The Three Dimension Isothermal Viscoelastic Numerical Simulation Of Gas-assisted Extrusion Molding Mechanism

The gas-assisted full slip extrusion molding process has special flow transport rules and dynamic character due to the coupling of the stresses on the interfaces in the gas-liquid multiphase-multilayer flow and the effect of the slip boundaries in the gas-assisted extrusion molding. So there are more complicated contents to study in the gas-assisted full slip extrusion molding process than in the traditional extrusion molding process. Therefore the mechanism of the gas-assisted extrusion die swell was studied and the influencing rules of the viscoelastic property parameters and process parameters on the gas-assisted full slip extrusion molding process, extrusion die swell and warpage were studied in this paper. The following main achievements were yielded:(1) Based on process characteristics of gas-assisted full slip extrusion molding and the theories of rheology and hydrokinetics etc., under reasonable assumption, full three dimension steady isothermal viscoelastic theoretical model of describing gas-assisted extrusion molding process is established. In order to establish the finite element model of the theoretical model easily, the expansions Giesekus constructive equation along x,y,z coordinates are derived.(2) Considering the non-convergence and unstable problem of solving the equation due to the coupling of the viscoelasticity, the tracing of the swell free surface and control equation, a full 3D isothermal viscoelastic gas-assisted extrusion molding finite element theory model were established on the basis of the stable finite element discrete techniques of Galerkin method, penalty function method, and EVSS/SU method etc.. And the tracking method of swell free surface for the gas-assisted full slip extrusion molding is put forward.(3 ) The gas-assisted full slip extrusion molding mechanism is studied by means of direct finite element numerical simulation, the influencing rules of the viscoelasticity property parameters and process parameters on the die swell of the gas-assisted full slip extrusion molding are analyzed. And the quantitative comparisons between the gas-assisted full slip extrusion molding process and traditional extrusion molding...