Fracture and Structural Integrity: The Podcast

Fracture and Structural Integrity: The Podcast@fis_podcast

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Season 74 episodes (25)

ENLO-SED: an innovative method for large-scale Strain Energy Density (SED) estimation in welded ...
S74:E27

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

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
S74:E26

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

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
S74:E25

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

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.

Studies on mechanical, fractured surface, wear, and thermal characteristics of TiC reinforced structural grade Al6061 MMCs
S74:E23

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

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
S74:E22

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

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
S74:E21

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

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
S74:E20

Dynamic damage analysis of carbon fiber reinforced polymer composite pressure vessels

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.

Advanced algorithms for early detection of first damage during static tensile tests
S74:E18

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

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
S74:E17

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

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
S74:E16

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

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
S74:E15

The static and modal analysis of concrete tank filled with water

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
S74:E14

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

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
S74:E13

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

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
S74:E12

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

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)
S74:E11

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

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
S74:E10

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

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
S74:E09

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

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
S74:E08

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

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
S74:E07

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

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
S74:E06

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

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
S74:E05

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

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
S74:E04

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

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
S74:E03

Optimizing different damaged reinforced concrete corbel characteristics utilizing CFRP sheets

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
S74:E02

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

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
S74:E01

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

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.