Numerical Damage and Failure Modelling of Lightweight Alloys during Metal Forming Processes

Abstract

There have been many efforts to investigate and develop a numerical damage and failure models during metal forming process of lightweight alloys. Due to the difficulties experienced during experimental determination of the incurred damage during forming of lightweight alloys, many researchers have sought to predict the damage, failure and forming limit curves using numerical simulations. Conventional finite element analysis of metal forming processes for lightweight parts which have been subjected to a nonlinear strain history often breaks down due to numerical difficulties. Many scientific research works have attempted to use different mathematical methods to model the damage progression and failure of alloying material under large deformation. The damage initiation, progression and also failure of alloys are a result of accumulated damage under plastic deformation [1-3]. These models (single and multi-damage parameters) are generally based on energy and constitutive equations to simulate the fracture and failure processes in metal alloys. However, these methods have serious short comes in predicting the damage and failure in metal forming process with strain rate effects. In the present study, following the in-depth study of damage initiation and progression in lightweight alloys, a frame work has been setup to develop a numerical model for damage accumulation during forming process. Based on the existing damage theory, a mathematical extension for damage initiation and also damage accumulation under wide range of stress triaxiality (including near pure shear) has been developed. An experimental program has also been carried out using samples made from lightweight alloys. One of the main contributions of this paper is to show the advantages of using plasticity-based modified damage models to investigate the damage accumulation in cast aluminium alloys.