Closure-free biaxial fatigue crack growth rate and life prediction under various biaxiality ratios in SAE 1045 steel
Using a pressurizing device attached to the confocal scanning laser microscope (CSLM), crack opening measurements were obtained. Crack opening measurements showed that the biaxial cracks were fully open at zero internal pressure for block strain histories containing in-phase PCO cycles of yield stress magnitude. Therefore, for the shear-strained samples, there was no crack face interference and the strain intensity range was fully effective. For PCO tests (with biaxial strain ratios of −0.625 and +1), effective strain intensity data were obtained from tests with positive stress ratios for which cracks did not close. A number of strain intensity parameters derived from well-known fatigue life parameters were used to correlate fatigue crack growth rates for the various strain ratios investigated. Predicted fatigue lifetimes based on a fatigue crack growth rate prediction program using critical shear plane parameters showed good agreement with the experimental fatigue life data.
Keywords: biaxial fatigue; confocal scanning laser microscopy; critical shear plane approaches; effective (closure-free) fatigue life and crack growth rate; effective strain intensity factor range; periodic compressive overstrain
Document Type: Research Article
Affiliations: Mechanical Engineering Department, University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
Publication date: 1999-08-01