ESTIMATION OF DEFECTS IN A PWS ROPE BY SCANNING MAGNETIC-FLUX LEAKAGE

Scanning the magnetic flux leakage (b) around a PWS rope which is magnetized to the saturated state in the longitudinal direction, an attempt has been made to prepare tomograms based on the degree of damage represented by magnetic charges (q). They are obtained as the solution to an inverse problem expressed by a simultaneous linear equation: (b) = [K](q), where [K] is a matrix determined by locations of the flux leakage sensors. These equations are based on the magnetic dipole theory: in this case, since the rope and the surrounding air can be regarded as a magnetically uniform medium, if a defect is produced within a rope due to a break or corrosion, it can be considered as a magnetic dipole. These equations were solved by using a least squares method with the restriction that the magnetic charge (q) must not be negative. Through defects located in the superficial layer of a rope could be accurately estimated by observation in any one direction (r, theta or z), generally, it is recommended to use the z and theta directions when observation in two directions is available.