Comparison of the Johnson-Cook and VPSC models to describe the constitutive behaviour of Ti-6Al-4V in an implicit finite element scheme

摘要

The use of finite element simulations has become one of the main tools of the mechanical engineer. The method is applied to the analysis and design of engineering structures, the study of manufacturing processes and even to perform virtual experiments. Traditionally, the constitutive laws chosen for finite element analysis have been as simple as possible, mainly due to the limitation imposed by the available computing power. However, the development of more powerful computers and more efficient methods is opening the possibility of using more elaborated (and, most often, more accurate) material models. In particular, polycrystal models capable of predicting not only the mechanical behaviour of the material, but also of the evolution of properties with increasing strain, are particularly well suited for the simulation of forming processes, for which a precise knowledge of the properties of the resulting product is of paramount importance.The present work studies how the Visco Plastic Self Consistent model (VPSC) can be used in combination with the implicit finite element package Abaqus/Standard to simulate the behaviour of Ti-6Al-4V sheet, and compares it with the more common (and much simpler) Johnson-Cook model. More specifically, the goal of this study is to determine whether or not, with using similar experimental calibration data, the use of the much more complex polycrystal model, justifies the increased complexity and execution time. Using standard tensile experiments at different strain rates, the parameters of the VPSC and Johnson-Cook models are fitted using a minimization method. Then, both models are used in finite element simulations and the results given by both models are compared.