Study on crack initiation from holes of one-piece brake disk for motor bicycles

Abstract

Cyclic braking tests under extremely severe conditions were carried out using large one-piece brake discs having several holes in their flange. When the number of braking cycles was beyond a certain number of cycles, some tiny cracks occurred in the radial direction around holes were found. They grew in the radial direction of the brake discs. In order to examine whether braking torque is a driving force for crack initiation or not, the time interval was altered 10 times longer than the normal condition. The experimental results showed that the number of total cracks around holes after the same rotations decreased as the braking interval was extended. The crack length also decreased. These results indicate that the braking torque itself does have less direct effect on the crack initiation.