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Vorrichtung zur Pruefung von ferromagnetischen Materialien

Tester for flaws, cracks or corrosion in ferromagnetic materials e.g. in pipelines - comprises two ultrasonic transducers positioned between pole pieces of premagnetising permanent magnet units for stray flux measurement.
: Willems, H.; Barbian, O.A.; Huebschen, G.

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DE 1995-19543481 A: 19951122
DE 1995-19543481 A: 19951122
EP 1996-117842 A: 19961107
DE 19543481 C2: 19971023
EP 775910 B1: 20040707
Patent, Electronic Publication
Fraunhofer IZFP ()

The tester incorporates two stray flux magnetisation units (3,4) in the form of U-shaped permanent magnets with axially aligned pole pieces (5,5',6,6') joined by a yoke (7,8). One unit (3) has an electromagnetic ultrasonic transducer (9) radiating at right angles to the static magnetic field. Another transducer (11) radiates parallel to the static field from a position between the neighbouring opposite poles of the two units. The function of these is solely to premagnetise the material under investigation and to measure the stray flux. USE - In pipelines (2) or similar structures. Sufficient signal/noise ratio is achieved by suppression of Barkhausen noise when transducers are moved.