抄録
A helmet of a baseball player is important protective gear to prevent a head injury when hit by a pitch. Although the impact performance of a helmet has been evaluated, the change in its impact performance when hit again has not yet been considered. This is because once a helmet receives a big impact, it is not re-used even if there is no visible damage to its surface. However, if the damage is not visible, there is a possibility that the same helmet is re-used. In this study, a baseball ball launcher was built, and a repeat impact experiment with a helmet put on the head model and a ball was conducted. The effect of the number of impact times on the acceleration which acts in the head model was considered.
