Pub Date : 2026-01-22DOI: 10.1016/j.ijfatigue.2026.109511
Zhizhuo Zhang , Mengchuang Zhang , Yan Li , Enrico Zappino , Zhiping Yin
Accurate detection and prediction of crack propagation are critical for maintaining the integrity and extending the service life of aerospace structures. We present a novel hybrid framework that integrates deep learning-based computer vision with physics-informed modeling to improve crack-growth forecasting. First, an enhanced You Only Look Once (YOLO) object-detection and segmentation network precisely extracts crack morphology from inspection images. These measurements feed into physics-informed neural network (PINN) that embeds the governing fracture mechanics equations to predict temporal growth trajectories. To maximize predictive accuracy, a Bayesian correlation scheme iteratively selects and refines the training set, ensuring inclusion of the most informative imaging samples. This feedback loop continuously enhances the model’s adaptability and reliability. Validation on benchmark datasets demonstrates that our hybrid approach significantly outperforms purely data-driven or purely physics-based methods, offering robust, real-time structural health monitoring. The proposed methodology provides a novel approach for predictive maintenance and lifecycle management of critical aerospace components.
裂纹扩展的准确检测和预测对于保持航天结构的完整性和延长其使用寿命至关重要。我们提出了一种新的混合框架，将基于深度学习的计算机视觉与物理信息建模相结合，以改进裂缝增长预测。首先，一个增强的You Only Look Once （YOLO）目标检测和分割网络精确地从检测图像中提取裂纹形态。这些测量结果输入到物理信息神经网络（PINN）中，该网络嵌入了控制断裂力学方程，以预测时间生长轨迹。为了最大限度地提高预测精度，贝叶斯相关方案迭代地选择和改进训练集，确保包含最具信息量的成像样本。这种反馈回路不断增强了模型的适应性和可靠性。在基准数据集上的验证表明，我们的混合方法明显优于纯粹的数据驱动或纯粹基于物理的方法，提供强大的实时结构健康监测。该方法为航空航天关键部件的预测性维护和生命周期管理提供了一种新的方法。
{"title":"Vision-driven and Bayesian-enhanced YOLO-PINN hybrid framework for crack propagation and fatigue life prediction","authors":"Zhizhuo Zhang , Mengchuang Zhang , Yan Li , Enrico Zappino , Zhiping Yin","doi":"10.1016/j.ijfatigue.2026.109511","DOIUrl":"10.1016/j.ijfatigue.2026.109511","url":null,"abstract":"<div><div>Accurate detection and prediction of crack propagation are critical for maintaining the integrity and extending the service life of aerospace structures. We present a novel hybrid framework that integrates deep learning-based computer vision with physics-informed modeling to improve crack-growth forecasting. First, an enhanced You Only Look Once (YOLO) object-detection and segmentation network precisely extracts crack morphology from inspection images. These measurements feed into physics-informed neural network (PINN) that embeds the governing fracture mechanics equations to predict temporal growth trajectories. To maximize predictive accuracy, a Bayesian correlation scheme iteratively selects and refines the training set, ensuring inclusion of the most informative imaging samples. This feedback loop continuously enhances the model’s adaptability and reliability. Validation on benchmark datasets demonstrates that our hybrid approach significantly outperforms purely data-driven or purely physics-based methods, offering robust, real-time structural health monitoring. The proposed methodology provides a novel approach for predictive maintenance and lifecycle management of critical aerospace components.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109511"},"PeriodicalIF":6.8,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146033259","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 : 2026-01-22DOI: 10.1016/j.ijfatigue.2026.109513
Tianyu Zhang , Yu Wang , Zhanqing Yin , Xiaoming Liu , Chenchong Wang , Lingyu Wang , Chi Zhang , Wei Xu
Carbide-free bainite (CFB) steel, consisting of bainitic laths and metastable retained austenite (RA), offers excellent static properties and fatigue resistance, making it a potential replacement for conventional axle steels. However, the relationships among its microstructure, fatigue life under various stresses, and fatigue crack growth (FCG) behavior remain unclear. This study designed two CFB axle steels, AT350 and AT300, by austempering at 350 °C or 300 °C followed by low-temperature tempering, producing different bainitic lath sizes and RA stabilities. Their mechanical properties, high-cycle fatigue (HCF) performance, and FCG behavior were systematically investigated. The AT300 sample featured finer bainite laths (average thickness: 231 nm) and higher RA stability than that of the AT350 sample, due to prior austenite grain segmentation by primary martensite. Consequently, AT300 achieved higher tensile strength (1575 MPa) and HCF strength (760 MPa, fatigue limit at 107 cycles). Under low-stress fatigue, the AT300 sample exhibited longer life and slower crack growth than the AT350 sample. Under high-stress fatigue, however, the fatigue lives of the AT350 and AT300 samples were nearly equivalent, as AT350′s greater ductility and secondary cracking compensated for its lower strength. In the FCG regime, AT300 showed a wider resistance plateau and a lower Paris exponent, indicating superior crack growth resistance. This enhancement arises from fine bainitic laths deflecting cracks and stable RA reducing martensitic transformation at the crack tip, thereby avoiding brittle martensite channels and absorbing strain energy. These findings provide valuable theoretical and experimental guidance for designing axle steels with superior fatigue resistance.
