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https://hdl.handle.net/2142/70124
Description
Title
Numerical Models for Compression Mold Filling
Author(s)
Lee, Ching-Chih
Issue Date
1984
Department of Study
Mechanical Engineering
Discipline
Mechanical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Mechanical
Abstract
Several models are developed using the finite element method to study the filling pattern of compression molding. The effects of charge size, temperature-dependent viscosity, mold temperature, and mold closing speed on the velocity and temperature distributions and flow front advancement are investigated.
For thin charges, a generalized Hele-Shaw model gives accurate and efficient predictions of the filling pattern. If the mold gap height is uniform and the charge is sufficiently thin, the mold temperature and the rheological property of the molding compound have no significant effect on the charge shape development.
Stratified viscosity models are used to study the change in flow behavior due to an increase of charge thickness and a transverse viscosity gradient. For a thick charge under non-isothermal compression, the material in a thin layer near the hot mold may flow preferentially to the material in the cold core region, resulting in a bulged velocity profile. A thick charge changes shape more slowly than a thin charge when compression molded.
The interaction between flow and heat transfer is examined in two-dimensional problems by solving the equations of motion and energy simultaneously on a time-invariant finite element mesh. For values characteristic of sheet molding compound, the flow is found to be largely extensional, although preferential flow does occur under certain circumstances. The temperature variation is largely in the gapwise direction; the variation in the charge plane is very small except at the flow front region, where the variation is caused by a foundation type of flow.
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