The Role of Cavitation in Creep-Fatigue Interaction

There are many empirical models for the development of creep and fatigue damage. The perhaps most well-known ones are Robison’s and Miner’s damage summation rules. They are based on the mechanical behavior during monotonous and cyclic loading. To improve the accuracy of the damage assessment, it is important to analyze the changes in the microstructure as well, not least the cavitation. To describe cyclic loading, special empirical models have often been used in the past, some with numerous adjustable parameters. Recently, a model for cyclic loading has been formulated that is based on the corresponding expressions for monotonous loading. The main change is that the value of the dynamic recovery constant is increased. In this way, cyclic hysteresis loops can be reproduced without adjustable parameters. Cavitation is believed to be of the same technical importance during cyclic as during static loading. In spite of this, the number of studies of cavitation during cyclic loading is quite limited. One set of data exists for a 1Cr0.5Mo steel. The static cavitation models have been transferred to cyclic conditions. It is demonstrated that these models can describe the cavitation both during low cycle fatigue (LCF) and combined creep and LCF.