproduction, this study focuses on the mechanical performance of PLA components designed for structural integration in restoration projects. The results show that the 3D-printed PLA components exhibit an average tensile strength of 44 MPa and an average Young’s modulus of 1270 MPa, values consistent with literature for fully dense PLA prints, and peak loads of about 6.4 kN in tension and 5 kN in bending for truss elements. Furthermore, this study provides data useful for future numerical modelling of 3D-printed structural elements in PLA, aimed at predicting their structural performance and supporting the design phase.

Phase-field modeling for investigating the effect of rebar positioning and uniform versus non-uniform corrosion on concrete frac

Sat, 24 May 2025 05:02:00 +0000

Rebar corrosion significantly affects the overall performance and the service life of reinforced concrete (RC) structures due to the reduction in the bond strength between concrete and rebar, leading to the delamination of the concrete cover. Numerous studies have been conducted using experimental, analytical, and simulation methods to explore corrosion-induced damage. Regarding simulation methods, previous studies have focused on either uniform or non-uniform corrosion, without an overall comparison between these two scenarios in terms of crack development and displacement of rust expansion. Furthermore, in brittle materials such as concrete, the strain tensor is split into a tension part and a compression part, in which only the strain energy of the tension part controls the crack development. Therefore, this paper provides some novel aspects: (i) Two parts of the strain tensor are orthogonal in the context of the inner product with the elastic stiffness tensor behaving as a metric. This orthogonal condition combined with the phase-field modeling, helps to improve the mechanical behaviors of the materials; (ii) The numerical method (i) is used to simulate and compare the crack path and displacement due to rust expansion of RC structures under uniform and non-uniform corrosion conditions. Several RC cross-sections are conducted as follows: (a) Cross-sections containing one or multiple asymmetrically arranged rebars, with the constant rebar area fraction and the concrete cover thickness unchanged; (b) Cross-sections containing four symmetrically arranged rebars with the 10mm rebar diameter (D10) and the concrete cover thicknesses changed; (c) Cross-sections containing four symmetric D10 rebars and the pores. Through several aforementioned numerical simulation examples, this paper provides an overview of uniform versus non-uniform corrosion-induced fracture in the typical RC cross-sections. This can guide the selection of the appropriate rebar positioning for the realistic RC structures, helping to mitigate rapid deterioration due to the rebar corrosion.

Prediction of the tensile strength of FDM specimens based on Tsai Hill criteria

Thu, 22 May 2025 15:22:00 +0000

This study investigates the mechanical behavior of 3D-printed polyethylene terephthalate glycol (PETG) polymer specimens subjected to tensile and shear testing, with a particular focus on the influence of raster orientation and shell contour. Specimens were fabricated using Fused Deposition Modeling (FDM) at three raster angles (0°, 45°, and 90°) and tested using both a mechanical extensometer and a Digital Image Correlation (DIC) system. The results indicate a significant influence of raster orientation on tensile and shear properties. 0° specimens exhibited the highest tensile strength, as the filament alignment was parallel to the loading direction. In contrast, 45° specimens demonstrated more ductile behavior. While the shell contour had minimal effect on 0° and 45° specimens, it enhanced stiffness and ductility in 90° specimens. Furthermore, the Tsai-Hill criterion was applied to predict the tensile strength at a 45° orientation. These findings contribute to a deeper understanding of the anisotropic behavior of 3D-printed materials and highlight the importance of raster orientation in optimizing mechanical performance.

Damage mechanisms in hybrid composites: experimentalcharacterisation and energy-based numerical analysis

Wed, 21 May 2025 15:10:00 +0000

This study analyses the failure mechanisms of bilayer hybrid composites, consisting of carbon and glass fibres embedded in an epoxy matrix, under bending loads. The objective is to evaluate how different hybrid configurations influence failure evolution and mechanical performance. To achieve this, specimens are submitted to 3-point bending tests, and 3D finite element models are developed to simulate the experimental setup. The numerical models incorporate a continuum damage mechanics model to capture intralaminar failure and a surface-based cohesive behaviour for interlaminar damage. The results show that hybrid laminates exhibit intermediate strength and displacement values compared to nonhybrid carbon and glass laminates, with the positioning of glass fibers significantly affecting bending force and displacement. Intralaminar damage is the primary failure mechanism in all configurations, followed by delamination. Additionally, placing glass fibers on the compression side reduces the overall damage, whereas placing them on the tensile side increases intralaminar failure before reaching the peak load. These findings contribute to optimizing the design of hybrid composites for bending applications by providing information about the relationship between material configuration and failure mechanisms, ultimately improving their structural efficiency and durability in engineering applications.

