Characterization of Crack Propagation along Bond Coat/Topcoat Interface of a TBC System
The crack propagation along the bond coat / topcoat interface of a TBC system has been studied in a previous work under a certain mode ratio (K2/K1). In order to discuss a parameter that describes the crack propagation, the growth behavior of a crack has to be studied under various K2/K1 ratios. In this work, BEM was used to determine the modifications that change K2/K1 ratios of the specimen employed in the previous study. Six characteristics of the specimen were modified: location of the applied load; height; length, position and direction of the notch, and its separation from the bond coat / topcoat interface. Among these modifications, the change of location of load point can effectively change K2/K1 ratio to values greater and smaller than those of the previous study. Crack propagation tests with three different positions of load point were performed using specimens with topcoat porosity of 5%, 15% and 20%. The results indicated that, independently of K2/K1 ratio, the parameter Ki dominated the crack growth behavior for an interface crack under mixed mode.
Kikuo Kishimoto, Masanori Kikuchi, Tetsuo Shoji and Masumi Saka
B. Gomez et al., "Characterization of Crack Propagation along Bond Coat/Topcoat Interface of a TBC System", Key Engineering Materials, Vols. 261-263, pp. 441-446, 2004