STATIC AND DYNAMIC PROPERTIES OF VARIOUS BASEBALLS

In this study we investigated the compressive quasi-static mechanical properties and dynamic impact behavior of baseballs. Our purpose was t o determine if static testing could be used to describe dynamic ball i mpact properties, and to compare static and dynamic properties between traditional and modified baseballs. Average stiffness and energy loss from 19 ball models were calculated from quasi-static compression dat a. Dynamic impact variables were determined from force-time profiles o f balls impacted into a flat stationary target at velocities from 13.4 to 40.2 m/s. Peak force increased linearly with increasing ball model stiffness, impulse of impact increased linearly with ball mass. Coeff icient of restitution (COR) decreased with increasing velocity in all balls tested, although the rate of decrease varied among the different ball models. Neither quasi-static energy loss nor hysteresis was usef ul in predicting dynamic energy loss (COR2). The results between tradi tional and modified balls varied widely in both static and dynamic tes ts, which is related to the large differences in mass and stiffness be tween the two groups. These results indicate that static parameters ca n be useful in predicting some dynamic impact variables, potentially r educing the complexity of testing. However some variables, such as bal l COR, could not be predicted with the static tests performed in this study.