THERMODYNAMIC CONSTITUTIVE MODEL BASED ON COUPLED FIELD AND ITS APPLICATION IN SIMULATING THE PLC EFFECT OF ALLOY

The intrinsic variables of coupled field were proposed to establish the thermodynamic constitutive model of coupled field in which the influence and cross influence of multiple physical fields can be considered. Different from the traditional thermodynamics that the variables of coupled field were considered as ‘parameters’ to modify the material coefficients to establish the constitutive model of coupled field under the thermodynamic framework, this paper considered the coupling of thermodynamic force as the key to model establishment, which was characterized. It overcame the problem in ‘parameter’ method that the coupling filed variable such as the temperature is not only a material parameter, but also an observable state variable, and the duality of thermodynamic forces can still be strictly satisfied in coupled field. Based on the Onsager reciprocal relation and the intrinsic variables of coupled field, the constraint matrix of hydrodynamic evolution equation in the thermodynamic coupled field was established to describe the effect of interaction on elasto-plastic mechanical properties of materials between coupled fields. An application of the generalized model was given at the end of this paper, which showed the degeneration of the generalized model. The applicability of the coupled field thermodynamic constitutive model proposed in this paper in describing the cross influence of multiple physical fields was verified by simulating the negative positive transition of steady-state strain rate sensitivity (Strain Rate Sensitivity) during the loss of high-temperature deformation stability of the alloy (Portevin-Le Chatelier).