Elastoplastic coupling for thermo-elasto-plasticity at high temperature

• Coupling of elastic properties with plastic strains, under non-isothermal conditions.
• Adiabatic elasto-plastic moduli.
• Refractory materials subjected to extreme temperature and stress conditions.
• Degradation of elastic stiffness due to plastic distorsional strains.
• Variation of elastic stiffness due to plastic volumetric compaction/dilation.

The coupling of elastic and plastic deformation is introduced in a framework allowing for the inclusion of thermal effects. In this context where high temperatures may be present, many laws governing materials behaviour become nonlinear functions of both temperature and strain. The understanding of this is crucial to model the behaviour of refractories, sintering processes, rocks at great depth and geo-energy. Two equivalent formulations are presented, one in terms of isothermal elastic quantities and the other in terms of adiabatic. In the former approach a Helmholtz free energy density need not be introduced and the contributions to the variations of elastic stiffness of both plastic flow and temperature can be clearly separated and hence a full explanation is given. A simple example using available experiments on sintered alumina shows the capability of the constitutive framework to describe the behaviour of refractories at high temperature.