Effect of edge and internal cracks in 8YSZ thermal barrier coatings subjected to mechanical loading: An numerical approach

Abstract

Abstract The paper presents fracture parameters for edge and internal cracks subjected to mechanical load by the finite element method. The influence of crack length and crack position on edge and internal crack in TBCs on the strain energy release rate (SERR) and stress intensity factor (SIF) are discussed in detail. The numerical results show that the edge crack near the top surface results in high SERR and SIF mode I. In edge crack, the decreasing trend in the SERR was observed with a decrease in crack length and crack position change towards the TC/BC interface. About 60.06% reduction in the SERR was observed for 100 µm edge crack positioned near the top surface when shifted towards TC/BC interface. Similarly, 60 µm and 80 µm edge crack show a 30% and 56% reduction in SERR. Whereas, 20 µm and 40 µm edge crack shows 1.76 and 1.48 times more value of SERR. The internal crack shows a small value of SERR and SIF mode I irrespective of crack length and position compared to edge crack. For internal crack, as the crack length was increased from 20 µm to 100 µm, the reduction in SERR value increases from 59.23% to 90.23%. Similarly, the edge crack shows high SIF mode I compared to internal cracks irrespective of crack length and position. The edge crack appears to be more unstable than the internal crack and propagates early to cause the failure. The crack length and position strongly influence the crack initiation and propagation, resulting in the failure mechanism.