Coupling of dissipative mechanisms of viscoplastic flow

Coupling effects between dissipative mechanisms of an elastic-viscoplastic material were described. A reasonable and physically justified theory of viscoplasticity within the framework of a material structure with internal state variables was constructed. The internal friction, the thermally activated and the high velocity dislocation damping mechanisms were emphasized. A discussion of coupling of dissipative effects for these mechanisms is presented and two groups of internal state variables are introduced. It was shown that the group of internal state variables describing dissipative effects of the internal friction mechanism can be eliminated. In this case, the evolution equations for a plastic flow mechanism were modified in such a way that the influence of internal friction effects are taken into account. The evolution equations for internal state variables describing the main mechanism take the form of integral or integro-differential equations. One dimensional examples were considered. Experimental results for titanium, aluminum, and copper were used to choose functions involved in the description.