TRANSIENT HEATING VS COOLING OF INTERFACIAL CRACKS IN CERAMIC-TO-METAL BONDS

The effects of transient heating and cooling on a ceramic-to-metal bond made of zirconia and cast iron that contains a center crack or an edge are compared by calculating the transient strain energy release rates via the finite element method. It is shown that for a center crack, the transient maximum G during cooling is larger than during heating. For an edge crack, the largest G occurs at steady-state and at the end of heating. These effects are related to the global deformations of the ceramic-to-metal structure resulting from the transient temperature distribution and the deformation process of the crack. Also, the effect of a transient cooling that follows initial heating and transient heating that follows initial cooling is considered for a thin ceramic layer. In this case, even for the edge crack, the largest G occurs during the transient heat transfer process.