Pub Date : 2026-02-09DOI: 10.1016/j.ijfatigue.2026.109559
Niklas Sayer-Duffhauß, Markus Fried, Sebastian Münstermann
With increasing capabilities in non-destructive testing methods, image-based modeling of porosity becomes more widely adopted. While some empirically- and fracture-mechanics-derived criteria exist in literature and standards, image-based models would benefit from a more thorough assessment of porosity interaction. In this paper we model the stress response of pairs of pores in a vast number of possible spatial configurations, using the example of the alloy MAR-M247 and real casting pores, whose morphologies were acquired using computed tomography (CT). Lastly, we compute the interaction distance and derive criteria for non-interaction for two popular types of image-based fatigue models (non-local and global), based on the size of the potentially interacting pores.
{"title":"Studying porosity interaction of real casting pore morphologies in image-based models during fatigue loading","authors":"Niklas Sayer-Duffhauß, Markus Fried, Sebastian Münstermann","doi":"10.1016/j.ijfatigue.2026.109559","DOIUrl":"https://doi.org/10.1016/j.ijfatigue.2026.109559","url":null,"abstract":"With increasing capabilities in non-destructive testing methods, image-based modeling of porosity becomes more widely adopted. While some empirically- and fracture-mechanics-derived criteria exist in literature and standards, image-based models would benefit from a more thorough assessment of porosity interaction. In this paper we model the stress response of pairs of pores in a vast number of possible spatial configurations, using the example of the alloy MAR-M247 and real casting pores, whose morphologies were acquired using computed tomography (CT). Lastly, we compute the interaction distance and derive criteria for non-interaction for two popular types of image-based fatigue models (non-local and global), based on the size of the potentially interacting pores.","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"35 1","pages":""},"PeriodicalIF":6.0,"publicationDate":"2026-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146146768","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-08DOI: 10.1016/j.ijfatigue.2026.109557
Yang Xin-Yi , Zhu Li-Na , Xu Zhong-Wei , Wang Xi-Shu
In this work, the key mechanics parameters such as ΔKth and critical damage tolerance size (DTS: a0H) were quantitatively estimated with a 95% probability through the weakest-link theory (WLT) and in-situ scanning electron microscopy (SEM) fatigue small crack (FSC) propagation tests for the cast AM60 magnesium, SLM-AlSi10Mg and SLM-Ti6Al4V alloys. A new probability evaluation model about the dispersion range in FSC growth rate curves of these materials was developed. The dispersions of da/dN indicated that the mapping correlation to ΔKth of SLM-Ti6Al4V alloy exhibits higher accuracy than that of the other two alloys. And the DTS of three alloys were also quantitatively obtained by comparison with fatigue cracking source and microstructure characteristic size. The probability of high cycle fatigue failure is reduced to only 5% when the DTS is respectively controlled within the estimated size such as 37.1 μm for cast AM60, 89.0 μm for SLM-AlSi10Mg and 75.3 μm for SLM-Ti6Al4V. The relative error between the 95% probability estimation values and average defect size is 25.8%, 8.4% and 4.6%, respectively. The effectiveness and reasonableness of these estimation values were validated by the experimental and literature data.
