The influence of mean stress or [formula omitted] on the fatigue crack threshold characteristics of steels—A review

Abstract

The present review attempts to describe an assessment of the effects of the R- Ratio on ΔK th values in steels and compares the predictions of the various approaches or models dealing with R- Ratio response, with experimentally determined threshold stress intensity range values. Essentially significant R- Ratio effects on ΔK th have been observed and that the extent of such effects are highly dependent on microstructural considerations. The two classical approaches dealing with R- Ratio effects, viz., the Barsom and the Klesnil and Lukas models, can adequately describe the R- Ratio response when the data are considered in terms of microstructural characteristics. However, the other approaches of Mazumdar and Conrad and McEvily and Groeger fall short in predictive terms while the Musuva and Radon approach needs more detailed high R- Ratio ΔK th data before it can be realistically assessed.