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Accession Number ADA564294
Title Porosity Evolution in a Creeping Single Crystal (Preprint).
Publication Date Aug 2012
Media Count 26p
Personal Author A. Ivastava A. Needleman
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 and/or 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 (force/unit current area) that is time independent; and an applied nominal stress (force/unit 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.
Keywords Creep
Creep tests
Crystal plasticity
Finite element analysis
Single crystals
Strain rate
Void collapse
Void growth

Source Agency Non Paid ADAS
NTIS Subject Category 71N - Nonferrous Metals & Alloys
46D - Solid State Physics
Corporate Author University of North Texas, Denton.
Document Type Technical report
Title Note Interim rept. 1 Jul-1 Aug 2012.
NTIS Issue Number 1302
Contract Number FA8650-08-C-5226

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