Plastic Deformation of Single Metallic Crystals

Abstract

IN a letter to NATURE (May 22, p. 720), Messrs. Millington and Thompson discussed the wedge-shaped fracture which ordinarily results from a tensile test on a single metallic crystal. On the assumption of uniform slip on a number of parallel planes they calculate the magnitude of an angle which they assume to be the angle of a wedge-shaped fracture produced by the slip. May I point out that uniform slip of the type they consider, on one or more sets of parallel planes, would result in uniform extension together with a uniform change in the cross-section over the whole of the portion of the specimen which is slipping, and consequently no wedge-shaped fracture could result? The angle which was calculated in the letter referred to is the inclination of the axis of the slipped portion of the specimen to the axis of the portion which has not slipped, and this has no connexion whatever with the angle of a wedge fracture.