机器人辅助激光超声检测系统及参量匹配方法

Robot assistant laser ultrasonic test system and its parameter matching method

为解决飞行器复合材料构件的非接触、高精度无损检测问题,提出基于关节型机器人的激光超声检测系统及光声学参量匹配方法。采用有限元方法建立层状复合材料模型,计算分析材料层状各向异性导致激光超声的非对称分布、声束倾斜和畸变特征,结合实验分析得出利用激光超声表征分层的光声学参量匹配方法。在系统设计上,利用1 064 nm波长的Nd:YAG脉冲激光器激励超声波,利用基于光折变效应的双波混合干涉测量系统探测超声信号,激励和探测激光由光纤传导并投射至被检测工件表面,采用精密六轴关节型机器人作为C型扫描装置,建立系统的实验室原型,实现碳/环氧复合材料试样的C型扫描检测,得到试样中模拟缺陷的分布、形状和尺寸特征,验证了检测系统及参量匹配方法的有效性。研究结果表明,研制的机器人辅助激光超声检测系统可以实现碳/环氧复合材料内部直径1 mm以上分层的检测与成像,在飞行器复合材料构件的无损检测方面具有应用前景。

In order to solve the problem of non-contact and high precision non-destructive test of aircraft composite material structures, a laser ultrasonic test system based on articulated robot and optoacoustic parameter matching method is proposed. The model of layered anisotropic composite material is built with finite element method, and the characteristics of the asymmetric distribution and beam tilt and distortion of laser ultrasonic induced by the layered anisotropic property of the material are calculated and analyzed. The optoacoustic parameter matching method using laser ultrasonic to characterize the delamination is obtained based on the numerical simulation and experiment results. In the system design, an Nd：YAG pulse laser with 1 064 nm wavelength is used to generate the ultrasonic signal, and the ultrasonic signal is detected by a two wave mixing laser interference system based on photorefractive effect. The exciting and detecting lasers are transmitted by the optical fibers and projected on the surface of the target under test. A precise six-axis articulated robot is adopted as the C-scan device. The laboratory prototype of the system was built, the C-scan test of the carbon fiber reinforced plastic （CFRP） specimen was realized, and the shape, size and distribution characteristics of the simulated defects in the specimen was obtained. Thus the effectiveness of the test system and parameter matching method is verified. The research results prove that the developed robot assistant laser ultrasonic test system can realize the detection and imaging of the internal delamination with diameter larger than 1 mm in the CFRP composite specimen, and has application prospect in the nondestructive test of aircraft composite material structures.