Characterisation of high strain rate material behaviour for high-speed forming and cutting applications

Abstract

Determination of the material behaviour for high speed forming processes is challenging due to high process velocity and small specimen geometry in experimental analysis. This paper proposes two different material characterisation concepts for high strain rates at 10³ s⁻¹ and higher, namely a pneumatically device and an electromagnetically accelerated hammer, for obtaining experimental values. Furthermore, two measuring principles of the hammer velocity and displacement are presented and compared. The authors describe a measurement system with an acceleration sensor for the pneumatic device and a shadowing principle for the electromagnetically driven concept. Using the measured data, material parameters are iteratively adapted in an optimisation procedure until an objective function, comparing the difference between numerical and experimental results, is satisfied. In this case the parameter identification is applied on a strain rate dependant flow curve approximation based on Johnson-Cook.