Magnetic Barkhausen Noise, Metal Magnetic Memory Testing and Estimation of the Ship Plate Welded Structure Stress

Using the Magnetic Barkhausen Noise (MBN) technique in combination with the Metal Magnetic Memory (MMM) technique, the stress in a welded steel ship plate was investigated. As part of this, the three dimensional image of the self-leakage magnetic field was obtained. In addition, MBN measurements were made in the same test area. The stress distribution, as deduced from the MBN measurements was found to correspond well with the MMM self-leakage image. As a consequence of this positive result, a new testing procedure using the combined MBN and MMM technique is proposed. First, the region with high residual stress is located rapidly using the MMM technique. Then, the actual level of residual stress is determined using the MBN technique, based on prior calibration using specimens made from the same material. This method combining with the X-ray testing method, the damage degree of the ship welded structure which suffered the navigation vibration and environment impact and so on is comprehensively estimated. This test method can not only reduce the workload of the non-destructive testing, but also improve the accuracy of the stress testing.