New Phenomenological Material Constitutive Models for the Description of the Ti6Al4V Titanium Alloy Behavior Under Static and Dynamic Loadings

摘要

The analysis and optimization of rapid or severe material forming process, where high gradients of plastic deformations, strain rates and temperatures are reached during the material flow, remains today a major challenge. Several light metallic alloys, as the titanium ones, are widely used in many industrial applications. Despite their wide spread adoption, particular phenomena are encountered during their machining: high plastic strains gradients, heavy strain rate localization, chip segmentation, accelerated tool wear, etc. Although the recent advances in the experimental devices, it is still difficult experimentally to investigate the instantaneous mesoscopic phenomena taking place during severe forming processes. Therefore, the use of numerical simulations, in addition to specific experimental measurements, presents an efficient alternative for a better understanding of machining processes. Given thought the significant sensitivity of the modelling to the reliable definition of the thermo-visco-plastic workpiece material behavior and referring to the physically based mesoscopic constitutive model proposed in previous works of Gavrus, this study focuses on formulating and identifying phenomenological rheological laws. Their ability to accurately reproduce the isotropic plastic behavior of the Ti6Al4V titanium alloy for both static and dynamic loadings states, as well as in a wide range of plastic strains, plastic strain rates and temperatures, is checked. A specific iterative non-linear regression method is used for the identification of all corresponding material parameters. Their adequacy is discussed and comparisons with experimental results of the literature are set up. A specific user material subroutine VUHARD is implemented into the commercial code Abaqus/Explicit. Numerical simulations of experimental compression tests are performed to valid the rheological models' identification and the material flow prediction. A 2D Finite Element Modelling of the Ti6Al4V orthogonal cutting is performed and the accuracy of proposed constitutive models is examined.