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A discrete dislocation dynamics model of creeping single crystals
Published in Institute of Physics Publishing
2018
Volume: 26
   
Issue: 3
Abstract
Failure by creep is a design limiting issue for metallic materials used in several high temperature applications. Current theoretical models of creep are phenomenological with little connection to the underlying microscopic mechanisms. In this paper, a bottom-up simulation framework based on the discrete dislocation dynamics method is presented for dislocation creep aided by the diffusion of vacancies, known to be the rate controlling mechanism at high temperature and stress levels. The time evolution of the creep strain and the dislocation microstructure in a periodic unit cell of a nominally infinite single crystal is simulated using the kinetic Monte Carlo method, together with approximate constitutive laws formulated for the rates of thermal activation of dislocations over local pinning obstacles. The deformation of the crystal due to dislocation glide between individual thermal activation events is simulated using a standard dislocation dynamics algorithm, extended to account for constant stress periodic boundary conditions. Steady state creep conditions are obtained in the simulations with the predicted creep rates as a function of stress and temperature in good agreement with experimentally reported values. Arrhenius scaling of the creep rates as a function of temperature and power-law scaling with the applied stress are also reproduced, with the values of the power-law exponents in the high stress regime in good agreement with experiments. © 2018 IOP Publishing Ltd.
About the journal
JournalModelling and Simulation in Materials Science and Engineering
PublisherInstitute of Physics Publishing
ISSN09650393
Open AccessNo
Concepts (17)
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    Chemical activation
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    Creep
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    Crystal microstructure
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    Dynamics
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    High temperature applications
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    Monte carlo methods
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    Single crystals
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    Stress analysis
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    CURRENT THEORETICAL MODELS
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    Discrete dislocation dynamics
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    Dislocation climb
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    DISLOCATION MICROSTRUCTURES
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    Kinetic monte carlo methods
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    Periodic boundary conditions
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    POWER LAW CREEP
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    Rate-controlling mechanism
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    Dislocations (crystals)