Ryuto Sano, Yuta Koga, Yusuke Sato, Takuto Kikuchi, Atsushi Hosoi, Kota Kawahara, Yoshiki Takebe, Hiroyuki Kawada
{"title":"Fatigue Properties of Carbon Fiber–Reinforced Foams and Experimental Observation of the Damage Growth Mechanism","authors":"Ryuto Sano, Yuta Koga, Yusuke Sato, Takuto Kikuchi, Atsushi Hosoi, Kota Kawahara, Yoshiki Takebe, Hiroyuki Kawada","doi":"10.1111/ffe.14518","DOIUrl":"https://doi.org/10.1111/ffe.14518","url":null,"abstract":"<div>\u0000 \u0000 <p>Carbon fiber–reinforced foams (CFRFs) are expanded thermoplastic composite materials reinforced with three-dimensional discontinuous carbon fibers. Herein, the effects of their unique internal structure on fatigue properties were investigated. Through tension-tension fatigue tests and the digital image correlation (DIC) method, distinct stiffness reduction behavior was observed across the entire specimen and at the fracture points. The results suggest that local stiffness reduction behavior affects the fatigue properties. From the DIC method, damage was observed by scanning electron microscopy and the fiber tortuosity, and the void fraction were quantified using X-ray computed tomography scans. In the case of three-dimensional oriented fibers, stress was concentrated at fiber ends, fiber intersections, and bent fibers, resulting in fiber pull-outs and matrix cracks. In the case of voids, the void size affected damage development, and the stress concentration around the voids caused fiber fracture and matrix cracks.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"967-975"},"PeriodicalIF":3.1,"publicationDate":"2024-11-20","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143117612","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}
Pavel Pokorný, Tomáš Vojtek, Radek Kubíček, Michal Jambor, Luboš Náhlík, Pavel Hutař
{"title":"Paradox of Shorter Residual Fatigue Life due to Omission of Low-Amplitude Cycles and Its Significance for Testing","authors":"Pavel Pokorný, Tomáš Vojtek, Radek Kubíček, Michal Jambor, Luboš Náhlík, Pavel Hutař","doi":"10.1111/ffe.14505","DOIUrl":"https://doi.org/10.1111/ffe.14505","url":null,"abstract":"<div>\u0000 \u0000 <p>The work investigates nonvalidity of the common presumption that the nondamaging cycles do not influence residual fatigue life. Paradoxically, application of the full loading spectrum (more cycles) resulted in approximately 2.3 times longer life of the fatigue crack growth specimens than application of the spectrum with 33% of the smallest amplitudes omitted. Unlike in humid air (controlled relative humidity of 50% at 23°C), the effect disappeared in a dry-air chamber (relative humidity <10% at 23°C), where both fatigue lives were short. The mechanism responsible for these effects was identified as the oxide-induced crack closure, an extrinsic mechanism unrelated to material damage. Oxide debris developed on fracture surfaces was observed by light and scanning electron microscopy, whereas crack closure was measured during the experiments. The presented counterintuitive behavior in humid air may result in wrong assessment or prediction of components residual fatigue lives, which can be nonconservative in some scenarios.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"956-966"},"PeriodicalIF":3.1,"publicationDate":"2024-11-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116919","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}
Chengji Mi, Yingang Xiao, Yingjian Deng, Yongqiang Li
{"title":"Fatigue Life Prediction of LF6 Aluminum Alloy Laser-Arc Hybrid Welded Joints Based on Energy Dissipation Method","authors":"Chengji Mi, Yingang Xiao, Yingjian Deng, Yongqiang Li","doi":"10.1111/ffe.14517","DOIUrl":"https://doi.org/10.1111/ffe.14517","url":null,"abstract":"<div>\u0000 \u0000 <p>To accurately characterize the heat dissipation behavior of LF6 aluminum alloy laser arc composite welded joint under low cycle fatigue, two fatigue life prediction methods based on dissipated energy were proposed. The experimental investigation has revealed four stages in the evolution of surface temperature increment, including initial temperature increase, subsequent decline, attainment of thermal equilibrium, and sudden temperature escalation leading to failure. Based on the energy dissipation method, two models predicting lifespan of welded joints have been formulated. Model I incorporates the effects of stress amplitude and mean stress, on lifetime demonstrating a strong linear correlation particularly under high-stress level according to experimental comparisons. Model II introduces a relationship between plastic strain amplitude and inherent dissipated energy to assess fatigue life of welded joints. Digital imaging correction technique has been utilized to quantify plastic strain amplitude. The predicted results from Model II agree well with experimental data.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"814-826"},"PeriodicalIF":3.1,"publicationDate":"2024-11-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116414","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}
