Electromagnetic ultrasonic critical refraction longitudinal wave excitation device

Abstract

The invention discloses an electromagnetic ultrasonic critical refraction longitudinal wave excitation device which comprises a wedge block, a printed circuit board, conductive paste and a permanent magnet. The device utilizes the excitation principle of the electromagnetic ultrasonic transducer to excite longitudinal waves in the conductive paste, and then the longitudinal waves are conducted through the wedge block so that critical refraction longitudinal waves are generated on the surface of a tested piece. Then the wave velocity of the critical refraction longitudinal wave under differentexcitation frequencies is measured, and the stress under different excitation frequencies is obtained according to the linear relation between the wave velocity of the critical refraction longitudinalwave and the stress in the acoustic elasticity principle; the penetration depth under different excitation frequencies is obtained according to the relationship between the penetration depth of thecritical refraction longitudinal wave on the surface of the tested piece and the excitation frequency, then the corresponding relationship between the penetration depth and the stress is obtained, andthe stress under different depths can be calculated. The conductive paste is a soft paste and can be used as a coupling agent while being used as a conductive medium so that the usage amount of the coupling agent is reduced, the conductive paste is conductive and is not liable to volatilize and the measurement accuracy is ensured.

Description

technical field [0001] The invention belongs to the field of electromagnetic ultrasonic detection, in particular to an electromagnetic ultrasonic critical refraction longitudinal wave excitation device. Background technique [0002] The residual stress generated by the non-uniform deformation of the material will affect its yield strength and structural stability, so the measurement of the residual stress is of great significance to the material structure and engineering safety. The residual stress of most specimens will vary with the depth of the outer surface. In the literature "Rickert Theo. Residual Stress Measurement by ESPI Hole-Drilling [J]. Procedia Cirp, 2016, 45: 203-206." The specimen is gradually drilled, and the measurement of the residual stress change at different depths is achieved by using the electronic speckle interferometry method, but this method will cause irreversible damage to the tested specimen. [0003] In recent years, non-destructive testing met...

AI Technical Summary

Problems solved by technology

However, the resonance frequency of the thickness vibration mode of the piezoelectric ultrasonic transducer is related to its thickness. The piezoelectric ultrasonic transducer has its fixed excitation frequency and bandwidth when the structure is determined, and it needs to be frequently used for stress measurement at different depths of the specimen. Replacing the Piezo Ultrasonic Transducer

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