Finite Element Modeling of a Baseball

Abstract

A baseball consists of a spherical cork core that is wrapped with two layers of rubber, three layers of wool, one layer of cotton, cement glue and one layer of cowhide. The respective nonlinear and time-dependent material properties of these layers make it challenging to capture the behavior of a baseball accurately over a range of impact speeds. As a result of this challenge, finite element models (FEMs) of the baseball typically treat the baseball as a single viscoelastic material where the respective material properties have been homogenized. These single-material models do not necessarily possess the same hyperelastic and viscoeleastic qualities as a real baseball, and these missing behaviors limit the applicability of these baseball models to simulate a bat-ball collision over a very narrow range of impact speeds. In the current work, a layer-by-layer approach is used to create a robust baseball FEM. The pill, which is a cork core wrapped in two layers of rubber, were subjected to bounce and compression testing at a wide range of impact speeds and compression rates. These data are used to tune the pill properties and ensure close agreement between experimental and FEM results. The remaining layers are added individually until the complete baseball is modeled and agrees closely with experimental results over a wide range of impact speeds. Possible applications for a new and improved baseball FEM include accurate simulations of baseball testing and bat-ball collisions. The improved ball model can also be used to predict performance of future bat designs not yet manufactured.