{"title":"Probabilistic evaluation on fatigue small cracking characteristics of light metallic alloys under in-situ SEM fatigue tests using the weakest link theory","authors":"Yang Xin-Yi , Zhu Li-Na , Xu Zhong-Wei , Wang Xi-Shu","doi":"10.1016/j.ijfatigue.2026.109557","DOIUrl":"10.1016/j.ijfatigue.2026.109557","url":null,"abstract":"<div><div>In this work, the key mechanics parameters such as ΔK<sub>th</sub> and critical damage tolerance size (DTS: <em>a</em><sub>0H</sub>) were quantitatively estimated with a 95% probability through the weakest-link theory (WLT) and <em>in-situ</em> scanning electron microscopy (SEM) fatigue small crack (FSC) propagation tests for the cast AM60 magnesium, SLM-AlSi10Mg and SLM-Ti6Al4V alloys. A new probability evaluation model about the dispersion range in FSC growth rate curves of these materials was developed. The dispersions of da/dN indicated that the mapping correlation to ΔK<sub>th</sub> of SLM-Ti6Al4V alloy exhibits higher accuracy than that of the other two alloys. And the DTS of three alloys were also quantitatively obtained by comparison with fatigue cracking source and microstructure characteristic size. The probability of high cycle fatigue failure is reduced to only 5% when the DTS is respectively controlled within the estimated size such as 37.1 μm for cast AM60, 89.0 μm for SLM-AlSi10Mg and 75.3 μm for SLM-Ti6Al4V. The relative error between the 95% probability estimation values and average defect size is 25.8%, 8.4% and 4.6%, respectively. The effectiveness and reasonableness of these estimation values were validated by the experimental and literature data.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109557"},"PeriodicalIF":6.8,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138671","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-08DOI: 10.1016/j.ijfatigue.2026.109558
Han Zhang , Weijian Qian , Feifei Hu , Boyu Nie , Liming Lei , Yali Li , Zhe Song , Liangliang Wu , Chengli Dong , Lei Shi , Shengchuan Wu
The Hastelloy X (HX), as a typical nickel-based superalloy valued for high-temperature engineering equipment, is susceptible to hot cracking during laser powder bed fusion (L‑PBF), which severely degrades the fatigue resistance of manufactured components. This study investigates the dual role of pre-existing hot cracks in the high‑temperature (700 °C) fatigue behavior of L‑PBF HX through in situ synchrotron X‑ray tomography coupled with microstructural analysis. Cyclic tests at 700 °C were performed using a customed high‑frequency (up to 30 Hz) hydraulic in situ fatigue rig integrated with synchrotron radiation. Ex situ or post-mortem and in situ experiments clearly reveal that pre-existing defects, particularly hot cracks aligned parallel to the loading direction and large lack-of-fusion pores, serve as primary sites for fatigue crack initiation and propagation, leading to considerable life scatter. Conversely, these cracks also promote crack‑tip blunting and path deflection, temporarily retarding failure. Microstructural analysis indicates that the initial network of high‑angle grain boundaries and annealing twins transforms into preferred pathways for hot‑crack propagation, with grain boundary sliding emerging as the dominant failure mechanism. Fatigue cracks propagate along crystallographic paths of high Schmid factor, whereas hot cracks open preferentially along slip systems of maximum deformability. The high‑temperature fatigue life of L‑PBF HX is governed by a three‑way competition among crystallographic driving forces, defect‑accelerated damage, and thermally assisted crack‑tip remodeling. This work provides unique real‑time insights into damage evolution and failure mechanisms in additively manufactured superalloys under service‑relevant conditions, highlighting the dominant role of defect-driven crack initiation in high-temperature fatigue life scatter.
{"title":"Time lapse X-ray imaging reveals dual-role significance of hot cracks in high-temperature fatigued L-PBF Hastelloy X","authors":"Han Zhang , Weijian Qian , Feifei Hu , Boyu Nie , Liming Lei , Yali Li , Zhe Song , Liangliang Wu , Chengli Dong , Lei Shi , Shengchuan Wu","doi":"10.1016/j.ijfatigue.2026.109558","DOIUrl":"10.1016/j.ijfatigue.2026.109558","url":null,"abstract":"<div><div>The Hastelloy X (HX), as a typical nickel-based superalloy valued for high-temperature engineering equipment, is susceptible to hot cracking during laser powder bed fusion (L‑PBF), which severely degrades the fatigue resistance of manufactured components. This study investigates the dual role of pre-existing hot cracks in the high‑temperature (700 °C) fatigue behavior of L‑PBF HX through <em>in situ</em> synchrotron X‑ray tomography coupled with microstructural analysis. Cyclic tests at 700 °C were performed using a customed high‑frequency (up to 30 Hz) hydraulic <em>in situ</em> fatigue rig integrated with synchrotron radiation. <em>Ex situ</em> or post-mortem and <em>in situ</em> experiments clearly reveal that pre-existing defects, particularly hot cracks aligned parallel to the loading direction and large lack-of-fusion pores, serve as primary sites for fatigue crack initiation and propagation, leading to considerable life scatter. Conversely, these cracks also promote crack‑tip blunting and path deflection, temporarily retarding failure. Microstructural analysis indicates that the initial network of high‑angle grain boundaries and annealing twins transforms into preferred pathways for hot‑crack propagation, with grain boundary sliding emerging as the dominant failure mechanism. Fatigue cracks propagate along crystallographic paths of high Schmid factor, whereas hot cracks open preferentially along slip systems of maximum deformability. The high‑temperature fatigue life of L‑PBF HX is governed by a three‑way competition among crystallographic driving forces, defect‑accelerated damage, and thermally assisted crack‑tip remodeling. This work provides unique real‑time insights into damage evolution and failure mechanisms in additively manufactured superalloys under service‑relevant conditions, highlighting the dominant role of defect-driven crack initiation in high-temperature fatigue life scatter.