Critical plane method is one of the most promising approaches to predict the fatigue life when the structure is subjected to the multiaxial loading.The stress-strain status and the critical plane position for smooth s...Critical plane method is one of the most promising approaches to predict the fatigue life when the structure is subjected to the multiaxial loading.The stress-strain status and the critical plane position for smooth specimens are calculated using theoretical approaches when the loading mode is a continuous function.However,because of the existence of stress concentration and the characteristic of multiaxial non-proportion,it is difficult to calculate the stress-strain status and the critical plane position of geometric discontinuity structure by theory method.In this paper,a new numerical simulation method is proposed to determine the critical plane of geometric discontinuity structure under multiaxial loading.Firstly,the strain status of dangerous point is analyzed by finite element method.Secondly,the maximum shear strain amplitude of arbitrary plane is calculated using coordinate transformation principle.Finally,the plane which has the maximum shear strain amplitude is defined as the critical plane.The critical plane positions are analyzed when loading mode and notch parameters are different.Meanwhile,the relationship between notch depth and associated parameters on critical plane as well as that between loading amplitude and associated parameters on critical plane are given quantitatively.展开更多
The prediction of the fracture plane orientation in fatigue is a scientific topic and remains relevant for every type of material. However, in this work, we compared the orientation of the fracture plane obtained expe...The prediction of the fracture plane orientation in fatigue is a scientific topic and remains relevant for every type of material. However, in this work, we compared the orientation of the fracture plane obtained experimentally through tests on specimens under multiaxial loading with that calculated by the variance method. In the statistical approach criteria, several methods have been developed but we have presented only one method, namely the variance method using the equivalent stress. She assumes that the fracture plane orientation is the one on which the variance of the equivalent stress is maximum. Three types of equivalent stress are defined for this method [1]: normal stress, shear stress and combined normal and shear stress. The results obtained were compared with experimental results for multiaxial cyclic stress states, and it emerges that the variance method for the case of combined loading is conservative as it gives a better prediction of the fracture plane.展开更多
The ability to predict multiaxial fatigue life of Al-Alloy 7075-T6 under complex loading conditions is critical to assessing its durability under complex loading conditions,particularly in aerospace,automotive,and str...The ability to predict multiaxial fatigue life of Al-Alloy 7075-T6 under complex loading conditions is critical to assessing its durability under complex loading conditions,particularly in aerospace,automotive,and structural applications.This paper presents a physical-informed neural network(PINN)model to predict the fatigue life of Al-Alloy 7075-T6 over a variety of multiaxial stresses.The model integrates the principles of the Geometric Multiaxial Fatigue Life(GMFL)approach,which is a novel fatigue life prediction approach to estimating fatigue life by combining multiple fatigue criteria.The proposed model aims to estimate fatigue damage accumulation by the GMFL method.The proposed GMFL-PINN combines this physics-based approach with data-driven neural networks.Experimental validation demonstrates that GMFL-PINN outperforms FS,Smith–Watson–Topper(SWT)and Li–Zhang(LZH)fatigue life prediction methods which provides a reliable and scalable solution for structural health assessment and fatigue analysis.展开更多
Ising superconductivity has garnered much attention in recent years due to its extremely high in-plane upper critical field (B_(c2)).Here,we fabricated 14 multilayer Pb_(1-x)Bi_(x) (0%≤x≤40%) thin films on Si (111)-...Ising superconductivity has garnered much attention in recent years due to its extremely high in-plane upper critical field (B_(c2)).Here,we fabricated 14 multilayer Pb_(1-x)Bi_(x) (0%≤x≤40%) thin films on Si (111)-7×7 reconstructed surface by molecular beam epitaxy.Large B_(c2) beyond the Pauli limit is observed in all the Pb_(1-x)Bi_(x) films,indicating that they may exhibit characteristics of Ising superconductivity.Moreover,the introduction of Bi doping can significantly enhance and effectively tune the in-plane B_(c2) of Pb_(1-x)Bi_(x) films,which will help us better understand Ising superconductivity and provide a new platform for the development of tunable Ising superconductors.展开更多
According to the concept of critical plane, a life prediction approach forrandom multiaxial fatigue is presented. First, the critical plane under the multiaxial randomloading is determined based on the concept of the ...According to the concept of critical plane, a life prediction approach forrandom multiaxial fatigue is presented. First, the critical plane under the multiaxial randomloading is determined based on the concept of the weight-averaged maximum shear strain direction.Then the shear and normal strain histories on the determined critical plane are calculated and takenas the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, amultiaxial fatigue life prediction model including the parameters resulted from multiaxial cyclecounting is presented and applied to calculating the fatigue damage generated from each cycle.Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue predictionlife is given. The experiments under multiaxial loading blocks are used for the verification of theproposed method. The prediction has a good correction with the experimental results.展开更多
According to the critical plane principle, a unified multiaxialfatigue damage parameter is presented based on the varying behaviourof the strains on the critical plane. Both the parameters of themaximum shear strain a...According to the critical plane principle, a unified multiaxialfatigue damage parameter is presented based on the varying behaviourof the strains on the critical plane. Both the parameters of themaximum shear strain amplitude and normal strain excursion betweenadjacent turning points of the maximum shear strain on the criticalplane are considered in the multiaxial fatigue damage parme- terpresented. An equivalent strain amplitude is made with bothparameters of the maximun shear strain amplitude and normal strainexcursion by means of von Mises criterion. Thus a new multiaxialfatigue damage model is given based on the critical plane approach.展开更多
