Pub Date : 2025-12-15DOI: 10.1016/j.engfracmech.2025.111809
Jinjin Xu , Zihao Yang , Xuan Wang , Bin Jiang , Minjie Wang , Yulong Li , Xiang Wang
Classical bond-based peridynamic (PD) models are limited in capturing the tensile-compressive asymmetry and strain rate dependence of glass materials. To address these issues, an improved rate-dependent and softening PD (RSPD) model was presented by introducing a damage correction factor to capture compression softening and incorporating dynamic increase factors to account for strain rate effects. The improved RSPD model presents superior performance in predicting crack density and kinetic energy dissipation compared with classical PD model. The ballistic impact response of aluminosilicate glass is investigated by combining the RSPD simulations and experiments. The effects of impact velocity and glass thickness on fracture behavior are analyzed, and the numerical predictions show good agreement with experimental observations. The results indicate that the critical penetration velocity increases with glass thickness, while radial crack density and damage diameter increase with impact velocity but decrease with thickness. Quantitative relationships among contact force, damage ratio, impact velocity, and glass thickness are also established, offering a preliminary evaluation for the design and optimization of impact-resistant glass structures in engineering applications.
{"title":"Fracture behavior of aluminosilicate glass under ballistic impact: An experimental and peridynamic study","authors":"Jinjin Xu , Zihao Yang , Xuan Wang , Bin Jiang , Minjie Wang , Yulong Li , Xiang Wang","doi":"10.1016/j.engfracmech.2025.111809","DOIUrl":"10.1016/j.engfracmech.2025.111809","url":null,"abstract":"<div><div>Classical bond-based peridynamic (PD) models are limited in capturing the tensile-compressive asymmetry and strain rate dependence of glass materials. To address these issues, an improved rate-dependent and softening PD (RSPD) model was presented by introducing a damage correction factor to capture compression softening and incorporating dynamic increase factors to account for strain rate effects. The improved RSPD model presents superior performance in predicting crack density and kinetic energy dissipation compared with classical PD model. The ballistic impact response of aluminosilicate glass is investigated by combining the RSPD simulations and experiments. The effects of impact velocity and glass thickness on fracture behavior are analyzed, and the numerical predictions show good agreement with experimental observations. The results indicate that the critical penetration velocity increases with glass thickness, while radial crack density and damage diameter increase with impact velocity but decrease with thickness. Quantitative relationships among contact force, damage ratio, impact velocity, and glass thickness are also established, offering a preliminary evaluation for the design and optimization of impact-resistant glass structures in engineering applications.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"333 ","pages":"Article 111809"},"PeriodicalIF":5.3,"publicationDate":"2025-12-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145789801","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-14DOI: 10.1016/j.engfracmech.2025.111794
Mohammad Naqib Rahimi , Lampros Svolos , George Moutsanidis
Functionally graded materials (FGMs) are advanced composite materials whose spatial gradation in structure and composition leads to tailored characteristics suitable for specific applications and operating conditions. FGMs have been employed in many fields including aerospace, automotive, defense, and biomedical, among others. Modeling crack initiation and propagation in such materials is therefore crucial in order to predict sudden loss of load-carrying capacity and prevent catastrophic failure in extreme environments and under severe loading conditions. A special class of FGMs is functionally graded ultra-high temperature ceramics (FG-UHTCs). These materials feature outer zones of thermally resistant components, such as zirconium diboride () or hafnium diboride (), that grade smoothly into tougher, less brittle inner layers, such as silicon carbide (SiC). FG-UHTCs have primarily been used in hypersonic applications, where the encountered temperatures and pressures are very high. Although the fracture behavior of FGMs and FG-UHTCs under mechanical loading has been studied, research on crack formation and propagation under strong thermal loads remains limited. In this work, motivated by their potential in hypersonic environments, we examine dynamic brittle fracture in FG-UHTCs subjected to extremely high thermal loads typical of hypersonic flight. Leveraging the phase-field method, our primary objective is to develop fundamental insights into whether and how material gradation influences fracture resistance and thermal protection. First, comprehensive mathematical and implementation details for the computational method are provided. Then, the framework is verified and validated against alternative computational approaches and experimental data. Finally, we conduct two representative high-temperature extreme scenarios in which the gradation profile is systematically varied. These examples are specifically designed to quantify how material gradation governs crack initiation, propagation, and overall thermal protection, thereby generating the fundamental insights on the effect of material gradation.
