A model of inelastic behavior of polycrystals that was based upon the idea of constrained grain-boundary sliding was developed. This model assumed that grain-boundary sliding was accommodated only through grain elastic deformation, which was valid under low stresses. By way of examples, the dynamic inelastic behavior and a decrease in the elastic moduli of polycrystals subjected to a small-amplitude ultrasonic field were investigated. It was shown that some of the available experimental data obtained on ultra fine-grained materials could be explained in terms of the model. The theory predicted that the decrease in the elastic moduli was a size effect that was bound to be observed when the grain size was small. These predictions were supported experimentally.

Constrained Grain-Boundary Sliding and Inelasticity of Polycrystals. S.K.Khannanov, S.P.Nikanorov: Technical Physics, 2006, 51[1], 52-6