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Parametric optimization of pulse-echo laser ultrasonic system for inspection of thick polymer matrix composites
Structural Health Monitoring ( IF 6.6 ) Pub Date : 2020-01-28 , DOI: 10.1177/1475921719852891
AD Abetew 1 , TC Truong 1 , SC Hong 1 , JR Lee 1 , JB Ihn 2
Affiliation  

One of the main challenges of using laser ultrasonic techniques for non-destructive testing applications is the typically low signal-to-noise ratio of the laser ultrasonic signals. In the case of thick composite structures, this is even more problematic since composite materials have very strong sound attenuation. This article investigates the effects of laser beam size and profile to the amplitude of pulse-echo laser ultrasonic signals with the constraint that the peak energy density (fluence) must be kept constant under the thermal damage threshold of material like polymer matrix composites. Such constraint is very important for the non-destructive feature of non-destructive testing, yet in a number of the existing parameter studies of laser ultrasonics, it was not fully investigated. In this article, a series of A-scan and C-scan experiments on thick composite specimens shows that the amplitude of the direct waves and the reflected waves increases with the increase in laser beam size with constant peak energy density. This amplitude enhancement significantly improves the propagation depth, thereby optimizing the system for inspection of thick composite structures. The validity of experimental results is verified theoretically by solving the thermoelastic model of epicenter displacement using Laplace–Hankel transformation.

中文翻译:

用于检测厚聚合物基复合材料的脉冲回波激光超声系统参数优化

将激光超声技术用于无损检测应用的主要挑战之一是激光超声信号的信噪比通常较低。在厚复合结构的情况下,这更成问题,因为复合材料具有非常强的声音衰减。本文研究了激光束尺寸和轮廓对脉冲回波激光超声信号幅度的影响,约束条件是峰值能量密度(注量)必须在聚合物基复合材料等材料的热损伤阈值下保持恒定。这种约束对于无损检测的无损特性非常重要,但在现有的一些激光超声参数研究中,还没有得到充分的研究。在本文中,对厚复合试样进行的一系列 A 扫描和 C 扫描实验表明,直接波和反射波的幅度随着激光束尺寸的增加而增加,峰值能量密度不变。这种振幅增强显着提高了传播深度,从而优化了用于检测厚复合结构的系统。通过使用拉普拉斯-汉克尔变换求解震中位移的热弹性模型,从理论上验证了实验结果的有效性。
更新日期:2020-01-28
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