Volume 6, Issue 4 (July 1978)
Proportional Biaxial Cyclic Hardening of Annealed Oxygen-Free High-Conductivity Copper
Cyclic-dependent hardening of annealed metals is by now a well-known experimental phenomenon. The annealed metal, when cycled between equal tensile and compressive strain limits, develops increasing stresses with each strain reversal. However, most previous experimental work on cyclic hardening has been restricted to axial or torsional loading. In this investigation hollow circular cylinders of annealed oxygen-free high-conductivity copper were subjected to combined axial-torsional cyclic proportional strain histories. The stress-strain histories for different proportional strain paths were correlated on the basis of effective stresses and strains defined previously by Tresca and Mises, and the correlations using Tresca's definitions were shown to be more representative than those of Mises. Power law hardening constants were determined for each stress-strain reversal. The power law hardening constants for axial cycling were predicted with reasonable accuracy from the corresponding torsional constants by employing correlations based on Tresca's definitions of effective stresses and strains.