Assessment Of The Local Mechanical Properties And The Damage Study For The Aluminium Alloy Welded Joints

As a result of the need for the modern automotive design to address energy savings and environmental issues, the aluminium space-frame has been used more and more widely. The welded joints were essential elements in the aluminium space-frame of automobile. It spends a large amount of manpower and money to perform the deformation, damage and destruct of the various joint experimental researches. Finite element simulation can economize effectively the cost such as adopting, raising the efficiency, plus the validation of key experiment.The micro structure and mechanical properties were nonuniform for the aluminium alloy welded joint. Before carrying on finite element simulation, it was significant to assess the local mechanical properties of welded joint for the accurate result. It was necessary that the local mechanical properties were measured accurately for the assessment of the mechanical properties of the whole welded joint and the improvement of the welded technique. The mechanical properties and deformation of the welded joint melted were nonuniform by means of the investigation of material micro structure, rigidity and strength in this paper. A new approach assessment of the local mechanical properties, which was the ball small punch test(SPT), has studied for the local material constitutive properties of welded joints of aluminum alloy. Its basic principle: the material resistance curve of local material was obtained from the rectangular slice specimen which extracted from the welded joint by means of the SPT experimentation. Combined with a revised FEM algorithm with ABAQUS computer code, The constitutive properties of the local material was indirectly obtained by the numerical model which was a special revised iterative process and worked out the true strain-stress curves for an unknown material. Although deviation of SPT was occurred, the technique was available and got an advantage over the conventional tensile test. Consequently SPT was a good method for the assessment of local material mechanical properties.The assessment of local material mechanical properties were carried out in the different area of the aluminum welded joint by SPT based applied research mentioned above. Finally the evolvement of nonuniform deformation, the initiation of damage and the propagation of cracks during the process evolution were forecasted and analyzed to the aluminum welded joint under the condition of uniaxial loading, using the data obtained from SPT. The result showed that the nonuniform deformation of TIG welding joint aluminium alloy 5A02H34 correlated with nonuniform mechanical properties and the deformation was occurred in WZ (Welding Zone) of joint for the undermatched joint. Combined with G-T-N damage model, the nonuniform deformation of TIG welding joint aluminium alloy 5A02H34 was forecasted by means of the large commercial ABAQUS computer code. The result showed that the damage mostly occurred in WZ which strength and plasticity were lower. The result was identical with the tensile experimental result. The investigation provided with the theoretic evidence and the consultable evidence for the investigated damage of the key the welded joint of the automobile components.