Pub Date : 2024-10-19DOI: 10.1016/j.ijfatigue.2024.108659
Pujono , M.N. Ilman , Kusmono , M.R. Muslih , T.H. Priyanto , R. Apriansyah , A. Isnaini
In this research, local mechanical tensioning treatment in the form of in-situ rolling tensioning (ISRT) was applied during friction stir welding of AA2024-T3 sheets. Two types of roller configurations were used. First, a single roller located at the rear of the tool which passed over the weld region and secondly, two rollers were located next to the weld zone symmetrically. Subsequently, several experiments comprising residual stress, distortion and fatigue crack growth (FCG) measurements were carried out combined with microstructure, texture, hardness and tensile tests. Results demonstrated that a single roller ISRT effectively diminished residual stress in the nugget zone (NZ) from + 11.7 MPa to −45.3 MPa accompanied by better weld FCG resistance. Apart from residual stress reduction, the improved weld fatigue performance was likely correlated with the modifications of weld microstructure and texture due to rolling tensioning.
{"title":"Diminishing residual stress and distortion by in-situ rolling tensioning to increase fatigue performance of friction stir welded AA2024-T3 joints","authors":"Pujono , M.N. Ilman , Kusmono , M.R. Muslih , T.H. Priyanto , R. Apriansyah , A. Isnaini","doi":"10.1016/j.ijfatigue.2024.108659","DOIUrl":"10.1016/j.ijfatigue.2024.108659","url":null,"abstract":"<div><div>In this research, local mechanical tensioning treatment in the form of in-situ rolling tensioning (ISRT) was applied during friction stir welding of AA2024-T3 sheets. Two types of roller configurations were used. First, a single roller located at the rear of the tool which passed over the weld region and secondly, two rollers were located next to the weld zone symmetrically. Subsequently, several experiments comprising residual stress, distortion and fatigue crack growth (FCG) measurements were carried out combined with microstructure, texture, hardness and tensile tests. Results demonstrated that a single roller ISRT effectively diminished residual stress in the nugget zone (NZ) from + 11.7 MPa to −45.3 MPa accompanied by better weld FCG resistance. Apart from residual stress reduction, the improved weld fatigue performance was likely correlated with the modifications of weld microstructure and texture due to rolling tensioning.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108659"},"PeriodicalIF":5.7,"publicationDate":"2024-10-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527881","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 : 2024-10-18DOI: 10.1016/j.ijfatigue.2024.108655
Ningyu Zhang, Wenqi Liu, Tao Shi, Jingyu Sun, Guian Qian
The porosity of the material produced by additive manufacturing technology gives rise to a notable dispersion of the crack initiation life in the very-high-cycle fatigue regime. The crack initiation life in the very high cycle fatigue regime can be divided into the initial crack initiation life and early microcrack growth life. This paper proposed a model considering the effect of pore morphology and location to predict the initial crack initiation life. The average local stress in a grain near the pore is modified by considering the relationship between pore roundness, inclination, position, and stress concentration factor. The growth life of early microcrack is determined by integrating empirical formulas based on dislocation theory. Subsequently, the probability distribution of crack initiation life is obtained, which is in good agreement with the experimental results. The competition factor is proposed to quantitatively evaluate the tendency of crack initiation from the surface or the interior, taking into account the influence of local average stress and grain size. The predicted load corresponding to the shift in crack initiation position is in accordance with the experimental results.
