Method for determining the strain rate sensitivity factor for the Johnson-Cook model in Charpy tests

Abstract

Abstract The basis for the study was the necessity to design a supporting structure of the road infrastructure subjected to high strain rates occurring during vehicle accidents. Mathematical models of hardening due to the high strain rates are reviewed. Commonly used methods for determining constants for one of the models, i. e., Johnson-Cook model are characterized. The main section of the study presents a proposed method for determining the strain rate sensitivity of the material. It is a hybrid method which requires Charpy tests using unnotched specimens and a series of calculations using the finite element method to simulate the tests. Several variants of strain measurement of specimen subjected to failure in Charpy tests, as required for the proposed method are analyzed. Using the suggested method, a strain rate sensitivity factor was obtained with a value similar to the value obtained using the split Hopkinson pressure bar technique. The advantages of the suggested method compared to the existing me...