{"title":"Functionally graded ultra-high temperature ceramics for hypersonic applications: A numerical study of fracture under high-temperature extremes","authors":"Mohammad Naqib Rahimi , Lampros Svolos , George Moutsanidis","doi":"10.1016/j.engfracmech.2025.111794","DOIUrl":"10.1016/j.engfracmech.2025.111794","url":null,"abstract":"<div><div>Functionally graded materials (FGMs) are advanced composite materials whose spatial gradation in structure and composition leads to tailored characteristics suitable for specific applications and operating conditions. FGMs have been employed in many fields including aerospace, automotive, defense, and biomedical, among others. Modeling crack initiation and propagation in such materials is therefore crucial in order to predict sudden loss of load-carrying capacity and prevent catastrophic failure in extreme environments and under severe loading conditions. A special class of FGMs is functionally graded ultra-high temperature ceramics (FG-UHTCs). These materials feature outer zones of thermally resistant components, such as zirconium diboride (<span><math><mrow><mi>Z</mi><mi>r</mi><msub><mrow><mi>B</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>) or hafnium diboride (<span><math><mrow><mi>H</mi><mi>f</mi><msub><mrow><mi>B</mi></mrow><mrow><mn>2</mn></mrow></msub></mrow></math></span>), that grade smoothly into tougher, less brittle inner layers, such as silicon carbide (SiC). FG-UHTCs have primarily been used in hypersonic applications, where the encountered temperatures and pressures are very high. Although the fracture behavior of FGMs and FG-UHTCs under mechanical loading has been studied, research on crack formation and propagation under strong thermal loads remains limited. In this work, motivated by their potential in hypersonic environments, we examine dynamic brittle fracture in FG-UHTCs subjected to extremely high thermal loads typical of hypersonic flight. Leveraging the phase-field method, our primary objective is to develop fundamental insights into whether and how material gradation influences fracture resistance and thermal protection. First, comprehensive mathematical and implementation details for the computational method are provided. Then, the framework is verified and validated against alternative computational approaches and experimental data. Finally, we conduct two representative high-temperature extreme scenarios in which the gradation profile is systematically varied. These examples are specifically designed to quantify how material gradation governs crack initiation, propagation, and overall thermal protection, thereby generating the fundamental insights on the effect of material gradation.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111794"},"PeriodicalIF":5.3,"publicationDate":"2025-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787410","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-14DOI: 10.1016/j.engfracmech.2025.111810
Tao Liu , Tian-Yu Gu , Chang-Feng Zhou , Bo Chen , Liang-Jiu Jia
This study investigates the micro ductile fracture mechanism of 6061-T6 aluminum alloy by capturing the physical process of internal void evolution during tensile loading through in-situ X-ray micro-computed tomography (micro-CT) and electron microscopy. Time-resolved three-dimensional reconstructions reveal a strong correlation between microscopic void evolution and macroscopic mechanical responses. The onset of necking corresponds to a critical porosity threshold, beyond which porosity increases rapidly and the material’s load-bearing capacity degrades. Three nucleation modes, i.e., matrix defects, particle rupture, and particle debonding, contribute to increase in porosity and void density, while promoting void growth and coalescence. Under a constant stress triaxiality condition, voids exhibit distinct growth rates affected by their projected area in the tensile direction, as well as by subsequent void nucleation and coalescence. Void coalescence becomes dominant after necking and will occur when the intervoid spacing ratio falls below a critical value of 0.7. Two coalescence mechanisms are identified: stable formation of horizontal microcracks due to intervoid necking, and rapid formation of inclined microcracks via intervoid shearing within local shear bands. The experimental findings enable a physics-informed calibration of Gurson-Tvergaard-Needleman (GTN) model parameters. CT-based finite element simulations using the GTN model, coupled with the proposed parameter calibration process, reproduce macroscopic fracture behavior but underestimate the microscale porosity. Micromechanical representative volume element analyses quantify how void shape and stress triaxiality affect void growth and rationalize the underestimation.