{"title":"Pore-based prediction of crack initiation life in very-high-cycle fatigue","authors":"Ningyu Zhang, Wenqi Liu, Tao Shi, Jingyu Sun, Guian Qian","doi":"10.1016/j.ijfatigue.2024.108655","DOIUrl":"10.1016/j.ijfatigue.2024.108655","url":null,"abstract":"<div><div>The porosity of the material produced by additive manufacturing technology gives rise to a notable dispersion of the crack initiation life in the very-high-cycle fatigue regime. The crack initiation life in the very high cycle fatigue regime can be divided into the initial crack initiation life and early microcrack growth life. This paper proposed a model considering the effect of pore morphology and location to predict the initial crack initiation life. The average local stress in a grain near the pore is modified by considering the relationship between pore roundness, inclination, position, and stress concentration factor. The growth life of early microcrack is determined by integrating empirical formulas based on dislocation theory. Subsequently, the probability distribution of crack initiation life is obtained, which is in good agreement with the experimental results. The competition factor is proposed to quantitatively evaluate the tendency of crack initiation from the surface or the interior, taking into account the influence of local average stress and grain size. The predicted load corresponding to the shift in crack initiation position is in accordance with the experimental results.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108655"},"PeriodicalIF":5.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527873","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 : 2024-10-18DOI: 10.1016/j.ijfatigue.2024.108656
Sangyeop Kim , Yong Hwi Kim , Taeksang Lee , Moon Ki Kim
The Small Punch Test (SPT) is a method of evaluating the mechanical properties of metallic materials that overcomes the limitations of the Uniaxial Test (UT), a traditional method of testing. Unlike UT, which provides strain data for each stress, SPT provides displacement data for each load. Therefore, SPT must be converted to UT to evaluate the mechanical properties of materials. However, SPT and UT employ disparate loading mechanisms. The difficulty in converting SPT to UT, which stems from the disparate loading mechanisms, has thus far limited SPT to mechanical property evaluation areas such as tensile and creep. This paper, therefore, aims to extend SPT to the fatigue domain, which is currently limited to the tensile and creep domains. The fatigue properties of metallic materials were evaluated based on the Finite Element Method (FEM) for the Small Punch Fatigue Test (SPFT). Moreover, the fatigue properties derived from the FEM for SPFT were converted to Uniaxial Fatigue Test (UFT) by employing the equivalent equation. Finally, an S-N curve was constructed based on SPFT and was validated by comparison with the same curve constructed based on UFT.
{"title":"Development of the small punch fatigue test method based on the finite element method","authors":"Sangyeop Kim , Yong Hwi Kim , Taeksang Lee , Moon Ki Kim","doi":"10.1016/j.ijfatigue.2024.108656","DOIUrl":"10.1016/j.ijfatigue.2024.108656","url":null,"abstract":"<div><div>The Small Punch Test (SPT) is a method of evaluating the mechanical properties of metallic materials that overcomes the limitations of the Uniaxial Test (UT), a traditional method of testing. Unlike UT, which provides strain data for each stress, SPT provides displacement data for each load. Therefore, SPT must be converted to UT to evaluate the mechanical properties of materials. However, SPT and UT employ disparate loading mechanisms. The difficulty in converting SPT to UT, which stems from the disparate loading mechanisms, has thus far limited SPT to mechanical property evaluation areas such as tensile and creep. This paper, therefore, aims to extend SPT to the fatigue domain, which is currently limited to the tensile and creep domains. The fatigue properties of metallic materials were evaluated based on the Finite Element Method (FEM) for the Small Punch Fatigue Test (SPFT). Moreover, the fatigue properties derived from the FEM for SPFT were converted to Uniaxial Fatigue Test (UFT) by employing the equivalent equation. Finally, an S-N curve was constructed based on SPFT and was validated by comparison with the same curve constructed based on UFT.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108656"},"PeriodicalIF":5.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527896","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 : 2024-10-18DOI: 10.1016/j.ijfatigue.2024.108657
Chengshuang Zhou , Changcheng Jiang , Yan Jin , Hongbin Zhou , Qingxiong Qiu , Yuqing Hu , Yuchen Xie , Lin Zhang , Jinyang Zheng
In this study, the hydrogen embrittlement behavior of quenched pipeline steel tempered at 550 °C to 650 °C in a high-pressure hydrogen environment was analyzed. Hydrogen permeation tests and microstructural analyses indicated that the dislocation density of the steel decreases with increasing tempering temperature, while precipitates gradually nucleate and grow. These hydrogen traps interact with hydrogen atoms, resulting in significantly higher diffusible hydrogen content in steel tempered at 550 °C compared to that tempered at 600 °C and 650 °C. Fatigue crack growth (FCG) test results show that steel tempered at 600 °C and 650 °C exhibits significantly better hydrogen embrittlement resistance than steel tempered at 550 °C. This is primarily due to the combined effect of the high hydrogen concentration, high dislocation density and low nano carbide content in the steel tempered at 550 °C, which inhibits dislocation slip and emission, leading to high crack tip stress and rapid crack propagation. In contrast, the low dislocation density and and dispersed nano carbides in steel tempered at 600 °C and 650 °C facilitate some dislocation slip and emission, result in crack tip stress relaxation and reduced crack propagation rate. Properly controlling the initial dislocation density and increasing the density of irreversible hydrogen traps can enhance the strength of materials while improving their resistance to hydrogen embrittlement.