Failure analysis of railway draw-hook coupler was carried out.The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler.Draw-Hook coupler is used to c...Failure analysis of railway draw-hook coupler was carried out.The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler.Draw-Hook coupler is used to connect with the same hook coupler or automatic coupler.The influence of each connection types on the coupler strength in this study was discussed.A numerical stress analysis using FEM was performed,and many approaches including critical plane approach were carried out on fatigue life prediction of coupler under different conditions.The results of the proposed fatigue criterion and fatigue life predictions,as well as static numerical analysis,are validated with experimental results.展开更多
The fatigue damage model based on theory of damage mechanics is capable of predicting the fatigue life under multiaxial loading.Meanwhile,the application of critical plane method in the prediction of multiaxial fatigu...The fatigue damage model based on theory of damage mechanics is capable of predicting the fatigue life under multiaxial loading.Meanwhile,the application of critical plane method in the prediction of multiaxial fatigue life has made certain progress.According to the law of thermodynamics,a new damage evolution equation is developed in the present study to predict the fatigue life of geometrically discontinuous structure under tension-torsion loading based on damage mechanics and the critical plane method.The essence of this approach is tha t the st rain parame ter of the uniaxial nonlinear fatigue damage model is replaced with the equivalent strain,which consists of the releva nt parame ters of the critical plane.However,it is difficult to calculate the stress-strain status and the critical plane position of geometrically dis?continuous structure by theoretical methods because of the existence of stress concentration and the multiaxial nonproportional characteristics.Therefore,a new numerical simulation method is proposed to determine the critical plane of geometrically discontinuous structure under multiaxial loading by means of the finite element method and MATLAB software.The fatigue life of notched specimens subjected to combined bending and torsion is predicted using the proposed met hod,and the result is compared with t hose from the experimen ts and the Manson-Cfiffin law.The comparisons show that the proposed method is superior to the Manson-Coffin law and is capable of reproducing the experimental results reasonably when the geometry of the structure is complex.It completely meets the needs of engineering practice.展开更多
This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its con...This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its contact surface.Then,the contact radius between the pad and the specimen is controlled by adjusting the radius of the pit.The stress distribution and slip amplitude of the contact surface under different contact geometries are compared.The critical plane approach is used to predict the crack initiation life and to evaluate the effect of processed specimen on its fretting fatigue performance.Both crack initiation life and angle can be predicted by the critical plane approach.Ruiz parameter is used to consider the effect of contact slip.It is shown that the crack initial position is dependent on the tensile stress.For same type of model,three kinds of critical plane parameters and Ruiz method provide very similar position of crack initiation.Moreover,the improved sample is much safer than the flat-specimen.展开更多
Both wear and fatigue occur in fretting condition,and they interact with one another during the whole process.Fretting fatigue is commonly analysed without considering the effect of wear in partial slip regime,althoug...Both wear and fatigue occur in fretting condition,and they interact with one another during the whole process.Fretting fatigue is commonly analysed without considering the effect of wear in partial slip regime,although wear affects the lifetime of crack initiation.This paper investigates,for the first time,the effect of wear debris on fretting fatigue crack initiation.To investigate the effect of debris,first fretting wear characteristics in partial slip regime are analysed for loading conditions.Then,the effect of wear on fretting fatigue crack initiation is investigated using Ruiz parameters and critical plane methods without considering the debris effect.Through the results,we can see that loading conditions affect the wear profiles in different ways.Moreover,wear has a significant effect on the fatigue in partial slip regime without considering debris especially on the crack initiation location.Finally,considering wear debris in the analysis,its effect on critical plane parameters is investigated.It is found that by considering the wear debris effect,the frtting fatigue crack initiation location is shifted towards the trailing edge.The predictions of both crack initiation location and lifetime show a good agreement with the experimental data.展开更多
基金the National Natural Science Foundation of China(Nos.51778273 and 51605212)the Universities and Colleges Innovation Ability Improvement Project of Gansu(No.2019A-225)
文摘Critical plane method is one of the most promising approaches to predict the fatigue life when the structure is subjected to the multiaxial loading.The stress-strain status and the critical plane position for smooth specimens are calculated using theoretical approaches when the loading mode is a continuous function.However,because of the existence of stress concentration and the characteristic of multiaxial non-proportion,it is difficult to calculate the stress-strain status and the critical plane position of geometric discontinuity structure by theory method.In this paper,a new numerical simulation method is proposed to determine the critical plane of geometric discontinuity structure under multiaxial loading.Firstly,the strain status of dangerous point is analyzed by finite element method.Secondly,the maximum shear strain amplitude of arbitrary plane is calculated using coordinate transformation principle.Finally,the plane which has the maximum shear strain amplitude is defined as the critical plane.The critical plane positions are analyzed when loading mode and notch parameters are different.Meanwhile,the relationship between notch depth and associated parameters on critical plane as well as that between loading amplitude and associated parameters on critical plane are given quantitatively.
