Pub Date : 2026-07-01Epub 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":"2026-07-01","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 : 2026-07-01Epub Date: 2026-02-10DOI: 10.1016/j.ijfatigue.2026.109562
Michael Jones , Ben Main , Simon Barter , Tim Wiley , Raj Das
Understanding and measuring the growth rates of small fatigue cracks is important for the ability to predict fatigue cracks in aircraft structures growing from small naturally occurring discontinuities. RMIT University, in collaboration with the Defence Science and Technology Group, have researched small fatigue cracks in common aerospace aluminium alloys for many years. Near-threshold crack growth rates have been collected for a range of materials, including aluminium alloys 7050-T7451, 7075-T7351 and 7085-T7452. In this paper, near-threshold crack growth rates are examined for aluminium alloy 2024-T351. Specially designed loading sequences were applied to coupons to create distinguishable markings on the fracture surface. Scanning electron microscopes and optical microscopes were utilised to determine crack growth rates. The findings were then compared to the extensive amount of experimental data and analytical methods available in the literature for near-threshold crack growth rates in AA2024 to highlight the differences in results between approaches. This paper presents new experimental data that further enhances the existing experimental data for near-threshold crack growth rate data for AA2024. Additionally, the paper aims to aid the aircraft engineer to navigate the vast amount of experimental data and analytical methods that can be utilised to predict small fatigue crack growth in AA2024 and other commonly used aerospace aluminium alloys.
了解和测量小疲劳裂纹的扩展速率对于预测飞机结构中由自然产生的小不连续面产生的疲劳裂纹的能力是非常重要的。澳大利亚皇家墨尔本理工大学（RMIT University）与国防科技集团（Defence Science and Technology Group）合作，多年来一直在研究普通航空航天铝合金的小疲劳裂纹。收集了一系列材料的近阈值裂纹扩展速率，包括铝合金7050-T7451, 7075-T7351和7085-T7452。本文研究了2024-T351铝合金的近阈值裂纹扩展速率。采用特殊设计的加载顺序，在断口表面形成可识别的标记。利用扫描电子显微镜和光学显微镜测定裂纹扩展速率。然后将研究结果与文献中关于AA2024近阈值裂纹扩展速率的大量实验数据和分析方法进行比较，以突出不同方法之间结果的差异。本文提出了新的实验数据，进一步完善了已有的AA2024近阈值裂纹扩展速率数据。此外，本文旨在帮助飞机工程师导航大量的实验数据和分析方法，这些数据和分析方法可用于预测AA2024和其他常用航空航天铝合金的小疲劳裂纹扩展。
{"title":"Navigating Near-Threshold crack growth rate data for aluminium alloy 2024","authors":"Michael Jones , Ben Main , Simon Barter , Tim Wiley , Raj Das","doi":"10.1016/j.ijfatigue.2026.109562","DOIUrl":"10.1016/j.ijfatigue.2026.109562","url":null,"abstract":"<div><div>Understanding and measuring the growth rates of small fatigue cracks is important for the ability to predict fatigue cracks in aircraft structures growing from small naturally occurring discontinuities. RMIT University, in collaboration with the Defence Science and Technology Group, have researched small fatigue cracks in common aerospace aluminium alloys for many years. Near-threshold crack growth rates have been collected for a range of materials, including aluminium alloys 7050-T7451, 7075-T7351 and 7085-T7452. In this paper, near-threshold crack growth rates are examined for aluminium alloy 2024-T351. Specially designed loading sequences were applied to coupons to create distinguishable markings on the fracture surface. Scanning electron microscopes and optical microscopes were utilised to determine crack growth rates. The findings were then compared to the extensive amount of experimental data and analytical methods available in the literature for near-threshold crack growth rates in AA2024 to highlight the differences in results between approaches. This paper presents new experimental data that further enhances the existing experimental data for near-threshold crack growth rate data for AA2024. Additionally, the paper aims to aid the aircraft engineer to navigate the vast amount of experimental data and analytical methods that can be utilised to predict small fatigue crack growth in AA2024 and other commonly used aerospace aluminium alloys.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109562"},"PeriodicalIF":6.8,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146152935","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 : 2026-07-01Epub Date: 2026-02-04DOI: 10.1016/j.ijfatigue.2026.109542
Hao Liu , Xiangxuan Geng , Jian Bao , Zhiquan Zuo , Guowen Yao , Jian Peng
