Electromagnetic acoustic sensor with consistent circumferential direction and single S0 mode Lamb wave

Abstract

The invention discloses an electromagnetic acoustic sensor with a consistent circumferential direction and single S0 mode Lamb wave and belongs to the field of nondestructive testing. The lower end of a protecting casing of the electromagnetic acoustic sensor is opened; an end part protecting casing is connected with the protecting casing at the opening of the protecting casing; an annular coil is arranged in the end part protecting casing and is provided with a gasket; a magnet is arranged right above the annular coil; a support sleeve is arranged on the magnet and is provided with an impedance matching circuit; another support sleeve is arranged between the upper top end of the protecting casing and the impedance matching circuit; the support sleeve is used for fixing the impedance matching circuit; and the impedance matching circuit is connected with the annular coil through a lead arranged in a square groove of the protecting casing and then is connected with a BNC (Bayonet Nut Connector) through two leads. The electromagnetic acoustic sensor has consistent exciting sensitivity and receiving sensitivity in a direction of 360 degrees, is a non-contact type sensor, can be used for exciting in a structure to generate the Lamb wave without a coupling agent and can be applied to unsmooth surfaces and bent and corrosive surfaces.

Description

technical field [0001] The invention belongs to the field of nondestructive testing, and in particular relates to a circumferentially consistent single S0 mode Lamb wave electromagnetic acoustic transducer (EMAT, Electromagnetic Acoustic Transducer). Background technique [0002] Ultrasonic Lamb wave is an ultrasonic guided wave that exists in plate structures. It is one of the common technologies for non-destructive testing and structural health monitoring. It is used in large industrial structures such as industrial pipelines, storage tanks, ships, spacecraft, wind turbines and It is widely used in the integrity detection of rails, etc. In recent years, it is also often used in the non-destructive testing of various composite material plates and combined structures of plates, such as welded plates, bonded plates and riveted plates, making it more important in the industrial field. [0003] There are three key issues in the design of ultrasonic guided wave sensors: [000...

AI Technical Summary

Problems solved by technology

Piezoelectric sensors and piezoelectric wafers are the two most commonly used. They are characterized by easy-to-use manufacturing. The main disadvantage is the need for couplants. It is difficult to excite symmetrical modes and the excited modes are not single. The other two The ultrasonic guided wave excited by the sensor has beam directivity, and the existence of the coupling agent also makes the final result of the measurement depend on the coupling conditions, and the error is large

The magnetostrictive sensor uses the magnetostrictive effect of the material and its inverse effect to work, and can excite a large in-plane displacement, which can be used to excite horizontal shear waves, but it is difficult to achieve circumferentially consistent Lamb waves. excitation

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