MAGNETIC METHODS FOR CRACK DETECTION IN CANNON BORES.
ARMY MATERIALS RESEARCH AGENCY WATERTOWN MASS
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An investigation was made of some of the factors influencing crack detection in cannon bores by magnetic techniques. A method of locally magnetizing a small portion of the tube, as it is being scanned, was developed and compared with residual magnetization of the complete tube. The detectors utilized in this work were of the tape-head type presently employed in the magnetic recording borescope MRB. Salient detector design features, including gap width and coil inductance, were examined. Measured crack indications are related to crack depth and width. Problems associated with the MRB method of scanning rifled portions of the tube are discussed. It is concluded that, although the MRB approach may be satisfactorily applied to the smooth-bore powder-chamber area, it is inadequate for the rifled portion of the tube. An alternate scanning technique utilizing a high-resolution field-sensitive detector is proposed for crack detection in rifled bores. Author
- Test Facilities, Equipment and Methods