Measuring and testing – Vibration – By mechanical waves
Patent
1987-12-17
1989-08-15
Levy, Stewart J.
Measuring and testing
Vibration
By mechanical waves
73620, 73626, G01N 2900, G01N 2904
Patent
active
048563366
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to means for inspection and analyses of materials by ultrasonic waves and, in particular, is concerned with ultrasonic flaw detectors.
BACKGROUND ART
Known in the art is an ultrasonic detector (A. K. Gurvich, I. N. Ermolov, Ultrazvukovoi kontrol svarnykh shvov, Tekhnika Publ., Kiev, 1972, p. 426) comprising a synchronizing signal generator connected to an acoustic pulse generator whose output is coupled to a piezoelectric crystal element whose output is connected to a recorder via a radio-frequency pulse amplifier, a video detector and a video amplifier, all coupled in series.
The piezoelectric element of this ultrasonic detector functions both as a transmitter and receiver of ultrasonic signals.
Sonic testing of a workpiece section is performed by longitudinal and transverse mechanical transportation of a fault locator. Test results are recorded.
The speed of testing is limited by the speed of mechanical movement of the fault locator and, also, by the necessity to maintain a reliable acoustical contact of this locator with the surface of the inspected workpiece. This affects the efficiency of the known ultrasonic flaw detector. In addition, in this ultrasonic detector any fault of acoustic contact has a substantial negative effect on the reliability of test results.
Known in the art is an ultrasonic flaw detector comprising transmitting and receiving channels, each channel having piezoelectric elements, a piezoelectric element switching unit inserted between the piezoelectric elements and an input of radio-frequency pulse amplifier, and a control unit coupled to this switching unit. These units are to switch groups of piezoelectric elements so as to connect them to the input of the radio-frequency pulse amplifier. This permits scanning of the ultrasonic beam along the piezoelectric transducer. The unit can be built around a multivibrator and electronic switches (FR, B, 2243435).
This ultrasonic flaw detector is deficient in that scanning is possible only along the piezoelectric transducer and not in a perpendicular plane, thus affecting the efficiency of ultrasonic testing.
Besides, the reliability of the ultrasonic detector and trustworthiness of test results are affected because the detector is equipped with only one and structurally complex unit for switching and control.
Also known in the art is an ultrasonic detector (SU, A, 463060) comprising an electrical signal transmission channel and an electrical signal receiving channel. The transmission channel comprises a synchronizing pulse generator whose output is connected to a an acoustic pulse generator connected, in turn, to transmitting piezoelectric elements.
The receiving channel comprises receiving piezoelectric elements and, connected in series, a radio-frequency pulse amplifier, a video detector, a video amplifier, and a recording device. This circuit is connected to a control voltage generator and coupled to receiving piezoelectric elements.
The synchronizing pulse generator is connected to a horizontal scanning generator coupled to a frequency divider having its output connected to a vertical scanning generator.
The receiving piezoelectric elements are spaced apart to a distance less than or equal to the length of the ultrasonic wave.
Sonic testing of a workpiece is performed by this prior art flaw detector by a narrow scanning beam, which is achieved by changing phases of ultrasonic oscillations of the receiving piezoelectric elements. The reflected echo signals are received and used to assess the quality of the workpiece. This ultrasonic flaw detector can record fault parameters in the scanning plane continuously throughout the testing period.
This ultrasonic flaw detector is deficient in that its efficiency is poor because test results are recorded even when no flaws are present. This means that the efficiency of this ultrasonic flaw detector depends on the recording speed, the recording being performed continuously over the entire tested zone irrespective of the presence or absence of flaws
REFERENCES:
patent: 4043321 (1977-08-01), Soldner et al.
patent: 4487070 (1984-12-01), Gerling et al.
patent: 4542653 (1985-09-01), Liu
patent: 4543829 (1985-10-01), Lerch
Falkevich, S. A., Issledovanie lineinoi reshetki piezovibratoror s elektricheskim skanirovaniem, 1979, Defektoskopia, No. 4, Moscow.
Falkevich Sergei A.
Fedotov Viktor N.
Naumov Mikhail V.
Sazonov Jury I.
Shkarlet Jury M.
Bell Robert P.
Levy Stewart J.
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