Creep-Fatigue-Oxidation Interactions

Abstract

AbstractThe fracture maps of Ashby display the various modes of creep fracture. Creep damage results from the nucleation of cavities on grain boundaries. Viscoplastic deformation can be the controlling mechanism. Hull and Rimmer model is at the basis of diffusion controlled nucleation. Viscoplasticity and diffusion can be coupled in the nucleation of creep cavities. Furthermore, overall deformation can constrain this phenomenon. The Monkman-Grant law is a phenomenological expression relating the time to fracture to the strain rate. Time to fracture contours in multiaxial loadings are found to lie between the von Mises and the maximum stress criteria. Continuous damage mechanics was introduced to predict creep fracture. This is exemplified by the cases of copper, Nimonic 80A and austenitic stainless steels. The behaviour of three types of alloys, 9–12 Cr steel, austenitic stainless steel and Ni-base superalloys, is explained by creep-fatigue-oxidation interactions. Various engineering methods allow predicting the creep fatigue life: limit load analysis, crack initiation and propagation related to the stress intensity factor in the case of creep brittle materials and to the C * parameter in the case of creep ductile materials, frequency modified fatigue life prediction, strain range partitioning, linear and nonlinear damage accumulation. Long crack propagation is linked with creep-fatigue interactions. Thermal barriers coatings and ceramic matrix composites are two examples of high temperature materials.KeywordsFatigue LifeCrack Growth RateAustenitic Stainless SteelHold TimeFatigue Crack Growth RateThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.