Electricity: measuring and testing – Magnetic – With means to create magnetic field to test material
Patent
1986-07-16
1988-07-05
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
With means to create magnetic field to test material
324200, 324213, 324260, 350377, 356237, G01N 2782, G01N 2121, G02F 109
Patent
active
047557524
ABSTRACT:
A method for the direct visualization of surface and near surface cracks, voids, flaws, discontinuities, etc. in a material is disclosed. The detection of flaws or the like is accomplished by the visualization of the static and/or dynamic magnetic fields, either ambient or induced, associated with various flaws in a target material. A magnetic garnet epitaxial film is deposited on either side of a non-magnetic substrate. In one embodiment, a reflective coating or material is provided adjacent to the epitaxial film, and the substrate with its associated layers is placed over the target material. A magnetic field is then applied to the target material and substrate. Polarized light is transmitted onto the target material and is reflected through the epitaxial layer and back out of the substrate. The existing magnetization within the epitaxial film interacts with nearby magnetic fields associated with near surface flaws in the target material, such that the domain structure of the epitaxial film is altered. The altered domain structure induces a rotation of the plane of polarization of the incident projected light. When viewed through a polarizing material disposed on the top epitaxial layer, the rotation of the reflected light renders the magnetic field variations associated with the flaws directly visible. Accordingly, surface and near surface flaws are optically detected.
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Fitzpatrick Gerald L.
Strecker Gerard R.
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