Parametric study on the effect of anchor’s geometry on the stress distribution and crack initiation direction in a concrete body

Wed, 14 May 2025 15:01:00 +0000

This work deals with investigations of the stress field distribution around a steel anchor embedded in a concrete. Tensile loading - pulling force of the steel anchor is considered, which is very often connected to concrete cone failure. Numerical simulations via finite element method were performed to obtain results for a large extent of geometrical configurations. In accordance with the basic idea of the maximum tangential stress criterion, the angle where this stress reaches its maximum was determined. The influence of selected geometrical parameters of the system on these angles was analyzed and it was found out that they can significantly affect the angle of the maximum tangential stress and consequently the shape of the cone failure. It was observed that the circumferential crack propagation is flatter with increasing length of the steel anchor’s embedment and with increasing anchor’s outer radius. The results obtained numerically agree sufficiently with experimental results especially when the crack direction is compared. Conclusions presented within this research are important for both design and assessment of anchor/concrete systems subjected to tensile loading.

Influence of contact interaction character on residual stresses arising over damaged area in composite plate

Tue, 13 May 2025 15:06:00 +0000

New data concerning the values of residual stresses that arise as a result of the contact interaction of a spherical indenter and a flat surface of composite plate have been obtained. The studies are performed for both static indentation and impact influence of a spherical indenter into a flat surface of coupons made of carbon fibre reinforced polymer with cross-ply stacking sequence. The high-quality interference fringe patterns, generated by through hole drilling in contact interaction zone, which are essential for residual stress deriving are visualized and quantitatively processed both inside and outside the contact dimple. The distributions of residual stresses obtained during static and impact contact interaction, which leads to the appearance of dimples of almost the same diameter, are compared. A comparison of the values of the principal residual stress components corresponding to the contact interaction of similar composite plates with a spherical impactor of different diameters for the same impact energy is presented. Several factors have been identified that relate the decrease in the residual strength of damaged specimens to the values of the residual stress components. Evaluation of the influence of coupon’s thickness as well as an impact energy level on the residual stress values inherent in the vicinity of contact dimple is presented.

A study on the crack presence effect on dynamical behavior of higher-order Quasi-3D composite steel-polymer concrete box section

Sun, 11 May 2025 04:46:00 +0000

This paper presents a dynamic and critical buckling analysis of the presence of a crack of steel-polymer concrete composite beams modelled using a refined quasi 3D beam theory. The beam model is a hollow steel box section filled with a composite concrete material. The presence of the crack is assumed on both inner concrete core and outer steel layer box, incorporating its effects into the mechanical behavior of the beam. The governing equations for the box beam are derived using the Differential Quadrature Finite Element Method (DQFEM) combined with Lagrange’s principle. The study investigates the natural frequencies and critical buckling loads of steel-polymer concrete composite beams under various crack location and crack depth. Validation is performed by comparing the results with numerical methods and experimental results available in the literature, demonstrating high accuracy. The findings of this research provide valuable insights into the dynamic and stability behavior of box-section beam with composite infill, offering practical guidelines for the design of material-based structures in engineering applications.

Predictive modeling of PMMA-based polymer composites reinforced with hydroxyapatite: a machine learning and FEM approach

Wed, 07 May 2025 03:46:00 +0000

This research examines the mechanical characteristics of polymer composites (PMMA) that are reinforced with Hydroxyapatite (HAp), with a particular emphasis on the Elastic Modulus and Compressive Strength. The investigation employs a multifaceted approach that integrates experimental methods, micromechanical analysis, and machine learning techniques. Experimental assessments of Elastic Modulus and Compressive Strength were conducted at various HAp concentrations (5%, 15%, and 30%) and were compared with theoretical predictions derived from Representative Volume Element (RVE) and micromechanical frameworks, including Voigt and Reuss bounds. Various machine learning algorithms, such as Feedforward Neural Network (FFNN), Radial Basis Neural Network (RBNN), and Support Vector Machine (SVM), were used to predict the mechanical properties. The RBNN exhibited high accuracy (R² = 0.92; MAE = 0.05) for intermediate HAp levels (20-30%) but displayed instability at the extremes % of reinforcements values . The FFNN consistently provided lower estimates of the properties, whereas the SVM yielded robust and stable predictions that closely matched both experimental and theoretical results with the error of (2-5) % (Result value). This research highlights the effectiveness of integrating micromechanical modeling with machine learning to improve the prediction and comprehension of composite behavior, thereby offering valuable insights for the design and application of advanced materials.

