Viscoplastic material modeling for the stretch blow molding simulation

In this paper, the viscoplastic material model of PET (polyethylene terepht halate), which is intended to be used in the FEM (finite element method) si mulation of stretch blow molding process, has been studied. Material tests of PET were performed with the constant strain rates varying from 0.01 to 1 (1/s), at temperatures ranging from 90 to 150 degrees C, based on the obta ined data a two-stage model was proposed. The proposed model could precisel y take into account the effects of strain hardening, strain rate sensitivit y, variation of the hardening index, and temperature dependency. This model has been implemented into the nonlinear finite element code PBLOW3D, which is developed in the Riken, and its performance in the stretch blow molding simulation has been studied. It has been demonstrated that the proposed ma terial model provides significant improvements, compared with two existing material models, in the simulation of the blow molding process of PET bottl es.