{"title":"Microstructural origins for the simultaneously enhanced high-cycle fatigue performance and fatigue crack growth resistance of a carbide-free bainite steel","authors":"Tianyu Zhang , Yu Wang , Zhanqing Yin , Xiaoming Liu , Chenchong Wang , Lingyu Wang , Chi Zhang , Wei Xu","doi":"10.1016/j.ijfatigue.2026.109513","DOIUrl":"10.1016/j.ijfatigue.2026.109513","url":null,"abstract":"<div><div>Carbide-free bainite (CFB) steel, consisting of bainitic laths and metastable retained austenite (RA), offers excellent static properties and fatigue resistance, making it a potential replacement for conventional axle steels. However, the relationships among its microstructure, fatigue life under various stresses, and fatigue crack growth (FCG) behavior remain unclear. This study designed two CFB axle steels, AT350 and AT300, by austempering at 350 °C or 300 °C followed by low-temperature tempering, producing different bainitic lath sizes and RA stabilities. Their mechanical properties, high-cycle fatigue (HCF) performance, and FCG behavior were systematically investigated. The AT300 sample featured finer bainite laths (average thickness: 231 nm) and higher RA stability than that of the AT350 sample, due to prior austenite grain segmentation by primary martensite. Consequently, AT300 achieved higher tensile strength (1575 MPa) and HCF strength (760 MPa, fatigue limit at 10<sup>7</sup> cycles). Under low-stress fatigue, the AT300 sample exhibited longer life and slower crack growth than the AT350 sample. Under high-stress fatigue, however, the fatigue lives of the AT350 and AT300 samples were nearly equivalent, as AT350′s greater ductility and secondary cracking compensated for its lower strength. In the FCG regime, AT300 showed a wider resistance plateau and a lower Paris exponent, indicating superior crack growth resistance. This enhancement arises from fine bainitic laths deflecting cracks and stable RA reducing martensitic transformation at the crack tip, thereby avoiding brittle martensite channels and absorbing strain energy. These findings provide valuable theoretical and experimental guidance for designing axle steels with superior fatigue resistance.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109513"},"PeriodicalIF":6.8,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146033267","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 : 2026-01-22DOI: 10.1016/j.ijfatigue.2026.109514
Weichang Wei , Chenyang Zhang , Yapeng Huang , Xia He , Yong Zhang , Guang Li , Yanjin Xu , Baoshuai Han , Cai Hu , Lingying Ye
The effects of pore characteristics and evolution on the fatigue performance of spray-formed 7055 aluminum alloy were investigated using synchrotron X-ray computed tomography (CT), electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results demonstrate that pore characteristics and their evolution during cyclic loading directly govern the fatigue performance. As the extrusion ratio increased from 7 to 48, the size and number density of pores decreased significantly, which was accompanied by a progressive improvement in low-cycle fatigue life. During fatigue cycling, severe local plastic deformation occurred around pores sized 10–20 μm, causing substantial pore growth and promoting rapid crack initiation. For pores sized 5–10 μm, the local plastic deformation was less pronounced, resulting in delayed crack initiation and extended fatigue life. Pores smaller than 5 μm underwent negligible plastic deformation and thus had a minimal impact on fatigue performance. Moreover, pores accelerated fatigue crack propagation by providing preferential paths for rapid crack growth.
