Inhomogeneous Material Modeling and Characterization for Aluminium Alloys and Welded Joints

Abstract

Structure functions are decided by the material properties which made of it. Material modelling and characterization are important to crashworthiness of automobile. Some times right material parameters are the key to the models which describe large deformation and failure behaviours of car body. Therefore aimed at the dynamic behaviours of aluminium alloy in certain crashing state with high strain rate, triaxiality, and damage initialization etc., large work has been done in this field including component and full scare crashing tests, which cost a lot. However, the result is not satisfied. Detail information about the crashing is hard to obtained from the experiments because of the high rate and limited time of deformation (in some specific cases, the strain rate is over 2X102). Simulation is an effective method to extend the experimental data for complete models of crashworthiness. In certain degree, the precision of simulation is depended on the authority of material parameters of modelling. Large deformation during crashing is an complicated process including various stages of elastic deformation, plastic deformation, damage initialization, evolution and failure. Strain rate, anisotropy and stress state make effects on this process. How do these factors exactly work? Still so many questions are left in this field. Smooth tension tests combined with simulation were carried out for material modelling and characterization of aluminium alloy AW 6061 (Blauel & Su, 2002; Sun, 2003). Static and dynamic response of typical aluminium alloy components is predicted successfully by using G-T-N damage mode for FEM simulation. The damage model explains the ductile fracture of the aluminium and its initiation and evolution by mechanism of growth of voids that could be applied in industry. Dynamical loading was established by using explicit solver of FEM code (Franck & Bruno, 2001). This model takes elastic flow and anisotropic into account. Thereby this could be used to predict situation of damage and fracture of materials with obvious texture deformation such as extruded aluminium alloys in circumstances of dynamic loading with large deformation. Another contribution of Frank’s research is to develop iterative algorithm which has an experiment combined with numerical simulation to achieve optimizing parameters in material characterization. This algorithm uses data from notch tensile as the basic input to derive parameters of G-T-N damage model, and revise these parameters by FEM calculation in consider of anisotropic influence. Eventually, the result of numerical simulation fit with experiments. In comparing with other method of