Electromagnetic acoustic transducer EMAT and inspection system with EMAR

摘要

An electromagnetic acoustic transducer for magnets and a sheet type coil unit. The magnets are permanent magnets or electromagnets to provide a static magnetic field to an object to be inspected. The coil unit includes a pair of spiral or meander coils of an electrically conductive material, sandwiched between upper and middle insulation sheet and middle and lower insulation sheet. The coils are used for transmission and reception, respectively. All the ends of the respective coils extend through throughholes formed through the upper and middle insulation sheets to the surface of the ultrasonic transducer, and are connected to external leads. The ends for earth are commonly connected to form a common ground terminal. The inspection system with the electromagnetic acoustic resonance which is a combination of resonant technique and a non-contact electromagnetic acoustic transducer can evaluates the absolute value of ultrasonic attenuation. The attenuation is highly sensitive to the accumulated fatigue damage, showing a maximum around 20-30% of the whole life. This system can assess damage and predict the fatigue life of metals.