Understanding the enhancement of coating's thermal cracking resistance by multiple segmentation cracks
首发时间:2011-01-17
Abstract:The cracking of coating is a common phenomenon for a coated medium subjected to thermal transients and usually causes subsequent delamination of coating. Experimental results showed the thermal cracking resistance of a coating could be greatly improved by introducing multiple segmentation cracks but the underlying mechanism remains to be revealed. In this paper, the thermally induced cracking behavior of a segmented coating on the outer surface of a hollow cylinder has been investigated. The driving force for the propagation of multiple segmentation cracks, represented by the Thermal Stress Intensity Factor (TSIF), was determined by combination of the principle of superposition and the finite element method. The maximum TSIF has been shown to occur neither at the beginning nor at the steady state of thermal transients, but at an intermediate instant. It has also been found that, as the spacing between multiple segmentation cracks decreases, the magnitude of TSIF first plateaus, and then decreases sharply. This quantitative mechanistic result rationalizes the experimental observations that a segmented coating can exhibit much higher thermal cracking resistance than an intact counterpart, if only the density of multiple segmentation cracks is high enough. Some other parameters affecting TSIF, such as segmentation crack depth and convection severity, were also discussed.
keywords: Cracking Segmented coating Segmentation crack Thermal stress intensity factor
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群体分割裂纹增强涂层抗开裂能力的机制
摘要:The cracking of coating is a common phenomenon for a coated medium subjected to thermal transients and usually causes subsequent delamination of coating. Experimental results showed the thermal cracking resistance of a coating could be greatly improved by introducing multiple segmentation cracks but the underlying mechanism remains to be revealed. In this paper, the thermally induced cracking behavior of a segmented coating on the outer surface of a hollow cylinder has been investigated. The driving force for the propagation of multiple segmentation cracks, represented by the Thermal Stress Intensity Factor (TSIF), was determined by combination of the principle of superposition and the finite element method. The maximum TSIF has been shown to occur neither at the beginning nor at the steady state of thermal transients, but at an intermediate instant. It has also been found that, as the spacing between multiple segmentation cracks decreases, the magnitude of TSIF first plateaus, and then decreases sharply. This quantitative mechanistic result rationalizes the experimental observations that a segmented coating can exhibit much higher thermal cracking resistance than an intact counterpart, if only the density of multiple segmentation cracks is high enough. Some other parameters affecting TSIF, such as segmentation crack depth and convection severity, were also discussed.
关键词: Cracking; Segmented coating; Segmentation crack; Thermal stress intensity factor
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