Flood-induced load effects on real-scale structures: a 3D multilevel dynamic analysis

Tue, 06 May 2025 15:58:00 +0000

In this work, the structural behavior of masonry buildings under flash flood actions is analyzed by using a novel 3D multilevel fluid/structure model. The proposed numerical framework consists of a macro-scale model based on the computational fluid dynamic, able to simulate the dynamic free-stream flow of a fluid impacting rigid solids and a meso-scale structural model that employs a coupled damage-plasticity approach to describe the nonlinear behavior of the masonry buildings, subjected to the fluid dynamic pressure extracted by the macro-scale fluid analysis. The integrated model was employed to assess the fluid-structure interaction effects on the global structural response, in terms of load-carrying capacity and damage patterns, of a real-scale masonry structure subjected to flood-induced loading conditions. Finally, a parametric analysis is performed in order to understand the influence of the fluid inlet velocity and water depth on the failure mechanisms of the structure. The results highlight the good numerical capabilities of the proposed multilevel model, establishing it as a valuable numerical tool for the structural vulnerability assessments under flood actions.

Experimental investigation on mechanical behavior of sandwich structures using Digital Image Correlation (DIC)

Sat, 26 Apr 2025 15:36:00 +0000

The aim of this work is to investigate the mechanical behavior of sandwich structures when subjected to edgewise and flatwise compression loadings, using 2D Digital Image Correlation (DIC). These structures are made of Glass Fiber Reinforced Polymer (GFRP) skins with polyurethane foam (PU) core. Initially, the mechanical characterization of each component within the sandwich structure is exanimated. Subsequently, flatwise and edgewise compression tests are conducted on the sandwich panels, in accordance with ASTM C365 and ASTM C364 standards, respectively. Different geometries are studied by testing various lengths of sandwich structures exposed to edgewise compression loads. The DIC technique is applied to analyze and comprehend the deformation and failure mechanisms of GFRP skins and sandwich structures. The results of the present study indicate that the flatwise compression test revealed condensation and densification of PU foam, accompanied by microcracks in GFRP skin. On the other hand, the edgewise compression test on sandwich structures with an equal length-to-width ratio identified several distinct failure modes, including skin-core debonding, shear sliding damage of the skin, and localized buckling. This localized buckling was initially observed in the mid-section of the specimens, followed by skin cracking on both sides, which then propagated across the width of the samples. For other geometric configurations of the sandwich structures, the Euler general buckling mode was observed. The results show that the length of samples has a significant effect on the collapse modes of sandwich structures under edgewise compression.

Size effect in concrete beams: a numerical investigation based on the size effect law

Sat, 26 Apr 2025 15:34:00 +0000

The size effect significantly influences the structural design of concrete elements, particularly when applying fracture mechanics principles. As structural dimensions increase, a significant outcome of the size effect is the decline in both strength and ductility. To characterize concrete fracture behavior, various fracture mechanics models have been proposed, integrating material fracture properties that are unaffected by changes in geometry and size. Bažant’s size effect law explains this phenomenon based on the transition from ductile to brittle failure in geometrically similar specimens. When failure is delayed after crack initiation, the size effect is mainly influenced by the energy released during macro-crack propagation. Conventional experimental studies on this phenomenon have typically utilized two-dimensional geometrically similar specimens, though they are often limited by laboratory constraints. While experimental studies on notched concrete beams under three-point bending (TPB) exist, their size is often restricted due to practical challenges in handling large specimens and also numerical modeling of large-scale fracture simulations remains limited due to high computational requirements. This research proposes an optimized finite element modeling approach to numerically examine the size effect on the fracture characteristics of notched concrete beams subjected to three-point bending (TPB). Beams with depths up to 1000 mm were analyzed using this approach. The numerical findings align well with experimental size-effect data from the literature, exhibiting the expected trends. Furthermore, fitting the results to Bažant’s size effect law demonstrated a strong correlation, validating the accuracy of the proposed numerical model.

