High strain rate behaviour of stainless-clad bimetallic steel

Abstract

To study the dynamic mechanical properties and to develop constitutive models of stainless-clad (SC) bimetallic steel at high strain rates, 11 groups of standard specimens (i.e. cylinders of 6 mm in diameter and 6 mm in height) are designed. Four different loading directions and clad ratios varying from 0.2 to 0.5 are considered. 123 compression tests are carried out at six strain rate levels (0.0005 s−1, 1000 s−1, 1500 s−1, 2000 s−1, 3000 s−1 and 4000 s−1). Johnson-Cook (J-C) constitutive model is used to fit the test data, and the fitting results are in good agreement with the experimental results. It can be found that the strain rate hardening has a prominent effect on stress development of the SC bimetallic steel at high strain rate compared with that in the quasi-static condition. With an increase of the clad ratio, the stress of the SC bimetallic steel grows slightly as the strain hardenability and sensitivity of the strain rate decrease. The SC bimetallic steel can be considered as an isotropic material in terms of high strain rate behaviour because different loading directions result in no obvious distinction. In addition, a formula for dynamic increase factor (DIF) for strengths as well as a general constitutive equation of J-C model for the SC bimetallic steel are developed and validated, which can be adopted in structural design under impact loading and promote engineering application of the SC bimetallic steel.