PHOTOPLASTIC STUDIES OF STRAIN DISTRIBUTIONS IN THE COLD DRAWING OF POLYCARBONATE CYLINDRICAL-BARS - THE RATE EFFECT

Strain distributions in the cold drawing of polycarbonate cylindrical bars were obtained at three nominal strain rates using the method of photoplasticity. Optical-mechanical constitutive equations were interpreted based on a physical model. The strain distribution in the necked portion of the rod is shown to be nonuniform, regardless of the strain rate. Comparison between the integrated diameters and the measured diameters gives an average error between 4 and 12 percent. An interesting trend in the fringe patterns with and without a central loop has been observed and attributed to the higher strain-rate effect for patterns without a central loop.