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109558"},"PeriodicalIF":6.8,"publicationDate":"2026-02-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146138670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-07DOI: 10.1016/j.ijfatigue.2026.109553
Han Yan , Dawei Huang , Aofei Li , Zhenyu He , Heming Xu , Naixian Hou , Xiaojun Yan
The disk groove structure of aero engines is affected by combined high and low cycle fatigue (CCF) loads during service, and the crack growth rate model is a critical input condition for the damage tolerance analysis of the disk. In this study, the crack propagation behavior of the Inconel 718 superalloy, a commonly used material for disks, is investigated under the CCF loads. Firstly, crack propagation tests are conducted on the superalloy under three loading conditions: pure low cycle fatigue (LCF), pure high cycle fatigue (HCF), and CCF. The influence of different loads on the crack growth rate is analyzed. Then, considering the coupling effect of the HCF and LCF loads, a CCF equivalent stress intensity factor Keq is proposed. A crack growth rate model is developed based on the Keq. The predicted crack growth rates fall within the 1.7-fold dispersion band. Furthermore, the influence mechanism of the stress ratio and CCF loads on crack propagation is explored through fracture analysis, revealing that under CCF loads, the high cycle component significantly governs the crack propagation process. This study can provide valuable methods and data support for evaluating the crack propagation life of the groove structure.
{"title":"Experimental investigation and modeling of the superalloy crack growth behavior under combined high and low cycle fatigue","authors":"Han Yan , Dawei Huang , Aofei Li , Zhenyu He , Heming Xu , Naixian Hou , Xiaojun Yan","doi":"10.1016/j.ijfatigue.2026.109553","DOIUrl":"10.1016/j.ijfatigue.2026.109553","url":null,"abstract":"<div><div>The disk groove structure of aero engines is affected by combined high and low cycle fatigue (CCF) loads during service, and the crack growth rate model is a critical input condition for the damage tolerance analysis of the disk. In this study, the crack propagation behavior of the Inconel 718 superalloy, a commonly used material for disks, is investigated under the CCF loads. Firstly, crack propagation tests are conducted on the superalloy under three loading conditions: pure low cycle fatigue (LCF), pure high cycle fatigue (HCF), and CCF. The influence of different loads on the crack growth rate is analyzed. Then, considering the coupling effect of the HCF and LCF loads, a CCF equivalent stress intensity factor <em>K</em><sub>eq</sub> is proposed. A crack growth rate model is developed based on the <em>K</em><sub>eq</sub>. The predicted crack growth rates fall within the 1.7-fold dispersion band. Furthermore, the influence mechanism of the stress ratio and CCF loads on crack propagation is explored through fracture analysis, revealing that under CCF loads, the high cycle component significantly governs the crack propagation process. This study can provide valuable methods and data support for evaluating the crack propagation life of the groove structure.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109553"},"PeriodicalIF":6.8,"publicationDate":"2026-02-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135261","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-06DOI: 10.1016/j.ijfatigue.2026.109541
Xu-xiang Yang , Xin Bai , Zhi-xin Dong , Zhen-jun Zhang , Meng-yang Wang , Zhe-feng Zhang
The present S-N curve modification from fatigue loads has significant estimation errors due to the wrong assumption of parallel S-N curves under different loads. In particular, the inconsistent selections of fatigue load parameters may result in significant estimation biases. To address these issues, this study systematically analyzes the fatigue strength modification models by substituting different fatigue load parameter values (i.e. mean stress Sm, stress ratio R, stress amplitude Sa), according to the fatigue testing data of the LC9 aluminum alloy and 45 steel. The results demonstrate that the fatigue strength modification by fixing mean stress Sm values provides the highest accuracy and the most robust performance, significantly outperforming modification strategies that fix R or Sa values, and the Walker model achieves the highest modification accuracy. Then, based on the life-dependent Walker model exponent γ, a systematic two-point modification framework by fixing mean stress Sm values is proposed for the S-N curve modification, which provides highly accurate S-N curves in fatigue design.
