基于激光超声技术的金属表面缺陷检测研究

发布时间：2018-03-05 22:08

本文选题：激光超声　切入点：金属铝　出处：《大连理工大学》2015年硕士论文　论文类型：学位论文

【摘要】：激光超声检测技术是近年来新兴的一种无损检测方法,它具有非接触、频带宽、分辨率高、适合恶劣环境等优点,特别适用于金属表面缺陷的检测。本文从数值模拟和实验两方面展开对激光超声技术应用于金属表面缺陷检测的研究,研究的主要内容有：采用有限元法数值模拟了脉冲激光在各向同性铝板材料中产生超声波的物理过程,分析了激光参数对超声场的影响,结果表明改变激光光斑半径和激光脉冲上升时间可对超声场产生较大影响,进而可以通过调节激光脉冲的参数来控制所激发的超声场。之后分析了激光超声作用于无缺陷铝板激发各种模态超声波的传播规律及特点,研究了激光超声与带表面缺陷的铝板材料的相互作用,分析了缺陷对超声波传播的影响,得到通过表面波对表面缺陷进行检测以及粗略定位的方法。利用激光超声检测系统,对人工制作的带缺陷铝板试件进行了检测研究。分析了激光超声与缺陷相互作用的反射波和透射波的产生原因及传播特点,又进一步对比研究了反射波和透射波的传播规律。结果表明,反射波缺陷信号的信噪比明显强于透射波信号。最后分析了缺陷尺寸参数对超声波的影响,得出了缺陷参数对超声波信号的影响规律,实验结果为缺陷定位和尺寸定量分析提供了依据。
[Abstract]:Laser ultrasonic testing technology is a new nondestructive testing method in recent years. It has the advantages of non-contact, frequency bandwidth, high resolution, suitable for harsh environment, etc. It is especially suitable for the detection of metal surface defects. In this paper, the application of laser ultrasonic technology to the detection of metal surface defects is studied from the aspects of numerical simulation and experiment. The main contents of the study are as follows: the physical process of ultrasonic produced by pulsed laser in isotropic aluminum plate is simulated numerically by finite element method, and the influence of laser parameters on ultrasonic field is analyzed. The results show that changing the radius of laser spot and the rising time of laser pulse can greatly influence the ultrasonic field. Then the ultrasonic field can be controlled by adjusting the parameters of laser pulse. The interaction between laser ultrasonic and aluminum plate with surface defects is studied, and the influence of defects on ultrasonic propagation is analyzed. The method of detecting and locating surface defects by surface wave is obtained. In this paper, the causes and propagation characteristics of reflection and transmission waves of laser ultrasonic and defect interaction are analyzed. The results show that the signal-to-noise ratio of the reflected wave defect signal is obviously stronger than that of the transmission wave signal. Finally, the influence of defect dimension parameters on ultrasonic wave is analyzed. The influence of defect parameters on ultrasonic signal is obtained. The experimental results provide the basis for defect location and quantitative analysis of size.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TN249;TP274

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