{"title":"Micro ductile fracture mechanism of 6061-T6 aluminum alloy via in-situ micro-CT testing and multi-scale simulation","authors":"Tao Liu , Tian-Yu Gu , Chang-Feng Zhou , Bo Chen , Liang-Jiu Jia","doi":"10.1016/j.engfracmech.2025.111810","DOIUrl":"10.1016/j.engfracmech.2025.111810","url":null,"abstract":"<div><div>This study investigates the micro ductile fracture mechanism of 6061-T6 aluminum alloy by capturing the physical process of internal void evolution during tensile loading through in-situ X-ray micro-computed tomography (micro-CT) and electron microscopy. Time-resolved three-dimensional reconstructions reveal a strong correlation between microscopic void evolution and macroscopic mechanical responses. The onset of necking corresponds to a critical porosity threshold, beyond which porosity increases rapidly and the material’s load-bearing capacity degrades. Three nucleation modes, i.e., matrix defects, particle rupture, and particle debonding, contribute to increase in porosity and void density, while promoting void growth and coalescence. Under a constant stress triaxiality condition, voids exhibit distinct growth rates affected by their projected area in the tensile direction, as well as by subsequent void nucleation and coalescence. Void coalescence becomes dominant after necking and will occur when the intervoid spacing ratio falls below a critical value of 0.7. Two coalescence mechanisms are identified: stable formation of horizontal microcracks due to intervoid necking, and rapid formation of inclined microcracks via intervoid shearing within local shear bands. The experimental findings enable a physics-informed calibration of Gurson-Tvergaard-Needleman (GTN) model parameters. CT-based finite element simulations using the GTN model, coupled with the proposed parameter calibration process, reproduce macroscopic fracture behavior but underestimate the microscale porosity. Micromechanical representative volume element analyses quantify how void shape and stress triaxiality affect void growth and rationalize the underestimation.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111810"},"PeriodicalIF":5.3,"publicationDate":"2025-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787459","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-14DOI: 10.1016/j.engfracmech.2025.111775
Peitao Wang , Qingru Liu , Yudong Ren , Yishan Zhang , Meifeng Cai
Real-time and remote monitoring of slope deformation is crucial for early detection of potential slope failure, serving as a key component in landslide early warning systems. In this study, digital image correlation (DIC) techniques were employed to conduct uniaxial compression tests on coal rock and concrete specimens. Failure precursor indices derived from strain field data in both brittle coal specimens and ductile jointed rock were analyzed using statistical methods. To quantify the extent of damage in the study area, an absolute standard deviation (ASD) index based on strain field dispersion was proposed. Additionally, a fracture precursor identification method was developed using the absolute variation coefficient (AVC) and the rate of variation (RV). The results demonstrated that an increase in the ASD of the strain field was correlated with the formation of localized bands and crack occurrence within the study region. A sudden increase in the AVC was closely associated with the initiation and rapid propagation of cracks or slips, as well as a sudden increase in the displacement rate. The advance ratio, calculated based on AVC and RV, was 11.25% for coal samples and 31.11% for concrete samples. Long-range DIC monitoring technology was used to investigate the slip rate and slope trend. The fracture precursor index indicated the absence of slip precursors in the slope, consistent with the engineering monitoring results.
