Coupling effects of dual-phase-lag heat conduction and property difference on thermal shock fracture of coating/substrate structures

This paper firstly studies the heat conduction in a coating/substrate structure subjected to a sudden cooling on the coating surface based on the dual-phase-lag heat conduction model. Then the thermally induced surface cracking problem is solved and the thermal stress intensity factor at the crack tip is evaluated. It is found that the coupling effects of the thermal properties (such as coefficients of thermal conductivity and diffusivity, and phase lags of heat flux and temperature gradient) on the thermoelastic behavior can be predicted by two introduced factors. Besides, the numerical examples reveal that the thermal stress intensity factor decreases with the ratio of substrate elasticity modulus to coating elasticity modulus. Especially if the ratio is greater than 1, namely the substrate is harder than the coating, the peak value of transient thermal stress intensity factor may decrease with the crack length.