Nondestructive Evaluation of Beryllium to Copper Joining for Iter By Using An Electromagnetic Acoustic Transducer (EMAT)

Beryllium has a higher magneto-mechanical coupling factor than any other metal and is possibly suitable for an application to Electromagnetic Acoustic Transducers (EMAT). EMAT excites and detects an ultrasonic wave in electrically conducting materials through a reaction of the induced eddy currents and static magnetic fields. This technique has the advantages of a non-contact nature and an easy selection of the desired wave mode. A shear horizontal (SH) wave can be generated easily by using EMAT and it has several attractive features over longitudinal (L) and shear vertical (SV) waves. But the experimental results of SH waves showed the no signal from the interface due to full transparency of the interface. However, in the case of the existence of a defect, several peaks at the higher resonant frequencies can be found through the Fourier Transform. A 10 MHz ultrasonic immersion test as well as an EMAT test have been conducted to compare them by using the same bonded structure.