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A fully associative, nonisothermal, nonlinear kinematic, unified viscoplastic model for titanium alloysSpecific forms for both the Gibb's and complementary dissipation potentials are chosen such that a complete (i.e., fully associative) potential base multiaxial, nonisothermal unified viscoplastic model is obtained. This model possesses one tensorial internal state variable (that is, associated with dislocation substructure) and an evolutionary law that has nonlinear kinematic hardening and both thermal and strain induced recovery mechanisms. A unique aspect of the present model is the inclusion of nonlinear hardening through the use of a compliance operator, derived from the Gibb's potential, in the evolution law for the back stress. This nonlinear tensorial operator is significant in that it allows both the flow and evolutionary laws to be fully associative (and therefore easily integrated), greatly influences the multiaxial response under non-proportional loading paths, and in the case of nonisothermal histories, introduces an instantaneous thermal softening mechanism proportional to the rate of change in temperature. In addition to this nonlinear compliance operator, a new consistent, potential preserving, internal strain unloading criterion has been introduced to prevent abnormalities in the predicted stress-strain curves, which are present with nonlinear hardening formulations, during unloading and reversed loading of the external variables. The specific model proposed is characterized for a representative titanium alloy commonly used as the matrix material in SiC fiber reinforced composites, i.e., TIMETAL 21S. Verification of the proposed model is shown using 'specialized' non-standard isothermal and thermomechanical deformation tests.
Document ID
19950019658
Acquisition Source
Legacy CDMS
Document Type
Conference Paper
Authors
Arnold, S. M. (NASA Lewis Research Center Cleveland, OH, United States)
Saleeb, A. F. (Akron Univ. Akron, OH., United States)
Castelli, M. G. (NYMA, Inc. Brook Park, OH., United States)
Date Acquired
September 6, 2013
Publication Date
May 1, 1995
Subject Category
Structural Mechanics
Report/Patent Number
NASA-TM-106926
NAS 1.15:106926
E-9644
Meeting Information
Meeting: Symposium on Thermomechanical Fatigue Behavior of Materials
Location: Phoenix, AZ
Country: United States
Start Date: November 13, 1994
End Date: November 18, 1994
Accession Number
95N26078
Funding Number(s)
PROJECT: RTOP 505-63-12
CONTRACT_GRANT: NAS3-27186
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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