A partially insulated embedded crack in an infinite functionally graded medium under thermo-mechanical loading

In high-temperature applications, the materials research community has recently been exploring the possibility of using new nonhomogeneous coatings made of functionally graded materials (FGMs) as an alternative to the conventional homogeneous ceramic coatings. In designing components involving FGMs, an important aspect of the problem is the fracture failure. In this paper, we consider an infinite functionally graded medium with a partially insulated crack subjected to a steady-state heat flux away from the crack region as well as mechanical crack surface stresses. The material is modeled as a nonhomogeneous isotropic elastic medium. The problem is solved under the assumption of plane elasticity. The equations of heat conduction and elasticity are converted analytically into singular integral equations which are solved numerically to yield the crack tip stress intensity factors under thermo-mechanical loading. A crack-closure algorithm is developed to handle the problem of having negative mode I stress intensity factors. The main objective of the paper is to study the effect of the material nonhomogeneity parameters, crack-closure and partial crack surface insulation on the crack tip stress intensity factors for the purpose of gaining better understanding of the thermo-mechanical behavior of graded materials. (C) 2003 Elsevier Ltd. All rights reserved.