{"title":"Low-cycle fatigue performance and porosity evolution in spray-formed 7055 Al-alloy","authors":"Weichang Wei , Chenyang Zhang , Yapeng Huang , Xia He , Yong Zhang , Guang Li , Yanjin Xu , Baoshuai Han , Cai Hu , Lingying Ye","doi":"10.1016/j.ijfatigue.2026.109514","DOIUrl":"10.1016/j.ijfatigue.2026.109514","url":null,"abstract":"<div><div>The effects of pore characteristics and evolution on the fatigue performance of spray-formed 7055 aluminum alloy were investigated using synchrotron X-ray computed tomography (CT), electron backscatter diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results demonstrate that pore characteristics and their evolution during cyclic loading directly govern the fatigue performance. As the extrusion ratio increased from 7 to 48, the size and number density of pores decreased significantly, which was accompanied by a progressive improvement in low-cycle fatigue life. During fatigue cycling, severe local plastic deformation occurred around pores sized 10–20 μm, causing substantial pore growth and promoting rapid crack initiation. For pores sized 5–10 μm, the local plastic deformation was less pronounced, resulting in delayed crack initiation and extended fatigue life. Pores smaller than 5 μm underwent negligible plastic deformation and thus had a minimal impact on fatigue performance. Moreover, pores accelerated fatigue crack propagation by providing preferential paths for rapid crack growth.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109514"},"PeriodicalIF":6.8,"publicationDate":"2026-01-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146033260","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 : 2026-01-21DOI: 10.1016/j.ijfatigue.2026.109512
Hao-Qi Fan , Kai-Shang Li , Ning Yao , Wen-Rui Nie , Run-Zi Wang , Ti-Wen Lu , Lu Cheng , Xiu-Fang Gong , Xian-Cheng Zhang , Shan-Tung Tu
Start-up and shut-down transients in turbomachinery impose varying strain rates that affect the in-service life of high-temperature components. However, the quantitative role of strain rate sensitivity in high-temperature fatigue of nickel-based superalloys remains inadequately reflected in damage mechanism and life prediction. In this study, fully-reversed strain-controlled low cycle fatigue (LCF) tests were performed at 650 ℃ over a wide range of strain rates from 5 × 10−5 to 1 × 10−2 s−1. The experimental results reveal the existence of a threshold strain-rate range for nickel-based superalloy IN718. When the strain rate exceeds this threshold, the fatigue life remains nearly constant with increasing strain rate. The cracking behavior is dominated by the transgranular-intergranular mixed mode. In contrast, at strain rates below this threshold, the fatigue life decreases rapidly due to the time available for oxidation- and creep-assisted damage. Based on these observations, a modified energy-based model incorporating the strain rate sensitivity was proposed using tensile-derived plastic strain energy density, achieving a prediction accuracy of 97% within a ±2 error band. These findings provide an effective strategy for enhancing the service reliability of high-temperature rotating components.
{"title":"Mechanistic insight and universal life prediction of strain rate-dependent fatigue in nickel-based superalloy at elevated temperature","authors":"Hao-Qi Fan , Kai-Shang Li , Ning Yao , Wen-Rui Nie , Run-Zi Wang , Ti-Wen Lu , Lu Cheng , Xiu-Fang Gong , Xian-Cheng Zhang , Shan-Tung Tu","doi":"10.1016/j.ijfatigue.2026.109512","DOIUrl":"10.1016/j.ijfatigue.2026.109512","url":null,"abstract":"<div><div>Start-up and shut-down transients in turbomachinery impose varying strain rates that affect the in-service life of high-temperature components. However, the quantitative role of strain rate sensitivity in high-temperature fatigue of nickel-based superalloys remains inadequately reflected in damage mechanism and life prediction. In this study, fully-reversed strain-controlled low cycle fatigue (LCF) tests were performed at 650 ℃ over a wide range of strain rates from 5 × 10<sup>−5</sup> to 1 × 10<sup>−2</sup> s<sup>−1</sup>. The experimental results reveal the existence of a threshold strain-rate range for nickel-based superalloy IN718. When the strain rate exceeds this threshold, the fatigue life remains nearly constant with increasing strain rate. The cracking behavior is dominated by the transgranular-intergranular mixed mode. In contrast, at strain rates below this threshold, the fatigue life decreases rapidly due to the time available for oxidation- and creep-assisted damage. Based on these observations, a modified energy-based model incorporating the strain rate sensitivity was proposed using tensile-derived plastic strain energy density, achieving a prediction accuracy of 97% within a ±2 error band. These findings provide an effective strategy for enhancing the service reliability of high-temperature rotating components.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109512"},"PeriodicalIF":6.8,"publicationDate":"2026-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146033266","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}
