It was recalled that a large class of solids, when subjected to significant deformation, underwent microstructural changes that led to a response which was quite different to that which existed before the microstructural changes occurred. Such microstructural changes usually led to an inelastic response. One such microstructural change, which was attributed to deformation-induced twinning, was studied from a macroscopic point of view within the framework of a continuum theory for crystalline materials. The intricate interplay, between the storage and dissipation of energy due to deformation, and its effect upon the propagation and arrest of twinning was considered. The onset of twinning was determined purely by energy considerations. It was shown that the entire constitutive structure of the material could be reduced to the use of 3 scalar functions to model so-called quasi-equilibrated twinning. These were the Helmholtz free-energy potential, the rate-of-dissipation function and the activation function. For the dynamic case, where inertial effects could not be ignored, an additional constitutive function for the kinetic energy that was associated with the twinning process had to be specified.

A Phenomenological Model of Twinning Based on Dual Reference Structures. A.R.Srinivasa, K.R.Rajagopal, R.W.Armstrong: Acta Materialia, 1998, 46[4], 1235-48