Study On Fatigue Damage Of Aluminum Alloy Based On Crack Growth

With the development of the light weight of automobile,the research on fatigue damage characteristics of aluminum alloy materials has been used as the basis for material popularization and application,which has led to in-depth research and exploration of it.In order to better match the applicability of mechanical working conditions,the damage analysis and service life evaluation have been the basis of aluminum alloy processing optimization.Based on fatigue failure,this paper studies the fatigue damage characteristics of aluminum alloy during the periodic loading process by discretizing the continuous fatigue damage process.The main research contents are as follows:(1)The mechanical properties of aluminum alloy 6061-T6 were obtained by static tensile test.Based on this,the loading test of the five stages,including 4000,8000,12000,16000 and 20000 times,was carried out,with a force value of 3600 N and the stress ratio of R= 0.1,and the mechanic characteristics for different stages were obtained.(2)X-ray computed tomography(CT)scans were used to characterize the defect at different stages and to reconstruct the defect features by AVIZO.The three-dimensional reconstruction model of each stage specimen is obtained,and the variation characteristics of the relevant parameters that characterize the damage evolution process,such as porosity and damage volume fraction are studied.(3)According to the parameters of damage evolution,the RVE model of microcosmic volume of damage evolution was established,and the elastic modulus was compared with the experiment to verify the validity of the model.The RVE model is divided into spherical defects,elliptic balls and mixed three types.The variation of elastic modulus under different defect shapes is different from that of experimental calculation.The damage model defined by the hybrid defect can reflect the actual defect characteristics,while the relative error of the elastic modulus is controlled in plus or minus 1%.(4)The surface roughness of the test pieces was tested by using the roughness tester.With the increase of the surface roughness of the model,the roughness can be used as the tendency of the damage.(5)The finite element model of RVE in ANSYS-Workbench was imported into n Code for life analysis,and the results showed that the minimum life span of the model was also the key point to limit the overall life of the model.Compared with the test results,the validity of the model is verified.