Study On Staged Fatigue Damage Of Aluminum Alloy Based On Mesoscopic Analysis

Due to the wide application of aluminum alloys,its mechanical properties,especially fatigue properties,have become important criteria for product design and research and development.Therefore,analysis of the internal damage evolution law of aluminum alloys and the use of fatigue damage accumulation mechanisms to predict their fatigue life have become important research directions.Based on fatigue failure,A combination of meso-statistics and macroscopic methods was proposed,by analyzing the fatigue damage evolution law of aluminum alloy materials during cyclic loading in stages,studying the relationship between damage variables and fatigue life,The main research contents of this paper were as follows:?1?A total of 15 groups of 15 aluminum alloy specimens in three groups were subjected to fatigue loading tests for five cycles?20,000,40,000,60,000,80,000,100,000 times?from initial specimen to rupture.The industrial CT nondestructive testing technology is used to scan the fatigue test pieces.AVIZO defect analysis software was used to visualize the damage defects inside the specimen and 3D reconstruction of internal defects was performed to obtain the 3D characteristic information of the defects?defect size,defect location,defect shape,etc.?.The variation characteristics of defects in each loading stage are analyzed.?2?According to the obtained defect volume information,three levels(10^-8mm³,10^-7mm³,10^-6mm³)were graded and the defect position information of each level was recorded in the matrix.Based on the volume and position information of holes,MATLAB solver was used equivalent damage model was established with ABAQUS subroutine.?3?Based on the equivalent damage model,simulated damage Young's modulus E_ds was obtained through static tensile simulation analysis in ABAQUS,and compared with the damage Young's modulus E_dt obtained from the static tensile test.Results showed that,the maximum error is 7.263%,which indicated the effectiveness of equivalent damage model.It can better reflect the actual damage status inside the test piece status.?4?Based on the continuum damage theory,damage variable D is constructed,and the relationship between the damage variable D and the number of loadings N of the specimen at each loading stage is plotted.Based on the data measured by non-destructive testing technology,a damage model is constructed,the model damage variable D is calculated,and the residual fatigue life of the test piece or component is calculated from the relationship curve between the damage variable D and its corresponding loading number N.