本研究分析了在高压氢环境下于 550 °C 至 650 °C 回火的淬火管线钢的氢脆行为。氢渗透试验和微观结构分析表明，钢的位错密度随着回火温度的升高而降低，同时析出物逐渐成核并长大。这些氢阱与氢原子相互作用，导致 550 °C 回火钢中的扩散氢含量明显高于 600 °C 和 650 °C 回火钢。疲劳裂纹增长（FCG）测试结果表明，600 ℃ 和 650 ℃ 回火钢的抗氢脆性能明显优于 550 ℃ 回火钢。这主要是由于在 550 ℃ 回火的钢中氢浓度高、位错密度高、纳米碳化物含量低，这些因素共同作用，抑制了位错的滑移和释放，导致裂纹尖端应力高，裂纹扩展速度快。相反，在 600 ℃ 和 650 ℃ 回火的钢中，低位错密度和分散的纳米碳化物有利于位错滑移和释放，导致裂纹尖端应力松弛，降低了裂纹扩展速度。适当控制初始位错密度和增加不可逆氢阱密度可提高材料强度，同时改善其抗氢脆性能。
{"title":"The regulation of dislocation and precipitated phase improving hydrogen embrittlement resistance of pipeline steel in high pressure hydrogen environment","authors":"Chengshuang Zhou , Changcheng Jiang , Yan Jin , Hongbin Zhou , Qingxiong Qiu , Yuqing Hu , Yuchen Xie , Lin Zhang , Jinyang Zheng","doi":"10.1016/j.ijfatigue.2024.108657","DOIUrl":"10.1016/j.ijfatigue.2024.108657","url":null,"abstract":"<div><div>In this study, the hydrogen embrittlement behavior of quenched pipeline steel tempered at 550 °C to 650 °C in a high-pressure hydrogen environment was analyzed. Hydrogen permeation tests and microstructural analyses indicated that the dislocation density of the steel decreases with increasing tempering temperature, while precipitates gradually nucleate and grow. These hydrogen traps interact with hydrogen atoms, resulting in significantly higher diffusible hydrogen content in steel tempered at 550 °C compared to that tempered at 600 °C and 650 °C. Fatigue crack growth (FCG) test results show that steel tempered at 600 °C and 650 °C exhibits significantly better hydrogen embrittlement resistance than steel tempered at 550 °C. This is primarily due to the combined effect of the high hydrogen concentration, high dislocation density and low nano carbide content in the steel tempered at 550 °C, which inhibits dislocation slip and emission, leading to high crack tip stress and rapid crack propagation. In contrast, the low dislocation density and and dispersed nano carbides in steel tempered at 600 °C and 650 °C facilitate some dislocation slip and emission, result in crack tip stress relaxation and reduced crack propagation rate. Properly controlling the initial dislocation density and increasing the density of irreversible hydrogen traps can enhance the strength of materials while improving their resistance to hydrogen embrittlement.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108657"},"PeriodicalIF":5.7,"publicationDate":"2024-10-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527884","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 : 2024-10-16DOI: 10.1016/j.ijfatigue.2024.108642
Paul Dario Toasa Caiza , Daiki Shiozawa , Yuya Murao , Thomas Ummenhofer , Takahide Sakagami
The crack growth monitoring is an important task for the maintenance policies of steel structures subjected to cyclic loading, such as bridges, cranes, off shore facilities and wind energy towers. A reliable crack detection method allows to survey properly the crack initiation and growth in responsive details of these structures, so that, they can be repaired or restored in time in order to avoid services interruption, accidents or structural collapses. In this paper, a crack detection system, which is based on inductive thermography is applied to survey the crack growth on a SM490 steel welded specimen subjected to cyclic loading. The required thermal excitation of this system is based on the generation of eddy currents, which cause a temperature increase on the crack tips. This temperature rise can be observed and recorded by using an infrared camera. Afterwards, the crack tip and growth are established by analysing the infrared (IR) images. The mentioned system allows to detect cracks on steel structures in real time and in situ, characteristics that represent the efficiency and the potential of this method in the field of NDT.
