Device and procedure for the detection of the test head formation in the non-destructive examination of metallic materials with electromagnetic ultrasonic converters

摘要

The device incorporates an electromagnetic ultrasonic sensor (2) which generates and receives an ultrasonic wave without using a coupling medium. Eddy current coils (5;15;25) are mounted perpendicularly to the plane of an ultrasonic transducer (4,4') which is connected to a transmission and reception circuit for measurement of the coil's complex impedance during the measurement intervals of the ultrasonic transducer. At least one ultrasonic transducer (4,4'), or a group of transducers (3,3'), can be enclosed by an eddy current coil (15;25), or a coil (5) can enclose the entire sensor. At least one of the coil's windings lies approximately in the plane of the transducer. The distance from the material surface to the transducer, and the material's condition, is evaluated by using impedance calibration reference curves, to compensate for the detected ultrasound amplitude/phase changes. IMAGE