| In modern industry,aluminum alloy is the most typical lightweight nonferrous metal,and the connection of different series of aluminum alloys is receiving increasing attention.It is a feasible method to weld two different aluminum alloys together by friction stir welding.The fatigue strength of lap joint of dissimilar aluminum alloy friction stir welding deserves further study.In this paper,the fatigue properties and fatigue life prediction of 7075/2A12 dissimilar aluminum alloy friction stir welding lap joints were studied by experimental testing and numerical simulation.The main content of this article is as follows:1.Conduct metallographic observation on lap joints without obvious defects on the surface to explore the microstructure distribution of the weld zone of the lap joint;Then the hardness distribution of the weld cross section of two groups of lap joints was tested.On this basis,static tensile testing and constant amplitude fatigue testing were conducted on two sets of lap joints to observe the failure forms of the lap joints.Finally,typical fracture observation was performed on two sets of fatigue failure specimens.2.Based on the data obtained from fatigue experiments,two methods are used to evaluate fatigue life.Firstly,two sets of notched stress method finite element models for lap joints are established to analyze the stress and strain in the weld zone;Then,the finite element stress results are used to predict the fatigue life;Furthermore,a local stress strain method finite element model was established to analyze the stress and strain in the weld area of two sets of lap joints,and the stress part of the Manson-Coffin(MC)damage model was modified using the Soderberg correction equation;Based on the results of finite element stress strain analysis,several damage models using the local stress strain method were used to predict the fatigue life of two failure locations.Finally,the applicability of the modified MC damage model was discussed in combination with fatigue data from other papers.3.According to the hardness test results,the stress-strain curve and fatigue performance parameters of the material can be estimated according to the hardness distribution in different areas of the weld cross section of two groups of lap joints;Then the corresponding finite element model is established to analyze the stress and strain in the weld area of the two sets of overlapping joints;Finally,several damage models of the local stress strain method are combined to predict fatigue life. |
