An investigation on a new creep constitutive model and its implementation with the effects of time- and temperature-dependent Poisson’s ratio

Abstract

In a viscoelastic material Poisson’s ratio is a function of time and temperature that depends on the time and temperature regime chosen to elicit it. In this paper, new creep constitutive models with the effects of time- and temperature-dependent Poisson’s ratio are proposed and demonstrated. In order to establish a suitable constitutive model, the classical creep constitutive model is improved by the Laplace transform method. The new creep constitutive model is discretized into an incremental model and utilized to deduce the material stiffness matrices and applied to the FEM code MSC.Marc. A fully viscoelastic time and temperature implementation of the constitutive equation in FEM is achieved that allows for elastic and viscoelastic Poisson’s ratio in the calculation. Uniaxial constant rate tensile tests are used to verify the applicability of the proposed creep model. A viscoelastic analysis of the pipe construction is conducted to check the numerical algorithm with the analytical solution. The analytic analysis, creep model solutions, and relaxation model solutions match well. Furthermore, a simplified axisymmetric solid rocket motor (SRM) composed of propellant, insulation, and case is established, and the response of SRM under ignition pressure loading is described.