On the interaction of channeling/segmentation cracks of coating: Study on the critical spacing

Abstract

Channeling/segmentation cracks may arise in the coating subjected to in-plane tensile stress. The interaction between these multiple cracks, say the effect of the spacing between two adjacent cracks on the behaviors of channels themselves and the interface around the interface corners, attracts wide interest. However, if the spacing is greater than a specific magnitude, namely the Critical Spacing (CS), there should be no interaction between such channeling/segmentation cracks. In this study, the mechanism of the effect of the crack spacing on the interfacial stress around the interface corner will be interpreted firstly. Then the existence of the CS will be verified and the relationship between the CS and the so-called stress transfer length in coating will be established for plane strain condition. Finally the dependence of the stress transfer length, simultaneously of the CS, on the sensitive parameters will be investigated with finite element method and expressed with a simple empirical formula.

On the cyclic bending behaviour of a hard coating on a ductile substrate with periodic surface hardened regions

“…Wu et al (2006a) and Hu et al (2005) reported that the thermal loading would introduce periodic segmentation cracks in the coating. These segmentation cracks are further reported by Wu et al (2006b) and Wu et al (2008) to be effective on decreasing the stress concentration around the interface corner when the spacing drop into certain range. Later on, Wu et al (2007) revealed experimentally that the controllable cracking of the coating can also be developed when the specimen is subjected to in-plane tension, which is considered to be largely due to the unique pattern of the yielding stresses and residual stresses in the structure.…”

“…However, left to this vertical crack or around the other two, there is no interface crack. This means that the interface stress is relatively low therein, which may be due to the effect of the vertical cracks on relaxing the stresses (Wu et al, 2008). Fig.…”