Design and implementation of a Split-Hopkinson-Pressure-Bar for the identification of material model parameters
Marcel Tiffe, Institute of Machining Technology / TU Dortmund University, Dortmund, GermanyAndreas Zabel, Institute of Machining Technology / TU Dortmund University, Dortmund, Germany
Machining processes are increasingly analyzed and optimized by finite element based simulation methods. In order to obtain realistic results, proper material models are essential. In contrast to other manufacturing processes like forming, the extreme conditions in cutting processes include large strains (up to 4 or even more), steep temperature gradients and high strain-rates up to 100000 per second. For an appropriate material characterization, which is essential to the setup of realistic material models even for these conditions, conventional material testing methods like tension and compression tests cannot be applied. To reach strain-rates of several thousand per second the Split-Hopkinson-Pressure-Bar-technique is well accepted and used by many researchers.
The Institute of Machining Technology at TU Dortmund University is currently putting a Split-Hopkinson-Pressure-Bar in operation for materials characterization. First tests on brass and steel alloys indicate a strong dependence of the flow stress on the strain-rate. The obtained data is used for the identification of material model parameters, e.g. for the Johnson-Cook flow stress model. The found parameters are utilized for the numerical assessment of chip formation processes in two- and three-dimensional FE-simulations.