Material indices controlling the threshold stress intensity factor range of arbitrarily long mechanical cracks based on plasticity-induced-crack-closure analyses

Abstract

The fatigue limits of smooth materials and various notched materials are determined by their non-propagating limit after the growth of a fatigue initiated crack; thus, the characterization of the threshold stress intensity factor range (ΔKth) is important for fatigue design. The material dependencies of ΔKth for small and long cracks differ significantly; however, the physical meaning for this has not adequately examined. In this study, the material indices of ΔKth for mechanical cracks of arbitrary length were clarified by plasticity-induced crack closure analysis using the Dugdale-model, which considers the work hardening effects. The discretization errors in space and time were discussed in detail to provide a mechanically well-founded conclusion. Furthermore, databases of past ΔKth values are discussed from the mechanical perspective using this conclusion.