Plasticity size effects in tension and compression of single crystals |
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Authors: | V.S. Deshpande A. Needleman |
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Affiliation: | a Department of Engineering, Cambridge University, Trumpington Street, Cambridge CB2 1PZ, UK b Division of Engineering, Brown University, Providence, RI 02912, USA c Materials Science Center, University of Groningen, Nyenborgh 4, 9747 AG Groningen, The Netherlands |
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Abstract: | The effect of size and loading conditions on the tension and compression stress-strain response of micron-sized planar crystals is investigated using discrete dislocation plasticity. The crystals are taken to have a single active slip system and both small-strain and finite-strain analyses are carried out. When rotation of the tensile axis is constrained, the build-up of geometrically necessary dislocations results in a weak size dependence but a strong Bauschinger effect. On the other hand, when rotation of the tensile axis is unconstrained, there is a strong size dependence, with the flow strength increasing with decreasing specimen size, and a negligible Bauschinger effect. Below a certain specimen size, the flow strength of the crystals is set by the nucleation strength of the initially present Frank-Read sources. The main features of the size dependence are the same for the small-strain and finite-strain analyses. However, the predicted hardening rates differ and the finite-strain analyses give rise to some tension-compression asymmetry. |
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Keywords: | Dislocations Size effects Plasticity Computer simulation |
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