{"title":"Two-point S-N curve modification framework from fatigue loads","authors":"Xu-xiang Yang , Xin Bai , Zhi-xin Dong , Zhen-jun Zhang , Meng-yang Wang , Zhe-feng Zhang","doi":"10.1016/j.ijfatigue.2026.109541","DOIUrl":"10.1016/j.ijfatigue.2026.109541","url":null,"abstract":"<div><div>The present <em>S-N</em> curve modification from fatigue loads has significant estimation errors due to the wrong assumption of parallel <em>S</em>-<em>N</em> curves under different loads. In particular, the inconsistent selections of fatigue load parameters may result in significant estimation biases. To address these issues, this study systematically analyzes the fatigue strength modification models by substituting different fatigue load parameter values (i.e. mean stress <em>S</em><sub>m</sub>, stress ratio <em>R</em>, stress amplitude <em>S</em><sub>a</sub>), according to the fatigue testing data of the LC9 aluminum alloy and 45 steel. The results demonstrate that the fatigue strength modification by fixing mean stress <em>S</em><sub>m</sub> values provides the highest accuracy and the most robust performance, significantly outperforming modification strategies that fix <em>R</em> or <em>S</em><sub>a</sub> values, and the Walker model achieves the highest modification accuracy. Then, based on the life-dependent Walker model exponent <em>γ</em>, a systematic two-point modification framework by fixing mean stress <em>S</em><sub>m</sub> values is proposed for the <em>S-N</em> curve modification, which provides highly accurate <em>S-N</em> curves in fatigue design.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109541"},"PeriodicalIF":6.8,"publicationDate":"2026-02-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134452","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1016/j.ijfatigue.2026.109535
Samira Ghadar, Ali Fatemi
Fretting fatigue is a complex mechanical failure phenomenon, characterized by damage caused by the combined effects of cyclic loading and small amplitude relative motion between contacting surfaces. It can significantly affect the performance of components; thus, prediction of fretting fatigue life is an important consideration in damage tolerant design. Fretting fatigue is inherently a multiaxial fatigue problem, characterized by non-proportional multiaxial stresses with high gradients. Among the prevalent modeling frameworks for fretting fatigue crack initiation, the most recognized are the critical plane, stress invariant, continuum damage mechanics, and fretting specific approaches. The critical plane approach is widely regarded as the most suitable model. This work provides an overview of multiaxial fretting fatigue life models in general and investigates the application of critical plane approach in particular. Fretting fatigue data from the literature were gathered including aluminum and Ti alloys with a broad range of pad radii and loading conditions. The employed modeling approach demonstrates robustness for predicting fretting fatigue.
