Experimental Investigation of the Parameters Influencing the Surface Defect Detection by Using the Critically Refracted Longitudinal Waves

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Djerir, Wahiba | Ourak, Mohamed | Boutkedjirt, Tarek

Edité par HAL CCSD ; MAIK Nauka/Interperiodica

International audience. 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 LCR 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 LCR wave was generated by transducers of center frequencies fc = 1 MHz and fc = 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 LCR 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 LCR 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 LCR 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. © 2021, Pleiades Publishing, Ltd.

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