Application of the sacks boring-out and finite element techniques to the measurement of residual stresses in oxygen free high conductivity-cu tubes

In the first phase of this study, a modified Electrochemical Machining (ECM) process was utilized in conjunction with the Sacks boring-out technique in order to experimentally measure the residual stress patterns throughout the walls of cold-drawn OFHC copper tubes representing 10.9% reduction (1/4 hard). ECM proved to be particularly suitable for this type of study due to its constant mass removal rate and its accuracy for material removal without disturbing the internal stress distributions. Principal residual stresses were determined and the effective stress distribution is presented and compared to the materials yield stress. In the second phase of this study, an elasto-plastic finite element code was employed to simulate the drawing process by which the tubes were manufactured. The finite element model, and the resulting residual stress distributions are presented and compared to the experimental results. Both techniques resulted in a pattern of residual stresses which were of compressive nature near the inner surface, and tensile at the outer surface of the tube.