{"title":"Multi-scales analysis of fracture evolution and failure identification of rocks based on digital image correlation","authors":"Peitao Wang , Qingru Liu , Yudong Ren , Yishan Zhang , Meifeng Cai","doi":"10.1016/j.engfracmech.2025.111775","DOIUrl":"10.1016/j.engfracmech.2025.111775","url":null,"abstract":"<div><div>Real-time and remote monitoring of slope deformation is crucial for early detection of potential slope failure, serving as a key component in landslide early warning systems. In this study, digital image correlation (DIC) techniques were employed to conduct uniaxial compression tests on coal rock and concrete specimens. Failure precursor indices derived from strain field data in both brittle coal specimens and ductile jointed rock were analyzed using statistical methods. To quantify the extent of damage in the study area, an absolute standard deviation (ASD) index based on strain field dispersion was proposed. Additionally, a fracture precursor identification method was developed using the absolute variation coefficient (AVC) and the rate of variation (RV). The results demonstrated that an increase in the ASD of the strain field was correlated with the formation of localized bands and crack occurrence within the study region. A sudden increase in the AVC was closely associated with the initiation and rapid propagation of cracks or slips, as well as a sudden increase in the displacement rate. The advance ratio, calculated based on AVC and RV, was 11.25% for coal samples and 31.11% for concrete samples. Long-range DIC monitoring technology was used to investigate the slip rate and slope trend. The fracture precursor index indicated the absence of slip precursors in the slope, consistent with the engineering monitoring results.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111775"},"PeriodicalIF":5.3,"publicationDate":"2025-12-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.engfracmech.2025.111808
Yunhao Wu , Hanpeng Wang , Qing Ma , Wei Wang , Dekang Sun , Jianguo Fan , Le Gao , Yuguo Zhou
In China, inclined and steeply inclined coal seams are widely distributed. layered anchoring structures are prone to failure under complex stress environments, posing significant challenges to the stability of roadway surrounding rock. Therefore, in-depth research on the coupled “layered rock mass + anchorage structure” system is of critical importance. To address this, uniaxial compression tests were conducted on Cross-layer anchored rock masses with varying anchoring methods and lithological layered rock characteristics, revealing their mechanical properties and fracture patterns. The results demonstrate that: (1) The peak strain of the end-anchored and full-length anchored rock increases, and the deformation capacity of the rock increases. Compared to no-anchored rock, the strength increases by 8.75 % and 15.20 % for end-anchored and full-length anchored, respectively. (2) The Cross-layer anchored mass mainly shows the mechanical properties of weak matrix rock mass. Combined with the harder rock, the compressive strength of the combined rock is higher. (3) The crack propagation path from low strength rock mass to high strength rock mass is adjusted by bolt and anchoring agent, and the initiation of tensile crack is inhibited to a certain extent. (4) Shear failure mainly occurs in coarse sandstone-fine sandstone composite rock, and spalling and tensile failure mainly occur in sandstone-coal composite rock. Finally, by analyzing the stress of cross-layer anchored rock, the support strengthening mechanism of bolt and anchoring agent is revealed, and the failure criterion of anchored rock under axial loading is established. The experimental results are in good agreement with the theoretical prediction model results.
{"title":"Study on the mechanical properties and failure mechanism of cross-layer anchored rock mass under axial loading","authors":"Yunhao Wu , Hanpeng Wang , Qing Ma , Wei Wang , Dekang Sun , Jianguo Fan , Le Gao , Yuguo Zhou","doi":"10.1016/j.engfracmech.2025.111808","DOIUrl":"10.1016/j.engfracmech.2025.111808","url":null,"abstract":"<div><div>In China, inclined and steeply inclined coal seams are widely distributed. layered anchoring structures are prone to failure under complex stress environments, posing significant challenges to the stability of roadway surrounding rock. Therefore, in-depth research on the coupled “layered rock mass + anchorage structure” system is of critical importance. To address this, uniaxial compression tests were conducted on Cross-layer anchored rock masses with varying anchoring methods and lithological layered rock characteristics, revealing their mechanical properties and fracture patterns. The results demonstrate that: (1) The peak strain of the end-anchored and full-length anchored rock increases, and the deformation capacity of the rock increases. Compared to no-anchored rock, the strength increases by 8.75 % and 15.20 % for end-anchored and full-length anchored, respectively. (2) The Cross-layer anchored mass mainly shows the mechanical properties of weak matrix rock mass. Combined with the harder rock, the compressive strength of the combined rock is higher. (3) The crack propagation path from low strength rock mass to high strength rock mass is adjusted by bolt and anchoring agent, and the initiation of tensile crack is inhibited to a certain extent. (4) Shear failure mainly occurs in coarse sandstone-fine sandstone composite rock, and spalling and tensile failure mainly occur in sandstone-coal composite rock. Finally, by analyzing the stress of cross-layer anchored rock, the support strengthening mechanism of bolt and anchoring agent is revealed, and the failure criterion of anchored rock under axial loading is established. The experimental results are in good agreement with the theoretical prediction model results.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111808"},"PeriodicalIF":5.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787417","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.engfracmech.2025.111804
Peijie Yue , Xiaoqi Li , Haibin Li , Kai Li , Yujia Cheng , Xiaoquan Cheng
In this paper, the flatwise compression, flatwise tension, and plate shear tests of graphitized coal-based carbon foam at 20 ℃ and 200 ℃ were conducted based on ASTM methods for sandwich cores. A stochastic mesostructure model was developed to analyze the mechanical response with the constitutive relation based on the isotropic solid-phase material, using periodic boundary conditions and the criteria of fracture. The measured compressive, tensile, and shear moduli were 1.63, 2.94, and 0.64 GPa, and the strengths were 5.45, 3.10, and 3.08 MPa. The compressive modulus was significantly lower than the tensile modulus, and the reason was suspected to be the different damage modes of ligament buckling under compression and fracture under tension by analyzing the loading processes. Brittle damage behavior was observed with a decreasing trend at elevated temperatures. Simulation results showed the great difference between mechanical properties in the longitudinal direction and the transverse iso-plane. Meanwhile, the stress in thinner ligaments were higher and a fracture band was formed nearby until damage, which was consistent with the cracks observed in the tests.
