Analysis of brittle fracture characteristics of an infinite plate with an FGM coating around a circular hole

Abstract

This study is concerned with the brittle fracture characteristics of an infinite plate with a functionally graded material (FGM) coating around a circular hole. The incompatible eigenstrain induced in the FGM coating after cooling from the sintering temperature, due to mismatch in the coefficients of thermal expansion (CTE), is taken into consideration. Two diametrically opposed radial edge cracks emanating from the circular hole are considered for the analysis of brittle fracture characteristic. A uniform internal pressure is assumed to be applied to the surfaces of the hole and cracks. The FGM coating is homogenized simulating the material nonhomogeneity by distribution of equivalent eigenstrain. Consequently, an approximation method of determining stress intensity factors (SIFs) is introduced representing the cracks by a continuous distribution of edge dislocations. This approximation method is used in analyzing the effects of material distribution in the coating, crack length, temperature, coating thickness and strength factor on fracture characteristics of the plate. Furthermore, apparent fracture toughness corresponding to prescribed material distributions is also analyzed as a function of the above mentioned parameters except for strength factor. To present numerical results, an infinite plate with TiC/Al2O3 FGM coating around a circular hole is considered. It is found that material distribution in the FGM coating around a circular hole has significant effects on the SIF and apparent fracture toughness which can be controlled by choosing the material distribution appropriately.