Comparison of torque and normal force responses of polycarbonate in one and two step torsional histories with a material clock model

Presented are the results of a study on torque and normal force responses of polycarbonate in one and two step torsional histories by using a material clock model. The Bernstein-Shoknob formulation in introducing the concept of an energy clock that depends on the strain energy function provided in the original Bernstein, Kearsley, and Zapas (BKZ) 1963 model. This has the advantage of suing a single scalar to determine the material clock whatever the type of deformation. Physically, the energy clock expresses the increase in molecular mobility with the internal energy. If valid, the use of the scalar provides the potential that experiments in one deformation geometry can be used to determine the material clock in other test geometries.