Numerical Simulation Method Of Glass Pressing Process

As an important glass manufacturing process, glass pressing has been an effective process for the advantages of mass-producing, net shape, and so on. However, some key features and characters of the process are still out of control. The integrated model of this process is not achieved, and also there are no complete theoretical foundations, experiment data and reliable design tools. This has slowed down the development of the glass-pressing process. So, it's an urgent issue to construct the integrated model, analyze the features of the process and clarify the mechanism of defects.Using the glass bulb panel as the research object, the processes of flow, heat transfer and residual stress are analyzed in this study. The whole pressing process was simulated before production, which can analyze the effects of the mould and processing parameters. According to this, the design of the mould and the parameters could be optimized. To be specific, the following work was included:During the glass flow simulation, the mathematical model is built by simplifying the governing equations with some assumptions based on the features of the pressing. The finite element method is employed to solve the governing equations. In order to prevent the potential numerical oscillation during the solution, the Galerkin/Least-squares (GLS) method and the Galerkin gradient least-squares (GGLS) method is introduced to discrete the equations.A numerical formulation is presented to simulate the part and mould cooling of picture tube panel forming process. Simulations of transient nonlinear heat conduction within the part, heat conduction within the mould, heat transfer of gas impingement cooling and a steady convective heat exchange between the coolant and mould, are simultaneously carried out to model the actual process conditions. A one-dimensional transient analysis in the thickness direction is adopted for the panel part, which employs finite-difference method. And a three-dimensional, boundary element method is used for the numerical implementation of the heat transfer analysis in the mould region, which is considered as three-dimensional conduction. The part and mould analyses are coupled so as to match the temperature and heat flux on the glass-mould interface. During the simulation of residual stresses and deformation of glass bulb panel, theory model and its numerical method of residual stresses are constructed. Based on the geometry characteristic of the glass part, shear plate assumption is employed. Applicable linear viscoelastic material model is used and suitable boundary conditions are employed. Based on the results of residual stresses, finite element method using flat triangular shell element is introduced to compute the deformation of glass panel.In the augmented heat transfer analysis, the mechanism of impinging jet and artificial roughness, two common technologies used in glass processing, is studied. Considering the practical process, further schemes are presented. The commercial package FLUENT 6.1 is used to simulate the process and optimize the schemes. The properties and the effects of the two technologies are finally achieved from the analysis.Compared with experiments and simulation results of commercial simulation packages, the approaches developed herein have a good performance. The corresponding simulation system has been developed at the same time, which can be used to simulate the entire pressing process. It is suggested that the developed system could be a good assistant of the glass pressing process.