Equilibrium temperature analysis and fill pattern reasoning for die casting process
There are usually two concerns for die casting designers, thermal characteristics and fill pattern because they are closely related to casting quality and die life. The traditional way to obtain the results is numerical simulation. However, due to the high computational cost, numerical simulation is not a perfect tool during the early stages of product development. In this study, a quick algorithm to compute the equilibrium temperature of the die and ejection temperature of the part is presented. The equilibrium temperature is defined as the time average temperature over a cycle after the process reaches the quasi steady state. This can help the cycle and die cooling/heating design. A few models to compute the heat released from part are tested and the combined asymptotic and surrogate model is applied. Special attention is paid to heat transfer calculation at the part-die interface and computational efficiency improvement. The algorithm also addresses the modeling of cooling/heat line, spray effects and techniques for die splitting at the parting line. The algorithm has been implemented in the software CastView based on the finite difference method. The previous algorithm used in CastView for fill pattern analysis based on geometric reasoning is redesigned. In this qualitative method, the flow behavior is calculated using the cavity geometric information. Many shortcomings in the old algorithm were fixed and improved. The new algorithm includes considerations which affect the flow behavior, such as flow resistance, more flow angle search and influence within neighborhood. Special attention is paid to computational efficiency improvement. The fill pattern algorithm for die casting process is adapted for slow fill processes including gravity casting and squeeze casting. The dominant term for flow behavior for different process is defined from dimensionless Navier-Stokes equations. Based on this analysis, the fill pattern algorithm for die casting is modified for slow fill processes. The analysis results using the algorithms presented in this dissertation are compared with those obtained from numerical simulations, historical data and experiments. The comparison shows good agreement. Given the typical computational time of a few minutes, the efficiency of the algorithms is remarkable.
School:The Ohio State University
School Location:USA - Ohio
Source Type:Master's Thesis
Keywords:die casting equilibrium temperature numerical analysis fill pattern geometric reasoning
Date of Publication:01/01/2004