| In the automobile frame structure of aluminium alloy, it is a kind of important structure form that T-type tubular joints are in charge of connecting. It spends a large amount of manpower to the strength of this kind of joint, experiment research out of shape.Finite element simulation can economize the cost effectively such as adopting, raising the efficiency. Aluminium alloy T-type tubular joints exhibit heterogeneity of mechanical properties, it must signify some local performance before carrying on finite element simulation and can just receive more accurate result like this, it is very essential to evaluating properties of the whole joint and improving the welding craft. This text has studied a new approach for determining local material constitutive properties of welded joints in aluminum alloy. In this method, drilling the double holes in the two sides of the point to be determined in welded joints, load material bridge by an indentor until it is broken, record the response between applied load and indentor displacement. We can call this method as double holes microshear test. According to the load-displacement curve obtained experimentally from the double holes microshear test, the true stress-strain curve of local material was calculated by means of the inverse methodology of finite element computation. Thus it determine the distribution of constitutive characteristic of plastic area out of shape in heated-effect zone of aluminium alloy butt welded joint. But above-mentioned methods will carry on a large number of finite element simulation after carrying on double-holes microshear test, adjusting the yield strength σ_y and work hardening index n constantly, it should spend a large amount of manpower and materials. Seting up the finite element model tested in double-holes microshear method, and choosing to surrender the material of the stress and work hardening index differently and carry on the finite element simulation, it provides the relevant relation between the parameter out of shape of material plasticity and the load-displacement curve of experiment. In this way , the parameter out of shape of plasticity of the material directly can received according to the experimental curve of double-holes microshear test. The accuracy of this method is proved with the aluminium alloy pushing type material. According to the load-displacement curve which is tested, utilizing the relevant relation between the material properties parameter σ_y,n and the characteristic parameter τ_y,n_τ of shear stress-shear strain curve to receive the true stress-strain curve of 6063 aluminium alloy T-type sample welded joints. The determination results show that, in the dissolution zones the yield stresses are lower but the work hardening exponent are higher, and in over aging zones both the yield stresses and the work hardeningexponent are lower.The welded joints are devided into the welding seam zone,the dissolution zones, the over aging zones 6063 aluminium alloy thin wall tube with the body of a motor car are welded into T-type tubular joints and are in charge of moment experiment, adopting ABAQUS finite element software to simulate the course of deforming with tube joints under moment experiment at the same time. In the finite element model , it utilizes the above-mentioned results of study among the material models, divides the area, inputs the local mechanical properties by double-holes microshear test. The result shows that the ensurence of the strength guideline and the course of the invalidation of the strength are different under static behavior of full-width and stepped aluminium T-type tubular joints subjected to bending,in the same time, the value of ultimate load-carringcapacity is also different and it has large effect of softens to the strength of joints with the welded zone and the heat-effect zone. So the research of this paper offers the effective basis and establishes the foundation for the further collision analyse of the automobile part. |
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