SURFACE FLAWS IN CYLINDRICAL SHAFTS UNDER ROTARY BENDING

The propagation of a surface flaw in a cylindrical shaft subjected to rotary bending is analysed using a two-parameter theoretical model. Th e stress-intensity factor distribution along the crack front is numeri cally determined for any position of the flaw with respect to the bend ing moment axis. The crack front is assumed to present an elliptical-a re shape with aspect ratio alpha = a/b (a, b =ellipse semi-axes), wher eas the relative depth xi of the deepest point on the front is equal t o the ratio between the maximum crack depth, a, and the bar diameter, D. The results for rotary bending are-compared to those for reversed c yclic bending.