文摘The prediction of the fracture plane orientation in fatigue is a scientific topic and remains relevant for every type of material. However, in this work, we compared the orientation of the fracture plane obtained experimentally through tests on specimens under multiaxial loading with that calculated by the variance method. In the statistical approach criteria, several methods have been developed but we have presented only one method, namely the variance method using the equivalent stress. She assumes that the fracture plane orientation is the one on which the variance of the equivalent stress is maximum. Three types of equivalent stress are defined for this method [1]: normal stress, shear stress and combined normal and shear stress. The results obtained were compared with experimental results for multiaxial cyclic stress states, and it emerges that the variance method for the case of combined loading is conservative as it gives a better prediction of the fracture plane.
文摘The ability to predict multiaxial fatigue life of Al-Alloy 7075-T6 under complex loading conditions is critical to assessing its durability under complex loading conditions,particularly in aerospace,automotive,and structural applications.This paper presents a physical-informed neural network(PINN)model to predict the fatigue life of Al-Alloy 7075-T6 over a variety of multiaxial stresses.The model integrates the principles of the Geometric Multiaxial Fatigue Life(GMFL)approach,which is a novel fatigue life prediction approach to estimating fatigue life by combining multiple fatigue criteria.The proposed model aims to estimate fatigue damage accumulation by the GMFL method.The proposed GMFL-PINN combines this physics-based approach with data-driven neural networks.Experimental validation demonstrates that GMFL-PINN outperforms FS,Smith–Watson–Topper(SWT)and Li–Zhang(LZH)fatigue life prediction methods which provides a reliable and scalable solution for structural health assessment and fatigue analysis.
基金supported by the National Natural Science Foundation of China (Grant Nos. 12374196, 92165201, and 11634011)the Innovation Program for Quantum Science and Technology (Grant No. 2021ZD0302800)+2 种基金the Chinese Academy of Sciences Project for Young Scientists in Basic Research (Grant No. YSBR-046)the Fundamental Research Funds for the Central Universities (Grant Nos. WK3510000006 and WK3430000003)Anhui Initiative in Quantum Information Technologies (Grant No. AHY170000)。
文摘Ising superconductivity has garnered much attention in recent years due to its extremely high in-plane upper critical field (B_(c2)).Here,we fabricated 14 multilayer Pb_(1-x)Bi_(x) (0%≤x≤40%) thin films on Si (111)-7×7 reconstructed surface by molecular beam epitaxy.Large B_(c2) beyond the Pauli limit is observed in all the Pb_(1-x)Bi_(x) films,indicating that they may exhibit characteristics of Ising superconductivity.Moreover,the introduction of Bi doping can significantly enhance and effectively tune the in-plane B_(c2) of Pb_(1-x)Bi_(x) films,which will help us better understand Ising superconductivity and provide a new platform for the development of tunable Ising superconductors.
基金This project is supported by National Natural Science Foundation of China (No.59775030).
文摘According to the concept of critical plane, a life prediction approach forrandom multiaxial fatigue is presented. First, the critical plane under the multiaxial randomloading is determined based on the concept of the weight-averaged maximum shear strain direction.Then the shear and normal strain histories on the determined critical plane are calculated and takenas the subject of multiaxial load simplifying and multiaxial cycle counting. Furthermore, amultiaxial fatigue life prediction model including the parameters resulted from multiaxial cyclecounting is presented and applied to calculating the fatigue damage generated from each cycle.Finally, the cumulative damage is added up using Miner's linear rule, and the fatigue predictionlife is given. The experiments under multiaxial loading blocks are used for the verification of theproposed method. The prediction has a good correction with the experimental results.