The anisotropy of high-temperature fatigue is a technical bottleneck restricting the long-term safe service of additively manufacturing (AM) alloys, and a systematic understanding of fatigue anisotropy and damage mechanisms is highly needed for safe application. For selective laser melting (SLM) GH4169, the microstructure is anisotropic, with X-Specimen dominated by columnar grains and Z-Specimen by equiaxed grains with enrichment of the Laves phase, which induces anisotropy in fatigue behaviour. The high temperature fatigue performance at 650 °C was investigated by small punch fatigue testing (SPFT), revealing anisotropy in cyclic plastic deformation, plastic energy dissipation, fatigue life and failure mechanisms. Comparing with X-Specimen, Z-Specimen is weaker in the cyclic deformation resistance, larger in the plastic deformation energy, inducing the shorter fatigue life. Fatigue life prediction models were established based on load and energy, quantifying the anisotropic effects on the fatigue life, and an equivalent stress-based life prediction model was preliminarily derived from the membrane stretching model and evaluated for Z-Specimen. Moreover, an anisotropic fracture mechanism map was constructed, showing that X-Specimen fails by parallel cracks, whereas Z-Specimen fails through radial fatigue cracks in a star shaped pattern. This study provides an efficient methodology and theoretical basis for assessing the anisotropy in the fatigue performance of SLM-GH4169 alloy.
{"title":"Revealing fatigue anisotropy of SLM-GH4169 alloy at high temperature via small punch fatigue testing","authors":"Hao Liu , Xiangxuan Geng , Jian Bao , Zhiquan Zuo , Guowen Yao , Jian Peng","doi":"10.1016/j.ijfatigue.2026.109542","DOIUrl":"10.1016/j.ijfatigue.2026.109542","url":null,"abstract":"<div><div>The anisotropy of high-temperature fatigue is a technical bottleneck restricting the long-term safe service of additively manufacturing (AM) alloys, and a systematic understanding of fatigue anisotropy and damage mechanisms is highly needed for safe application. For selective laser melting (SLM) GH4169, the microstructure is anisotropic, with X-Specimen dominated by columnar grains and Z-Specimen by equiaxed grains with enrichment of the Laves phase, which induces anisotropy in fatigue behaviour. The high temperature fatigue performance at 650 °C was investigated by small punch fatigue testing (SPFT), revealing anisotropy in cyclic plastic deformation, plastic energy dissipation, fatigue life and failure mechanisms. Comparing with X-Specimen, Z-Specimen is weaker in the cyclic deformation resistance, larger in the plastic deformation energy, inducing the shorter fatigue life. Fatigue life prediction models were established based on load and energy, quantifying the anisotropic effects on the fatigue life, and an equivalent stress-based life prediction model was preliminarily derived from the membrane stretching model and evaluated for Z-Specimen. Moreover, an anisotropic fracture mechanism map was constructed, showing that X-Specimen fails by parallel cracks, whereas Z-Specimen fails through radial fatigue cracks in a star shaped pattern. This study provides an efficient methodology and theoretical basis for assessing the anisotropy in the fatigue performance of SLM-GH4169 alloy.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109542"},"PeriodicalIF":6.8,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146134463","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":"2026-07-01","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 : 2026-07-01Epub 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":"2026-07-01","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}
Pub Date : 2026-07-01Epub Date: 2026-02-10DOI: 10.1016/j.ijfatigue.2026.109563
Hu Xiaoan, Xiao Baolu, Sui Tianxiao, Yang Qinzheng
Thermomechanical fatigue (TMF) of aeroengine hot-section components is strongly affected by temperature gradients induced by internal cooling. In this study, a thermomechanical gradient fatigue (TGMF) testing methodology was developed and applied to thin-walled tubular specimens and specimens with holes made of the directionally solidified superalloy DZ125. Strain-controlled OP-TGMF tests were conducted over 500–1000℃ with a stable inner–outer wall temperature gradient of approximately 50℃. Coupled electromagnetic–thermal simulations and a viscoplastic constitutive model were employed to analyze stress–strain evolution and damage mechanisms. A cyclic damage accumulation model incorporating temperature-gradient-modified oxidation damage was further developed. The results indicate that the temperature gradient alters the crack initiation location and propagation behavior; however, its effect on fatigue life remains limited, as it increases the stress gradient while simultaneously reducing the temperature as well as the stabilized peak and mean stresses. The predicted TMF and TGMF lives fall within a factor-of-1.5 scatter band.
