Void Growth and Collapse in a Creeping Single Crystal

Description:

Aircraft engine components can be subjected to a large number of thermo-mechanical loading cycles and to long dwell times at high temperatures. In particular, the understanding of creep in single crystal superalloy turbine blades is of importance for designing more reliable and fuel efficient aircraft engines. Creep tests on single crystal superalloy specimens have shown greater creep strain rates for thinner specimens than predicted by current theories. Therefore, it is necessary to develop a more predictive description of creep processes in these materials for them to be used effectively. Experimental observations have shown that the crystals have an initial porosity and that the progressive growth of these voids plays a major role in limiting creep life. In order to understand void growth under creep in single crystals, we have analyzed the creep response of three dimensional unit cells with a single spherical void under different types of isothermal creep loading. The growth behavior of the void is simulated using a three dimensional rate dependent crystal plasticity constitutive relation in a quasi-static finite element analysis. The aim of the present work is to analyze the effect of stress traixiality and Lode parameter on void growth under both constant true stress and constant engineering stress isothermal creep loading.

Creator(s): Srivastava, Ankit
Creation Date: August 2011
Partner(s):
UNT Libraries
Collection(s):
UNT Theses and Dissertations
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Total Uses: 147
Past 30 days: 6
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Publisher Info:
Publisher Name: University of North Texas
Publisher Info: Web: www.unt.edu
Place of Publication: Denton, Texas
Date(s):
  • Creation: August 2011
Description:

Aircraft engine components can be subjected to a large number of thermo-mechanical loading cycles and to long dwell times at high temperatures. In particular, the understanding of creep in single crystal superalloy turbine blades is of importance for designing more reliable and fuel efficient aircraft engines. Creep tests on single crystal superalloy specimens have shown greater creep strain rates for thinner specimens than predicted by current theories. Therefore, it is necessary to develop a more predictive description of creep processes in these materials for them to be used effectively. Experimental observations have shown that the crystals have an initial porosity and that the progressive growth of these voids plays a major role in limiting creep life. In order to understand void growth under creep in single crystals, we have analyzed the creep response of three dimensional unit cells with a single spherical void under different types of isothermal creep loading. The growth behavior of the void is simulated using a three dimensional rate dependent crystal plasticity constitutive relation in a quasi-static finite element analysis. The aim of the present work is to analyze the effect of stress traixiality and Lode parameter on void growth under both constant true stress and constant engineering stress isothermal creep loading.

Degree:
Level: Master's
PublicationType: Master's Thesis
Language(s):
Subject(s):
Keyword(s): creep | single crystal | finite element | superalloy | crystal plasticity
Contributor(s):
Partner:
UNT Libraries
Collection:
UNT Theses and Dissertations
Identifier:
  • ARK: ark:/67531/metadc84281
Resource Type: Thesis or Dissertation
Format: Text
Rights:
Access: Public
Holder: Srivastava, Ankit
License: Copyright
Statement: Copyright is held by the author, unless otherwise noted. All rights reserved.