Abstract
Creep failure occurs through excessive strain or premature fracture. From many empirical relationships proposed to predict the strain incurred in a given time at a specified stress and temperature, some are selected in terms of their practical usefulness and their scientific basis is discussed. It is shown that distinctive mechanisms can operate, dependent upon the material and on the creep conditions and it is important that these are individually considered. It is also noted that these mechanisms may be coupled in ways which may smooth the transitions between them. This may account for some empirical approaches being applicable for approximate predictions over relatively wide ranges. Different mechanisms leading to creep fracture can also be distinguished. Limits of extreme behavior can be clearly identified and explained but, under intermediate conditions, the form of coupling of different mechanisms leads to continuity in transitional regions. Concepts of creep damage can be developed in terms of cavity nucleation and growth, with the value of microstructural examination clearly recognised. Whilst much remains to be done, a scientific framework for the understanding of the mechanisms of creep and creep fracture is already in place and there is opportunity for detailed physical modelling to assist the prediction of behaviour in practical situations.