{"title":"Mechanical properties of graphitized coal-based carbon foam: Sandwich core test and stochastic mesostructure FEM simulation","authors":"Peijie Yue , Xiaoqi Li , Haibin Li , Kai Li , Yujia Cheng , Xiaoquan Cheng","doi":"10.1016/j.engfracmech.2025.111804","DOIUrl":"10.1016/j.engfracmech.2025.111804","url":null,"abstract":"<div><div>In this paper, the flatwise compression, flatwise tension, and plate shear tests of graphitized coal-based carbon foam at 20 ℃ and 200 ℃ were conducted based on ASTM methods for sandwich cores. A stochastic mesostructure model was developed to analyze the mechanical response with the constitutive relation based on the isotropic solid-phase material, using periodic boundary conditions and the criteria of fracture. The measured compressive, tensile, and shear moduli were 1.63, 2.94, and 0.64 GPa, and the strengths were 5.45, 3.10, and 3.08 MPa. The compressive modulus was significantly lower than the tensile modulus, and the reason was suspected to be the different damage modes of ligament buckling under compression and fracture under tension by analyzing the loading processes. Brittle damage behavior was observed with a decreasing trend at elevated temperatures. Simulation results showed the great difference between mechanical properties in the longitudinal direction and the transverse <em>iso</em>-plane. Meanwhile, the stress in thinner ligaments were higher and a fracture band was formed nearby until damage, which was consistent with the cracks observed in the tests.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111804"},"PeriodicalIF":5.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787420","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.engfracmech.2025.111800
Ammar Al-Hagri , Henrik Stang , Jacob Paamand Waldbjørn , Athanasios Kolios , Evangelos Katsanos
Offshore steel jacket structures are exposed to harsh marine environments and cyclic loading, leading to fatigue damage that undermines their structural integrity. Among the most vulnerable areas are the welded joints, which are susceptible to crack initiation and propagation, highlighting the need for reliable fatigue assessment during design and operation to ensure durability and safety. To address this challenge, this study introduces a machine learning (ML)-based surrogate modeling framework for efficient and reliable fatigue assessment. The framework comprises three integral components: (1) a multi-fidelity finite element (FE) modeling to substantially minimize computational demand; (2) a surrogate model for predicting stress intensity factor (SIF); and (3) a crack propagation and fatigue life prediction module. The surrogate model was trained on a dataset from simulations in Abaqus and Franc3D. The multi-fidelity models reproduced the first five vibration periods with mean errors below 3.3 %, and mode shapes showed strong agreement with a high-fidelity reference. Among eight ML models assessed for SIF prediction, a deep neural network (DNN) achieved the highest accuracy (MAE ≈ 3 %), whereas XGBoost attained a balanced trade-off between accuracy and computational efficiency (MAE ≈ 11 %). Beyond model-level assessment, two additional full-case verifications at the weld toe (crown and saddle) matched FE-computed SIF and fatigue life within ± 5 % and 1.6 %, respectively, while delivering results in 3 s compared with about 5 h for the FE simulations. These findings demonstrate that the proposed framework provides a reliable, efficient alternative to fracture mechanics-based FE simulations for fatigue assessment of complex structures under realistic loading.
