Fully Coupling Chemomechanical Yield Theory Based on Evolution Equations

Coupling chemomechanical yield is one of the key issues in the oxidation of metal and polymer matrix materials. In this paper, the evolving equations for fully coupled thermal-chemical-mechanical processes were derived using the theory of thermodynamics. Then, the coupled chemomechanical yield condition and flow rule were directly obtained from the evolution equations by extending the von Mises theory of plasticity. The coupled yield condition reveals that only the chemical reactions or diffusions may lead to the yield of material even without the mechanical stress, which significantly differs from the previous works. In addition, the currently proposed yield condition combined with the flow rule as a new criterion, may be applicable in predicting the durability of materials within the allowed plastic deformation resulted from time dependent diffusion and chemical reactions. Particular attention is paid to the isothermal systems and isotropic materials for simplicity. Finally, three examples on how the deformation and reaction evolves simultaneously were given to show the applications of the present theory.