Nondestructive magnetic inspection of spot welding

A method of Magnetic adaptive testing (MAT), which is based on systematic measurement and evaluation of minor hysteresis loops is suggested as simple, reliable and sensitive characterization of welded spots. The method is based on the fact that the welding process has a great influence on the microstructure of the welded area, which modifies the magnetic properties. A series of welded spots, produced by different energy of welding current on car-body sheets was investigated. Good correlation was found between the result of destructive characterization and nondestructive magnetic descriptors.