{"title":"Fatigue crack propagation and life prediction in offshore steel jackets using multi-fidelity modeling and machine learning","authors":"Ammar Al-Hagri , Henrik Stang , Jacob Paamand Waldbjørn , Athanasios Kolios , Evangelos Katsanos","doi":"10.1016/j.engfracmech.2025.111800","DOIUrl":"10.1016/j.engfracmech.2025.111800","url":null,"abstract":"<div><div>Offshore steel jacket structures are exposed to harsh marine environments and cyclic loading, leading to fatigue damage that undermines their structural integrity. Among the most vulnerable areas are the welded joints, which are susceptible to crack initiation and propagation, highlighting the need for reliable fatigue assessment during design and operation to ensure durability and safety. To address this challenge, this study introduces a machine learning (ML)-based surrogate modeling framework for efficient and reliable fatigue assessment. The framework comprises three integral components: (1) a multi-fidelity finite element (FE) modeling to substantially minimize computational demand; (2) a surrogate model for predicting stress intensity factor (SIF); and (3) a crack propagation and fatigue life prediction module. The surrogate model was trained on a dataset from simulations in Abaqus and Franc3D. The multi-fidelity models reproduced the first five vibration periods with mean errors below 3.3 %, and mode shapes showed strong agreement with a high-fidelity reference. Among eight ML models assessed for SIF prediction, a deep neural network (DNN) achieved the highest accuracy (MAE ≈ 3 %), whereas XGBoost attained a balanced trade-off between accuracy and computational efficiency (MAE ≈ 11 %). Beyond model-level assessment, two additional full-case verifications at the weld toe (crown and saddle) matched FE-computed SIF and fatigue life within ± 5 % and 1.6 %, respectively, while delivering results in 3 s compared with about 5 h for the FE simulations. These findings demonstrate that the proposed framework provides a reliable, efficient alternative to fracture mechanics-based FE simulations for fatigue assessment of complex structures under realistic loading.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111800"},"PeriodicalIF":5.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787460","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.engfracmech.2025.111805
Xuan Wang, Xiaoyue Yang, Yunfei Deng
Aluminum alloys are widely used in various fields including aerospace, vehicle engineering, and ship engineering with the advantages of low density, high specific strength, strong chemical stability and good processing performance. However, in practical engineering applications, aluminum alloy structures are often subjected to impacts from foreign objects under various impact scenarios. Among them, due to the impact randomness, it is necessary to study the ballistic resistance of targets under different impact angles. Hence, ballistic impact tests and numerical simulations at different impact angles are conducted on Al6061-T651 target plates to investigate the velocity response, failure mechanism and impact angle effect of target plates under hemispherical projectile impact. The results indicate that: On the one hand, as the impact angle increases, the ballistic limit velocity of the aluminum alloy target shows an exponential growth trend. On the other hand, during the impact process, the target mainly experiences tensile shear mixed failure. Besides, as the impact angle increases, the proportion of tensile failure for damaged elements gradually increases, and the influence of Lode parameters accordingly decreases.