Advanced power plants demand steels with enhanced high-temperature low-cycle fatigue (LCF) performance. However, the insufficient understanding of ferrite’s role in crack propagation limits both optimization design and application of the novel Si-enriched ferritic/martensitic (F/M) steels. Hence, the crack propagation behavior during LCF was investigated in steels with varied ferrite structures obtained through two distinct treatments: normalizing & tempering process (NT) and hot rolling & tempering process (HR). The ferrite for NT is “clearer” with few and large sub-grains, whereas, for HR, the ferrite contains high density of small sub-grains. These sub-grains with slightly different orientation effectively deflect the crack propagation path. Moreover, hot rolling produced a pronounced texture characterized by a large misorientation between the crack plane and the {100} cleavage plane, thereby increasing the energy required for crack propagation. The sub-grain structure together with the strong texture indicates a higher resistance to crack propagation for HR. However, the notably higher ferrite fraction for HR results in a lower fatigue life, as the suboptimal strength ultimately leads to a premature onset of stage III with sharply decreasing stress, which limits the period of stable crack propagation, thereby, inducing an early failure. This excessive ferrite was formed due to the temperature drop during hot rolling, which shifted the calculated equilibrium ferrite from <5 % to nearly 45 %. Overall, these results highlight the importance of ferrite refinement and fraction control in optimizing the fatigue resistance of Si-enriched F/M steels. Guided by this insight, potential processing strategies are proposed for future optimization.
{"title":"Effect of distinct ferrite structures on the crack propagation behavior in a Si-enriched ferritic/martensitic (F/M) steel under low-cycle fatigue (LCF) at 600 ℃","authors":"Jun Zhang , Xiaoxin Zhang , Hao Ren , Decang Zhang , Yingxue Chen , Feifei Zhang , Xinhao Zhang , Qingzhi Yan","doi":"10.1016/j.ijfatigue.2026.109517","DOIUrl":"10.1016/j.ijfatigue.2026.109517","url":null,"abstract":"<div><div>Advanced power plants demand steels with enhanced high-temperature low-cycle fatigue (LCF) performance. However, the insufficient understanding of ferrite’s role in crack propagation limits both optimization design and application of the novel Si-enriched ferritic/martensitic (F/M) steels. Hence, the crack propagation behavior during LCF was investigated in steels with varied ferrite structures obtained through two distinct treatments: normalizing & tempering process (NT) and hot rolling & tempering process (HR). The ferrite for NT is “clearer” with few and large sub-grains, whereas, for HR, the ferrite contains high density of small sub-grains. These sub-grains with slightly different orientation effectively deflect the crack propagation path. Moreover, hot rolling produced a pronounced texture characterized by a large misorientation between the crack plane and the {100} cleavage plane, thereby increasing the energy required for crack propagation. The sub-grain structure together with the strong texture indicates a higher resistance to crack propagation for HR. However, the notably higher ferrite fraction for HR results in a lower fatigue life, as the suboptimal strength ultimately leads to a premature onset of stage III with sharply decreasing stress, which limits the period of stable crack propagation, thereby, inducing an early failure. This excessive ferrite was formed due to the temperature drop during hot rolling, which shifted the calculated equilibrium ferrite from <5 % to nearly 45 %. Overall, these results highlight the importance of ferrite refinement and fraction control in optimizing the fatigue resistance of Si-enriched F/M steels. Guided by this insight, potential processing strategies are proposed for future optimization.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109517"},"PeriodicalIF":6.8,"publicationDate":"2026-01-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146014559","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 : 2026-01-19DOI: 10.1016/j.ijfatigue.2026.109499
Max Ahlqvist , Viktor Norman , Daniel Leidermark
Numerous methods have been suggested to quantify fatigue-initiating defect size on fracture surfaces, the most prevalent are based on the Murakami–Endo -parameter. However, there is an ambiguity in how to systemically determine defect areas. For instance, in literature on high-cycle fatigue of ductile cast irons the several different methods have been suggested: (i) the traced contour, (ii) the convex hull, (iii) the minimum circumscribed circle, and (iv) the minimum bounding rectangle. This work focuses on comparing and evaluating these methods by assessing the fatigue-initiating defect area distributions, and the influence on fatigue assessment using the -parameter. To this end, very high cycle fatigue data on ductile cast irons with different microstructures is used, where complex shaped defects are the root-cause for fatigue failures. It is shown that there is a significant difference in the area distributions, originating from the applied area measurement method. In addition, to enable and include fatigue assessment of high strength ausferritic ductile irons, two improved Murakami–Endo type models are proposed, which show satisfactory prediction capabilities over a wide range of ductile cast iron microstructures. To further evaluate the different area measurement methods, the suggested models are validated against ductile cast iron high-cycle fatigue data from literature having artificial defects and notches. Finally, it is concluded that the traced contour defect measurement method yields the best agreement between artificial and natural defects, and overall, the least prediction errors.
