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Stress versus temperature dependent activation energies in creepThe activation energy for creep at low stresses and elevated temperatures is lattice diffusion, where the rate controlling mechanism for deformation is dislocation climb. At higher stresses and intermediate temperatures, the rate controlling mechanism changes from that of dislocation climb to one of obstacle-controlled dislocation glide. Along with this change, there occurs a change in the activation energy. It is shown that a temperature-dependent Gibbs free energy does a good job of correlating steady-state creep data, while a stress-dependent Gibbs free energy does a less desirable job of correlating the same data. Applications are made to copper and a LiF-22 mol. percent CaF2 hypereutectic salt.
Document ID
19900014457
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Freed, A. D. (NASA Lewis Research Center Cleveland, OH., United States)
Raj, S. V. (Cleveland State Univ. OH., United States)
Walker, K. P. (Engineering Science Software, Inc., Smithfield RI., United States)
Date Acquired
September 6, 2013
Publication Date
January 1, 1990
Subject Category
Structural Mechanics
Report/Patent Number
E-5580
NASA-TM-103192
NAS 1.15:103192
Meeting Information
Meeting: International Conference on Constitutive Laws for Engineering Materials: Theory and Applications and Workshop on Innovative Use of Materials in Industrial and Infrastructure Design and Manufacturin
Location: Tucson, AZ
Country: United States
Start Date: January 7, 1991
Sponsors: Arizona Univ.
Accession Number
90N23773
Funding Number(s)
PROJECT: RTOP 505-63-1B
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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