Font Size: 

Fatigue growth of a surface flaw in a round bar under rotary bending is examined through a
two-parameter theoretical model. For any position of the elliptical-arc part-through defect with respect to
the bending moment axis, the stress-intensity factor distribution along the crack front is determined by
employing a three-dimensional finite element analysis and the superposition principle. The flaw
propagation paths in the diagram of the flaw aspect ratio against the relative crack depth are numerically
obtained for rotary bending and compared to those for reversed cyclic bending. It is shown that, during
crack growth, the defect front under the former loading case becomes flatter than that under the latter
one; moreover the fatigue life for rotary bending is shorter than that for reversed cyclic bending.