Elasto/Visco-Plastic Impact of Two Equivalent Spheres Made of SUJ2

Abstract

Impacts spheres are one of the basic problem in engineering field. The severity of impact is generally characterized by Coefficient of Restitution. This paper intends to investigate the effects of inelastic deformation on the Coefficient of Restitution in direct central impact of two equivalent spheres. The experiments of diret central impact of two spheres were conducted for bearing steel balls (JIS SUJ2). The steel balls were impacted by pendulum motions. Static tensile tests and split Hopkinson bar tests were conducted to obtain the static and dynamic stress-strain relations of SUJ2. The test pieces and the spheres were annealed under same condition before the experiments. The rise of yield stress with the strain rate was confirmed. The author han already dealt with the elastoplastic impact of SUJ2 balls. The elasto-plastic analysis underestimated the Coefficient of Restitution. Present paper deals with the elasto/visco-plastic impact of SUJ2 balls. Coefficients of Restitution and contact duration obtained from the experiments and those obtained from Finite Element Analysis were compared. It was shown that the experimental results were simulated well by elasto/visco-plastic analysis considering the dynamic stress-strain relation for SUJ2. It was recognized that the effect of dynamic stress-strain relation could not ignore in the low speed impacts.