{"title":"Impact angle effect on the ballistic resistance of Al6061-T651: An experimental and numerical research","authors":"Xuan Wang, Xiaoyue Yang, Yunfei Deng","doi":"10.1016/j.engfracmech.2025.111805","DOIUrl":"10.1016/j.engfracmech.2025.111805","url":null,"abstract":"<div><div>Aluminum alloys are widely used in various fields including aerospace, vehicle engineering, and ship engineering with the advantages of low density, high specific strength, strong chemical stability and good processing performance. However, in practical engineering applications, aluminum alloy structures are often subjected to impacts from foreign objects under various impact scenarios. Among them, due to the impact randomness, it is necessary to study the ballistic resistance of targets under different impact angles. Hence, ballistic impact tests and numerical simulations at different impact angles are conducted on Al6061-T651 target plates to investigate the velocity response, failure mechanism and impact angle effect of target plates under hemispherical projectile impact. The results indicate that: On the one hand, as the impact angle increases, the ballistic limit velocity of the aluminum alloy target shows an exponential growth trend. On the other hand, during the impact process, the target mainly experiences tensile shear mixed failure. Besides, as the impact angle increases, the proportion of tensile failure for damaged elements gradually increases, and the influence of Lode parameters accordingly decreases.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111805"},"PeriodicalIF":5.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.engfracmech.2025.111779
Aman Arora , Hibiki Okano , Sungcheol Park , Ryosuke Matsumoto , Hisao Matsunaga
Environment-assisted, time-dependent subcritical cracking is a significant concern in high-pressure storage systems and pipelines, as minor flaws can evolve into critical failures under sustained stress over time. Moreover, hydrogen gas storage facilities are known to experience pressure and temperature fluctuations during pressurization and depressurization. In this study, the impact of such fluctuating conditions on hydrogen-induced delayed fracture was investigated. Constant-displacement bolt-load tests were conducted using low-alloy steel JIS-SCM435H. Threshold stress intensity factors for crack arrest, KTHa, were measured in high-pressure hydrogen gas under both constant and fluctuating pressure and temperature conditions. For tests conducted in constant environments, KTHa values increased at high temperatures compared with room temperature, which may be associated with lower hydrogen trap-site occupancy at elevated temperatures. Furthermore, under temperature and pressure fluctuations, KTHa values appeared to correlate with the hydrogen trap-site occupancy, which in turn was likely affected by the instantaneous combination of temperature and pressure. Consequently, it was revealed that the mechanical state at the crack tip, potentially influenced by yield strength and hydrogen occupancy, could govern the subcritical crack propagation behavior in the material. This study provides valuable insights for mitigating hydrogen embrittlement risks in practical applications and offers a comprehensive understanding of how environmental fluctuations can influence material integrity in hydrogen storage systems.
{"title":"Effects of temperature and pressure fluctuations on the crack-arrest threshold stress intensity factor for high-strength low-alloy steel in high-pressure hydrogen gas","authors":"Aman Arora , Hibiki Okano , Sungcheol Park , Ryosuke Matsumoto , Hisao Matsunaga","doi":"10.1016/j.engfracmech.2025.111779","DOIUrl":"10.1016/j.engfracmech.2025.111779","url":null,"abstract":"<div><div>Environment-assisted, time-dependent subcritical cracking is a significant concern in high-pressure storage systems and pipelines, as minor flaws can evolve into critical failures under sustained stress over time. Moreover, hydrogen gas storage facilities are known to experience pressure and temperature fluctuations during pressurization and depressurization. In this study, the impact of such fluctuating conditions on hydrogen-induced delayed fracture was investigated. Constant-displacement bolt-load tests were conducted using low-alloy steel JIS-SCM435H. Threshold stress intensity factors for crack arrest, <em>K</em><sub>THa</sub>, were measured in high-pressure hydrogen gas under both constant and fluctuating pressure and temperature conditions. For tests conducted in constant environments, <em>K</em><sub>THa</sub> values increased at high temperatures compared with room temperature, which may be associated with lower hydrogen trap-site occupancy at elevated temperatures. Furthermore, under temperature and pressure fluctuations, <em>K</em><sub>THa</sub> values appeared to correlate with the hydrogen trap-site occupancy, which in turn was likely affected by the instantaneous combination of temperature and pressure. Consequently, it was revealed that the mechanical state at the crack tip, potentially influenced by yield strength and hydrogen occupancy, could govern the subcritical crack propagation behavior in the material. This study provides valuable insights for mitigating hydrogen embrittlement risks in practical applications and offers a comprehensive understanding of how environmental fluctuations can influence material integrity in hydrogen storage systems.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111779"},"PeriodicalIF":5.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787060","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2025-12-13DOI: 10.1016/j.engfracmech.2025.111795
Lei Wang, Jun-Dong Yin, Chao Ling, Esteban P. Busso, Dong-Feng Li
An extension of the Gurson–Tvergaard–Needleman (GTN) constitutive formulation is proposed to investigate the effects of carbides on the rate-dependent deformation behaviour and creep failure of a commercial martensitic steel (P91). Inelastic deformation is assumed to be controlled by both the precipitate population and intrinsic microstructural obstacles, such as dislocations, grain boundaries, and creep damage in the form of microvoids arising from precipitate decohesion from the surrounding matrix. The proposed formulation accounts for key microstructural mechanisms, including dislocation multiplication and dynamic recovery, precipitate coarsening, and void nucleation and growth. Taylor homogenisation is relied upon to link the material behaviour at the grain level with the macroscopic response.
