US Patent No. 5,572,434

METHOD FOR SIMULATING MOLD FILLING OF SEMI-SOLID MATERIAL

Issued: November 5, 1996

Inventor: Kuo K. Wang, Shau-poh Wang, both of Ithaca, New York

Assignee: Cornell Research Foundation, Inc., Thornwood Drive, Ithaca, NY 14850

An efficient numerical procedure for the simulation of Newtonian fluids with non-negligible inertial effect which satisfies the Navier-Stokes equations and the energy equation. The method simulates the molding-filling process of incompressible viscous liquid, e.g. semi-solid metal, in a thin and irregular cavity. The moving free surfaces in an irregular domain is tracked using a fixed-mesh method. The material discontinuities across the interface between air and the liquid are removed by replacing the air with a pseudo-gas which has small density and dynamic viscosity but its kinematic viscosity is the same as that of the liquid. During the filling process, the (semi-solid) liquid may solidify on the mold surface. As a result, the effective cavity thickness reduces non-uniformly according to the result thermal analysis. The Navier-Stokes equations are integrated across the remaining gap by assuming that the velocity profile (not magnitude) is similar to that in a fully-developed flow. The method incorporates general viscosity and solidification models to simulate the filling and solidification processes for the injection molding of Semi-Solid Metal in a two-dimensional thin cavity. The predictions have been compared with experimental results. The simulation results showed not only good agreement with the experiments but also helped explain the flow marks observed on the surface and the phase segregation in the cross section of a rheomolded spiral part.


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