{"title":"Role of Loading Rate on Cracking Behavior in Granite Disks With Laboratory Experiments and Grain-Based Modeling","authors":"Yingming Yang, Ruide Lei, Qingheng Gu, Chao Hu, Linsen Zhou, Shirong Wei, Xuejia Li","doi":"10.1111/ffe.14515","DOIUrl":"https://doi.org/10.1111/ffe.14515","url":null,"abstract":"<div>\u0000 \u0000 <p>The investigation of the tensile properties of rock materials is essential for understanding the failure mechanism of engineering rock masses. In this study, we conducted a series of Brazilian splitting tests on granite specimens under three different loading rates, concurrently monitored using acoustic emission (AE) and digital image correlation (DIC) techniques. The results show that the mechanical parameters of granite disks are positively correlated with the loading rate. The AE waveforms are found to be associated with the lower frequency band, suggesting that this frequency range primarily dominates the failure mechanism in granite disks. Furthermore, the onset of micro-tensile fractures precedes the development of micro-shear ones. The elevation distribution of the fractured surfaces of the granite disks follows a Gaussian function. The fractal dimension increases progressively with the loading rate, whereas the complexity and irregularity of the fractured surface decrease. Moreover, the cracking mechanism of granite disks at the microscale was revealed using grain-based modeling (GBM). The intergranular tensile cracks predominantly form along the radial direction, and the proportion of intergranular shear cracks is the smallest.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"764-782"},"PeriodicalIF":3.1,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116206","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}
{"title":"An Implicit Fillet-Weld Element Formulation for Mesh-Insensitive Fatigue Evaluation of Complex Structures","authors":"Lunyu Zhang, Shengjia Wu, Pingsha Dong","doi":"10.1111/ffe.14486","DOIUrl":"https://doi.org/10.1111/ffe.14486","url":null,"abstract":"<div>\u0000 \u0000 <p>In fatigue evaluation of welded structures, explicit weld representations in finite element (FE) models are needed for reliably capturing stress or strain concentration behaviors at critical weld locations, for example, weld toe or weld root, in using widely accepted traction structural stress or extrapolation hot-spot stress methods. The laborious efforts needed for generating weld geometry have been a major challenge for fatigue evaluation of complex structures containing many welds. In this paper, we present a user-defined fillet-weld element formulation and its numerical implementation for computing traction mesh-insensitive structural stresses. The fillet-weld element is formulated by connecting several linear four-nodes Mindlin shell elements around weld region as a user-defined element. The resulting elements can be directly used with major commercial FE codes through an available user subroutine interface. A number of well-documented fillet-welded components are then used for validating the accuracy and robustness of the developed fillet-weld elements.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"797-813"},"PeriodicalIF":3.1,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116208","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}
{"title":"Nonuniformity of Fatigue Properties of Two-Sided Electron Beam Welded Joint of Superthick Titanium Alloy","authors":"Jian Long, Lin-Jie Zhang, Yong-Qiang Liu, De-An Deng, Ming-Xiang Zhuang","doi":"10.1111/ffe.14508","DOIUrl":"https://doi.org/10.1111/ffe.14508","url":null,"abstract":"<div>\u0000 \u0000 <p>The TC4 titanium (Ti) alloy has been widely utilized in various industries such as aerospace and shipbuilding, owing to its numerous advantages. Its exceptional properties have made it a material of choice for applications requiring high performance and reliability. The total weld thickness was 140 mm, and microstructures and high-cycle fatigue properties were investigated at three different layers within the 140-mm section. Experimental results show that the overlap area at two weld roots has the highest microhardness and largest nonuniformity of the overall joints, so the area is found to have the poorest high-cycle fatigue properties. The microstructures in every layer of the weld metal of the joints were analyzed to determine the causes of the poor fatigue properties in the overlapping area at the weld roots. Significant amounts of α′ acicular microstructure are present in the weld metal of joints, while the overlap area at weld roots contains more α′ acicular microstructure with a finer size. Compared with other layers, the weld metal and base metal in Layer 2 (overlap area) have the largest microhardness gradient, where the stress concentration is more serious in the fatigue experimental process. Heat dissipation conditions was a critical factor for the inhomogeneity of microstructure and mechanical properties along the thickness direction of 140-mm double-sided electron beam welding joint. Fatigue damage (micropore) is formed at β phases in priority, and fatigue cracks propagate via series connection of micropores, indicative of transgranular ductile cracks.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"738-750"},"PeriodicalIF":3.1,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116205","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}