{"title":"A review of fretting fatigue life prediction models and application of the critical plane approach to selected literature datasets","authors":"Samira Ghadar, Ali Fatemi","doi":"10.1016/j.ijfatigue.2026.109535","DOIUrl":"10.1016/j.ijfatigue.2026.109535","url":null,"abstract":"<div><div>Fretting fatigue is a complex mechanical failure phenomenon, characterized by damage caused by the combined effects of cyclic loading and small amplitude relative motion between contacting surfaces. It can significantly affect the performance of components; thus, prediction of fretting fatigue life is an important consideration in damage tolerant design. Fretting fatigue is inherently a multiaxial fatigue problem, characterized by non-proportional multiaxial stresses with high gradients. Among the prevalent modeling frameworks for fretting fatigue crack initiation, the most recognized are the critical plane, stress invariant, continuum damage mechanics, and fretting specific approaches. The critical plane approach is widely regarded as the most suitable model. This work provides an overview of multiaxial fretting fatigue life models in general and investigates the application of critical plane approach in particular. Fretting fatigue data from the literature were gathered including aluminum and Ti alloys with a broad range of pad radii and loading conditions. The employed modeling approach demonstrates robustness for predicting fretting fatigue.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109535"},"PeriodicalIF":6.8,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134457","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Welded joints are critical components in engineering structures, yet accurate fatigue life prediction remains challenging due to multiaxial loading complexity and material nonlinearity. Conventional physics-based models often fail to capture intricate load–material interactions, while data-driven approaches demand extensive datasets and lack physical interpretability. To address these limitations, this study introduces CINAS-PINN, a causal inference-based neural architecture search integrated with physics-informed neural networks for welded joint fatigue life prediction. By constructing equivalent tensors, multiaxial load paths are converted into scalar strain energy densities, aiming to capture the physical characteristics of multiaxial loading and provide input support for neural networks. We integrate causal inference with neural architecture search (NAS) in physics-informed neural networks (PINNs). Based on this, we implemented the PINN structure and optimized the model parameters, addressing the challenge of accurate fatigue life prediction. To overcome issues related to poor model interpretability and low accuracy, we employed a causal graph-constrained architecture, enabling the model to focus on key physical factors. Additionally, a dynamic loss function, adjusted through Granger causality analysis, prioritizes key physical constraints during training, improving model efficiency and physical consistency. Case studies on AISI316L, GH4169, and TC4 alloys demonstrate that CINAS-PINN achieves superior accuracy, reducing prediction errors by more than 30% compared with benchmark methods. The proposed framework offers enhanced physical consistency, robustness, and generalization for fatigue life prediction under complex service conditions.
{"title":"CINAS-PINN: Causal inference-based neural architecture search in physics-informed neural networks for fatigue life prediction with welding strain energy","authors":"Jiashan Gao , Chao Zhang , Shaoping Wang , Enrico Zio , Yuwei Zhang , Rentong Chen","doi":"10.1016/j.ijfatigue.2026.109539","DOIUrl":"10.1016/j.ijfatigue.2026.109539","url":null,"abstract":"<div><div>Welded joints are critical components in engineering structures, yet accurate fatigue life prediction remains challenging due to multiaxial loading complexity and material nonlinearity. Conventional physics-based models often fail to capture intricate load–material interactions, while data-driven approaches demand extensive datasets and lack physical interpretability. To address these limitations, this study introduces CINAS-PINN, a causal inference-based neural architecture search integrated with physics-informed neural networks for welded joint fatigue life prediction. By constructing equivalent tensors, multiaxial load paths are converted into scalar strain energy densities, aiming to capture the physical characteristics of multiaxial loading and provide input support for neural networks. We integrate causal inference with neural architecture search (NAS) in physics-informed neural networks (PINNs). Based on this, we implemented the PINN structure and optimized the model parameters, addressing the challenge of accurate fatigue life prediction. To overcome issues related to poor model interpretability and low accuracy, we employed a causal graph-constrained architecture, enabling the model to focus on key physical factors. Additionally, a dynamic loss function, adjusted through Granger causality analysis, prioritizes key physical constraints during training, improving model efficiency and physical consistency. Case studies on AISI316L, GH4169, and TC4 alloys demonstrate that CINAS-PINN achieves superior accuracy, reducing prediction errors by more than 30% compared with benchmark methods. The proposed framework offers enhanced physical consistency, robustness, and generalization for fatigue life prediction under complex service conditions.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109539"},"PeriodicalIF":6.8,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134453","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1016/j.ijfatigue.2026.109552
Ivo Šulák , Markéta Gálíková , Tomáš Babinský , Ladislav Poczklán , Ivo Kuběna , Stefan Guth
Additively manufactured nickel-based superalloy Inconel 939 (IN939) was subjected to in-phase and out-of-phase thermomechanical fatigue loading in the temperature range of 400–800 °C. Horizontally and vertically built cylindrical specimens were subjected to a three-step heat treatment and subsequently tested with mechanical strain amplitudes in the range of 0.3–0.9%. A constant heating and cooling rate of 10 °C/s was utilised, making the cycle period 80 s. Representative hysteresis loops, fatigue hardening/softening curves, cyclic stress–strain curves, and fatigue life curves are reported. The results show that, regardless of the load cycle, the horizontally built IN939 exhibits lower lifetimes than the vertically built alloy. This stems from a distinctive 〈001〉 texture in the building direction, which influences the stress response of the material. Higher stress amplitude values observed for horizontally built material contribute to faster fatigue crack initiation and propagation. The SEM observation revealed that, regardless of the building direction, the damage is mainly intergranular for in-phase loading and mixed for out-of-phase loading. Plastic strain localisation into persistent slip markings and formation of nanotwins was typical for out-of-phase loading. In contrast, dense dislocation networks and stacking fault formation within γ́ precipitates were observed for in-phase loading.
