Abstract

The aim of this work is the detection of surface defects by the refracted longitudinal wave and the study of the parameters that influence the use of this wave in transmission and reflection modes in order to optimize the non-destructive testing (NDT) conditions with the L_CR waves. For this, two types of defects are considered, cylindrical defects of different lengths 5 and 8 mm with depth of 10 mm and a rectangular groove of length 8 mm, width 2 mm and depth of 10 mm. The L_CR wave was generated by transducers of center frequencies f_c = 1 MHz and f_c = 3.5 MHz with an inclination at a fixed-angle equal to 27° in aluminum. This study is divided into two parts. The first explains the changes in the signals caused by this interaction from a temporal point of view. The second part analyzes the energy losses induced on the spectrum. The reference signal is acquired in a defect-free sample. By comparison between the time signals and the respective reference signals, it has been found experimentally a decrease in the amplitude and a time shift of the L_CR wave due to the presence of the defect. The sample spectra with a defect are modified relative to the spectrum obtained for the sample without defect, these are narrowed particularly for high frequencies. A shift of the centre frequency to lower values can also be noticed. The influences of the sensor frequency and the transmitter/receiver distance have been studied. When the frequency-sensor increases, the effects on the L_CR wave by the defect increase. The study showed, that the increase in frequency allows the detection of smaller defects. Also, because of the inclination of the L_CR beam, the choice of the distance between the transmitter and the receiver affects the defect detection. The reducing of the distance between the transmitter and the receiver improves the defects detection. The natures of the defects influence also the defects detection. In reflection mode, it is also possible to detected defect and the results found are satisfactory. Therefore this method is very effective because it identifies the defect and its location.

中文翻译：

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临界折射纵向波影响表面缺陷检测参数的实验研究

摘要

这项工作的目的是通过折射的纵波检测表面缺陷，并研究影响该波在透射和反射模式下使用的参数，以优化L的无损检测（NDT）条件。_CR波。为此，考虑了两种类型的缺陷，即长度为5和8 mm，深度为10 mm的圆柱形缺陷和长度为8 mm，宽度为2 mm，深度为10 mm的矩形凹槽。的大号_CR波是由中心频率的换能器产生˚F _{c ^} = 1 MHz和˚F _Ç= 3.5 MHz，铝制的固定角度倾斜度等于27°。本研究分为两个部分。第一部分从时间的角度解释了由这种相互作用引起的信号变化。第二部分分析了在频谱上引起的能量损失。在无缺陷的样本中获取参考信号。通过时间信号和相应参考信号之间的比较，实验发现L _CR的幅度减小和时移由于缺陷的存在而产生波动。相对于无缺陷样品获得的光谱，具有缺陷的样品光谱进行了修改，特别是对于高频，这些光谱变窄了。也可以注意到中心频率向较低值的偏移。研究了传感器频率和发射器/接收器距离的影响。当频率传感器增加时，缺陷对L _CR波的影响增加。研究表明，频率的增加可以检测出较小的缺陷。另外，由于L _CR的倾斜对于光束，发射器和接收器之间距离的选择会影响缺陷检测。发送器和接收器之间的距离的减小改善了缺陷检测。缺陷的性质也会影响缺陷检测。在反射模式下，还可以检测到缺陷，并且发现的结果令人满意。因此，该方法非常有效，因为它可以识别缺陷及其位置。