Mechanisms governing the failure modes of dense vertically cracked thermal barrier coatings
Mechanisms governing the failure modes of dense vertically cracked thermal barrier coatings
复制标题
致密垂直裂纹热障涂层失效模式的控制机制
DOI：
10.1016/j.engfracmech.2017.11.037
复制
发表时间：
2018
影响因子：
5.4
通讯作者：
Wang Tiejun
中科院分区：
文献类型：
--
作者：
Li Biao;Fan Xueling;Okada Hiroshi;Wang Tiejun
在陶瓷涂层中引入致密的垂直裂纹是提高热障涂层应变容限和使用寿命的有效途径。然而，这些预先存在的裂纹的进一步增长可能导致涂层的分层，形成各种失效模式。本研究的目的是数值模拟研究致密垂直裂纹热障涂层失效模式的形成机理。讨论了垂直裂纹密度和材料性能对断裂行为的影响。基于能量准则处理双材料界面的表面裂纹偏转/穿透行为，并利用非连续材料的相互作用积分方法来评估断裂参数。通过研究裂纹尖端驱动力在整个断裂过程中的连续变化，构建了热障涂层的失效图。结果表明，引入高密度垂直裂纹可以提高界面抗断裂性能。同时，这些裂纹倾向于渗透到粘结层中，导致粘结层/基材界面处或两个界面处的脱粘。除了有利于减轻界面失配应力，它被发现，高密度的垂直裂纹给增韧增加的涂层系统从多个路径释放更多的能量。此外，还讨论了复合型界面韧性和初始残余应力对失效模式形成的影响。
The introduction of dense vertical cracks in ceramic top coat has been recognized as an efficient way to improve the strain tolerance and service durability of thermal barrier coatings (TBCs). However, further growth of these pre-existing cracks may cause the delamination of the coatings to form various failure modes. The motivation of this work is to numerically study the mechanisms that govern the formation of failure modes in dense vertically cracked TBCs. The effects of vertical crack density and material properties on the fracture behaviors are discussed. An energy-based criterion is employed to deal with the surface crack deflection/penetration behavior at a bimaterial interface, and an interaction integral method for discontinuous materials is utilized to evaluate the fracture parameters. The failure maps of TBCs are constructed by examining the continuous variations of crack tip driving forces over the whole fracture process. It is verified that the interfacial fracture resistance could be enhanced by introducing high-density vertical cracks. At the same time, these cracks tend to penetrate into the bond coat that results in debonding at bond coat/substrate interface or at both interfaces. In addition to benefit in alleviating the interfacial mismatch stress, it is found that the high-density vertical cracks give toughening increases to the coating system by releasing more energy from multiple paths. Moreover, the effects of mixed-mode interface toughness and initially residual stress on the formations of failure mode are discussed.