飞机GLARE层板结构空气耦合超声兰姆波成像检测方法研究

The subject is proposed to carry out the theory and experimental research on no contact air-coupled array ultrasonic Lamb waves imaging testing technique for GLARE laminate structure's damages of aircraft. Aim to the actual fatigue damage property of GLARE laminate structure, this research subject try to establish a three dimensional interface lay mechanical model based on the multiple interface lay model theory, finite element and interface element method. Combined with the various research means such as theoretical analysis, numerical calculation, experimental testing and signal processing, the excitation and propagation mechanism and scattering characteristic of Lamb waves in GLARE laminate will be selective analyzed. Meanwhile, the interaction and scattering properties between Lamb waves with typical damages in GLARE laminate, and interrelation between Lamb waves signal with typical damages and acoustic parameter will also be studied selectively. Based on the numerical modeling and experiment means, a single side, air coupled ultrasonic array Lamb waves non-destructive testing mode will be adopted to detect damages in GLARE laminate structure. Through extracting and constructing linear and nonlinear acoustic parameter from the scattered Lamb waves and try to improve signal noise ratio, how to develop a higher resolution imaging method will be investigated. Then a new no contact, air coupled ultrasonic Lamb waves array imaging detection method for GLARE laminate structure of aircraft will be obtained. Based on the research work above, the air coupled array Lamb waves imaging testing prototype instrument for GLARE laminate structure will be developed and be used in field experimental research. The research subject will establish the theoretical and methodological basis of in service air coupled ultrasonic Lamb waves testing technology for GLARE laminate structure, and provide a new in service, in field rapid nondestructive technique for imaging testing GLARE laminate structure of modern aircraft.

本研究提出开展飞机GLARE层板结构的空气耦合超声兰姆波阵列成像检测的理论与实验研究。针对GLARE层板结构疲劳损伤特性，引入界面单元，采用有限元方法，在多界面层模型理论基础上建立准确描述GLARE层板损伤特性的三维界面层物理模型。以理论分析、数值计算和实验测试等多种手段相结合，研究空气耦合超声兰姆波在层板中的激发、传播和散射特性，研究兰姆波与层板缺陷的相互作用机制及散射规律，研究兰姆波信号与缺陷和声学参数的关系。采用空气耦合阵列探头同侧收发分置的探测方式，研究如何提取缺陷散射回波的线性和非线性声学参量特征及提高缺陷反射回波信噪比的信号处理方法，实现飞机GLARE层板结构的高精度非接触空气耦合超声兰姆波快速特征成像检测。在此基础上，研制出层板结构非接触、空气耦合阵列超声兰姆波检测实验样机并开展现场实验，建立起飞机GLARE层板结构现场、在役超声兰姆波成像检测技术的理论和方法基础。

纤维增强金属层板（FRMLs）和碳纤维树脂基复合材料(CFRP)层板具有高强度和刚度、优越方向延展性、低热膨胀系数、耐腐蚀等突出特点而成为航空航天制造工程领域中首选材料。GLARE（Glass fiber reinforced aluminium laminate）是第二代纤维金属层板，由薄的铝合金板和含有单向高强度玻璃纤维胶粘剂层组交替层压而成。 GLARE层板以其优异的综合性能被广泛应用于现代飞机制造，尤其是一些对疲劳敏感的结构上，如飞机机翼和机身。GLARE层板结构件在使用过程中的疲劳损伤主要表现为层间分层扩展、冲击损伤、层板内组分金属的裂纹扩展及层板基体裂纹扩展。.本课题提出开展飞机GLARE层板结构的非接触空气耦合超声兰姆波阵列成像检测方法的理论与实验研究。首先，针对GLARE层板结构疲劳损伤特性，引入界面单元，采用有限元方法，在多界面层模型理论基础上建立准确描述GLARE层板损伤特性的三维界面层物理模型。采用有限元、有限差分数值方法和实验方法研究了空气耦合超声兰姆波在层板中的激发、传播和散射特性。掌握了入射角度与检测模式波信号的关系，基于兰姆波波结构分析选择A0模式兰姆波作为检测模式波。研究了A0模式兰姆波与层板缺陷的相互作用机制及散射规律，获得了兰姆波散射信号与缺陷声学参数的关系。其次，设计和制作了带分层缺陷、金属层断裂和带冲击损伤的GLARE层板试样。数值计算和测量了空气耦合超声探头的声场特性，采用空气耦合阵列探头同侧收发分置的探测方式，提取缺陷散射回波的线性和非线性声学参量特征进行缺陷成像，引入损伤指数表征缺陷损伤程度，结合概率算法成像理论实现了缺陷位置和形状特征的描述；同时通过脉冲压缩、时间反转和加权全聚焦等技术提高散射回波信噪比，以实现GLARE层板结构的高精度非接触空气耦合超声兰姆波快速特征成像检测。最后，开发了层板结构空气耦合阵列超声兰姆波检测实验样机并对某型直升机尾梁构件开展现场实验验证。本课题研究为增强我国自主知识产权的航空航天复合材料结构件的现场在役非接触超声兰姆波成像检测技术提供了方法基础。