Interfacial crack behavior in the stationary temperature field conditions

Abstract

The brittle coatings, made of different materials, when subjected to elevated temperatures and in the heat exchange conditions, are susceptible to delamination. Those coatings, as well as thin films, can be used for various therm insulating deposits, e.g. in turbines of thermal power plants. Due to environmental temperature change, in layers made of materials having different thermal expansion coefficients, appear thermal stresses. In this paper driving forces causing delamination of one layer from the other are analyzed i.e. the interfacial fracture in the two-layered, bi-material sample. This analysis was limited to considering the sample behavior when exposed to the stationaiy temperature field. The energy release rate G, which is the driving force for this interfacial fracture, is changing with temperature and that variation is increasing with increase of the temperature difference between the environment and the sample. Analysis of this relation, between the G variation and temperature difference, can be used to predict the maximal temperature difference, which the two-layered sample can be subjected to, without appearance of delamination between layers.