Analysis of Impact Phenomena in a Tennis Ball-Racket System : Effects of Frame Vibrations and Optimum Rocket Design

Abstract

The performance of a tennis racket in terms of the coefficient of restitution(COR)is closely related to impact phenomena. This paper investigates the effects of frame vibrations on the coefficient of restitution and the contact time during impact of a ball / string system and a simulated frame model, using FEM simulation and modal analysis. The results show that the COR is mainly affected by a rigid motion and a bending vibration with two nodes of racket frame. In addition, the COR increases with an increase of frame rigidity, but then saturates at a certain rigidity depending on the impact velocity. Furthermore, the COR increases as the impact point approaches the center of rotation and the node of racket frame vibration.