Creep of Metals Under Variable Complex Loadings
In recent years, numerous material models and experimental observations on the inelastic behavior of metals at elevated temperatures have been proposed and reported. Despite their various forms, the models can in general fit into some common structures. Identification of such structures is essential in the development of constitutive equations. It is also far more important than finding a specific relation for a specific material. The same is also true in the experimental work. In order to systematically characterize the material behavior or validate the models, a structured approach is necessary. In the current paper, instead of reviewing the details of the available theoretical and experimental work, it is attempted to summarize the current progress in terms of some basic theoretical structures and experimental methodology. Examples derived from these structures and their capability for predicting the creep deformation of metals under variable complex stresses are discussed. Finally emphasis of future research on creep under nonproportional loadings is suggested.
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