Coupled chemomechanical theory with strain gradient and surface effects

Coupled chemomechanical problems have been demonstrated to exist in many engineering fields. In this paper, we constructed a coupled chemomechanical model in which strain gradient effect and surface/interface effect are considered. Based on the thermodynamical laws, evolving equations in the body and at the interface are derived. The governing equations and boundary conditions are obtained from the chemical Gibbs function variational principle based on irreversible thermodynamics. The boundary conditions are thus quite clear, particularly chemical and diffusion conditions at the interface. In the end, a numerical example is given to illustrate a moving sharp interface when chemical reaction is going on. When the strain gradient effect is taken into account, the abrupt change of radial strain at the interface in classical results is replaced by a moderate transition. As for radial and tangential stresses, they have a larger absolute value in the interfacial zone with gradient effect considered.