Modeling and simulation of mechanical-thermal-diffusional-reactional interactions in ceramic oxidation process

Abstract

The multi-field coupling problem in ceramic oxidation considering the effects of force, heat and chemistry involves complex dynamic process of multi-component substance in an open system. This work developed a fully-coupled mechanical-thermal-diffusional-reactional constitutive model to characterize the complex interactions among the effects. The concept of inertial effects was used to describe the dynamic of the multiple fields with finite propagation velocity. The contributions of mass diffusion and chemical reaction were separated to consider their different influential mechanisms. The weak forms of the governing equations were derived by using the chemical Gibbs function variational principle that was established based on the universal variational principle of thermodynamics. The model has the ability in predicting the concentration and entropy jump conditions on the moving interface. To verify the proposed model, the oxidation processes of Si3N4 and SiC were numerically calculated, by which the evolutions of oxide thickness and stress were presented. The results agree with the reference results, indicating that the model is able to reflect the evolution laws of the stress field, concentration field, temperature field and displacement field of Si3N4 and SiC under the coupling effect of multi-physical fields.