热障涂层涡轮叶片残余应力及高温行为模拟
RESIDUAL STRESS AND HIGH-TEMPERATURE MECHANICAL BEHAVIOR OF THERMAL BARRIER COATED TURBINE BLADES
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摘要: 热障涂层涡轮叶片可以有效地提高航空发动机的热效率和性能, 对航空发动机的安全稳定运行具有重要的意义. 在热冲击服役过程中, 热障涂层系统易出现表面裂纹、界面裂纹等多种形式损伤, 从而严重影响涡轮叶片的服役稳定性. 考虑到热障涂层涡轮叶片制备过程中产生的残余应力会对热障涂层的质量产生较大影响, 故本工作通过有限元方法首先研究了热障涂层沉积到具有实体形状的涡轮叶片后自然对流冷却过程的残余变形及应力, 进一步对高温热冲击下热障涂层涡轮叶片的温度及应力状态进行了模拟分析, 并揭示带热障涂层的涡轮叶片基底和不带涂层的合金叶片在高温下力学行为差异的应力机制. 研究结果表明, 由于曲率叶片几何结构影响, 热障涂层叶片制备后产生的变形及残余应力分布复杂, 叶根局部压应力最大接近200 MPa; 高温服役下的热障涂层为叶片基底提供了明显的热保护, 最大Mises应力降低可达600 MPa, 但尾缘区域的热保护效果有限; 陶瓷涂层叶根尾缘附近的叶背区域最大主应力达到159.5 MPa; 因此高温服役的热障涂层涡轮叶片会优先在陶瓷层叶根及尾缘区域出现较高应力, 成为裂纹萌生、扩展及剥落发生的起始位置.Abstract: Thermal barrier coated turbine blades can effectively improve the thermal efficiency and performance of aero-engines. They exert significant importance on security and stability of aero-engines. In the process of thermal shock service, the thermal barrier coating system is prone to various forms of damage such as surface cracks and interface cracks, which seriously affects the service stability of turbine blades. Considering that the residual stress generated during the preparation of turbine blades with thermal barrier coating will have a great impact on the quality of thermal barrier coating, this work firstly studied the residual deformation and stress during the natural convection cooling process after the thermal barrier coating was deposited into turbine blades with certain shape by using the finite element method. Furthermore, the temperature and stress state of turbine blades with thermal barrier coating under high temperature thermal shock were simulated and analyzed, and the stress mechanism of mechanical behavior difference between blade with thermal barrier coating and alloy blade without thermal barrier coating under high temperature was revealed. The results show that the distribution of deformation and residual stress after the preparation of thermal barrier coating blade is complex due to the geometrical structure of the curvature blade, and the maximum local compressive stress at the blade root is close to 200 MPa. The thermal barrier coating can provide obvious thermal protection for the blade under high temperature service, and the maximum Mises stress can be reduced 600 MPa, but the thermal protection effect in the trailing edge area is limited. The maximum principal stress in the suction surface near the trailing edge of the ceramic coated blade root reaches 159.5 MPa. Therefore, the thermal barrier coating turbine blade in high temperature service will preferentially show higher stress in the blade root and trailing edge of the ceramic layer, which becomes the starting position of crack initiation, propagation and spalling.