In the last years a Real-Time-Scanner-System for the operation with linear multielement-probes has been designed, constructed and testes in the Laooratory for UltrasonicMethods at the BAM. The system consists of a control unit, an ultra fast transient-recorder-unit and a computer. The displacement, the focusing and the skewing of the sound beamof a group of 8 elements may be performed electronically over a total of 64 elements.
The control-unit contains stages for the excitement, amplification and the displacement-control of the probe elements. The amplitude of the transmitter pulses may be adjusted upto 320 Vp while the rise time is less than 10 ns. The selection of the active elements isperformed by video-multiplexor-units. Voltage-controlled wide-band amplifiers provide adynamic range of more than 80 dB. In both the transmitter and the receiver channels atotal signal delay of 1 micros may be switched in increments of 1 ns. The bandwidth extendsfrom 1,8 MHz to 23 MHz (- 3 dB).
The analog to digital conversion is performed by a high speed transient-recorder-unit. Theinversion rate may be increased up to 200 MSPS. The unit is integrated into thecomputer-hardware (PC 80486). Various software-modules for the beam-control and theimage-presentation have been developed and tested (A-Scan, TD-Scan, C-Scan).
A linear array of 32 elements was designed and manufactured based on PVDF-foil with acenter frequency of 17 MHz. For the laboratory-test a specimen with flat bottom holes ofvarious depths and diameters was used. A diameter of 0,3 mm could be proved preciselyas well as the thickness of a metal sheet of 0,5 mm!
Applications are to be found wherever the mechanical scan might be performedelectronically for one direction and reducing inspection time significantly by this. This isreasonable for the spot weld inspection, the pipe inspection, the inspection of aircraftcomponents. corrosion inspection etc.
G. Schenk, A. Erhard, J. Döring, W Möhrle, (BAM) - Berlin
Kurzfassungen der Vorträge und Plakatbeiträge der ZfP Jahrestagung 1996.
Hier der Bericht über die Jahrestagung or Conference Report in English.
Volltext-Bezugsquelle: DGZfP Berlin Email: 100335,3315@compuserve.com
Sprache:Deutsch
Rolf Diederichs 1. Aug 1996, info@ndt.net