To the description of non-isothermic elastic-plastic deformation

Natalija Naerlović-Veljković

Theoretical and applied mechanics, Tome 8 (1982) no. 1, p. 105 .

Résumé

The paper examines the elastoplastic deformation process in which, in addition to the deformation tensor and temperature, heat flux and two groups of internal variable states play the role of independent variables. The rate of change of this second group of internal variable states is conditioned by the sign of the so-called load index and disappears, whenever the latter is not positive. Otherwise, the rates of change of the heat flux, as well as both groups of internal variable states, are governed in accordance with the assumed laws of evolution. With the thus adopted material model, the thermodynamic limitations that follow from the Second Law of Thermodynamics were derived and a discussion was conducted. On that occasion, instead of the specific free energy, the function of the specific free enthalpy was introduced, whose form is compatible with the assumption that the thermoelastic moduli of the material are independent of the dissipative variables in which they are included: heat flux, a set of viscous and a set of plastic internal variables. The thermodynamic basis of the appearance of the Bausehinger effect is shown, whereby the negative effect of work on plastic deformation covers the positive contribution related to the influence of configurational entropy, a quantity that originates from plastic deformation as well as its history and from the heat conduction process in the absence of temperature gradients.