Abstract
To make fine grain material by plastic working is one of the methods for improvement of material strength. In this study, from the viewpoint of basic plastic working, the variations of static ultimate tensile strength and fatigue strength after the application of plastic torsional deformation on pure copper were investigated. Tensile test, Vickers hardness test and Rotating bending fatigue test were performed. The hardness of the materials varied from surface layer to center section in cross sectional area. The tensile strength was improved after applying torsional deformation. However, the fatigue strength was not improved. This is strongly related to hardness distribution around the surface layer of the specimen. Thus, the plastic softening was occurred in surface layer when the very fine grain was created by torsional deformation.
