Abstract: A SQUID (Superconducting Quantum Interference Device) magnetometer, by far the most sensitive means for detecting small magnetic field variations, is utilized to detect defects inadvertently produced in the manufacture and draw-down of wires. Detection is effected by moving any electrically-conducting wire directly under a shielded SQUID magnetometer with a small aperture to permit the sensing of the magnetic field associated with injected or induced alternating electrical current. Shielding may be provided either by a mu-metal cylinder with a small concentric bottom hole or an open superconducting cylinder strategically placed around the SQUID sensor. Initially, the position of the cryogenic containment vessel (dewar) is oriented to produce a null magnetic signal at the squid sensor location. Any phase-sensitive-detected) signal that appears after wire is spooled under the sensor must be related to non-concentric deviations of the current path in the wire.

Abstract: The magnetoelectric coefficient in iron-based alloys has a stress value of about 0.6 of that of the elastic limit. A reversal in sign is caused by structural phase slip which is the basis for the onset of metal fatigue. Based on this phenomenon, a method is provided for determining the onset of metal fatigue. The method includes applying a periodic mechanical stimulus at a given frequency to a test structure, and using a magnetometer, sensing the magnetic field of said structural element during the application of stimulus, and then determining whether or not there is a 180 degree difference between the phase of the stimulus and that of the magnetic response for various regions of the test structure.