5:31

S77:E05 Apr 5, 2026

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

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.

5:14

S77:E04 Apr 4, 2026

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

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.

5:28

S77:E03 Apr 3, 2026

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

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.

5:34

S77:E02 Apr 3, 2026

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

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.

5:20

S77:E01 Apr 3, 2026

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

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.