{"title":"Thermomechanical fatigue performance of additively manufactured Inconel 939","authors":"Ivo Šulák , Markéta Gálíková , Tomáš Babinský , Ladislav Poczklán , Ivo Kuběna , Stefan Guth","doi":"10.1016/j.ijfatigue.2026.109552","DOIUrl":"10.1016/j.ijfatigue.2026.109552","url":null,"abstract":"<div><div>Additively manufactured nickel-based superalloy Inconel 939 (IN939) was subjected to in-phase and out-of-phase thermomechanical fatigue loading in the temperature range of 400–800 °C. Horizontally and vertically built cylindrical specimens were subjected to a three-step heat treatment and subsequently tested with mechanical strain amplitudes in the range of 0.3–0.9%. A constant heating and cooling rate of 10 °C/s was utilised, making the cycle period 80 s. Representative hysteresis loops, fatigue hardening/softening curves, cyclic stress–strain curves, and fatigue life curves are reported. The results show that, regardless of the load cycle, the horizontally built IN939 exhibits lower lifetimes than the vertically built alloy. This stems from a distinctive 〈001〉 texture in the building direction, which influences the stress response of the material. Higher stress amplitude values observed for horizontally built material contribute to faster fatigue crack initiation and propagation. The SEM observation revealed that, regardless of the building direction, the damage is mainly intergranular for in-phase loading and mixed for out-of-phase loading. Plastic strain localisation into persistent slip markings and formation of nanotwins was typical for out-of-phase loading. In contrast, dense dislocation networks and stacking fault formation within γ́ precipitates were observed for in-phase loading.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109552"},"PeriodicalIF":6.8,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146135262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1016/j.ijfatigue.2026.109543
Gen Li , Xiaorui Liu , Hao Li , Tianyu Chen , Zhengmao Yang , Huan Tu , Rubing Zhang
A progressive fatigue damage model is proposed in this paper to model the FRP fatigue behaviors and damage progression in high cycle and very high cycle fatigue (HCF and VHCF) regimes. Firstly, a new stiffness degradation model is proposed and validated for FRP stiffness degradation behaviors in HCF and VHCF regimes. Then the progressive fatigue damage model is generated by combining anisotropic elastic equations, the new stiffness degradation model, strength degradation model and failure criterion. The progressive fatigue damage model is applicable to model uniaxial and bending fatigue behavior of FRP, and determine different failure modes as fiber tensile failure, matrix tensile failure and interface shear failure. The HCF and VHCF fatigue behaviors of GFRP and CFRP under uniaxial and bending fatigue loads are modeled by the progressive fatigue damage model on finite element software. The full field stress and stiffness data for the simulated fatigue specimens are provided, and the damage progression in HCF and VHCF regimes is quantified efficiently. The S-N curves, stiffness degradation process and failure behavior achieve good consistency with the uniaxial and bending fatigue test results. The proposed progressive fatigue damage model effectively extends the analysis approach for FRP fatigue behaviors and damage progression in HCF and VHCF regimes.
