热障涂层TGO与热疲劳损伤的激光超声无损检测机理与关键技术研究

The stripping of TBC (thermal barrier coating) on the surface of aero-engine turbine blade is one of the major factors that cause the accident, thus the nondestructive testing and evaluation technique of TBC has become the urgent requirements in many fields, including the aviation field. The TGO (Thermally Growth Oxide) and thermal fatigue are the two major factors that result in the stripping of TBC, therefore, we propose to combine laser ultrasonic technique with spectrum analysis technique used to nondestructively measure the thickness of TGO, and we create a novel nonlinear ultrasonic testing technique based on the collinear mixing frequency SAW(surface acoustic wave) excited by the double pulse laser , in order to characterize the thermal fatigue in this work.The influence of TGO thickness on the ultrasonic longitudinal velocity and the influence of thermal fatigue on the nonlinear acoustic parameter(including the interference frequency and the phase of mixing frequency SAW) are explored in the present work, which are important to reveal the constitutive relation between the TGO thickness and ultrasonic longitudinal velocity, and the relation between the thermal fatigue and the nonlinear acoustic parameter, respectively. The present work provides the basis of real-time nondestructive testing for TGO and thermal fatigue of TBC, and lays the foundation for establishing the TBC ultrasonic testing and evaluation technique with our own intellectual property.

航空发动机涡轮叶片表面热障涂层的脱落是引发事故主要因素之一，热障涂层无损检测与评价技术研究已成为航空等众多领域的迫切工程需求。针对引起热障涂层脱落两个主要因素：TGO（Thermally Growth Oxide）和热疲劳损伤，本项目提出利用激光超声技术结合频谱分析技术对TGO厚度进行实时检测的方法研究；创建双脉冲激光激励共线性混频表面波的非接触式非线性超声检测技术，进行热障涂层热疲劳损伤程度的无损检测方法研究。探索TGO厚度变化对超声波纵波声速的影响和热障涂层热疲劳损伤程度对非线性超声参量（包括混频波的干涉频率和相位值）的影响，对揭示TGO厚度与超声波纵波声速之间的本构关系和热疲劳损伤程度与非线性参量之间的本构关系具有重要意义，为工程实际中TGO厚度和热疲劳损伤的实时检测提供了依据，并为创建具有我国自主知识产权的航空发动机热障涂层TGO厚度和热疲劳损伤超声无损检测与评价技术奠定了基础。

航空发动机涡轮叶片表面热障涂层的脱落是引发事故主要因素之一，热障涂层无损检测与评价技术研究已成为航空等众多领域的迫切工程需求。针对引起热障涂层脱落两个主要因素：TGO（Thermally Growth Oxide）和热疲劳损伤，本项目开展了基于激光超声技术的检测研究工作。首先，研制了具有自适应特性的双波混合式激光干涉仪，通过实验及数值计算揭示了激光辐照材料的温升规律，澄清了激光激励的超声纵波及横波声场指向性。采用小波软阈值法实现了激光超声检测热障涂层过程中噪声抑制，信噪比提高了约20dB。创建了TGO激光超声表征的超声纵波传递函数，并据此实现了0~100次循环氧化热障涂层试样中TGO厚度的检测，检测结果与扫描电镜结果相符。在对热障涂层表面残余应力有限元分析的技术，采用激光超声表面波声弹系数法，实现了0~50次热循环试样的热疲劳损伤检测，检测结果与Raman光谱检测结果一致。本研究创建具有我国自主知识产权的航空发动机热障涂层TGO厚度和热疲劳损伤超声无损检测与评价技术奠定了基础。