Viscoelastic Constitutive Model for the Creep Response of Polyurethane Rubber(Progress Report to the NSWC, Carderock for the Period September 1996 to December 1997)

摘要

A viscoelastic model is developed to describe the behavior of a polyurethanerubber provided to NIST by NSWC, Carderock. The model is based on concpts of time-dependent rubber elasticity and single integral models of viscoelasticity. The strain energy density function is assumed to be of a Valanis-Landel form, while its time-dependence is analyzed using the 'perfect elastic fluid' model of Bernstien, Kearsley and Zapas. In addition, time-strain separability and time-temperature superposition are assumed to apply to the polyurethane in the temperature range of interest. Single step stress relaxation experiments in uniaxial extension are used to determine the model parameters. From these, multiple step stress relaxation and creep histories are applies to the material and it is found that the model can describe the nonlinear time-dependent viscoelastic response of the polyurethane resin to these cyclic histories to