Portable Contactless EMA Thickness Gauge

Bezlyudko, G.Ya.; Dolbnya, E. V.; Muzhitskii, V. F.; Remezov, V. B.

doi:10.1023/b:runt.0000026014.39223.ec

Cited by 1 publication

(3 citation statements)

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“…The data on the modern developments intended to create EMA thickness gages were reported in [12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. The advantages of using radio-frequency (RF) pulses in measurements of thickness were shown in [18].…”

Section: Suchkovmentioning

confidence: 97%

“…In order to study the capacities provided by the correlation analysis used in a thickness gage, a laboratory setup with a digital oscilloscope and a personal computer was used [20]. As in the devices reported in [16,22,24], this device is equipped with a liquid-crystal display to visualize the accepted detection scheme. This approach ensures that reliability of the correctly performed measurements is significantly enhanced.…”

Section: Suchkovmentioning

confidence: 99%

“…The " äêå -ñ -ÑÂÎ¸Ú ‡ " thickness gage [14,22,24] is equipped with a graphical liquid-crystal display. The image on the screen is used to precisely position the measuring cursors on the intended places of the implemented detection scheme.…”

Section: Suchkovmentioning

confidence: 99%

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The capacities of modern EMA thickness gages

Сучков

2004

Russ J Nondestruct Test

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The literature concerned with the problem of studies and development of thickness gages based on the EMA method of exciting and detecting ultrasound pulses is analyzed. A new approach to the design of EMA thickness gages is developed. A prototype of the "manual" EMA thickness gage is designed and tested. It is shown that the EMA device offers considerable benefits when using the correlational data processing.The capabilities of the electromagnetic-acoustic method of exciting and detecting ultrasonic (US) vibrations are most promising as pertaining to measurements of thickness [1]. The studies and the development of equipment in this line have been intensively developed . The authors of [2] carried out extensive studies on measuring the thickness of ferromagnetic tubes using the pulse EMA technique and created a prototype for a thickness gage. The magnetic field required for excitation and detection of US vibrations is created by a pulsed electromagnet. An articles' thickness is tested by measuring shear-vibration ultrasound pulses, which, all things being equal, allows the testing of smaller thicknesses. In order to process a signal, two approaches are used: either the time interval between the probing pulse and any bottom echo-pulse or the time interval between any pair of bottom signals is measured. Measurement of the interval between the bottom pulses is the most beneficial for the EMA method of thickness testing because it ensures elimination of both conventional inaccuracies and inaccuracies caused by bulk distribution of the electromagnetic dynamic forces in the surface layer of the tested object (TO) during excitation and detection of US vibrations. This regime should most reasonably be used in the measurement of the thickness of thin articles made from nonferromagnetic metals with low electric conductivity. Moreover, the "dead zone" decreases. However, this method cannot be used to test the material of a TO with high damping of US vibrations or for articles with corroded surfaces. The authors of [2] established that, apart from the useful echo signals that hold the information on the article's thickness, disturbance pulses are observed. This is because the transducer excites both shear (useful) US vibrations and longitudinal US vibrations, the latter being transformed into the shear mode during detection. Therefore, it is necessary to take measures to exclude the effect of coherent interference. The authors of [2] also established that, in the testing process, owing to a change in the gap between the EMA transducer (EMAT) and the article's surface or owing to the effect of the quality of the tested surface, etc., the total signal level at the output of the transducer can change fivefold or more. Thus, measures should be taken against the above interference; otherwise, its effect on the results of measurement must be excluded. The authors assert that, at optimum parameters of the probing pulse and biasing pulses, the thickness gage can test ferromagnetic pipes with 3-to 50-mm-thick walls with an accuracy o...

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Section: Suchkovmentioning

confidence: 97%

Section: Suchkovmentioning

confidence: 99%