Research On Fatigue Propagation And Remaining Life Of Mixed-Mode Cracks Under Sliding Friction

Fatigue cracks are inevitable in the actual engineering structure.Fatigue fracture is an important cause of mechanical component failure,which poses a great threat to human life and property safety.2024 aluminum alloy has a wide range of applications in many fields,especially in the aerospace industry.Based on the important influence of fatigue crack on the life of mechanical components and the wide application of 2024 aluminum alloy,the fatigue crack propagation law of 2024 aluminum alloy with initial crack under the combined action of sliding friction and tensile stress is studied.The life prediction and reliability of mechanical components are studied.The optimization assessment has important guiding significance.Based on the theory of linear elastic fracture mechanics and extended finite element method,the fatigue crack propagation model of 2024 aluminum alloy specimen with initial crack under the combined action of sliding friction and tensile stress is taken as the research object,considering the initial crack length a0,tensile stress ?,The factors affecting the normal load P and the friction factor fs are studied by the combination of test and simulation.The main research work is as follows.Firstly,the ABAQUS finite element software is used to establish the fatigue crack propagation model under sliding friction,and the crack propagation process under the combined action of sliding friction and tensile stress is simulated.It is found that the crack propagation direction is deflected and no longer expands along the initial crack direction.Considering the factors such as initial crack length a0,tensile stress ?,normal load P and friction factor fs,the variation of stress intensity factors K? and K? during sliding process is studied.The initial crack length,tensile stress and normal are studied.The influence of factors such as load and friction factor on crack cracking angle.Secondly,the pre-fabrication of the initial crack was designed by the controlled crack prefabrication device.A tensile stress applying fixture was designed.The friction test of the 2024 aluminum alloy specimen with initial crack was carried out by HSR-2M high speed friction and wear tester.The factors affecting the crack length a0,tensile stress ? and normal load P are studied.The fatigue growth rate of the crack under the combined action of sliding friction and tensile stress is studied.The fatigue crack growth rate model under the corresponding conditions is proposed according to the Paris formula.Finally,the fatigue crack growth rate model obtained by the experiment is used to estimate the residual life of the crack-containing component,and the calculated results are compared with the life calculation results of FRANC3D analysis.The validity of the proposed residual life estimation model is verified.