Simulating Sport Ball Impact Through Material Characterization

In finite element models of sport ball impacts, modeling the ball has been much more challenging than modeling equipment. Clubs, racquets, and bats tend to be largely linear-elastic, while sport balls are often non-linear, inelastic, and rate dependent. Obtaining ball material properties is further complicated by the difficulty in achieving the high deformation rates representative of impact. The following describes the implementation of a dynamic impact test apparatus that was designed to characterize sport ball materials. The apparatus was used to construct a loading and unloading stress-strain curve of polyurethane foam at deformation rates and magnitudes representative of play. The stress-strain response was used in explicit finite element simulations of ball impacts. The simulated impacts were compared with instrumented ball impacts. The foam material model provided closer agreement with experiment over a range of impact speeds and surfaces than viscoelastic material models that are commonly used.