近场激光声表面波用于微裂纹检测的机理研究

项目名称： 近场激光声表面波用于微裂纹检测的机理研究

项目编号： No.60878023

项目类型： 面上项目

立项/批准年度： 2009

项目学科： 电工技术

项目作者： 倪晓武

作者单位： 南京理工大学

项目金额： 35万元

中文摘要： 本项目从理论和实验两方面研究了利用激光激发的近场声表面波进行裂纹探测的机理。建立了激光热弹机制激发近场声表面波的理论模型，系统研究带有表面和亚表面裂纹金属材料中声表面波及其特征；实验上建立了激光声表面波的宽带激发和探测系统，通过理论和实验研究相结合，系统研究表面裂纹和亚表面裂纹的参数对激光激发的近场声表面波各种模式的定量影响，包括裂纹的位置、深度、取向、埋藏深度等对近场声表面波模式的反射、透射、模式转换后各种声波模式的幅值、频谱，以及时延的定量影响关系；研究了利用激光近场激发声表面波探测表面及亚表面裂纹的深度、取向、埋藏深度等的原理和技术，特别是深度和取向信息。在此基础上，进一步研究了结合扫描激光源法和激光加热辅助的方法提高激光近场声表面波检测裂纹灵敏度的可能性，成功应用于实际微裂纹的检测。

中文关键词： 激光；近场；声表面波；裂纹

英文摘要： This project investigated the mechanism of crack detection by laser induced near-field surface acoustic waves (SAWs). A theoretical model for the generation of SAW by laser was developed to study the characters of SAWs in metals with surface-breaking or sub-surface cracks; An wide-band experimental setup was built to measure the effect of the cracks' parameters on the characters of SAWs; Based on a detailed theoretical and experimental discussion of the effects of crack location, depth, inclination on the amplitude, frequency spectra, time delay of the SAWs and other transformed modes, principles and techniques for measuring the depth and inclination of the cracks by using the laser induced near field SAW was developed. Furthermore, the possibility of improving the dection sensitivity by using the method of combining scanning laser source technique and another-laser heating was studied experimentally and this method was succesfully used in real crack detection.

英文关键词： Laser; near field; surface acoustic waves; crack