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A Continuum Model for Slip-Twinning Interactions in Magnesium and Magnesium Alloys

Citation

Chang, Yingrui (Ray) (2016) A Continuum Model for Slip-Twinning Interactions in Magnesium and Magnesium Alloys. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/Z96M34RX. http://resolver.caltech.edu/CaltechTHESIS:01252016-164549986

Abstract

Due to their high specific strength and low density, magnesium and magnesium-based alloys have gained great technological importance in recent years. However, their underlying hexagonal crystal structure furnishes Mg and its alloys with a complex mechanical behavior because of their comparably smaller number of energetically favorable slip systems. Besides the commonly studied slip mechanism, another way to accomplish general deformation is through the additional mechanism of deformation-induced twinning. The main aim of this thesis research is to develop an efficient continuum model to understand and ultimately predict the material response resulting from the interaction between these two mechanisms.

The constitutive model we present is based on variational constitutive updates of plastic slips and twin volume fractions and accounts for the related lattice reorientation mechanisms. The model is applied to single- and polycrystalline pure magnesium. We outline the finite-deformation plasticity model combining basal, pyramidal, and prismatic dislocation activity as well as a convexification based approach for deformation twinning. A comparison with experimental data from single-crystal tension-compression experiments validates the model and serves for parameter identification. The extension to polycrystals via both Taylor-type modeling and finite element simulations shows a characteristic stress-strain response that agrees well with experimental observations for polycrystalline magnesium. The presented continuum model does not aim to represent the full details of individual twin-dislocation interactions, yet it is sufficiently efficient to allow for finite element simulations while qualitatively capturing the underlying microstructural deformation mechanisms.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Magnesium; Crystal plasticity; Twinning; Polycrystalline material; Finite strain; Constitutive behavior; Continuum mechanics; Finite element method;
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Mechanical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Kochmann, Dennis M.
Thesis Committee:
  • Ortiz, Michael (chair)
  • Andrade, Jose E.
  • Lloyd, Jeffrey T.
  • Kochmann, Dennis M.
Defense Date:15 January 2016
Non-Caltech Author Email:yingryic (AT) gmail.com
Funders:
Funding AgencyGrant Number
U.S. Army Research LaboratoryW911NF-12-2-0022
Projects:Materials under Extreme Dynamic Environments (MEDE)
Record Number:CaltechTHESIS:01252016-164549986
Persistent URL:http://resolver.caltech.edu/CaltechTHESIS:01252016-164549986
DOI:10.7907/Z96M34RX
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.ijplas.2015.03.008DOIArticle adapted for parts of chapters 3,4,5 and 6
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:9548
Collection:CaltechTHESIS
Deposited By: Yingrui Chang
Deposited On:28 Jan 2016 20:51
Last Modified:18 May 2017 16:53

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