3. Flaw Characterization
Certainly, the area of magnetic testing is old, and what I have to discuss today is a refinement of what has existed for a long time, namely, magnetic field measurement. However, as opposed to the common use of magnetic particles to visually produce a signature, in the magnetic perturbation method the magnetic field is controlled and the specimen is scanned to measure the magnitude and direction of the magnetic field.
Barton, John R., "Advanced Magnetic Methods of Flaw Detection" (1974). Proceedings of the Interdisciplinary Workshop for Quantitative Flaw Definition, June 1974. 1.