{"title":"Effect of fatigue-initiating defect area measurement on defect size distributions and fatigue assessment of ductile cast iron","authors":"Max Ahlqvist , Viktor Norman , Daniel Leidermark","doi":"10.1016/j.ijfatigue.2026.109499","DOIUrl":"10.1016/j.ijfatigue.2026.109499","url":null,"abstract":"<div><div>Numerous methods have been suggested to quantify fatigue-initiating defect size on fracture surfaces, the most prevalent are based on the Murakami–Endo <span><math><msqrt><mrow><mi>a</mi><mi>r</mi><mi>e</mi><mi>a</mi></mrow></msqrt></math></span>-parameter. However, there is an ambiguity in how to systemically determine defect areas. For instance, in literature on high-cycle fatigue of ductile cast irons the several different methods have been suggested: (i) the traced contour, (ii) the convex hull, (iii) the minimum circumscribed circle, and (iv) the minimum bounding rectangle. This work focuses on comparing and evaluating these methods by assessing the fatigue-initiating defect area distributions, and the influence on fatigue assessment using the <span><math><msqrt><mrow><mi>a</mi><mi>r</mi><mi>e</mi><mi>a</mi></mrow></msqrt></math></span>-parameter. To this end, very high cycle fatigue data on ductile cast irons with different microstructures is used, where complex shaped defects are the root-cause for fatigue failures. It is shown that there is a significant difference in the area distributions, originating from the applied area measurement method. In addition, to enable and include fatigue assessment of high strength ausferritic ductile irons, two improved Murakami–Endo type models are proposed, which show satisfactory prediction capabilities over a wide range of ductile cast iron microstructures. To further evaluate the different area measurement methods, the suggested models are validated against ductile cast iron high-cycle fatigue data from literature having artificial defects and notches. Finally, it is concluded that the traced contour defect measurement method yields the best agreement between artificial and natural defects, and overall, the least prediction errors.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109499"},"PeriodicalIF":6.8,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000570","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 : 2026-01-19DOI: 10.1016/j.ijfatigue.2026.109496
Pietro Foti , Michele Zappalorto , Filippo Berto
When designing mechanical components, their functional requirements often lead to geometrical discontinuities with severe stress concentrations and gradients. These discontinuities, known as notches, can markedly reduce the structural reliability and fatigue strength of components. Depending on the notch severity, conventional point-based approaches may significantly overestimate their detrimental effects on fatigue behaviour. Notches are generally classified as blunt or sharp with the fatigue behaviour of the sharp ones not accurately captured by point-based approaches. Numerous studies have attempted to define the transition between these two behaviour and to develop design methodologies capable of consistently addressing both. Among these, the averaged Strain Energy Density (SED) method has demonstrated high accuracy and robustness for both blunt and sharp notches. In this work, the SED method is employed to identify a limiting condition, expressed through a limit notch radius, , that distinguishes between blunt and sharp notches. This condition is investigated through numerical simulations and validated against an extensive fatigue database from the literature. Defining the limit condition as a notch radius simplifies components design and may also serve as guideline for determining the required notches tolerances. Finally, a methodology is proposed for fatigue-oriented material selection, coupling bulk material properties, component geometry and notch sensitivity. Indeed, in fatigue design, the highest-performing component is not necessarily obtained using the material with the highest intrinsic fatigue strength. For sharp notches, materials with lower intrinsic fatigue strength, but reduced notch sensitivity, can indeed yield superior fatigue performance. The methodology can be readily extended to lightweight design applications.
