Estimation of johnson-cook constitutive model constants from sheppard and jockson model

Abstract

This work introduces a novel approach for determining the material constants of the Johnson Cook constitutive model, which is used to estimate flow stress when a material is open to higher strain rates, stresses, and temperatures. In this study the material characteristics/constants of the Johnson-Cook constitutive model were derived by using another flow stress model which was introduced by Sheppard and Jackson. The input data was collected from published hot compression test results. This method can potentially reduce the experimental efforts required for evaluating the data of the Johnson-Cook model. In this work aluminum alloys 7075-T65I and Ti- 6Al-4V have been considered for analysis. These materials have their mechanical properties at high temperatures and are of excellent significance for new manufacturing procedures that use deformation to produce a bonding in the solid state, such as friction stir welding and magnetic impulse welding. The flow stress variation of the two models and similar characteristics have been observed at some points over the temperature range. The strain rate constant (c ) and temperature softening coefficient (m) for each material have been determined and results were compared with experimental data which were found in the literature. By adopting this method it is possible to eliminate torsion test to know the strain rate effect on a material. These data could also be used to simulate possibly the best processes as forging, rolling at higher temperatures, and creep.