Increase of Stress With Permanent Strain and Stress-Strain Relations in the Plastic State for Copper Under Combined Stresses

Abstract

Annealed-copper specimens in the shape of hollow cylinders have been tested by subjecting them to combined axial tension and internal pressure. A given ratio of the internal pressure to the axial load has been maintained throughout each test, but for different tests this ratio was changed so as to cover the range from pure tension at one extreme to the case of equal biaxial tensions at the other. The results have been used to study the manner in which the plastic strains increase with increasing stress and also to determine the relationships between the three principal strains at any instant during the test. Also, a few observations are made on the types of fracture obtained under various conditions of loading.