An Examination of Short Fatigue Crack Growth

An overview of studies conducted during the past fifteen years of the apparent anomalous behavior of short fatigue cracks is presented. Reference is made to both experimental results and proposed explanations for the observed behavior. Particular attention is focused on the transition range of crack lengths between very short cracks which are on a scale of the microstructural details and long cracks for which linear fracture mechanics analyses can be applied; i. e. , "physically" short cracks. The recent emphasis on the role of obstruction to closure is recognized as providing a valid explanation for some of the results which have been observed. Early analytical results obtained by Rice on the limitations of small scale yielding at the crack tip and its relevance to short cracks are discussed. It is concluded that the analysis of short fatigue cracks should include consideration of the coupled effects of both closure and the plastically induced process zone at the crack tip. Suggestions for future work are made. These include the acquisition of additional experimental and analytical results which could form the basis for the development of predictive codes