Article Periodicals » Materials Evaluation » Article
Magnetostrictive Transducer for Torsional Guided Waves in Pipes and Plates

The use of low frequency (up to 300 kHz) guided waves as a screening tool for different kinds of structures has become increasingly popular over the past decade. Three predominant types of probes have typically been used for generating and receiving guided waves: piezoelectric, electromagnetic-acoustic and magnetostrictive. The major benefit of the magnetostrictive type is the relatively low cost of materials, which makes them promising as a cost effective approach for permanent monitoring of components. Generation of torsional mode guided waves using conventional magnetostrictive sensors requires the permanent magnetic bias field to be oriented along the magnetostrictive strip. The residual magnetic field, together with a time varying magnetic field, provides generation and reception of the waves. The typical designs, however, limit the power level of the time varying magnetic field, which also has the effect of reducing the residual magnetic field. A magnetostrictive transducer design developed at our company allows the use of a low cost generator of the bias magnetic field as an embedded part of the transducer. When the bias field is actively sustained, there is no limitation to the time varying magnetic field. As a result, the power output of the transducer as well as the sensitivity can be maintained at a higher level. The magnetostrictive transducer design was successfully tested over a frequency range of 16 to 250 kHz. A number of prototypes have been developed for different applications and components, including permanent monitoring and rapid screening of structures using a dry coupling technique. Applicability and limitations of the magnetostrictive transducer for application to screening and monitoring of piping will be discussed herein and some trial data will be presented.

References
EPRI, Nondestructive Evaluation: Guided Wave Ultrasonic Technology Applications for Balance-of-Plant Heat Exchanger Tubes and Tube Support Plate Degradation, Palo Alto, California, EPRI, 2008. Kwan, H., J. Crane, S. Kim, A. Parvin and G. Light, “A Torsional Mode Guided Wave Probe for Long Range In-Bore Testing of Heat Exchanger Tubing,” Materials Evaluation, Vol. 63, 2005, pp. 430–433. Kwun, H., S. Kim and J. Crane, “Method and Apparatus Generating and Detecting Torsional Wave Inspection of Pipes or Tubes,” US Patent 6,429,650, 2002. Kynch, G.J., “The Fundamental Modes of Vibration of Uniform Beams for Medium Wavelength,” British Journal of Applied Physics, Vol. 8, 1957, pp. 64-73. Raskin, Donald, James E. Kearney and Errol A. Haznedar, “Magnetostrictive Acoustic Transducer,” US Patent 4,716,556, 1987. Shin, H.J. and J.L. Rose, ”Guided Wave Tuning Principles for Defect Detection in Tubing,” Journal of Non-destructive Evaluation, Vol. 17, 1998, pp. 27–36. Vinogradov, S., “Tuning of Torsional Mode Guided Wave Technology for Screening of Carbon Steel Heat Exchanger Tubing,” Materials Evaluation, Vol. 66, 2008, pp. 419–424. Vinogradov, S. and N. Muthu, “Development of a Screening Method for SeaCure Tubing using Guided Waves,” Tenth EPRI Balance-of-Plant Heat Exchanger NDE Symposium, San Antonio, 16–18 June 2008. Vinogradov, S., B. Jacobs and J. Godwin, “Experimental and Theoretical Investigation for the Use of Guided Waves to Detect and Size Corrosion/Erosion Defects in Heat Exchanger Tubes,” Seventh EPRI Balance of Plant Heat Exchanger NDE Symposium, Santa Ana Pueblo, New Mexico, 2002. Vogt T., D. Alleyne and B. Pavlakovic, “Application of Guided Wave Technology to Tube Inspection,” NDT.net, www.ndt.net/article/ecndt2006 /doc/Th.3.1.5.pdf.
Metrics
Usage Shares
Total Views
51 Page Views
Total Shares
0 Tweets
51
0 PDF Downloads
0
0 Facebook Shares
Total Usage
51