Effects of complex geometry, shell thickness and firing regimes on shell cracking in investment casting shells during rigid polymer pattern removal

Author

Samrat Krishna Bharadwaj Komaragiri

Abstract

"The application of rigid polymeric foam for large investment casting patterns with complex geometries can improve the dimensional tolerances and the surface quality of the casting. However, these pattern materials have a tendency to promote crack formation in investment casting shells during pattern removal by firing. In the course of realizing the ultimate objective of preventing shell cracking during firing, the effects of three main technological parameters were determined. They are complex geometry, shell thickness and firing regimes. Experimental methods were combined with finite element modeling to predict stress development in the shell. Thermal and mechanical properties of both the pattern and shell materials were determined according to the ASTM standards and subsequently used in a three-dimensional thermo-mechanical coupled finite element model to predict possible crack formation in the shells during pattern removal. The predictions made by the model were experimentally validated on the basis of crack length and location. Patterns were designed with deep internal pockets, which are sensitive to crack formation. Shells made at industrial foundries using these patterns were tested for cracking during firing. The mitigation of crack formation in simple shaped patterns by taking the outputs of the first two sets of experiments was suggested. To do so, the use of hollow foam patterns was conceived. For comparison, hollow foam patterns with vent and solid foam patterns were also studied. Shell building and testing were done at Missouri S&T. Recommendations to decrease the stress and prevention of shell cracking during firing were based on the understanding of the dependence of shell cracking on the above parameters"--Abstract, page iii.

Advisor(s)

Richards, Von

Committee Member(s)

Lekakh, S. N. (Semen Naumovich)
Chandrashekhara, K.

Department(s)

Materials Science and Engineering

Degree Name

M.S. in Metallurgical Engineering

Sponsor(s)

American Foundry Society

Comments

Funded by the American Foundry Society and Superior Weapons through casting program. Supported by the industrial foundries Apollo Valves and Mercury Marine; technical inputs and the process of shell building

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2013

Pagination

xi, 81 pages

Note about bibliography

Includes bibliographical references (pages 77-80).

Rights

© 2013 Samrat Krishna Bharadwaj Komaragiri, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Subject Headings

Precision casting -- Thermal propertiesShell molding (Founding)Strength of materials

Thesis Number

T 10328

Print OCLC #

860993281

Electronic OCLC #

908763932

Recommended Citation

Komaragiri, Samrat Krishna Bharadwaj, "Effects of complex geometry, shell thickness and firing regimes on shell cracking in investment casting shells during rigid polymer pattern removal" (2013). Masters Theses. 4468.
https://scholarsmine.mst.edu/masters_theses/4468