Shear mode growth of short surface-breaking RCF cracks

Shear crack growth dominated for all four crack lengths and the net crack growth rate was greater than zero. The paths of crack advance were calculated for each crack; they show that the three shortest continue to grow parallel to the surface of the disc. The 0.4 mm crack, however, grows upward; thus, it may lead to spalling failure. The results are compared with others from similar twin disc tests and discussed in terms of their application to real train traffic situations where crack coalescence may occur.