Comparing the vibrational behavior of wood and aluminum baseball bats

Abstract

Experimental modal analysis was performed on a variety of wood and aluminum baseball bats to study the differences and similarities in vibrational behavior. Wood bats were found to exhibit split pairs of vibrational modes whose frequencies depend on whether the plane of vibration is along or across the grain. The frequency separation for these duplicate modes varies considerably from bat to bat and appears to be dependent on the quality of wood. Data will be presented for bats made from ash, maple, an ash–hickory–maple combination, and 6-ply laminated ash. Aluminum bats exhibit a single set of bending modes, with similar shapes but wider frequency spacing than wood bats. However, aluminum bats also vibrate with several cylindrical bell-type modes, the lowest of which is found to be responsible for the loud ‘‘ping’’ produced when a metal bat strikes a ball. Aluminum bats also allow greater modifications for improved bat performance. An example of an aluminum bat with a dynamic absorber will be compared to other metal and wood bats.