Electricity: measuring and testing – Magnetic – Stress in material measurement
Patent
1981-04-08
1983-10-04
Strecker, Gerard R.
Electricity: measuring and testing
Magnetic
Stress in material measurement
324228, 324235, 324238, 73587, 73779, 73801, 7386236, 7386269, 73DIG2, G01B 724, G01N 2772, G01R 3312
Patent
active
044081600
ABSTRACT:
This disclosure is directed to an acoustic Barkhausen stress detector apparatus and a method of obtaining measurements of stress in or determination of the microstructure of ferromagnetic materials. In the preferred and illustrated embodiment, stress or microstructure information in a ferromagnetic specimen is tested and measured through application of a variable magnetic field. A sensitive acoustic detecting device including an input transducer(s) and amplifier(s) forms a signal based on Barkhausen acoustic phenomena which arise from a change in the magnetic field strength. Barkhausen acoustic information is in the form of vibrations produced within the material which occur as magnetic domain walls shift. The domain wall shifts occur at various locations within the material of interest, and the acoustic vibrations are propagated through the material and are observable at the surface by one or more transducers. The transducer and amplifier system forms output signals dependent on the stress levels and influenced by the microstructure in the material. After amplification and display on a suitable recording device, the signals are scaled to relate the stress and microstructure within the specimen. An array of transducers and associated amplifiers enables spatial resolution of stress distribution in a specimen.
REFERENCES:
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patent: 3783370 (1974-01-01), Birdwell et al.
Karjalainen et al, Influence of Tensile and Cyclic Loading Upon Barkhausen Noise in a Mild Steel, Materials Evaluation, Aug. 1979, pp. 45-51.
Ono et al, Magnetomechanical Acoustic Emission of Iron and Steel, Materials Evaluation, Jan. 1980, pp. 55-61.
Ono et al, Magnetomechanical Acoustic Emission for Residual Stress and Prior Strain Determination, Technical Report to the Office of Naval Research, 10/79.
Pasley, Barkhausen Effect-An Indication of Stress, Materials Evaluation, vol. 28, No. 7, Jul. 1970, pp. 157-161.
Sundstrom et al, The Use of Barkhausen Noise Analysis in Nondestructive Testing, Materials Evaluation, Feb. 1979.
Barton John R.
Burkhardt Gary L.
King James D.
Matzkanin George A.
Edmonds Warren S.
Southwest Research Institute
Strecker Gerard R.
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