Steel cables are used in many containment buildings for post tensioning. In most cases, the ends of these cables are or can be made accessible. There is concern about the presence of broken stands and overall corrosion of the cables. In addition, there is a desire to measure the tension in the cables. SwRI developed the magnetostrictive sensor (MsS) technology for detecting defects in ferromagnetic materials with cylindrical geometry, such as steel cables. The MsS technique allows an elastic wave to be electromagnetically coupled into the cable. This elastic wave travels the entire length of each cable strand and is reflected by broken strands and scattered by corrosion of the strands. The MsS signals can be treated like ultrasonic A-scan data, so the time location of reflected signals can be used to locate defects and the attenuation of the signal from the end of the cable can be used to estimate the amount of corrosion. This technique can also be used to measure the tension in the cable.The purpose of this paper is to discuss the theory of magnetostrictive sensor technology, the design of the MsS probes, and the results obtained from various types of inspection will be discussed.
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