Mechanism and application of EMAT technology based on NDT

摘要

Electromagnetic acoustic transducer (short for EMAT) technique is a relatively new method in domestic non-destructive testing (short for NDT). Compared to Piezoelectric technique, EMAT does not need couplant and surface pre-treatment; in addition, it can produce many kinds of ultrasonic. No need for couplant enables real-time measurement of stress of high temperature equipment and pipe thickness due to corrosion caused by erosion. Several of waveforms make it more methods for measurement, such as Guided Wave can detect internal defects in long straight pipe by line scanning. Surface wave can detect the defects on the entire circumferential surface at any point on the circumference. To analyse electromagnetic ultrasonic excitation principle of non-magnetic materials and magnetic materials, use Maxwell functions to derive the expression of Lorentz force, magnetostrictive fore and magnetizing force in infinite plate. And describes the working principle of an electromagnetic ultrasonic device