Keywords

Casting simulation, simulation validation, convective phenomena, solidification process modeling, multi-mode transient heat transfer

Abstract

The equiaxed investment casting process is a multi-physics problem which requires knowledge from engineers who have expertise in materials, metallurgy, fluid dynamics, thermodynamics, and heat transfer. Process modeling is a tool used by foundries to help predict casting defects such as shrinkage porosity, hot tears, dimensional distortion, and poor grain structure. ProCAST is the numerical simulation suite used in this dissertation and is considered an industry standard due to its extensive proven track record. The reliability of these predictions is strongly dependent on the accuracy of the thermal boundary conditions set in the model. This dissertation consists of two studies. The first investigation focused on a new methodology for defining the external heat transfer coefficient and depended on the same parameters as the natural convection heat transfer mechanism. The methodology was applied to a solidification process model of an SGT5-2000E Vane 4 cast in Rene 80 nickel-based superalloy. The model results, with the proposed nonuniform spatially varying heat transfer coefficient methodology, predicted qualitatively the same defects detected by x-ray inspection. The second investigation was focused on validating the hypothesis of the nonuniform spatially varying heat transfer coefficient concept methodology through experimentation. A SGT6-5000FD 3/4 Blade 4 cast in Alloy 247 was instrumented with thermocouples and temperature readings were recorded throughout the entire casting sequence of events. Analytical models were developed to use the thermocouple data as input to derive the emissivity and the local transient external heat transfer coefficients of the mold. The derived external conditions were validated in the ProCAST numerical simulation suite by comparing predicted external mold temperatures to the thermocouple data. The predicted temperature profiles agreed within reasonable error with the experimental data. The analytical models also uncovered some nonintuitive phenomena associated with the convective heat transfer mechanism for the equiaxed investment casting process.

Completion Date

2024

Semester

Fall

Committee Chair

Kapat, Jayanta

Degree

Doctor of Philosophy (Ph.D.)

College

College of Engineering and Computer Science

Department

Mechanical and Aerospace Engineering

Degree Program

Thermo-Fluids Mechanical Engineering

Format

PDF

Identifier

DP0029023

Language

English

Release Date

12-15-2024

Access Status

Dissertation

Campus Location

Orlando (Main) Campus

Accessibility Status

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