Fundamental Equations of the Theory of Creep

This chapter deals with the equations of state of the theory of creep both for homogeneous and heterogeneous substances wherein the properties of the constituent materials depend on spatial coordinates. Attention is mainly directed towards heterogeneity of a specific nature resulting from the fact that the age of the material varies from point to point. We shall also examine several other forms of heterogeneity which are important for application to special cases. The structure of the kernel of creep and relaxation reflecting the most characteristic feature of deformation of materials over time is likewise investigated. Equations which consider the effect of high levels of stress and temperature on the properties of aging materials and correlations of the quasilinear theory, which takes into consideration partial irreversibility of creep deformation, unrelated to aging, are introduced. Section 5 describes equations of elastoplastic deformation of materials that take the rate of loading into consideration.