Dynamic hardening properties identification utilizing acceleration data by the Virtual Fields Method

Finite element (FE) simulations are very important in the field of automotive, aerospace and defense to evaluate crashworthiness of high strength reinforcing parts. Reliable material properties at high strain rates should be used for the FE simulation to acquire accurate simulation results. However, at high strain rates, it is difficult to obtain accurate stress-strain data because reasonable load data is not easily achieved from the experiments due to ringing problem caused by inertia effect. In this study, the virtual fields method (VFM) which is one of the inverse methods suggests another possibility of identifying hardening properties by utilizing acceleration data from the experiments without using load data. In the current study, a methodology is introduced for this purpose. The minimum magnitude of acceleration necessary to retrieve the hardening properties at high strain rate testing is investigated numerically and experimentally. In addition, a new type of high strain rate testing equipment, impact frame high speed tester (IFHS) is described. Various aspects allowing an increase of the acceleration magnitude in the IFHS are discussed for an optimum application of the methodology. Lastly derived hardening properties with the acceleration by the VFM are discussed.