基金the National Doctoral Foundation of ChinaNational Natural Science Foundation of China
文摘According to the critical plane principle, a unified multiaxialfatigue damage parameter is presented based on the varying behaviourof the strains on the critical plane. Both the parameters of themaximum shear strain amplitude and normal strain excursion betweenadjacent turning points of the maximum shear strain on the criticalplane are considered in the multiaxial fatigue damage parme- terpresented. An equivalent strain amplitude is made with bothparameters of the maximun shear strain amplitude and normal strainexcursion by means of von Mises criterion. Thus a new multiaxialfatigue damage model is given based on the critical plane approach.
文摘Failure analysis of railway draw-hook coupler was carried out.The nondestructive testing method was undertaken on some failed couplers in service to designate critical areas of a coupler.Draw-Hook coupler is used to connect with the same hook coupler or automatic coupler.The influence of each connection types on the coupler strength in this study was discussed.A numerical stress analysis using FEM was performed,and many approaches including critical plane approach were carried out on fatigue life prediction of coupler under different conditions.The results of the proposed fatigue criterion and fatigue life predictions,as well as static numerical analysis,are validated with experimental results.
基金the National Natural Science Foundation of China(Grant No.51605212)the Natural Science Foundation of Gansu Province(Grant No.17JR5RA122)the Project of Hongliu First-class Disciplines Development Program of Lanzhou University of Technology.
文摘The fatigue damage model based on theory of damage mechanics is capable of predicting the fatigue life under multiaxial loading.Meanwhile,the application of critical plane method in the prediction of multiaxial fatigue life has made certain progress.According to the law of thermodynamics,a new damage evolution equation is developed in the present study to predict the fatigue life of geometrically discontinuous structure under tension-torsion loading based on damage mechanics and the critical plane method.The essence of this approach is tha t the st rain parame ter of the uniaxial nonlinear fatigue damage model is replaced with the equivalent strain,which consists of the releva nt parame ters of the critical plane.However,it is difficult to calculate the stress-strain status and the critical plane position of geometrically dis?continuous structure by theoretical methods because of the existence of stress concentration and the multiaxial nonproportional characteristics.Therefore,a new numerical simulation method is proposed to determine the critical plane of geometrically discontinuous structure under multiaxial loading by means of the finite element method and MATLAB software.The fatigue life of notched specimens subjected to combined bending and torsion is predicted using the proposed met hod,and the result is compared with t hose from the experimen ts and the Manson-Cfiffin law.The comparisons show that the proposed method is superior to the Manson-Coffin law and is capable of reproducing the experimental results reasonably when the geometry of the structure is complex.It completely meets the needs of engineering practice.
基金the National Natural Science Foundation of China(Grant Nos.11372138 and 11572157)the Research Foundation-Flanders(FWO),The Luxembourg National Research Fund(FNR)and Slovenian Research Agency(ARRS)in the framework of the FWO Lead Agency project:G018916N‘Multi-analysis of fretting fatigue using physical and virtual experiments.'The authors would like to acknowledge thefinancial support of the grants from the China Scholarship Council(201806840127)。
文摘This paper analyses the effect of surface treatment on fretting fatigue specimen by numerical simulations using Finite Element Analysis.The processed specimen refers to artificially adding a cylindrical pit to its contact surface.Then,the contact radius between the pad and the specimen is controlled by adjusting the radius of the pit.The stress distribution and slip amplitude of the contact surface under different contact geometries are compared.The critical plane approach is used to predict the crack initiation life and to evaluate the effect of processed specimen on its fretting fatigue performance.Both crack initiation life and angle can be predicted by the critical plane approach.Ruiz parameter is used to consider the effect of contact slip.It is shown that the crack initial position is dependent on the tensile stress.For same type of model,three kinds of critical plane parameters and Ruiz method provide very similar position of crack initiation.Moreover,the improved sample is much safer than the flat-specimen.
文摘Both wear and fatigue occur in fretting condition,and they interact with one another during the whole process.Fretting fatigue is commonly analysed without considering the effect of wear in partial slip regime,although wear affects the lifetime of crack initiation.This paper investigates,for the first time,the effect of wear debris on fretting fatigue crack initiation.To investigate the effect of debris,first fretting wear characteristics in partial slip regime are analysed for loading conditions.Then,the effect of wear on fretting fatigue crack initiation is investigated using Ruiz parameters and critical plane methods without considering the debris effect.Through the results,we can see that loading conditions affect the wear profiles in different ways.Moreover,wear has a significant effect on the fatigue in partial slip regime without considering debris especially on the crack initiation location.Finally,considering wear debris in the analysis,its effect on critical plane parameters is investigated.It is found that by considering the wear debris effect,the frtting fatigue crack initiation location is shifted towards the trailing edge.The predictions of both crack initiation location and lifetime show a good agreement with the experimental data.
