Finite element analysis of modified high strength aluminium alloys using progressive failure algorithm

Abstract

The primary objective of this thesis was to develop a reliable finite element analysis procedure to model the complete fracture of ductile specimens using the progressive degradation of the material stiffness algorithm under tensile load. The ductile specimens in this study were three different aluminum 7075 alloys. Another objective was to establish the structure and property relationship of these alloys. The progressive failure algorithm used here was based on the assumption that the material behaves like a stable progressively fracturing solid. The stiffness reduction was carried out at the integration gauss points of the finite element mesh depending on the mode of failure. A number of material properties were necessary for such simulation to carry out and experimentation of the alloys were needed to evaluate these properties. The actual tensile tests data were applied to the finite element simulation. A renowned finite element analysis software Abaqus was used in this study. Besides, different tests were carried out to evaluate the structure-property relationship. It was found that the addition of alloying elements changed these alloys to obtain higher strength, hardness, and toughness. Effects of different mesh sizes on the mode of failure were also investigated. As the mesh sizes became smaller the time required for simulation increased but yielded results closer to the actual tensile test failure. Selected simulation results were verified by comparing true stress with von Mises stress in Abaqus. Computed stress triaxialities were also evaluated in various points on the modeled tensile test samples. Highest stress triaxialities was found near the failure zone of these modeled samples. The verified simulation method has a great importance in practical design of structures and materials.