| Filling is the initial stage of injection molding. It has great effect on the locations of melt-line or weld line, the air traps and the magnitude of injection pressure as well as clamp force. The melt pressure, temperature and stress at the filling stage play an important role on the final quality of the molding part. Flow simulation is the tool which is used to predict the scale, distribution and variation of physical variables such as velocity, pressure and temperature etc. by numerical methods during filling period. It can also be used to study the effects of process conditions on the quality of injection molding products as well as to find a feasible or an optimal design. Flow simulation has become an important tool for modern plastic design and process.There are three main approaches including mid-plane, dual domains and solid for flow simulation of injection molding. In this thesis, we proposed some new methods and algorithms to improve these approaches based on systematically studying them and developed the corresponding programs. The validity of the proposed methods was testified by analytic solution and experiments. As domain decomposition and parallel computation have become important tools for large scale calculation, we generalized this technique to flow analysis for injection molding and studied how to construct the sub-problem and the reasonability of interface conditions. The main results are shown as follow:1. We proposed a new method to update the melt front filling factors of the corresponding control-volume by Taylor-Galerkin approach and derived the recursive formula to calculate the derivatives of filling factor in every order. This method overcomes the limitation that only one control volume should be filled within one step. It can improve the calculating efficiency for fine mesh part and the precisions for rough mesh part simulation.2. In this thesis, we proposed a mesh scheme for finite element methods after analyzing the characters of melt flow in mold cavity. In this scheme, the surfaces of solid part are meshed by two dimensional elements with the nodes coupling along thickness direction and an additional imaginary pipe element in which the temperature keeps constant is added to the mesh model. Then apply the traditional mid-plane method to simulate the melt flow process. The pipe elements allow the melt flow freely between the two surfaces and play the nature boundary conditions in calculation. These nature boundary conditions can avoid the theory problems such as mass dis-conservation and keep the melt flow along the two surfaces unanimously during filling stage.3. The velocity and pressure are coupled in the governing equations of threedimensional flow analysis. In order to avoid the simultaneous determination of the coupled velocity and pressure, we derived a Poisson-like equation about pressure by modifying the variational formulation and solves the components independently at any given time step in this thesis. The iterative procedure was employed both for velocity-pressure and velocity-viscosity solutions of the coupled equations. This method can enhance the stability of numerical scheme and reduce memory needed in simulation. The mixed implicit and 'up-wind' approach was employed to discrete the energy equation. The algebraic equations about the discreted temperatures were solved by over relaxation method. In this way, the temperature oscillations which may occur by directly discreting the energy equation with Galerkin method can be avoided. The implicit scheme was also employed to discrete the Navier-Stokes equation. We derived the algebraic equations and proposed an iterative method to get the final solutions. This method can improve the stability of numerical scheme.4. The domain decomposition was applied to flow analysis for injection molding. The Dirichlet and Neumann type boundary conditions for elliptic equation were proposed for non-overlapping domains. Both the sub-problems for domain decomposition and the solving steps for D-N scheme were constructed...
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