A Survey of Electromagnetic Methods of Nondestructive Testing

Abstract

Electromagnetic methods of nondestructive testing (NDT) can be classified according to their mode of specimen excitation: Direct current excitation results in active leakage fields around defects in ferromagnetic materials. Residual leakage fields around defects in ferromagnetic materials occur after removal of the dc excitation current. Alternating current excitation of conducting materials results in induced eddy currents which are sensitive to a wide variety of specimen properties.