基于激光辅助加热的声表面波微裂纹检测的实验研究
关键词 超声检测 激光加热 声表面波 微裂纹
毕业设计说明书（论文）外文摘要
Title Applications of Laser Heating of Ultrasonic Surface Waves for the Detection of Micro-cracks
Abstract
Fatigue crack is usually generated by abrupt change of local stress due to the geometry irregularity of specimen and the inhomogeneous of material. Traditional detecting techniques using ultrasound, such as pulse-echo method, are difficult to distinguish the fatigue crack effectively, because the size of the cracks are so small that they are often hidden from ultrasonic detection by a stronger scattering from the very same structural imperfection, such as surface grooves, corrosion pits, coarse grains, etc. It is well-known that the ultrasonic surface waves are susceptible to crack closure and therefore exhibit strong parametric modulation, a method based on laser heating of ultrasonic surface waves generated by laser for detecting micro-crack of sample is presented by Dong Li-ming and Li Jia. It is found that the micro-cracks can be detected successfully.Thus the method is used for the test of the black glass in this paper.The influence on the acoustic pulses transmission caused by the closure degreen of the micro-crack is analyzed when the laser irradiated on the micro-crack in the condition of different heating power in the same time as well as in the condition of the same heating power in different time.
Keywords ultrasonic detection laser heating ultrasonic surface waves micro-crack
目 次
1 绪论 1
1．1 研究背景 1
1．2 研究意义 2
1．3 国内外研究概况及发展趋势 3
1．4 本文的主要研究内容 4
2 激光超声的激发与检测 6
2．1 激光超声产生机理 6
2．2 热弹机制下激发超声的点线光源模型 6
2.2.1 热弹机制下激发超声的点光源模型 6
2.2.2 热弹机制下激发超声的线光源模型 7
2．3 激光超声表面波的特性 9
2.3.1 激光超声表面波的波形 9
2.3.2 激光超声表面波的方向性 10
2．4 激光超声的检测 11
3 基于激光辅助加热的声表面波微裂纹检测的实验研究 13
3．1 加热激光对裂纹的影响 13
3．2 基于激光辅助加热的声表面波微裂纹检测的实验研究 14