System and method for defect monitoring

摘要

A defect monitoring system has ultrasound transmitters and receivers on a wall of a structure under test such as a pipeline. The receivers are arranged in an array of locations that substantially encloses an area under test on a wall of a structure under test. The array may comprise two circumferential rings along a pipeline at different axial positions. The array of ultrasound receivers is used to measure signals that result ultrasound that leave the area through the wall for other parts of the wall. From the measured signals backward propagated signals are computed for a location within the enclosed area, compensated for a modelled effect of propagation from the location within the area to the locations of the receivers at the perimeter. The backward propagated signals for the location in the enclosed area are summed over the locations of the receivers to obtain an approximate integral over the perimeter of the area. The integral is used as a normalization factor for the backward propagated signals for the location within the area. In this way reflection and/or transmission coefficients are obtained that are indicative of the size of defects in the wall, independent of calibration of ultrasound coupling coefficients.