Semester

Spring

Date of Graduation

1999

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Bruce Kang.

Abstract

Direct chill (DC) semi-continuous casting is the most efficient way to produce large aluminum ingots. This process consists of three main stages; transient stage, steady-state stage, and post-drop stage. During transient stage, the ingot is subjected to rapid cooling rate and thus resulted in the build-up of high thermal stresses that can often lead to ingot cracking failure.;Based on a fully coupled heat-transfer and thermal-stress analysis model, which has been developed using a commercial finite element (FE) package ABAQUS(TM) with a user subroutine developed in-house, the temperature and stress fields were obtained for various casting conditions. Three post-processing programs were developed to analyze and present the FE simulation results. The first program, CONVERT, processes data files from ABAQUS(TM) and then determines the normalized stresses in the ingot. The magnitude, location of maximum stress level, and the directions of maximum principal stresses are determined to assess the mechanism of ingot cracking. The second program, REGRESS, is used for statistical regression analysis, which involves casting parameters such as casting speed, water flow rate, ingot aspect ratio, and comer radius. Results of REGRESS are input to a program, PREDICTION, which provides visualization of the temperature and stress fields on a PC monitor. Further, the user can choose desired casting parameters in PREDICTION to predict temperature and stress fields at selected ingot lengths during casting. Validity of the program PREDICTION is checked with additional simulation results from ABAQUS(TM) and good agreement is noted.

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