{"title":"Thermomechanical fatigue damage mechanisms and life prediction of thin-walled nickel-based superalloy tubes considering temperature gradients effect","authors":"Hu Xiaoan, Xiao Baolu, Sui Tianxiao, Yang Qinzheng","doi":"10.1016/j.ijfatigue.2026.109563","DOIUrl":"10.1016/j.ijfatigue.2026.109563","url":null,"abstract":"<div><div>Thermomechanical fatigue (TMF) of aeroengine hot-section components is strongly affected by temperature gradients induced by internal cooling. In this study, a thermomechanical gradient fatigue (TGMF) testing methodology was developed and applied to thin-walled tubular specimens and specimens with holes made of the directionally solidified superalloy DZ125. Strain-controlled OP-TGMF tests were conducted over 500–1000℃ with a stable inner–outer wall temperature gradient of approximately 50℃. Coupled electromagnetic–thermal simulations and a viscoplastic constitutive model were employed to analyze stress–strain evolution and damage mechanisms. A cyclic damage accumulation model incorporating temperature-gradient-modified oxidation damage was further developed. The results indicate that the temperature gradient alters the crack initiation location and propagation behavior; however, its effect on fatigue life remains limited, as it increases the stress gradient while simultaneously reducing the temperature as well as the stabilized peak and mean stresses. The predicted TMF and TGMF lives fall within a factor-of-1.5 scatter band.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109563"},"PeriodicalIF":6.8,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146152924","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 : 2026-07-01Epub 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":"2026-07-01","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 : 2026-07-01Epub 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":"2026-07-01","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 : 2026-07-01Epub Date: 2026-02-01DOI: 10.1016/j.ijfatigue.2026.109530
Yu Xia, Wanlin Guo
Additively manufactured (AM) Ti-6Al-4V alloys often exhibit poor fatigue quality due to the presence of inherent defects, posing a major challenge for their widespread engineering application. Here, we developed a fatigue quality assessment approach based on three-dimensional fatigue fracture method, by a unified correlation between the Stress-Life (S-N) and fatigue crack growth properties of AM materials. It has been shown that the predicted probabilistic S-N curves derived from the actual defect size distribution capture the experimental fatigue life data within their scatter. The equivalent initial flaw size distribution of AM Ti-6Al-4V was back-extrapolated from S-N data, showing a reasonable correspondence, particularly in terms of magnitude, with the defect sizes observed at the fracture origins. It was further found that the fatigue crack growth behavior shows a weak dependence on the defect population, indicating that the fatigue quality of AM materials can be directly evaluated from their intrinsic defect quality. This provides a practical basis for optimizing AM process parameters with fatigue quality as the design target. As a demonstration, the proposed approach was further applied to evaluate the fatigue quality of Ti-6Al-4V alloys produced by additive manufacturing, conventional forging, and powder metallurgy routes, showing a reasonable agreement with experimental trends.