{"title":"Monitoring of crack length growth on welded specimens by applying square wave inductive thermography","authors":"Paul Dario Toasa Caiza , Daiki Shiozawa , Yuya Murao , Thomas Ummenhofer , Takahide Sakagami","doi":"10.1016/j.ijfatigue.2024.108642","DOIUrl":"10.1016/j.ijfatigue.2024.108642","url":null,"abstract":"<div><div>The crack growth monitoring is an important task for the maintenance policies of steel structures subjected to cyclic loading, such as bridges, cranes, off shore facilities and wind energy towers. A reliable crack detection method allows to survey properly the crack initiation and growth in responsive details of these structures, so that, they can be repaired or restored in time in order to avoid services interruption, accidents or structural collapses. In this paper, a crack detection system, which is based on inductive thermography is applied to survey the crack growth on a SM490 steel welded specimen subjected to cyclic loading. The required thermal excitation of this system is based on the generation of eddy currents, which cause a temperature increase on the crack tips. This temperature rise can be observed and recorded by using an infrared camera. Afterwards, the crack tip and growth are established by analysing the infrared (IR) images. The mentioned system allows to detect cracks on steel structures in real time and <em>in situ</em>, characteristics that represent the efficiency and the potential of this method in the field of NDT.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108642"},"PeriodicalIF":5.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527876","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}
Pub Date : 2024-10-16DOI: 10.1016/j.ijfatigue.2024.108647
Xi Deng , Shun-Peng Zhu , Lanyi Wang , Changqi Luo , Sicheng Fu , Qingyuan Wang
Establishing a unified fatigue life prediction model and quantifying the uncertainty in the mechanical behavior of materials are critical to ensure the structural integrity and equipment performance. For the commonly-used strain-based fatigue methods, existing estimation methods exhibit inevitable deviations, while data-driven methods have shown poor extrapolation ability and interpretability. Therefore, this paper aims to develop a probabilistic framework for strain-based fatigue life prediction and uncertainty quantification (UQ) to provide an indication for fatigue design/assessment using interpretable machine learning (ML) techniques. Based on Shapley additive explanations (SHAP) and symbolic regression (SR), interpretable prediction models with concise expressions and outstanding prediction performance are established and optimized according to the priori physical knowledge. Moreover, accounting for the material variability, the probabilistic assessment with UQ excellently validates the prediction model, and quantifies the variability of ε-N curves. The proposed framework provides a valuable reference and shows promising prospects in fatigue design for engineering components.
{"title":"Probabilistic framework for strain-based fatigue life prediction and uncertainty quantification using interpretable machine learning","authors":"Xi Deng , Shun-Peng Zhu , Lanyi Wang , Changqi Luo , Sicheng Fu , Qingyuan Wang","doi":"10.1016/j.ijfatigue.2024.108647","DOIUrl":"10.1016/j.ijfatigue.2024.108647","url":null,"abstract":"<div><div>Establishing a unified fatigue life prediction model and quantifying the uncertainty in the mechanical behavior of materials are critical to ensure the structural integrity and equipment performance. For the commonly-used strain-based fatigue methods, existing estimation methods exhibit inevitable deviations, while data-driven methods have shown poor extrapolation ability and interpretability. Therefore, this paper aims to develop a probabilistic framework for strain-based fatigue life prediction and uncertainty quantification (UQ) to provide an indication for fatigue design/assessment using interpretable machine learning (ML) techniques. Based on Shapley additive explanations (SHAP) and symbolic regression (SR), interpretable prediction models with concise expressions and outstanding prediction performance are established and optimized according to the priori physical knowledge. Moreover, accounting for the material variability, the probabilistic assessment with UQ excellently validates the prediction model, and quantifies the variability of ε-N curves. The proposed framework provides a valuable reference and shows promising prospects in fatigue design for engineering components.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108647"},"PeriodicalIF":5.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527878","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 : 2024-10-16DOI: 10.1016/j.ijfatigue.2024.108653
C. Boursier Niutta, A. Tridello, D.S. Paolino
In the present work, the feasibility of axial ultrasonic tests for exploring the fully reversed fatigue response of composite materials even in the Very High Cycle Fatigue (VHCF) regime is proved. VHCF tests are run on hourglass specimens made of twill 2x2 carbon woven fabric impregnated with epoxy resin with stacking sequences [0]8 and [0/90/+45/-45]s and designed through Finite Element (FE) modal analysis. The stress distribution within the specimen and the absence of buckling are first determined through an extensive strain gage campaign, which has validated the FE model. As the temperature is a main concern in ultrasonic tests, the temperature increment within the composite specimen is investigated by means of an embedded fiber optic sensor and controlled during the tests with an infrared sensor. With the proposed experimental setup, fully reversed ultrasonic tests have been carried out up to 109 cycles and the failure of the two investigated specimen types has been analyzed by comparing the failure origin location in relation to the stress distributions.
