Title page for ETD etd-11152006-102208


Type of Document Master's Thesis
Author Zigoneanu, Lucian
Author's Email Address lzigon1@lsu.edu
URN etd-11152006-102208
Title Mesoscale Simulation of Grain Boundary Diffusion Creep in the Presence of Grain Growth
Degree Master of Science in Mechanical Engineering (M.S.M.E.)
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Dorel Moldovan Committee Chair
Srinath V. Ekkad Committee Member
Wen Jin Meng Committee Member
Keywords
  • materials simulation
  • inhomogeneity
  • mesoscale simulation
  • grain growth
  • diffusion creep
Date of Defense 2006-11-10
Availability unrestricted
Abstract
Grain-boundary (GB) diffusion creep (Coble creep) is the dominant deformation mechanism for the fine-grained materials under low stress and at elevated temperature. During creep deformation the grains become elongated in the tensile direction because of atoms diffusion along GBs from places in compression to those in tension. Consequently, the GB diffusion rate depends on the normal stress gradient along the boundaries.

It is widely accepted that the GB migration generally plays two important roles during Coble creep: one leading to the decrease of the creep rate due to the increase of the grain size by GB migration mediated grain growth and the other one leading to the relaxation of the stress concentrations along the GBs and at the triple junctions.

In this study we use mesoscopic simulations to investigate the influence of the external stress and grain-boundary migration (static grain growth) on creep deformation of polycrystalline materials. Our simulation methodology is based on the variational principle of dissipated power and the simulation results reveal that the grains comprising the microstructure remain almost equiaxed during grain-boundary diffusion creep with accommodation by GB migration. In addition, the average grain size of the evolving microstructure is controlled by the interplay between the static and dynamic grain growth and depends strongly on both the externally applied stress and the strain.

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