Transducer and method for improving electromagnetic acoustic signal strength

Abstract

The invention provides a transducer and method for improving the electromagnetic acoustic signal strength. The transducer comprises an upper guide rail, an upper screw rod, a coil, an upper magnet, an upper fixing base, an upper slide block, a to-be-tested piece, a lower guide rail, a lower screw rod, a lower magnet, a lower fixing base and a lower slide block. The magnetic field strength, in the direction perpendicular to the to-be-tested piece, in the to-be-tested piece is enhanced after being subjected to vector addition through magnetic field superposition of the two magnets, and therefore the strength of lorentz force, stimulating ultrasonic waves, in the to-be-tested piece is improved, and the strength of emissive ultrasonic wave signals is improved. The transducer can meet the requirement for online non-contact automatic scanning detection of nonferromagnetic metal plates such as aluminum plates.

Description

[0001] Technical field: [0002] The invention relates to electromagnetic ultrasonic nondestructive testing technology, in particular to a transducer and a method for improving the strength of electromagnetic ultrasonic signals. [0003] Background technique: [0004] Electromagnetic acoustic transducer (EMAT for short) is a device that excites and receives ultrasonic waves. The device does not require an acoustic coupling agent, has a simple structure, can easily excite multiple modes of ultrasonic waves, and can realize non-contact measurement, so it has attracted wide attention from researchers. There are usually two methods for exciting electromagnetic ultrasound in metal conductors, one is based on the Lorentz force mechanism, and the other is based on the magnetostrictive mechanism. Electromagnetic ultrasonic transducers based on the Lorentz force are usually used for the detection of non-ferromagnetic conductive materials, and are usually composed of a magnet, a coil an...

AI Technical Summary

Problems solved by technology

When J is constant, in order to increase the signal strength, the only way to increase the magnetic induction of the static bias magnetic field is to increase the magnetic induction B. However, when the magnetization reaches a certain value, it is very costly and technically difficult to increase the magnetic induction. Yes, at the same time, there is a problem of magnetic saturation in the magnet, so there are limitations in increasing the magnetic induction intensity alone

At present, improving the ultrasonic signal strength is usually achieved by reducing the lift-off height and increasing the number of coil turns, but the effect is not very obvious

Due to the low conversion efficiency of the electromagnetic ultrasonic transducer, the weak excitation of the ultrasonic signal leads to the low signal-to-noise ratio of the received signal, and the limited transmission distance due to the weak signal strength, which brings great problems to large-scale and long-distance detection. difficulty

Images