{"title":"Rotating Bending Fatigue of Laser Powder Bed Fused 316L Stainless Steel at Various Stress Levels: Microstructural Evaluation and Predictive Modeling","authors":"Yahya Aghayar, Alireza Behvar, Meysam Haghshenas, Mohsen Mohammadi","doi":"10.1111/ffe.14501","DOIUrl":"https://doi.org/10.1111/ffe.14501","url":null,"abstract":"<p>This research studies the effect of variable stress levels on the rotating bending fatigue (RBF) tests of 316L stainless steel fabricated by the laser powder bed fusion (LPBF) method. The mechanical properties and fatigue behavior were evaluated to ascertain the correlation between the applied stress levels and microstructural changes that occurred during the fatigue experiments. These relationships were further investigated using a classical model developed on the Python platform. The microstructural analysis demonstrated that the face-centered cubic structure was maintained throughout the application of stresses, varying from 255 to 402 MPa along with no phase changes. Nevertheless, the density of shear lines on the surface was substantially influenced by variations in stress levels as demonstrated by high-stress areas in Kernel average misorientation maps. At lower stress levels, the model analysis exhibited a higher degree of reliability, with <i>R</i><sup>2</sup> values of 96.25% at lower stress rather than 89.30% at higher stress.</p>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"783-796"},"PeriodicalIF":3.1,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://onlinelibrary.wiley.com/doi/epdf/10.1111/ffe.14501","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116207","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":2,"RegionCategory":"材料科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"Influence of the Loading Frequency on Very High Cycle Fatigue Behavior of Structural Steels","authors":"M. C. Teixeira, M. Awd, F. Walther, M. V. Pereira","doi":"10.1111/ffe.14483","DOIUrl":"https://doi.org/10.1111/ffe.14483","url":null,"abstract":"<div>\u0000 \u0000 <p>In ultrasonic fatigue tests, the VHCF properties can be determined in a reasonable time. Nevertheless, the high frequency can affect the fatigue behavior for some materials. This study investigated the fatigue capability of 34CrNiMo6 and 42CrMo4 steels, both of which find widespread applications in several mechanical components. These steels were carried out for conventional and ultrasonic fatigue tests under fully reversed testing conditions. A microplasticity strain amplitude was calculated, indicating an order of magnitude decreases around 10–100, when compared with the experimental results from low-frequency tests. Cyclic strain rates were estimated for each steel and correlated with the number of cycles to failure. A conversion constant was obtained by fitting a curve to convert the high frequency results into theoretical results at low frequency. The experimental and predicted results were evaluated. The results proved the relevance of the strain rate in frequency effect. The converted results showed strong agreement with the experimental results in low-frequency tests for the steels being studied.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"751-763"},"PeriodicalIF":3.1,"publicationDate":"2024-11-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143116204","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}
Xiaochen Zhang, Di Wu, Dongcen Hou, Jianqiu Wang, En-Hou Han
{"title":"Further Understanding of Formation Mechanisms of Micropits and Microcracks on Precision-Bearing Raceway Surfaces Under Light Load Condition","authors":"Xiaochen Zhang, Di Wu, Dongcen Hou, Jianqiu Wang, En-Hou Han","doi":"10.1111/ffe.14512","DOIUrl":"https://doi.org/10.1111/ffe.14512","url":null,"abstract":"<div>\u0000 \u0000 <p>In this study, precision-bearing samples were tested on bearing test bench under light load condition for different time periods. Surface morphologies of damage bearing samples were characterized from two aspects (2D and 3D) by various methods. Numerous micropits can be observed on surfaces of raceways and steel balls. Combing with surface damage morphologies and thickness of oil films, it can be speculated that main formation mechanism of micropits is that the surface asperities puncture the oil film firstly and then squeezed into surface in contact with it. Potential effect of vibration during the formation process of micropits had been found by repetitive experiments on RCF test machine. Micropits can form more easily under higher vibration values. Surface microcracks can initiate and propagate with the synergistic effects of repeated plastic deformation and oxide-assisted.</p>\u0000 </div>","PeriodicalId":12298,"journal":{"name":"Fatigue & Fracture of Engineering Materials & Structures","volume":"48 2","pages":"711-724"},"PeriodicalIF":3.1,"publicationDate":"2024-11-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143114888","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}