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During the cooling of protective oxide layers on high-temperature alloys, the oxide is usually placed under compression. This paper considers buckling and wedging processes of decohesion of the oxide in this situation. It is shown that the wedging mechanism, in which a tensile wedge crack grows at the oxide–metal interface, is favoured for thick oxides and an intrinsically strong oxide–metal interface. The results of numerical analyses of such wedging failure are presented for the particular case of a chromia film on an austenitic steel. Both elastic and creep deformation processes were considered. It is shown that creep relaxation within the steel markedly reduces the rate of growth of the interfacial crack compared with purely elastic behaviour. Agreement with experimental oxide spallation data is reasonable for this creep case.

Recent publications have highlighted the effectiveness of using a consistent tangent modulus when solving elastic‐plastic problems. The formulation of a consistent tangent modulus is closely related to the scheme used to integrate the constitutive equations. Recent work has shown how many of these schemes currently in use can be derived from certain broad classes of algorithms. In this paper these procedures are examined for a number of commonly used yield/failure criteria. For certain cases a remarkably simple formulation results which can lead to considerable savings in computational time.

SUMMARYIssues related to the constitutive modelling and computational treatment of strain localization are examined for the class of rate independent solids. The significance of the constitutive description in localization problems is emphasized and constitutive models currently employed are briefly reviewed. Difficulties faced in finite element analysis, fundamentally associated with the loss of ellipticity of the related boundary value problem, and present trends in the computational treatment are discussed and illustrated by numerical examples.