Non-destructive testing of thick plates by the third harmonic ultrasonic pulse echo method Deng Mingxi (College of Logistics Engineering, Chongqing 400016) Abstract Ultrasonic echo pulse measurements were performed at two different locations on the same thick plate surface, one with micro-cracks and the other without micro-cracks. The experimental results show that even though the fundamental frequency spectra of the echoes at the two locations are very close, there is still a significant difference between the corresponding third harmonic echo spectra. . Keywords echo, third harmonic, sheet, nondestructive testing Nondestructive testing of thick solid plates using third-harmonic ultrasonic echo Deng Mingxi (Logistics Engineering University, Chongqing 400016) Abstract The ultrasonic pulse echo measurements are performed for the two different positions on the surface of a thick solid plate, where there are micro-flaws in one position and no micro-flaws in another one. The experiment results show that although the fundamental characteristics of the ultrasonic echo for the two different positions are almost the same, the corresponding third-harmonic ones may be of great difference. This result may be used in the ultrasonic nondestructive testing of thick solid plates with the micro-defects. Key words Echo, Third-harmonic, Plate material, NDT 1 Introduction It is of practical significance to perform non-destructive testing on plates with a plate thickness much greater than the acoustic wavelength. For example, in the production and processing of aluminum alloys, accurate non-destructive testing of thick aluminum plate ingots is required. Before the aluminum sheet ingot is rolled into various profiles, if the defect of the aluminum sheet ingot can be accurately and non-destructively detected, the production quality can be effectively controlled. When the defects in the thick plate are small, the usual ultrasonic inspection method can not confirm whether there is a defect; the current inspection method is to directly cut and sample from the aluminum plate ingot, and then perform metallographic analysis. When ultrasonic waves propagate through a solid body, the nonlinear effects of solid body elasticity will cause harmonics to occur. The amplitude of the harmonics is closely related to the amplitude of the fundamental wave, the solid high-order elastic constant and the propagation distance. It is now recognized that higher-order elastic constants are closely related to solid microstructure, internal components or defects, and are an important characteristic parameter of elastic solids. In the process of ultrasonic nondestructive testing, even if the changes in solid linear acoustic parameters (density, sound velocity or acoustic impedance, etc.) caused by defects and other factors are not very obvious, but the corresponding harmonic amplitudes closely related to the solid higher-order elastic constants (taking into account The accumulation effect of harmonics) can still have significant changes compared to the harmonic amplitude in the defect-free state. This situation is expected to be used for ultrasonic non-destructive testing of thick plates with micro-defects [1]. In view of the simplest self-sponsored and self-receiving detection method of a single ultrasonic transducer, considering that the second harmonic reception response of this method is very small, the emphasis can be placed on the detection of the third harmonic. Disclaimer: The copyright of all technical documents belongs to the original author and the original publishing house. Jianke is only to share and spread the essence of other people ’s technical research for direct use for learning and research. Please use it for other purposes without permission. If any legal problems occur, it is not our responsibility. If you have any questions, please contact us in time, and we will correct or delete them immediately. Aluminium Garden Lounger Furniture
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