Uniaxial and biaxial stress states were employed to compare the measured macroscopic yield behaviour of oriented polycarbonate, polyethylene, and polypropylene with a proPosed anisotropic and pressure-dependent yield criterion. A good correlation between theory and experiment was found for each material.

The deliberate orientation of polymers is sometimes induced by the propagation of a stable neck due to uniaxial tensile loading; this has been called cold drawing. This highly anisotropic material is often used for various types of experiments. In this paper it is shown that the necked material can be quite nonuniform over the full cross section of the neck and any assumption of uniformity, as it influences subsequent findings, can be quite erroneous.