Charpy specimen—a simply supported beam or a constrained free–free beam?

Abstract

This paper investigates the validity of assuming simply supported end conditions in the impact loading of the Charpy specimen in the light of the experimental and numerical results published recently on the effect of overhangs. Following a discussion on the inadequacy of modeling the specimen as hinged, a new approach to the dynamic analysis of the impact test is proposed by considering the specimen as a free–free beam under elastic constraints at the supports. The mode shape of the beam vibration is approximated by summation of the fundamental vibration mode and a translation mode. The load–point displacement is prescribed as the traction boundary condition to the model and all the impact parameters, namely the impact load, anvil reaction and the beam response are computed. The theoretical predictions are compared with the experimental results published elsewhere. The effect of higher modes of vibration are discussed by comparing the analytical results with finite element computations. The results support the standpoint that the Charpy specimen is a constrained free–free beam and not a simply supported beam.