On kinetic and quasi‐equilibrium modes of propagation of chemical reaction fronts in viscoelastic solids

Abstract A coupled problem of chemo‐mechanics for the case of viscoelastic reaction product is considered within the framework based on the chemical affinity tensor. A chemical reaction localized at the transformation front is studied. Two modes of the reaction front propagation called kinetic and quasi‐equilibrium modes are distinguished. In the kinetic mode, the propagation of the front is driven by the normal component of the chemical affinity tensor defining corresponding configurational force. Quasi‐equilibrium mode corresponds to the propagation of the front at which a chemical equilibrium is maintained. 1D problem statement is considered in detail. Kinetic equations determining the front velocity are derived analytically for both modes. It is shown that the choice of the mode is dictated by the parameter defined by characteristic times of diffusion, chemical reaction, and mass supply through the outer boundary. This dimensionless parameter plays the role of the Damköhler number used in chemical engineering. Special attention is paid to considering nonstationary diffusion and motivation of using stationary diffusion approximation.