热-机械疲劳载荷下抗高温材料表面冷却孔的变形研究

Thermal barrier coatings (TBCs) provide protection against high temperature corrosion of superalloy substrates in gas turbines. However, the lateral growth of the thermally-grown oxide (TGO) ，the thermal expansion misfit between TGO and the metal substrate and stress concentration near the cooling hole induce internal stresses which can be sufficient to activate deformation or buckling in the TBC. We suspect that the cooling hole could be another major source of TBC failure..This work will investigates the behavior of a cooling hole on an alumina-forming alloy coupon subjected to cyclic loading. The experiments will using a unique facility, to reveal the deformation on a cooling hole during thermal and thermo-mechanical cycling. To explain the phenomenon, analysis the stress near a cooling hole by theoretical approaches based on material properties of TGO and the substrate, oxidation rate and growth strain. The method include the experiments and numerical analysis can be used to understand and predict the deformation or failure on the cooling holes.

热胀陶瓷系统（Thermal Barrier Coating system; TBCs）和叶片冷却孔技术已广泛应用于航空涡轮发动机的高温零件中。但由于热生长氧化层（Thermally Grown Oxide; TGO）生长引起的内部应力；热疲劳中热生长氧化层TGO和金属基体不同热膨胀系数引起的TGO内部应力；叶片旋转导致的机械疲劳和冷却孔周围应力集中等因素的作用下热胀陶瓷系统很容易发生变形，最终导致热胀陶瓷层脱落和失效。本项目对冷却孔周围热生长氧化层的变形为研究对象。采用实验，理论分析，有限元分析等方法对热疲劳和机械疲劳作用下冷却孔的变形机理进行研究。以热疲劳和机械疲劳作用下检测到的冷却孔周围的变形为实验基础，建立合理的理论模型以明确冷却孔的变形原因。从而建立一种预测热疲劳和机械疲劳下冷却孔变形的方法。

热胀陶瓷系统（Thermal Barrier Coating system; TBCs）和叶片冷却孔技术已广泛应用于航空涡轮发动机的高温零件中。但由于热生长氧化层（Thermally Grown Oxide; TGO）生长引起的内部应力；热疲劳中热生长氧化层TGO和金属基体不同热膨胀系数引起的TGO内部应力；叶片旋转导致的机械疲劳和冷却孔周围应力集中等因素的作用下热胀陶瓷系统很容易发生变形，最终导致热胀陶瓷层脱落和失效。本项目对冷却孔周围热生长氧化层的变形为研究对象。实施了热疲劳和热-机械疲劳实验，从实验测出不同载荷和循环次数下的微小孔的应变。为分析微小孔的变形原因和机理，建立与实验同样条件下的力学模型，并分析了微小孔周围的应力和应变。为证明理论模型的可靠性进行了有限元分析，得到与理论分析一致的结果。再通过D-optimal试验设计建立多目标全局优化方法，对微小孔进行优化分析，从而确认理论模型的准确性和可行性。