热载荷下热障涂层表面裂纹-界面裂纹的相互作用

针对热障涂层在热循环载荷下陶瓷层表面和氧化层/黏结层界面形成裂纹而导致涂层失效的问题,采用扩展有限元和内聚力单元建立陶瓷层表面裂纹与氧化层/黏结层界面裂纹相互作用的有限元模型,得到不同裂纹附近应力分布和开裂程度,分析了这2种裂纹之间的相互影响,结果表明:表面裂纹对界面裂纹影响较大,而界面裂纹对表面裂纹影响较小;氧化层几何参数以及材料参数对2种裂纹演变的影响研究结果表明:氧化层正弦幅值和厚度主要影响界面裂纹,在热载荷下,氧化层越粗糙,界面裂纹扩展速度越快。黏结层弹性模量主要影响界面裂纹扩展程度,而陶瓷层弹性模量主要影响表面裂纹扩展程度,对界面裂纹间接地产生较大影响。

Interaction between Surface Crack and Interface Crack in Thermal Barrier Coatings under Thermal Load

The cracks accured in the surface of Top ceramic Coating(TC)and the interface of Thermally Grown Oxide(TGO)/Bond Coating(BC)can bring out cracks under thermal cycle load.To fix the failure the finite element model of the interaction between the surface crack of ceramic layer and the interface crack of TGO/BC was established using extended finite element and cohesive element.The stress distribution and cracking degree near different cracks were obtained,and the interaction between the two kinds of cracks was analyzed.The results show that the surface crack has great influence on the interface crack,while the interface crack has little influence on the surface crack.The influence result of the geometrical parameters and the material parameters of TGO on the two kinds of cracks evolution show that the sinusoidal amplitude and thickness of TGO mainly affect the interface crack.Under thermal load,the rougher the TGO is,the faster the interface crack propagation speed is.The elastic modulus of BC mainly affects the degree of interface crack propagation,while the elastic modulus of TC mainly affects the degree of surface crack propagation,which has a great influence on the interface crack indirectly.