A simplified nonlinear model for bamboo-reinforced concrete beams based on lumped damage mechanics

Sat, 26 Apr 2025 15:33:00 +0000

Bamboo’s renewability may justify bamboo-reinforced concrete (BRC) structures. For practical applications, the accurate description of BRC flexural behaviour is paramount. Lumped damage mechanics is an interesting alternative among some possibilities on nonlinear models since it is based on key concepts of classic fracture and damage mechanics. Therefore, this paper presents a novel lumped damage model for BRC beams. The model’s accuracy is tested with experiments found in the technical literature. Regarding the analysed experiments, the proposed model presents well-fitted results. Finally, the proposed model is feasible for practical applications, even considering structural reliability analysis like Monte Carlo, since it is easy to implement and presents low computational effort.

The assessment of the severity of local impact on a pro-bionic composite lattice shell by the use of fiber-optic sensors

Sat, 26 Apr 2025 15:21:00 +0000

The paper considers a pro-bionic lattice shell (PBLS) for civil aviation structures and the problem of getting the parameters of a local low-velocity impact taking the value of residual strain by fiber optic sensors (FOS) installed in PBLS. There was developed a numerical model of an equivalent smooth shell with a detailed part as an impact zone. This detailed part have been constructed from a load-bearing rib containing layers of UD composite, matrix polymer, a protective tab and a skin. The matrix polymer layers and the protective tab had elastic-plastic properties, in the developed numerical model. The UD composite layers and the skin were orthotropic elastic media. FEM calculations showed that the location of FOS directly on the rib surface does not provide the required accuracy of getting impact residual strain. However, FOS installation into elastic-plastic protective tab makes solving the problem. Localized Bragg grating sensors must be installed into the FOS with a high density (every 1-2 cm along the rib) to indicate the impact location, which is technically difficult to implement. Distributed sensors (Brillouin scattering) have an advantage, allowing both to indicate the impact location by residual strain recording and to get possibility calculate later the most important parameter - the impact energy.

Papers published in 2023-2024 on F&SI focused on Additive Manufactured Materials

Wed, 29 Jan 2025 05:23:00 +0000

This audio recording presents a discussion of recent research papers on additive manufacturing (3D printing) of materials for various sectors. The conversation highlights the significant advancements in 3D printing, moving beyond simple prototypes to applications in creating stronger, more sustainable materials for diverse uses, such as enhancing PLA plastic with graphene for increased strength, producing eco-friendly car engine parts, and even restoring historical architecture. A key focus is on addressing challenges like residual stress in 3D-printed metal parts and optimising the printing process for consistent results, utilising techniques like the Taguchi method. Finally, the discussion looks towards the future of 3D printing, including the development of novel materials and the integration of artificial intelligence to improve efficiency and sustainability.

Issue 70

Thu, 16 Jan 2025 15:58:00 +0000

The TOC is: Exploring the elastocaloric effect of Shape Memory Alloys for innovative biomedical devices: a review Girolamo Costanza, Ilaria Porroni, Maria Elisa Tata Numerical study of the influence of the parameters of statistical distribution of the structural elements’ ultimate strength on deformable bodies’ fracture processes Eugeniia Feklistova, Artur Mugatarov, Valeriy Wildemann Modeling turning performance of Inconel 718 with hybrid nanofluid under MQL using ANN and ANFIS Paresh Kulkarni, Satish Chinchanikar ANSYS implementation of the phase field fracture approach Dmitry Kosov, Andrey Tumanov, Valery Shlyannikov Tool wear evaluation of self-propelled rotary tool and conventional round tool during turning Inconel 718 Satish Chinchanikar, Nitin Motgi Self-similarity of damage-failure transition and the power laws of fatigue crack advance Mikhail Bannikov, Vladimir Oborin, Oleg Naimark Impact of hybrid nanoparticle reinforcements on Mechanical properties of Epoxy-Polylactic Acid (PLA) Composites M. A. Umarfarooq, K. Dileep, A. Srinath, N.R. Banapurmath, Ashok M. Sajjan Predicting Damage in Notched Functionally Graded Materials Plates through extended Finite Element Method based on computational simulations Hakim Siguerdjidjene, Amin Houari, Kouider Madani, Salah Amroune, Mohamed Mokhtari, Barhm Mohamad, Chellil Ahmed, Abdelkrim Merah, Raul Campilho Mechanical Evaluation of Recycled PETG Filament for 3D Printing Liviu Marsavina, Vlad, Sergiu Rubberized reinforced concrete columns under axial and cyclic loading Mohamed Ahmed, Heba A. Mohamed, Hilal. Hassan, Mahmoud Zaghlal An interface-based microscopic model for the failure analysis of masonry structures reinforced with timber retrofit solutions Fabrizio Greco, Lorenzo Leonetti, Paolo Lonetti, Paolo Nevone Blasi, Arturo Pascuzzo, Giacinto Porco Optimization of the internal structure of 3D-printed components for architectural restoration Valentina Tomei, Ernesto Grande, Maura Imbimbo Correlation coefficients of vibration signals and machine learning algorithm for structural damage assessment in beams under moving load Toan Pham Bao, Vien Le-Ngoc Effect of printing process parameters on tensile strength and wear rate of 17-4PH stainless steel deposited using SLM process Priya Sahadevan , Pon Selvan Chithirai, Avinash Lakshmikanthan, Amiya Bhaumik, Agustin Flores Cuautle Elastic-viscoplastic deformation models of salt rocks Alexander Baryakh, Andrey Tsayukov Application of deep learning for technological parameter optimization of laser shock peening of Ti-6Al-4V alloy Mikhail Verezhak, Aleksei Vshivkov, Elena Gachegova, Maria Bartolomei, Alexander Mayer, Sathya Swaroop Introduction and application of a drive-by damage detection methodology for bridges using variational mode decomposition Shahrooz Khalkhali Shandiz, Hamed Khezrzadeh, Saeed Eftekhar Azam Enhancing Generalizability of a Machine Learning Model for Infrared Thermographic Defect Detection by Using 3D Numerical Modeling Vladimir Vavilov, Arsenii Chulkov, Alexey Moskovchenko

