Plastic deformation in the compression test of pure copper

Abstract

A technique is developed for measuring accurately the strains in a cylindrical compression specimen both on the cylindrical surface and on the flat ends. It is found that by using polytetrafluorethylene (p.t.f.e.) sheets as lubricants, a bollard-shaped specimen is produced, and that a suitable amount of this lubricant produces deformations very nearly the same as those in the ideal compression test. The deviations from the deformations in the ideal compression test are represented by the strain paths of particles on the surfaces of the specimen. The stress-strain relationship based on the middle section of the specimen with optimum amount of lubricant is considered to be the standard, and comparison is made with corresponding stress-strain relationships in barrel- and bollard-shaped specimens.