2015 Volume 64 Issue 11 Pages 902-909
This study was aimed at showing the validity of the strain intensity factor for predicting crack growth of low-cycle fatigue regime. First, by reviewing the fatigue test results of Type 316 stainless steel, roles of the stress and strain ranges for determining the fatigue life and validity of the strain intensity factor for predicting the crack growth were investigated. The test results obtained using cold worked specimens revealed that fatigue life correlated better with the strain range rather than stress amplitude. Crack initiation and growth investigations using replica technique showed that the fatigue life was almost equivalent to the cycles for a small crack of few tens micrometers growing to the critical size. The crack growth rates of small cracks correlated well with range of the strain intensify factor. It was concluded that the strain intensity factor is valid for predicting the crack growth rate because the fatigue life was correlated well with the strain range and was almost equivalent to cycles for a small crack growing to critical size. In order to discuss the closure effect on the crack growth rate, plate specimens were subjected fully reversed cyclic loading. Then, the effect of single overloading on crack opening strain and growth rate were investigated. It was shown that the crack growth was accelerated more by compressive overloading than by tensile overloading. The change in the growth rate was reasonably assessed by considering change in the effective strain intensify factor.
