Wave Propagation in a Conical Bar Subjected to Impulsive Loadings and Impact Fracture

Abstract

The study of wave propagation in the machine-structures with varying cross-sectional parts has become very important from the view point of the impact strength of structures.
In the present paper, first, the stress wave propagation and the impact fracture of a conical bar were treated experimentally. The changes of the crack location and the number of fracture points were investigated at several different impact velocities. Next the wave propagation in a conical bar was calculated by the finite element method, and its change with time was considered in detail. Furthermore the estimation of a crack location was tried.
The results obtianed are as follows:
(1) The wave speed, obtained from the experiment of the wave propagation in the conical bar, agreed with that of the one-dimensional theory.
(2) When the impact velocity increased, the number of fracture points increased and the crack location approached to the top end of the conical bar.
(3) The wave front of compressive strain was reflected at the top end as the tensile strain. These reflected tensile waves were superposed to the following tensile wave, and high tensile stress appeared often as observed in the experiment.
(4) The crack location simulated in a conical bar of gypsum agreed fairly well with the experimental result.