The behaviour of a single crystal of α-iron subjected to alternating torsional stresses

Abstract

The object of the investigation described in the present paper was to obtain some information relating to the mechanism of deformation and failure of a single crystal of α-iron subjected to alternating torsional stresses. With this particular type of applied straining action it has been shown previously that complete fracture of metallic specimen may be produced while the total distortion of the specimen as a whole is extremely small and, in some cases, inappreciable. This has been shown to apply to ductile metals in the form of a finely divided aggregate and also to the case of large single crystals of aluminium. Fracture of this kind is of considerable scientific interest; its practical interest is due to the fact that a very large proportion of the failures of components of modern machines and prime movers are of precisely this type. The absence of change of shape of the specimen under these conditions of test does not permit of the employment of the method of distortion measurements devised by Taylor and Elam, but experience has shown that careful observation of the characteristics of the slip bands formed affords a valuable and unique method of relating the mechanism of deformation with the crystal structure and the applied stressing system, and this method has been employed in the present experiment.