A Nondestructive Evaluation Approach to Characterize Tennis Balls

Abstract

Sometimes, nondestructive evaluation (NDE) or structural health monitoring methods commonly used in engineering structures are used for the betterment of consumer goods. A classic example is the use of sensor systems to monitor the pressure and the quality of car tires. In this paper, we present a nondestructive method to characterize tennis balls. The International Tennis Federation (ITF) specifies which characteristics a tennis ball must have in order to be commercialized. One of these characteristics is bounciness and the standardized method to measure it is the rebound test, where a ball is released from 2.54 m onto a smooth rigid surface and, in order to be approved, the ball must bounce within a certain range. This test can be staged by manufacturers and testing authorities but the equipment necessary to perform it is not readily available to the average consumer. In the study presented in this paper, an empirical method based on the propagation of highly nonlinear solitary waves (HNSWs) is proposed to establish whether a given ball conforms the specifications set by the ITF in terms of bounciness and allowed deformation. The experiments conducted in this study aim to discover a correlation between some features of the waves and the values obtained with the rebound test and the compression test in which the deformation of the ball under a known load is measured. The presence of such correlations could represent a viable alternative to establish the conformity of tennis balls. Based on the empirical evidences collected in this study, a possible new standard is suggested.