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Other Titles: Особливості збудження ультразвукових імпульсів ємнісним перетворювачем.
Excitation of ultrasonic pulses with a capacitive transducer.
Authors: Е.Л. Ноздрачева, K.L. Nozdrachova
Г.М. Сучков, G.M. Suchkov
О.Н. Петрищев, O.N. Petrischev
Keywords: ультразвуковой неразрушающий контроль
ultrasonic nondestructive testing
емкостной преобразователь
capacitive transducer
плотность зарядов
charge density
Issue Date: May-2015
Publisher: Донецький національний технічний університет
Citation: Наукові праці Донецького національного технічного університету. Серія: Обчислювальна техніка та автоматизація. Випуск 1 (28). - Красноармійськ, ДонНТУ, 2015.
Series/Report no.: Наукові праці Донецького національного технічного університету. Серія: Обчислювальна техніка та автоматизація. Випуск 1 (28). - Красноармійськ, ДонНТУ, 2015. - C. 165-170.;
Abstract: Экспериментальными исследованиями подтверждены результаты теоретических исследований о том, что акустическое поле, возбуждаемое емкостным ультразвуковым способом, зависит от размера электрода преобразователя. Установлено, что возбуждающая ультразвуковые импульсы поверхность объекта контроля превышает размер электрода емкостного преобразователя. Показано, что формирование импульсного акустического поля обусловлено неравномерным распределением электрических зарядов на поверхности металла изделия под и возле проекции электрода емкостного преобразователя на металл.
Description: This article describes the possibility of implementing capacitive method of ultrasonic non-destructive testing. To perform the research capacitive ultrasonic transducer (CUT) mode excitation of ultrasonic pulses has been developed and new stand blocks were manufactured: the short pulses high-voltage unipolar generator; wideband low-noise pre-amplifier; small-sized partially damped receiving piezoelectric transducer. The applied method of performing experiments made it possible to qualitatively determine the distribution of the charge density on the surface of the sample along the radius of the capacitive transducer electrode. Experimentally we confirmed theoretical calculations. The stand includes a conductive plate with thickness of 25 mm (sample). Plate thickness was chosen from the conditions of formation on the opposite side of the flat front of the ultrasonic field ("Spotlight" area). Plate via a dielectric with thickness of 0.4 mm was placed round copper electrode with thickness of 30 microns and a diameter of 24 mm. The electrode was connected to a variable dc polarizing field and the source of a packet of pulses with adjustable their frequency, duration and amplitude of the voltage. Due to the interaction of the polarizing DC voltage and pulsed AC voltage in the surface layer of metal ultrasonic pulses are excited that propagate deep into the control object. On the opposite side of the plate a serial piezoelectric transducer (PZT) was connected to an amplifier. With the amplifier the output signal is passed to an oscilloscope. Studies were conducted in the amplitude of ultrasonic pulses depending on the relative displacement of 1 mm pitch axes probe with a diameter of 2 mm plate and a copper thickness of 30 microns, electrode capacitive transducer diameter of 31 mm. (CUT) excited a voltage period of 5 MHz frequency. PZT and CUT in the initial state are mounted coaxially on opposing sides of a steel sample having thickness of 9.5 mm. We measured amplitudes of the first and second half-periods of the first received signal passing through the product. From the analysis of the data presented in the paper it follows that the charge density on the surface of the half-space is not uniform and varies to the edge of the projection of the electrode EP. Furthermore, the presence of significant signal is observed beyond the projection of electrode EP. Moreover, the displacement of the receiving electrode PZT beyond CUT displacement occurs at the time of the received signal. That is, the received pulses emitted normal to the surface of the metal, rather than at an angle to it. The duration of the received pulse also increases, that practically excludes receiving of the signal at an angle to PZT receiver.
ISSN: 2075-4272
Appears in Collections:Випуск 1(28)

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