"This thesis is a collection of papers that discuss shell cracking in investment casting during pattern removal. 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.
The first two papers discuss the factors affecting shell cracking and methods to prevent it. Experimental methods were combined with finite element modeling to predict stress in the shell. A 3D nonlinear finite element model was developed to predict possible crack formation in the shells during pattern removal. The effects of the thermomechanical properties of the foam and the shell, as well as the firing process parameters were modeled. Also, an experimentally measured delay of the thermal expansion of the pattern was incorporated in the model to simulate the effect of aging. Extreme cases were experimentally validated. Recommendations for firing process parameters and pattern design to decrease stress and eliminate crack formation in the shell were formulated.
The third paper discusses the strength of investment casting shells in comer regions. The comer and edge regions have different structure and thickness and can experience large mechanical stress during processing. Experimental methods were combined with finite element modeling to predict stress in edge regions of the shell. A general equation was developed to account for these variables. The model was experimentally verified with wedge tests for various cases"--Abstract, page iv.
Lekakh, S. N. (Semen Naumovich)
Materials Science and Engineering
M.S. in Metallurgical Engineering
Army Armament Research, Development, and Engineering Center (U.S.)
Steel Founders' Society of America
Missouri University of Science and Technology
Journal article titles appearing in thesis/dissertation
- Crack formation during pattern firing in the investment casting process.
- Foam pattern aging and its effect on crack formation in investment casting ceramic shells.
- Corner strength of investment casting ceramic shells
x, 74 pages
© 2011 Wesley Alexander Everhart, All rights reserved.
Thesis - Restricted Access
Library of Congress Subject Headings
Precision casting -- Defects
Polymeric composites -- Thermal properties
Print OCLC #
Electronic OCLC #
Link to Catalog RecordElectronic access to the full-text of this document is restricted to Missouri S&T users. Otherwise, request this publication directly from Missouri S&T Library or contact your local library.http://laurel.lso.missouri.edu:80/record=b10131385~S5
Everhart, W. A., "Crack formation in investment casting ceramic shells" (2011). Masters Theses. 4475.