{"title":"Blunt and sharp notches: Revisiting the limit notch radius via the averaged SED method and validating it against a wide fatigue strength reduction database","authors":"Pietro Foti , Michele Zappalorto , Filippo Berto","doi":"10.1016/j.ijfatigue.2026.109496","DOIUrl":"10.1016/j.ijfatigue.2026.109496","url":null,"abstract":"<div><div>When designing mechanical components, their functional requirements often lead to geometrical discontinuities with severe stress concentrations and gradients. These discontinuities, known as notches, can markedly reduce the structural reliability and fatigue strength of components. Depending on the notch severity, conventional point-based approaches may significantly overestimate their detrimental effects on fatigue behaviour. Notches are generally classified as blunt or sharp with the fatigue behaviour of the sharp ones not accurately captured by point-based approaches. Numerous studies have attempted to define the transition between these two behaviour and to develop design methodologies capable of consistently addressing both. Among these, the averaged Strain Energy Density (SED) method has demonstrated high accuracy and robustness for both blunt and sharp notches. In this work, the SED method is employed to identify a limiting condition, expressed through a limit notch radius, <span><math><msub><mi>ρ</mi><mrow><mi>limit</mi></mrow></msub></math></span>, that distinguishes between blunt and sharp notches. This condition is investigated through numerical simulations and validated against an extensive fatigue database from the literature. Defining the limit condition as a notch radius simplifies components design and may also serve as guideline for determining the required notches tolerances. Finally, a methodology is proposed for fatigue-oriented material selection, coupling bulk material properties, component geometry and notch sensitivity. Indeed, in fatigue design, the highest-performing component is not necessarily obtained using the material with the highest intrinsic fatigue strength. For sharp notches, materials with lower intrinsic fatigue strength, but reduced notch sensitivity, can indeed yield superior fatigue performance. The methodology can be readily extended to lightweight design applications.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109496"},"PeriodicalIF":6.8,"publicationDate":"2026-01-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"146000568","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 : 2026-01-18DOI: 10.1016/j.ijfatigue.2026.109489
Arianna Mena , Jiashi Miao , Daniel Veghte , Bruce Williams , Aeriel D. Murphy-Leonard
In this study, the evolution of deformation mechanisms during cyclic loading in an extruded, solution-treated Mg–2Nd–1Y–0.1Zr–0.1Ca alloy was investigated using a combination of in-situ loading, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and focused ion beam (FIB) nanofabrication. The initial microstructure exhibited a crystallographic texture where the c-axis were orie. Flat, rectangular dog-bone specimens were subjected to load-controlled, fully reversed fatigue for 50 cycles, during which the same region was sequentially mapped to track microstructural changes. After 10 cycles of loading deformation twins were observed. During tensile reloading detwinning or narrowing of those twinned regions occurred. After 20 cycles, detwinning ceased and residual twins remained in the material. SEM imaging revealed numerous surface slip traces after cyclic loading. EBSD-assisted slip trace analysis identified the activation of prismatic < a > and pyramidal < c + a > slip systems during low-cycle fatigue. Site-specific scanning transmission electron microscopy (STEM) further revealed that deformation was also accommodated by basal < a > slip and the dissociation of < c + a > dislocations. Center-of-symmetry (COS) analysis confirmed that the dissociation of < c + a > dislocations resulted in the formation of I1 intrinsic stacking faults after cyclic loading. These findings provide new insights into the complex interplay of dislocation mechanisms governing fatigue deformation in rare-earth-containing Mg alloys.