Revisiting classical concepts of Linear Elastic Fracture Mechanics

Fri, 27 Dec 2024 10:58:00 +0000

The audio deep dive explores linear elastic fracture mechanics, analyzing how mathematical models predict crack behavior. Key concepts such as the mathematical crack, stress intensity factors (SIFs), and contact stresses are discussed, highlighting how classical models can lead to impossible overlaps. The analysis also includes the effects of material properties, different loading modes, and stress neutralization techniques. The deep dive emphasizes the importance of refined models and damage tolerance in engineering design.

ESIAM23: an interview with Jan Torgersen

Fri, 27 Dec 2024 10:53:00 +0000

The interview with Yan Torgersen highlights the advantages of additive manufacturing in the energy sector. Torgersen notes that additive manufacturing uses only the material needed for printing, which reduces waste, and this is a significant benefit in the energy sector, where there is often a lot of waste. Additionally, additive manufacturing provides the geometric freedom to design transport paths inside electrochemical or electrical structures. With the advent of electrically conductive micro and nanoscale devices, additive manufacturing is considered a game changer.

ESIAM23: an interview with Nima Razavi

Fri, 27 Dec 2024 10:51:00 +0000

The interview with Nima Razavi discusses the importance of structural integrity in additive manufacturing, emphasizing the need for predictive tools. The discussion includes the evolution of additive manufacturing from prototyping to real-life applications, where qualification and certification are essential. The importance of understanding structural integrity and developing predictive tools is highlighted. This includes considering the scale effect in printing, from nanoscale to meters. Razavi also stresses that a physics-based approach is needed, integrating material science, mechanical engineering, and chemistry for a comprehensive understanding from process to design to performance

ESIAM23: an interview with Liviu Marsavina

Fri, 27 Dec 2024 10:42:00 +0000

The interview with Livio Marsavina highlights the importance of additive manufacturing and structural integrity. It discusses a successful conference that is expected to continue in the future. Marsavina mentions that additive manufacturing is growing a lot and that structural integrity is a key aspect. Additionally, he expresses appreciation for thesis TC 15 and its co-chairmen for organizing the European conference on the structural integrity of additive manufacturing.

ESIAM23: an interview with Abilio De Jesus

Fri, 27 Dec 2024 10:35:00 +0000

The interview with Abilio de Jesus, a professor at the University of Porto and one of the co-Chairpersons of ESIAM23, focuses on the importance of a specialized event on additive manufacturing. De Jesus emphasizes how, despite numerous global conferences, there is a lack of events focused on specific topics such as structural integrity, which is the central theme of this conference. The event was considered a success, with in-depth discussions on progress and future trends in this field.

ESIAM23: an interview with Sara Bagherifard

Fri, 27 Dec 2024 10:27:00 +0000

The interview with Sarah Bagherifard discusses the importance of customizable solutions and the mixing of materials in additive manufacturing. She mentions that to move forward in the competitive market of additive manufacturing, there's a need to invest in more customizable solutions, including material selection and the mixing of different materials to leverage the synergy of their different properties. She also highlights the need for technologies enabling tighter tolerances, more complex geometries, and site-specific properties, all with an eye toward material efficiency