Propagation of physically short cracks in a bainitic high strength bearing steel due to fatigue load

• Straight closure free short cracks were made by compressive cycles on sharp notches.
• For nominal ΔKI, short cracks grew faster than, and below ΔKth, of long cracks.
• Considering effective ΔKI, short and long cracks propagated at equal rate.
• Rate limiting mechanisms at the crack tip reduced the effective ΔKI.
• The short crack lives were predicted by effective ΔKI and rate limiting SIF.

Physically short cracks in a bainitic high strength bearing steel were fatigue loaded. The rapid propagation rate of early open short cracks agreed with that of long closure free cracks. After some rapid growth, the short cracks entered a transition period to the rate of growth limited long cracks. Potential drop showed that the short cracks were open to the tip throughout the growth sequence, which excluded crack face closure in the wake as the growth limiting mechanism in this material. Instead the short crack effect was related to residual stresses and other mechanisms at the crack tip. Crack manufacturing procedures were determined for straight long and short start cracks in the present material. LEFM with effective material parameters and limit compensation predicted the short crack lives.