{"title":"Progressive fatigue damage modeling for FRP in high cycle and very high cycle fatigue regimes","authors":"Gen Li , Xiaorui Liu , Hao Li , Tianyu Chen , Zhengmao Yang , Huan Tu , Rubing Zhang","doi":"10.1016/j.ijfatigue.2026.109543","DOIUrl":"10.1016/j.ijfatigue.2026.109543","url":null,"abstract":"<div><div>A progressive fatigue damage model is proposed in this paper to model the FRP fatigue behaviors and damage progression in high cycle and very high cycle fatigue (HCF and VHCF) regimes. Firstly, a new stiffness degradation model is proposed and validated for FRP stiffness degradation behaviors in HCF and VHCF regimes. Then the progressive fatigue damage model is generated by combining anisotropic elastic equations, the new stiffness degradation model, strength degradation model and failure criterion. The progressive fatigue damage model is applicable to model uniaxial and bending fatigue behavior of FRP, and determine different failure modes as fiber tensile failure, matrix tensile failure and interface shear failure. The HCF and VHCF fatigue behaviors of GFRP and CFRP under uniaxial and bending fatigue loads are modeled by the progressive fatigue damage model on finite element software. The full field stress and stiffness data for the simulated fatigue specimens are provided, and the damage progression in HCF and VHCF regimes is quantified efficiently. The S-N curves, stiffness degradation process and failure behavior achieve good consistency with the uniaxial and bending fatigue test results. The proposed progressive fatigue damage model effectively extends the analysis approach for FRP fatigue behaviors and damage progression in HCF and VHCF regimes.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109543"},"PeriodicalIF":6.8,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134456","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2026-02-05DOI: 10.1016/j.ijfatigue.2026.109526
Qia Zhao , Jing Cao , Boda Wang , Yuan Tao , Xiang Xie , Weixing Yao
This study investigates the pronounced size effect in high-cycle fatigue of additively manufactured metallic specimens and proposes a probabilistic fatigue life assessment approach that combines a size-effect physical model with a Bayesian neural network (BNN). The model takes two physical-model parameters and the applied stress level as inputs, with these two parameters jointly capturing the influences of specimen size, defect characteristics, and Vickers hardness. By normalizing these inputs, the BNN is able to learn fatigue response patterns in a concise yet comprehensive manner. Statistical fatigue test data are used to construct training, validation, and test sets, followed by a systematic hyperparameter search to determine the optimal model configuration for the dataset in this study. Cross-validation is then performed on three different materials with a total of eight specimen sizes. The results show that the proposed Bayesian Physics-Informed Neural Network model delivers reliable fatigue life predictions across multi-material and multi-size conditions, demonstrating strong generalization capability.
{"title":"A Bayesian physics-informed neural network model for probabilistic fatigue life assessment considering the size effect in additively manufactured materials","authors":"Qia Zhao , Jing Cao , Boda Wang , Yuan Tao , Xiang Xie , Weixing Yao","doi":"10.1016/j.ijfatigue.2026.109526","DOIUrl":"10.1016/j.ijfatigue.2026.109526","url":null,"abstract":"<div><div>This study investigates the pronounced size effect in high-cycle fatigue of additively manufactured metallic specimens and proposes a probabilistic fatigue life assessment approach that combines a size-effect physical model with a Bayesian neural network (BNN). The model takes two physical-model parameters and the applied stress level as inputs, with these two parameters jointly capturing the influences of specimen size, defect characteristics, and Vickers hardness. By normalizing these inputs, the BNN is able to learn fatigue response patterns in a concise yet comprehensive manner. Statistical fatigue test data are used to construct training, validation, and test sets, followed by a systematic hyperparameter search to determine the optimal model configuration for the dataset in this study. Cross-validation is then performed on three different materials with a total of eight specimen sizes. The results show that the proposed Bayesian Physics-Informed Neural Network model delivers reliable fatigue life predictions across multi-material and multi-size conditions, demonstrating strong generalization capability.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109526"},"PeriodicalIF":6.8,"publicationDate":"2026-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134455","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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