A Measuring Theory of Impact Force Acting on a Bar with Two Different Diameters

Abstract

The true value of impact force, in high speed deformation test of metals, is commonly measured by the Hopkinson-bar method. But, a drawback to this method is the restriction of measurable time because of the length of the bar. One of the authors suggested construction a measuring theory for impact force acting on a bar with uniform cross sectional area, based on the theory of the propagation of longitudinal elastic stress waves. From the stresses detected at two points on the bar, two stress waves travelling in opposite directions along the bar axis are separated, and the impact force is estimated, without the restriction of the measuring time. This paper presents a new theory for measuring the impact force which acts on a bar having two different diameters. The results of the experiments clearly confirm the validity and usefulness of this theory.