Stress intensity factors for circumferential semi-elliptical surface cracks in a hollow cylinder subjected to pure torsion

• The compendia for SIF KII, KIII and Keq were given for a/c and crack depths a/t.
• The Keq/KIII,0 ratio has values between 0.45 and 0.5 for c/a = 2 at any crack depth.
• Experiment confirms fatigue crack propagation under significant influence of Mode II.

The stress-intensity factor for the circumferential semi-elliptical surface cracks in a hollow cylinder’s cross section under torsion is calculated using a finite-element technique. The configuration of standard semi-elliptical surface cracks is described using the outer surface crack-lengths and the crack depths. The compendia for the stress-intensity factor solutions for Mode II, Mode III and both mixed modes are given for the broader aspect ratios and relative crack-depths than previously available. The magnitude of the stress-intensity factor of Mode II near the free surface becomes more significant for stable crack-initiation than that of Mode III at any point along semi-elliptical crack.