Crack closure-based analysis of fatigue tests with mean stresses

The recently developed crack-closure based fatigue method seems to hold great promise for analyzing a wide range of fatigue problems, particularly those involving large mean stress and/or occasional overloads. The method, however, requires the determination of material constants which characterize the influence of loading history on the closure mechanism. Such material fatigue properties generally take a great deal of experimental effort involving fatigue crack measurements and hence are not widely available yet. In this paper it is found that by using the closure-based method to analyze fatigue tests with mean stress, constant maximum stress tests and constant minimum stress tests not only help record mean stress effects on fatigue, they also help derive the material constants that are required for applying the closure-based fatigue method.