Abstract
MAGNETIC methods have proved useful in the detection of cracks, too inconspicuous to be seen without such aid, in steel. This handbook is in the main a description of the apparatus for carrying out such tests in the laboratory or workshop. Several commercial forms of instrument are described, with a general account of the principles of the method. In one type a direct current is passed through the object being tested, and the concentrated field at the edges of a crack is made visible by pouring on a suspension in light paraffin of a highly magnetic preparation of iron oxide. In the second type, suitable for steels with a higher retentivity, a heavy but very short electrical impulse is sent through the object, and the ink is applied afterwards. Only actual experience enables an observer to decide on the significance of the indications given by the magnetic ink, and to distinguish between cracks and accumulations of the magnetic material caused by sudden changes of section or by casual scratches. Methods of demagnetization have to be applied when, for example, parts for aircraft are being tested.
Principles of Magnetic Crack Detection
A Practical Treatise specially written for those about to Operate the Process. By H. Bevan Swift. Pp. vi + 105. (London: E. and F.N. Spon, Ltd., 1944.) 10s. 6d.
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[Book Reviews]. Nature 155, 378 (1945). https://doi.org/10.1038/155378d0
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DOI: https://doi.org/10.1038/155378d0