{"title":"Ultrasonic fully reversed axial tests for exploring the very high cycle fatigue of composite materials","authors":"C. Boursier Niutta, A. Tridello, D.S. Paolino","doi":"10.1016/j.ijfatigue.2024.108653","DOIUrl":"10.1016/j.ijfatigue.2024.108653","url":null,"abstract":"<div><div>In the present work, the feasibility of axial ultrasonic tests for exploring the fully reversed fatigue response of composite materials even in the Very High Cycle Fatigue (VHCF) regime is proved. VHCF tests are run on hourglass specimens made of twill 2x2 carbon woven fabric impregnated with epoxy resin with stacking sequences [0]<sub>8</sub> and [0/90/+45/-45]<sub>s</sub> and designed through Finite Element (FE) modal analysis. The stress distribution within the specimen and the absence of buckling are first determined through an extensive strain gage campaign, which has validated the FE model. As the temperature is a main concern in ultrasonic tests, the temperature increment within the composite specimen is investigated by means of an embedded fiber optic sensor and controlled during the tests with an infrared sensor. With the proposed experimental setup, fully reversed ultrasonic tests have been carried out up to 10<sup>9</sup> cycles and the failure of the two investigated specimen types has been analyzed by comparing the failure origin location in relation to the stress distributions.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108653"},"PeriodicalIF":5.7,"publicationDate":"2024-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142527875","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 : 2024-10-14DOI: 10.1016/j.ijfatigue.2024.108652
Michael Fitzka , Gabriel Stadler , Bernd M. Schönbauer , Gerald Pinter , Herwig Mayer
The fatigue properties of 14 wt-% short glass fiber reinforced polyetheretherketone (PEEK–GF14) have been investigated in the high and very high cycle fatigue (VHCF) regime. Experiments were performed at a load ratio of –1 with servohydraulic and electrodynamic equipment at cycling frequency 10–20 Hz, and with ultrasonic equipment at 19 kHz. A new specimen geometry has been developed that allows ultrasonic tests up to high stress amplitudes. The same specimen shape was used in both testing series to exclude size effects, which enabled to focus on the influence of cycling frequency and testing technique. Ultrasonic fatigue testing with intermittent loading served to avoid heating of specimens. The S-N curves measured at 10–20 Hz and 19 kHz show a similar slope exponent (i.e., 10 % deviation). Mean S-N curve determined with ultrasonic equipment is shifted to slightly lower stress amplitudes, which may be attributed to statistical scatter. PEEK–GF14 does not show a fatigue limit and failures still occurred above 109 cycles. The VHCF strength of PEEK-GF14 is approximately two times higher compared with unreinforced PEEK. Fractographic investigations revealed fiber fracture and, less frequently, fiber pull-out.
{"title":"Very high cycle fatigue properties of short glass fiber reinforced polyetheretherketone (PEEK)","authors":"Michael Fitzka , Gabriel Stadler , Bernd M. Schönbauer , Gerald Pinter , Herwig Mayer","doi":"10.1016/j.ijfatigue.2024.108652","DOIUrl":"10.1016/j.ijfatigue.2024.108652","url":null,"abstract":"<div><div>The fatigue properties of 14 wt-% short glass fiber reinforced polyetheretherketone (PEEK–GF14) have been investigated in the high and very high cycle fatigue (VHCF) regime. Experiments were performed at a load ratio of –1 with servohydraulic and electrodynamic equipment at cycling frequency 10–20 Hz, and with ultrasonic equipment at 19 kHz. A new specimen geometry has been developed that allows ultrasonic tests up to high stress amplitudes. The same specimen shape was used in both testing series to exclude size effects, which enabled to focus on the influence of cycling frequency and testing technique. Ultrasonic fatigue testing with intermittent loading served to avoid heating of specimens. The <em>S-N</em> curves measured at 10–20 Hz and 19 kHz show a similar slope exponent (i.e., 10 % deviation). Mean <em>S-N</em> curve determined with ultrasonic equipment is shifted to slightly lower stress amplitudes, which may be attributed to statistical scatter. PEEK–GF14 does not show a fatigue limit and failures still occurred above 10<sup>9</sup> cycles. The VHCF strength of PEEK-GF14 is approximately two times higher compared with unreinforced PEEK. Fractographic investigations revealed fiber fracture and, less frequently, fiber pull-out.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108652"},"PeriodicalIF":5.7,"publicationDate":"2024-10-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445266","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}
