Accession Number:

ADA564294

Title:

Porosity Evolution in a Creeping Single Crystal (Preprint)

Descriptive Note:

Interim rept. 1 Jul-1 Aug 2012

Corporate Author:

UNIVERSITY OF NORTH TEXAS DENTON

Personal Author(s):

• Srivastava, A.
• Needleman, A.

Report Date:

2012-08-01

Pagination or Media Count:

26.0

Abstract:

Experimental observations on tensile specimens in 1 indicated that the growth of initially present processing induced voids in a nickel based single crystal superalloy played a significant role in limiting creep life. Also, creep tests on single crystal superalloy specimens typically show greater creep strain rates andor reduced creep life for thinner specimens than predicted by current theories. In order to quantify the role of void growth in single crystals in creep loading, we have carried out three dimensional finite deformation finite element analyses of unit cells containing a single initially spherical void. The materials are characterized by a rate dependent crystal plasticity constitutive relation accounting for primary and secondary creep. Two types of imposed loading are considered an applied true stress forceunit current area that is time independent and an applied nominal stress forceunit initial area that is time independent. Isothermal conditions are assumed. The evolution of porosity is calculated for various values of stress triaxiality and of the Lode parameter. The evolution of porosity with time is sensitive to whether constant true stress or constant.

Descriptors:

• *SINGLE CRYSTALS
• *SUPERALLOYS
• CREEP
• CREEP TESTS
• FINITE ELEMENT ANALYSIS
• GROWTH(GENERAL)
• ISOTHERMS
• POROSITY
• STRAIN RATE

Subject Categories:

• Metallurgy and Metallography
• Crystallography

Distribution Statement:

APPROVED FOR PUBLIC RELEASE