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Ultrasound generation with high power and coil only EMAT concepts

  • Electro-magnetic acoustic transducers (EMATs) are intended as non-contact and non-destructive ultrasound transducers for metallic material. The transmitted intensities from EMATS are modest, particularly at notable lift off distances. Some time ago a concept for a “coil only EMAT” was presented, without static magnetic field. In this contribution, such compact “coil only EMATs” with effective areas of 1–5 cm2 were driven to excessive power levels at MHz frequencies, using pulsed power technologies. RF induction currents of 10 kA and tens of Megawatts are applied. With increasing power the electroacoustic conversion efficiency also increases. The total effect is of second order or quadratic, therefore non-linear and progressive, and yields strong ultrasound signals up to kW/cm2 at MHz frequencies in the metal. Even at considerable lift off distances (cm) the ultrasound can be readily detected. Test materials are aluminum, ferromagnetic steel and stainless steel (non-ferromagnetic). Thereby, most metal types are represented. The technique is compared experimentally with other non-contact methods: laser pulse induced ultrasound and spark induced ultrasound, both damaging to the test object’s surface. At small lift off distances, the intensity from this EMAT concept clearly outperforms the laser pulses or heavy spark impacts.

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Author:Dirk Rüter, Tino Morgenstern
Parent Title (German):Ultrasonics
Document Type:Article
Year of Completion:2014
Date of first Publication:2019/02/07
Release Date:2019/02/07
First Page:2141
Last Page:2150
Institutes:Fachbereich 4 - Institut Mess- und Senstortechnik
DDC class:600 Technik, Medizin, angewandte Wissenschaften / 621.3 Elektrotechnik, Elektronik
Licence (German):License LogoCreative Commons - Namensnennung-Nicht kommerziell-Keine Bearbeitung