涂层式裂纹监测系统中基体裂纹穿越行为研究

STUDY OF THE SUBSTRATE CRACK PENETRATION MECHANISMS IN CRACK-DETECTED COATING SYSTEM

建立了智能涂层的两相模型与三相模型,基于能量准则分别用这两种模型研究了基体裂纹达到涂层界面后的穿越/偏转行为.用有限元法分析了相对裂纹扩展长度、弹性错配参数及界面层厚度对偏转裂纹与穿越裂纹能量释放率之比的影响,结果表明当基体裂纹到达驱动层与基体界面时,能量释放率之比不仅与基体和驱动层之间的弹性错配相关,而且当驱动层较薄时对驱动层与传感层之间的弹性错配亦有较强的依赖性.此外,随着驱动层厚度的增加,能量释放率之比对驱动层与传感层之间的弹性错配的依赖性逐渐降低.通过与实验结果相比,建立的模型能够较好的解释基体裂纹在界面的扩展行为,可用于智能涂层裂纹传感器的优化设计.

The two-phase model and three-phase model of crack penetration/deflection at the interfaces in the crack- detected smart coating system were established utilizing the energy-based criterion. The effects of the relative crack growth length, the elastic mismatch parameters and the thickness of the interface layer on the ratio of energy release rates for the penetrated and deflected cracks were studied by the finite dement method. When the substrate crack reaches an interface between substrate and driving layer, the results show that the ratio of energy release rate not only has a strong dependence on elastic mismatch between driving layer and substrate, but elastic mismatch between sensing layer and driving layer for the thinner driving layer as well. Moreover, with increase of the thickness of the driving layer, the dependence on elastic mismatch between sensing layer and driving layer decreases gradually. Compared with the experiment results, the numerical results can interpret the interface behavior of substrate crack and can be used for the optimization design of the crack-detected coating sensors.