Modular Modelling of Stress-Strain Behaviour of Ferritic Steel Grades in Strain Rate Ranges Relevant for Automotive Crash Situations

Abstract

The constitutive model due to Kocks, Mecking and Estrin, the so-called One Internal Variable Model, which was developed to describe quasi-static stress-strain behaviour of metallic materials, has been extended to provide modular modelling of the material behaviour under strain rates relevant for automotive applications (10-3/s to 250/s). The extended description applies to particle strengthened, fine grained and lamellar microstructures and also accounts for the effect of deformation induced heat release. Strain rate dependence of the yield stress in ferritic steels has been included. A first application of the extended model to the response to dynamic loading of a deep drawing quality (DC06) and a microalloyed steel grade (HX420LAD) is presented. Other possibilities of modular modelling mentioned are the prediction of work hardening behaviour at high strains, extension of model to cyclic behaviour and the prediction of deformation instabilities. Basics of the ModelA constitutive relation between the true stress a and the true strain 8 for the plastic region of a stress-strain curve can be represented through the so-called kinetic equation, in which E denotes the plastic strain rate and S is a state variable that is to represent the microstructural state of the material; T denotes the absolute temperature. This quantity, in tum, varies with the plastic strain and may also be strain rate and temperature dependent: account for various microstructural mechanisms contributing to strain hardening in metallic materials. Model calculations performed on this basis and verified through comparison with experimental data are presented in this paper, with special emphasis on high-speed deformation behaviour of two ferritic steel grades.(2)(1)

A New Approach to Modeling the Flow Curve of Hot Deformed Austenite

“…(6)). The temperature dependences of b 14) and μ 15) were taken into account and M and α were set equal to 3 and 0.5, 16) respectively. For the description of , r´ was calculated using…”

Analytical and numerical approaches to modelling severe plastic deformation

“…in body centred cubic (BCC) metals. An example was provided in [403], where the strain hardening of ferritic steels was modelled. To a first approximation, the Peierls stress p  entered Eq.…”

Simulation of Austenite Flow Curves under Industrial Rolling Conditions Using a Physical Dynamic Recrystallization Model

“…2θσ vs. σ 2 Plots Curves As mentioned above, the work hardening parameters r and h were obtained by converting the stress-strain curves into 2θσ vs. σ 2 plots. The temperature dependences of b 19) and μ 20) were taken into account and M and α were set equal to 3 and 0.5, 21) respectively. Some of the plots calculated from the steel A, B and C compression curves are illustrated in Fig.…”