本研究采用原位加载、扫描电子显微镜（SEM）、电子背散射衍射（EBSD）和聚焦离子束（FIB）纳米加工相结合的方法，研究了挤压、固溶处理Mg-2Nd-1Y-0.1Zr-0.1Ca合金在循环加载过程中的变形机制演变。初始微观结构表现为c轴偏纵的晶体织构。扁平的矩形狗骨试件经受载荷控制的完全反向疲劳50次，在此期间，同一区域被依次绘制以跟踪微观结构变化。在10次循环加载后，观察到变形孪晶。在拉伸再加载过程中，孪晶区域发生脱孪或缩窄。20次循环后，脱孪生停止，材料中仍有残留的孪晶。扫描电镜成像显示了循环加载后大量的表面滑动痕迹。EBSD-assisted滑痕量分析确定激活棱镜 & lt; 比; 和锥体 & lt; c + 祝辞 滑移系统在低循环疲劳。特定站点扫描透射电子显微镜(STEM)进一步显示,变形也适应了基底 & lt; 比; 滑的离解 & lt; c + 祝辞 混乱。对称中心（COS）分析证实，循环加载后， <； c + a >； 位错的解离导致I1本征层错的形成。这些发现为研究控制稀土镁合金疲劳变形的位错机制的复杂相互作用提供了新的见解。
{"title":"In-situ observations of cyclic deformation in an extruded Mg-2Nd-1Y-0.1Zr-0.1Ca alloy","authors":"Arianna Mena , Jiashi Miao , Daniel Veghte , Bruce Williams , Aeriel D. Murphy-Leonard","doi":"10.1016/j.ijfatigue.2026.109489","DOIUrl":"10.1016/j.ijfatigue.2026.109489","url":null,"abstract":"<div><div>In this study, the evolution of deformation mechanisms during cyclic loading in an extruded, solution-treated Mg–2Nd–1Y–0.1Zr–0.1Ca alloy was investigated using a combination of in-situ loading, scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and focused ion beam (FIB) nanofabrication. The initial microstructure exhibited a crystallographic texture where the c-axis were orie. Flat, rectangular dog-bone specimens were subjected to load-controlled, fully reversed fatigue for 50 cycles, during which the same region was sequentially mapped to track microstructural changes. After 10 cycles of loading deformation twins were observed. During tensile reloading detwinning or narrowing of those twinned regions occurred. After 20 cycles, detwinning ceased and residual twins remained in the material. SEM imaging revealed numerous surface slip traces after cyclic loading. EBSD-assisted slip trace analysis identified the activation of prismatic < a > and pyramidal < c + a > slip systems during low-cycle fatigue. Site-specific scanning transmission electron microscopy (STEM) further revealed that deformation was also accommodated by basal < a > slip and the dissociation of < c + a > dislocations. Center-of-symmetry (COS) analysis confirmed that the dissociation of < c + a > dislocations resulted in the formation of I<sub>1</sub> intrinsic stacking faults after cyclic loading. These findings provide new insights into the complex interplay of dislocation mechanisms governing fatigue deformation in rare-earth-containing Mg alloys.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109489"},"PeriodicalIF":6.8,"publicationDate":"2026-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995479","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 : 2026-01-16DOI: 10.1016/j.ijfatigue.2026.109495
Aniclelson Raony Alves de Moura , Franck Morel , Etienne Pessard , Daniel Bellett , Louis Augustins , Damien Herisson
The gears used in aircraft engines are typically made from high-strength steels reinforced by thermochemical treatments (TCT). These treatments increase surface fatigue strength through microstructural modifications, enhancing hardness and adding compressive residual stresses. In some cases, the combination of material, TCT, and applied stress can lead to a bi-modal fatigue behavior, notably in failures at the gear tooth root. This work investigates the bi-modal fatigue response of M50NiL case-hardened steel by characterizing and analyzing crack initiation mechanisms to propose a relevant fatigue modeling approach. A comprehensive experimental fatigue test campaign was carried out on notched specimens under plane bending and on gear specimens using a Single Tooth Bending Fatigue (STBF) method. The resulting Wöhler diagram shows significant scatter in fatigue life for several stress levels, suggesting a bi-modal behavior with two distinct populations. Fractographic analyses confirmed the competition between two different crack initiation mechanisms depending on stress level and number of cycles to failure. A statistical analysis using a mixture model also indicates that a bi-modal distribution best represents the results. Accordingly, a probabilistic model is proposed to describe the bi-modal fatigue behavior from a global perspective, based on the maximum applied hot-spot surface stress for a fixed stress ratio. Finally, a complementary local stress analysis shows that the combined effect of stress and material property distributions significantly influences local maximum stress variation. Correcting for these factors reduces scatter in the bi-modal stress levels.