Pub Date : 2024-10-13DOI: 10.1016/j.ijfatigue.2024.108648
Dianyin Hu , Miaodong Zhao , Jinchao Pan , Rusong Chen , Juncai Zhang , Yang Gao , Rongqiao Wang
The mechanism behind why internal defects are less competitive than surface roughness in low cycle fatigue (LCF) failure is still an issue for inclusion-containing powder metallurgy (PM) superalloys. Differentiating the differences in applied energy and fatigue resistance at various failure sites is crucial to addressing this issue. This study first captures the dependence of failure site on applied loading from the fractographic observations to quantify the characteristics such as surface roughness, internal defects, and sub-surface facets. Subsequently, an LCF lifetime model is developed based on fracture mechanics principles, considering the difference in applied energy and cracking energy requirements due to underconstraint degree at different sites. A representative volume element (RVE) with similar grain characteristic is then established, and different boundary conditions are applied to describe the energy differences around internal and surface. By comparing the energy at different failure sites, the model predicts the tendency of failure sites under varying loading conditions. The developed LCF lifetime model distinguishes energy input and fatigue resistance differences at surface, sub-surface, and interior of the specimen, which reduces the lifetime prediction error from a scatter band of 9 times to within 3 times.
{"title":"A novel LCF lifetime model for PM superalloys considering crack energy differences induced by surface underconstraint","authors":"Dianyin Hu , Miaodong Zhao , Jinchao Pan , Rusong Chen , Juncai Zhang , Yang Gao , Rongqiao Wang","doi":"10.1016/j.ijfatigue.2024.108648","DOIUrl":"10.1016/j.ijfatigue.2024.108648","url":null,"abstract":"<div><div>The mechanism behind why internal defects are less competitive than surface roughness in low cycle fatigue (LCF) failure is still an issue for inclusion-containing powder metallurgy (PM) superalloys. Differentiating the differences in applied energy and fatigue resistance at various failure sites is crucial to addressing this issue. This study first captures the dependence of failure site on applied loading from the fractographic observations to quantify the characteristics such as surface roughness, internal defects, and sub-surface facets. Subsequently, an LCF lifetime model is developed based on fracture mechanics principles, considering the difference in applied energy and cracking energy requirements due to underconstraint degree at different sites. A representative volume element (RVE) with similar grain characteristic is then established, and different boundary conditions are applied to describe the energy differences around internal and surface. By comparing the energy at different failure sites, the model predicts the tendency of failure sites under varying loading conditions. The developed LCF lifetime model distinguishes energy input and fatigue resistance differences at surface, sub-surface, and interior of the specimen, which reduces the lifetime prediction error from a scatter band of 9 times to within 3 times.</div></div>","PeriodicalId":14112,"journal":{"name":"International Journal of Fatigue","volume":"190 ","pages":"Article 108648"},"PeriodicalIF":5.7,"publicationDate":"2024-10-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142445269","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 : 2024-10-13DOI: 10.1016/j.ijfatigue.2024.108650
Liang Han , Xiaofan He , Yu Ning , Yanjun Zhang , Yan Zhou
An aircraft structural risk assessment method based on fatigue damage diagnosis and prognosis has been developed, considering fatigue crack propagation. The process is divided into three stages: initial crack diagnosis, crack diagnosis, and prediction, utilizing Monte Carlo simulation. Using 2024 aluminum alloy specimens with central holes, the study indicates that in the initial crack diagnosis stage, an inspection standard with a Single Flight Probability of Failure (SFPOF) less than 10-7 and a threshold method enhances structural fatigue crack diagnosis. In the crack diagnosis and prediction stages, iterative updates using Gaussian Process Regression (GPR) within a Dynamic Bayesian Network (DBN) improve crack propagation prediction and risk assessment accuracy. The diagnostic interval significantly impacts SFPOF, with an optimized interval balancing accuracy and computation time. Simplified and precise K value calculation methods enhance efficiency and accuracy. The method reduces costs and improves risk assessment accuracy, providing new insights for SPHM-based aircraft structural risk assessment.
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