{"title":"Fatigue quality assessment of additive manufactured Ti-6Al-4V alloy by unified three-dimensional fatigue fracture method","authors":"Yu Xia, Wanlin Guo","doi":"10.1016/j.ijfatigue.2026.109530","DOIUrl":"10.1016/j.ijfatigue.2026.109530","url":null,"abstract":"<div><div>Additively manufactured (AM) Ti-6Al-4V alloys often exhibit poor fatigue quality due to the presence of inherent defects, posing a major challenge for their widespread engineering application. Here, we developed a fatigue quality assessment approach based on three-dimensional fatigue fracture method, by a unified correlation between the Stress-Life (<em>S-N</em>) and fatigue crack growth properties of AM materials. It has been shown that the predicted probabilistic <em>S-N</em> curves derived from the actual defect size distribution capture the experimental fatigue life data within their scatter. The equivalent initial flaw size distribution of AM Ti-6Al-4V was back-extrapolated from <em>S-N</em> data, showing a reasonable correspondence, particularly in terms of magnitude, with the defect sizes observed at the fracture origins. It was further found that the fatigue crack growth behavior shows a weak dependence on the defect population, indicating that the fatigue quality of AM materials can be directly evaluated from their intrinsic defect quality. This provides a practical basis for optimizing AM process parameters with fatigue quality as the design target. As a demonstration, the proposed approach was further applied to evaluate the fatigue quality of Ti-6Al-4V alloys produced by additive manufacturing, conventional forging, and powder metallurgy routes, showing a reasonable agreement with experimental trends.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109530"},"PeriodicalIF":6.8,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146110151","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 : 2026-07-01Epub Date: 2026-01-31DOI: 10.1016/j.ijfatigue.2026.109522
A. Ince
A baseline Deep Neural Network (DNN) and two Physics-Informed Neural Networks (PINN-R and PINN-Kmax) were developed for predicting fatigue crack growth rates (da/dN) in Ti–6Al–4V, IN625, and 17-4PH alloys produced by laser powder bed fusion (LPBF). Unlike traditional analytical models that rely only on driving force parameters such as ΔK and R, the network models integrate process parameters, mechanical properties, and fracture mechanics driving forces to capture complex interdependencies between manufacturing, material behavior, and crack growth response. The PINN models enforce monotonic constraints on the crack growth rate with respect to ΔK and either R (PINN-R) or the maximum stress-intensity factor Kmax (PINN-Kmax) by ensuring physical consistency while improving generalization. Models’ performance is assessed under two data splitting methods based on random K-fold cross-validation and grouped split by dataset IDs. A classical Walker model fitted on the same data provided a fracture-mechanics baseline. Under both data split methods, predictions from all neural models mainly fall within a ±3 × scatter band for all three alloys. The PINNs, particularly PINN-Kmax generally achieved better performance with lower RMSE and higher R2 than the baseline DNN and Walker model, especially in the Paris and rapid-growth regimes. The results highlight the novelty of embedding physics into data-driven models by indicating a robust, physics-aware machine learning framework for fatigue crack growth prediction in LPBF alloys.
{"title":"Physics-informed deep neural network framework for prediction of fatigue crack growth in LPBF-manufactured metallic alloys","authors":"A. Ince","doi":"10.1016/j.ijfatigue.2026.109522","DOIUrl":"10.1016/j.ijfatigue.2026.109522","url":null,"abstract":"<div><div>A baseline Deep Neural Network (DNN) and two Physics-Informed Neural Networks (PINN-R and PINN-K<sub>max</sub>) were developed for predicting fatigue crack growth rates (<em>da/dN</em>) in Ti–6Al–4V, IN625, and 17-4PH alloys produced by laser powder bed fusion (LPBF). Unlike traditional analytical models that rely only on driving force parameters such as <em>ΔK</em> and <em>R</em>, the network models integrate process parameters, mechanical properties, and fracture mechanics driving forces to capture complex interdependencies between manufacturing, material behavior, and crack growth response. The PINN models enforce monotonic constraints on the crack growth rate with respect to <em>ΔK</em> and either <em>R</em> (PINN-R) or the maximum stress-intensity factor <em>K<sub>max</sub></em> (PINN-K<sub>max</sub>) by ensuring physical consistency while improving generalization. Models’ performance is assessed under two data splitting methods based on random K-fold cross-validation and grouped split by dataset IDs. A classical Walker model fitted on the same data provided a fracture-mechanics baseline. Under both data split methods, predictions from all neural models mainly fall within a ±3 × scatter band for all three alloys. The PINNs, particularly PINN-K<em><sub>max</sub></em> generally achieved better performance with lower RMSE and higher R<sup>2</sup> than the baseline DNN and Walker model, especially in the Paris and rapid-growth regimes. The results highlight the novelty of embedding physics into data-driven models by indicating a robust, physics-aware machine learning framework for fatigue crack growth prediction in LPBF alloys.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"208 ","pages":"Article 109522"},"PeriodicalIF":6.8,"publicationDate":"2026-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146089477","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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