Evaluation of the effect of crack closure on fatigue crack growth of simulated short cracks

This paper examines the influence of crack closure on fatigue crack growth (FCG) rates of short cracks. Using the standard compact tension specimen, test procedures were devised to evaluate closure loads in the wake of the crack behind its tip. One procedure determined the magnitude of the crack closure as a function of the fatigued crack wake by incrementally removing the contacting wake surfaces and measuring closure load at each increment. Another procedure used a low-high loading sequence to simulate short crack behavior. It was concluded that crack closure is not the major reason for the more rapid growth of short cracks as compared to long cracks.