The Effect of Discontinuity Size on the Initiation of Shattered Rim Defects

Shattered rim defects are the result of large fatigue cracks that propagate roughly parallel to the wheel tread surface. They form and grow 12 to 20 millimeters (1/2 to 3/4 in.) below the tread surface. A typical shattered rim is shown in Figure 1. The clamshell pattern of the fracture surface is also typical of shattered rims. The clamshell pattern is formed because fatigue cracks at this depth in wheels have a shear component and, when the rolling direction is opposite, the cracks grow in a different direction forming a series of ridges and valleys. Miezoso, et alia have presented a mixed mode fracture mechanics analysis of the process of forming a clam-shell fatigue crack surface in wheels.