Using modal analysis to investigate bat-ball performance of baseball bats

The relationship between the vibration response of wood and nonwood baseball bats and batted-ball performance was investigated for a representative set of collegiate and major league bats of various lengths. The nonwood bats had hollow barrels of either aluminum or fiber-reinforced composite. The bats were performance tested using a high-speed air cannon where the baseball was projected at a stationary bat. Performance metrics of Ball Exit Speed Ratio (BESR), Batted-Ball Speed (BBS) and Bat-Ball Coefficient of Restitution (BBCOR) were calculated using the speeds measured in the air cannon tests and the appropriate physical properties of the bats and balls. Modal analysis was performed on the bats to measure the first and second bending mode frequencies for the wood and nonwood bats and to measure the first and second hoop mode frequencies of the nonwood bats. The hoop modes were used to examine the trampoline effect of the hollow nonwood bats. A nonlinear mass-spring-damper model was used to explore the effect of the hoop-mode frequency on performance. For wood bats, it was found that the performance increases as the frequency of the first bending mode increases. For nonwood bats, it was observed that the performance increases as the frequency of the first hoop mode approaches the optimal value which is ∼1250 Hz.