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Magnetostrictive acoustic transducer based torsional wave generation in pipes using magnetic tapes
Date Issued
14-05-2007
Author(s)
Abstract
Long range torsional guided wave generation in pipes using magnetostrictive sensor (MsS), made of video magnetic tape material, that has a potential application in nondestructive pipe line testing in oil and gas industry is reported in this paper. Generally, magnetic metal strips of Nickel or amorphous Cobalt alloys are used as magnetostricitive strips in these types of sensors. Though in principle, the technique is an established one, there is still scope for improving its sensitivity by getting rid of eddy current losses in these metallic strips. And also corrosion and oxidation will pose a problem in the long run resulting in signal degradation. To avoid such problems, a magnetic oxide based Ms strip material is a good choice. Further, a field enhancer strip in between the coil and Ms strip can also be added to increase the magnetic field on the Ms strips thus reducing the power to drive the coils. The present sensor is designed to have a video magnetic tape as the magnetostrictive strip, and permalloy strip as field enhancer. Results obtained from a systematic study to assess the quality of the torsional wave generated by this sensor in terms of the amplitude and its frequency dependence with two different orientations of magnetostrictive strips and also the defect sensitivity of the sensor to radial notch and drill hole are reported in this paper. © 2007 American Institute of Physics.
Volume
894