Anisotropic Responses of a Ti-6Al-4V alloy, and development of a strain rate and temperature dependent yield criterion and constitutive model for HCP alloys

Title	Anisotropic Responses of a Ti-6Al-4V alloy, and development of a strain rate and temperature dependent yield criterion and constitutive model for HCP alloys
Author	Yu, Shaojuan
Advisors	Khan, Akhtar S ;
Program	Engineering, Mechanical
UMBC Department	Mechanical Engineering
Document Type	dissertation
Sponsors	University of Maryland, Baltimore County (UMBC)
Keywords	Anisotropy; Assymetry; FEA; Mechanical Response; Ti Alloy; Yield Criterion
Date Issued	2011-01-01
Abstract	The deformation induced anisotropic mechanical responses of an electron beam single melt Ti-6Al-4V alloy are characterized over wide ranges of strain rates, temperatures and hydrostatic pressures, along different directions. Based on the experimental observation, the KHL model is used to predict the observed mechanical behaviors. Close agreement is found between the predicted results and the experimental observations. Based on the experimental results, a yield criterion is proposed to describe the anisotropy and tension compression asymmetry characteristics of this alloy. In the proposed anisotropic yield criterion, a novel method is introduced to decouple the anisotropy and tension compression asymmetry characteristics; the anisotropic coefficients and tension compression asymmetry parameter can be determined independently. The KHL model is used as the hardening response, and subsequently used to determine the material constants in the proposed yield criterion. Moreover, the newly proposed yield criterion is used to correlate the yield loci of the Ti-6Al-4V alloy at different strain levels, strain rates and temperatures. Excellent agreement between predicted yield surfaces and corresponding experimental data is obtained A generalized anisotropic associative constitutive model is established for anisotropic metals with tension-compression asymmetry. The stress strain hardening behavior of the Ti-6Al-4V alloy, based on KHL constitutive model, is adopted to include the influences of strain rate and temperature on the plastic deformation of the material. The newly proposed yield criterion is introduced to predict the initial yield and subsequent working-hardening surfaces of the Ti alloy under loading conditions. Based on the associative flow rule, the KHL hardening model and the newly proposed yield criterion are combined into the anisotropic, strain rate and temperature dependent associative constitutive model. A user defined material subroutine (UMAT) for ABAQUS, is programmed based on the backward Euler's stress integration and radial return mapping techniques. By establishing the finite element models and implementing the UMAT in ABAQUS, the mechanical responses of the Ti alloy under uniaxial loadings are simulated. Moreover, the validity of the proposed associative constitutive model and the UMAT is further verified by comparing the simulation and experimental results on the mechanical response of the alloy under multiaxial loading conditions.
Identifier	10558
Format	application:pdf
Language	en
Collection	UMBC Theses and Dissertations.
Rights Statement	This item may be protected under Title 17 of the U.S. Copyright Law. It is made available by UMBC for non-commercial research and education. For permission to publish or reproduce, please see http://aok.lib.umbc.edu/specoll/repro.php or contact Special Collections at speccoll(at)umbc.edu.
Source	Yu_umbc_0434D_10558.pdf

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Anisotropic Responses of a Ti-6Al-4V alloy, and development of a strain rate and temperature dependent yield criterion and constitutive model for HCP alloys

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