Modelling of interaction between creep and oxditaion behaviour for engineering materials

Mechanical test data for design of high temperature components are mainly c ollected from tests conducted in air even though these are used in differen t environment. Therefore, in order to predict accurately the performance of a component in actual service it is necessary to develop appropriate const itutive equations taking into consideration the environmental effect. The p aper briefly describes how our current knowledge on Continuum Damage Mechan ics (CDM) can be utilized to formulate the same. In absence of sufficient e xperimental data, most of the existing approaches provide only qualitative support for their models. Creep test on specimens having different section sizes, under identical conditions, can provide valuable information on cree p/environment interaction. A simple analytical method has been developed to extract the material parameters determining the kinetics of environmental attack from a creep strain-time plot. It has been shown that the material c onstants thus obtained provide good explanation of the observed section siz e and geometry effects in steels and nickel base superalloys.