Electricity: measuring and testing – Magnetic – Stress in material measurement
Patent
1990-11-06
1992-11-24
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
Stress in material measurement
324232, 7386269, 73779, G01B 724, G01N 2780, G01R 3312
Patent
active
051666138
ABSTRACT:
A system for identifying and measuring stress at specific locations within a ferromagnetic material by the production and detection of Barkhausen noise during magnetization of the material. The method involves introducing into the material a time varying magnetic field component and a spatially-varying magnetic field component that in combination create a singular zero magnetic flux element within the material that "sweeps" from one position within the material to another and back. By time-gating the detected acoustic Barkhausen signal that results as this zero flux element moves within the material, the signal is isolated as having been generated at a specific depth within the specimen. Since the level of Barkhausen noise varies with stress, a tomographic mapping of stress is obtained for the interior of the ferromagnetic specimen. Through the use of a computer, a three dimensional map of stress in the ferromagnetic material is obtained.
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Pasley, R., Barkhausen Effect--An Indication of Stress, Materials Evaluation, vol. 28, No. 7, Jul. 1970, pp. 157-161.
Edmonds Warren S.
Southwest Research Institute
Strecker Gerard R.
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