ABSTRACT
Magneto-strictive transducer based guided wave method is presented for detection of cable damages such as wire breakage and corrosion. At first, a wave dispersion analysis is carried out on a 7-wire strand with a twist angle of 7.9° using a semi-analytical finite element (SAFE) method, which provides the wave velocities and mode shapes of the wave propagation in the helical cable for a wide range of the exciting frequencies. A magneto-strictive (MS) transducer is designed and used, which consists of a permanent magnet unit and a coil unit. The former is for generation of a static magnetic field, while the latter is for dynamic actuation and sensing. Experimental study is carried out for multiple cases of wire breakage and corrosion using the pulse-echo method. The first longitudinal mode is actuated using the MS transducer, whereas excitation frequencies are selected based on the dispersion curve from the SAFE analysis. Wavelet transformations are carried out on the measured signals to determine the damage severity more accurately. It has been found that the locations and severities of the damages can be determined reasonably well using the time of flight information and wavelet coefficients for the wave packets reflected from the damages.