The proposed constitutive model has been numerically implemented into the finite element method using an implicit Euler-backward scheme. It is then relied upon to investigate the effects of the size and coarsening behaviour of carbides on the steady-state creep response and time to rupture of the P91 steel at 600 and 650 . The effect of the initial size on creep-life is predicted using a modified Larson–Miller parameter. The formulation is also successfully extended to predict the high temperature behaviour of other widely used martensitic steels by only re-calibrating two or three material parameters from those of the P91 model.
Creep lifetime predictions are in good agreement with published experimental data. They show that the steady creep rate increases and the creep rupture time decreases with initial carbide size. Furthermore, the detrimental effect of precipitate coarsening on the long-term creep failure has been quantified and successfully predicted. A comparison between the model predictions and experimental data for notched specimens demonstrates the model’s capability to accurately capture multiaxial creep deformation in the notched bar and the associated time to rupture.
{"title":"An extension of a Gurson-type formulation to study precipitate effects on the deformation behaviour and creep damage of martensitic steels","authors":"Lei Wang, Jun-Dong Yin, Chao Ling, Esteban P. Busso, Dong-Feng Li","doi":"10.1016/j.engfracmech.2025.111795","DOIUrl":"10.1016/j.engfracmech.2025.111795","url":null,"abstract":"<div><div>An extension of the Gurson–Tvergaard–Needleman (GTN) constitutive formulation is proposed to investigate the effects of <span><math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mn>23</mn></mrow></msub><msub><mrow><mi>C</mi></mrow><mrow><mn>6</mn></mrow></msub></mrow></math></span> carbides on the rate-dependent deformation behaviour and creep failure of a commercial martensitic steel (P91). Inelastic deformation is assumed to be controlled by both the precipitate population and intrinsic microstructural obstacles, such as dislocations, grain boundaries, and creep damage in the form of microvoids arising from precipitate decohesion from the surrounding matrix. The proposed formulation accounts for key microstructural mechanisms, including dislocation multiplication and dynamic recovery, precipitate coarsening, and void nucleation and growth. Taylor homogenisation is relied upon to link the material behaviour at the grain level with the macroscopic response.</div><div>The proposed constitutive model has been numerically implemented into the finite element method using an implicit Euler-backward scheme. It is then relied upon to investigate the effects of the size and coarsening behaviour of <span><math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mn>23</mn></mrow></msub><msub><mrow><mi>C</mi></mrow><mrow><mn>6</mn></mrow></msub></mrow></math></span> carbides on the steady-state creep response and time to rupture of the P91 steel at 600 <span><math><mrow><mo>°</mo><mtext>C</mtext></mrow></math></span> and 650 <span><math><mrow><mo>°</mo><mtext>C</mtext></mrow></math></span>. The effect of the initial <span><math><mrow><msub><mrow><mi>M</mi></mrow><mrow><mn>23</mn></mrow></msub><msub><mrow><mi>C</mi></mrow><mrow><mn>6</mn></mrow></msub></mrow></math></span> size on creep-life is predicted using a modified Larson–Miller parameter. The formulation is also successfully extended to predict the high temperature behaviour of other widely used martensitic steels by only re-calibrating two or three material parameters from those of the P91 model.</div><div>Creep lifetime predictions are in good agreement with published experimental data. They show that the steady creep rate increases and the creep rupture time decreases with initial carbide size. Furthermore, the detrimental effect of precipitate coarsening on the long-term creep failure has been quantified and successfully predicted. A comparison between the model predictions and experimental data for notched specimens demonstrates the model’s capability to accurately capture multiaxial creep deformation in the notched bar and the associated time to rupture.</div></div>","PeriodicalId":11576,"journal":{"name":"Engineering Fracture Mechanics","volume":"332 ","pages":"Article 111795"},"PeriodicalIF":5.3,"publicationDate":"2025-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145787461","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"工程技术","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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