Prediction of Growth Rate of Short Fatigue Cracks : Series A : Solid-Mechanics, Strength of Materials

Abstract

A method based on crack closure was proposed to predict the growth rate of short fatigue cracks in either smooth specimens or notched specimens. The material properties used in this prediction were the growth behavior of long cracks and the fatigue limit of smooth specimens. The predicted results for notched specimens showed that the growth rate of short fatigue cracks first decreased with crack length, and then increased when the applied stress range was high or kept decreasing to zero when the range was low. Good agreement was obtained between the predicted results and the experimental results of a low-carbon steel. In the case of smooth specimens, the predicted results showed that the crack growth rate increased continuously with crack length. The difference in the growth behavior between notched specimens and smooth specimens was attributed to the difference in the increasing rate of the maximum stress intensity factor, Kmax, with crack length ; for a crack at a notch root, the increasing rate of Kmax may be smaller than the increasing rate of crack opening stress intensity facto, Kop.