{"title":"Understanding the bi-modal fatigue behavior of the case-hardened M50NiL steel","authors":"Aniclelson Raony Alves de Moura , Franck Morel , Etienne Pessard , Daniel Bellett , Louis Augustins , Damien Herisson","doi":"10.1016/j.ijfatigue.2026.109495","DOIUrl":"10.1016/j.ijfatigue.2026.109495","url":null,"abstract":"<div><div>The gears used in aircraft engines are typically made from high-strength steels reinforced by thermochemical treatments (TCT). These treatments increase surface fatigue strength through microstructural modifications, enhancing hardness and adding compressive residual stresses. In some cases, the combination of material, TCT, and applied stress can lead to a bi-modal fatigue behavior, notably in failures at the gear tooth root. This work investigates the bi-modal fatigue response of M50NiL case-hardened steel by characterizing and analyzing crack initiation mechanisms to propose a relevant fatigue modeling approach. A comprehensive experimental fatigue test campaign was carried out on notched specimens under plane bending and on gear specimens using a Single Tooth Bending Fatigue (STBF) method. The resulting Wöhler diagram shows significant scatter in fatigue life for several stress levels, suggesting a bi-modal behavior with two distinct populations. Fractographic analyses confirmed the competition between two different crack initiation mechanisms depending on stress level and number of cycles to failure. A statistical analysis using a mixture model also indicates that a bi-modal distribution best represents the results. Accordingly, a probabilistic model is proposed to describe the bi-modal fatigue behavior from a global perspective, based on the maximum applied hot-spot surface stress for a fixed stress ratio. Finally, a complementary local stress analysis shows that the combined effect of stress and material property distributions significantly influences local maximum stress variation. Correcting for these factors reduces scatter in the bi-modal stress levels.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109495"},"PeriodicalIF":6.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995465","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 : 2026-01-16DOI: 10.1016/j.ijfatigue.2026.109494
Quan-Heng Yao, Rong Chen, Wen-Qing Lu, Xu-Yang Mo, Ming-Liang Zhu, Fu-Zhen Xuan
Materials with coarse grains are believed to have higher fatigue threshold with respect to damage tolerance design, in such a context, the mechanisms for fine grains governing fatigue crack propagation are not clear. In this study, the near-threshold fatigue crack propagation behavior of L907A steel welded joints with micrometer-size grains (∼2.5 μm) was investigated, and the associated damage mechanisms near crack-tip were analyzed. It was found that fine grains tended to have lower transition rate down to the near-threshold regime due to the interaction of cyclic plasticity and microstructures, which promoted the formation of nanovoids, nanograins, and amorphization near crack-tip. A modified Zhu-Xuan model was established by taking into account the local microhardness and stress ratios. These findings underscore the importance of grain size engineering in enhancing fatigue resistance and show promise for streamlining the fatigue threshold testing process, thereby reducing associated time and costs.
{"title":"Near-threshold fatigue resistance of micrometer-grained steel welds: mechanisms and modeling","authors":"Quan-Heng Yao, Rong Chen, Wen-Qing Lu, Xu-Yang Mo, Ming-Liang Zhu, Fu-Zhen Xuan","doi":"10.1016/j.ijfatigue.2026.109494","DOIUrl":"10.1016/j.ijfatigue.2026.109494","url":null,"abstract":"<div><div>Materials with coarse grains are believed to have higher fatigue threshold with respect to damage tolerance design, in such a context, the mechanisms for fine grains governing fatigue crack propagation are not clear. In this study, the near-threshold fatigue crack propagation behavior of L907A steel welded joints with micrometer-size grains (∼2.5 μm) was investigated, and the associated damage mechanisms near crack-tip were analyzed. It was found that fine grains tended to have lower transition rate down to the near-threshold regime due to the interaction of cyclic plasticity and microstructures, which promoted the formation of nanovoids, nanograins, and amorphization near crack-tip. A modified Zhu-Xuan model was established by taking into account the local microhardness and stress ratios. These findings underscore the importance of grain size engineering in enhancing fatigue resistance and show promise for streamlining the fatigue threshold testing process, thereby reducing associated time and costs.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"207 ","pages":"Article 109494"},"PeriodicalIF":6.8,"publicationDate":"2026-01-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145995464","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}
扫码关注我们
求助内容：
应助结果提醒方式：
京公网安备 11010802042870号