An ultimate crack resistance concept

Abstract

The ultimate crack resistance is regarded as a two-parameter fracture criterion. The concept of ultimate crack resistance enables one to estimate the state of a material and to compute the crack resistance of machine parts in the processes of brittle, transient, and viscous fracture. In relations used for numerical analysis, the stress intensity factors are preserved but the corresponding characteristic of the material is made more complicated.In recent years, a two-parameter fracture criterion was introduced in the form of a single common relation used to describe both brittle and ductile fracture, including intermediate fracture conditions varying within fairly broad ranges. This criterion seems to be especially useful for the determination of admissible crack lengths in the case where fracture conditions are different for different crack lengths.Various analytic relations can be used as two-parameter criteria. The R 6-criterion proves to be the most populax. These criteria use various physical and mechanical effects to predict the critical state. However, the results given by different criteria are similar. However, there exists certain divergence in the region of small cracks explained by the fact that this is just the region where these criteria are somewhat different. For all other cracks, they practically coincide. Therefore, we can conclude that these criteria are good enough to describe fracture processes.In the present work, we analyze the concept of ultimate crack resistance (due to its universal and multipurpose character).