Short fatigue crack behaviour under low cycle fatigue regime

This paper addresses the important issue of the description of short fatigue crack behaviour. It is typical for these cracks that they propagate under large scale yielding conditions at the crack tip, which means that the non-linear fracture mechanics has to be applied. This paper presents results of experiments designed to measure the short crack growth rates in five different materials - 316L steel, Eurofer 97 steel, ODS Eurofer steel, Duplex 2205 steel and Al 6082 alloy. The crack growth rates of these materials are described using different fracture mechanics parameters - the stress intensity factor, the J-integral and the plastic part of the J-integral. These approaches are evaluated and compared. The comparison revealed that the plastic part of the J-integral is the parameter governing the short crack growth rate in large scale yielding conditions. Moreover, crack growth rate data from all the tested materials measured at various loading levels lies on a unique curve. This remarkable observation suggests that the crack growth rate is determined by the extent of energy spent to plastic deformation, irrespective of the other materials properties.