Masters Theses

Abstract

"Shell cracking is an age-old problem facing the investment casting industry. One of the major reasons for shell cracking thermal expansion of pattern wax during autoclaving. Parameters of the wax pattern-making process were considered, including injection flow orientation, reclamation procedures, and injection pressure. The effects of glassy and crystalline components of wax the structure were examined. Thermal expansion was measured by a non-contact method to ensure unrestricted expansion measurements. Modulus of rupture of to ceramic shell material is often reported as three-point bend measurements. It is a known fact that the four-point bend method puts more sample volume under uniform stress (Richards, 2001). A two-way Analysis Of Variance (ANOVA) with replication (which explores the possibility of interaction) is used to compare the two bend tests. The four-point method subjects the tensile portion of the sample to a uniform stress over a specified region. By comparison, the stress varies over the test length of the three-point modulus of rupture test, reaching the calculated value at only one point. Sample preparation that avoids the introduction of additional flaws in the structure while minimizing the stress exposure during sample preparation was also proposed and compared to standard sawed and sanded samples. Fractographic analysis was used to find the cause of failure of ceramic shells during fourpoint bending. Results showed shell build flaws were responsible for some of the failures; therefore, fracture toughness of these broken samples was determined using fractography. The determination of plane-strain fracture toughness, K1c, is important in understanding the material characteristics of investment casting shells. Additionally, artificially induced flaws using a knoop indenter in conjunction with the four-point bend test to obtain fracture toughness was also explored."--Abstract, page iv.

Advisor(s)

Von L. Richards

Committee Member(s)

Christopher W. Ramsey
Frank Liou
Jeffery D. Smith

Department(s)

Mechanical and Aerospace Engineering

Degree Name

M.S. in Manufacturing Engineering

Publisher

University of Missouri--Rolla

Publication Date

Fall 2003

Journal article titles appearing in thesis/dissertation

  • Thermal expansion of investment casting pattern wax
  • Fracture toughness of investment casting shells using fractography
  • Statistical analysis of three-point and four-point bend testing for the characterization of ceramic mold shells

Pagination

xi, 62 pages

Note about bibliography

Includes bibliographical references (pages 19, 30 and 46)

Rights

© 2003 Sony Antoney Mascreen, All rights reserved.

Document Type

Thesis - Restricted Access

File Type

text

Language

English

Subject Headings

FoundingShell molding (Founding)

Thesis Number

T 8282

Print OCLC #

54783579

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