Topic
Dislocation
About: Dislocation is a research topic. Over the lifetime, 36899 publications have been published within this topic receiving 872267 citations. The topic is also known as: dislocation in crystals.
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TL;DR: The structure, morphology and surface topography of multilayer carbon nanotubes have been studied by transmission electron microscopy and atomic force microscopy (AFM) as discussed by the authors, and it has been found that a large proportion of carbon tubes have a cylindrical shaped body, with a significant number being polygonal in appearance.
23 citations
TL;DR: In this paper, the authors present simulations of homogeneous uniaxial compression and recovery of large polycrystalline iron samples and reveal significant recovery of the body-centered cubic grains with some deformation twinning driven by shear stress, in agreement with experimental results by Wang et al.
Abstract: Despite a number of large-scale molecular dynamics simulations of shock compressed iron, the morphological properties of simulated recovered samples are still unexplored Key questions remain open in this area, including the role of dislocation motion and deformation twinning in shear stress release In this study, we present simulations of homogeneous uniaxial compression and recovery of large polycrystalline iron samples Our results reveal significant recovery of the body-centered cubic grains with some deformation twinning driven by shear stress, in agreement with experimental results by Wang et al [Sci Rep 3, 1086 (2013)] The twin fraction agrees reasonably well with a semi-analytical model which assumes a critical shear stress for twinning On reloading, twins disappear and the material reaches a very low strength value
23 citations
TL;DR: In this paper, a 3D discrete dislocation dynamics model was used to investigate the initial stages of the primary creep in nickel base superalloy and showed that a very sharp minimum in creep rate is observed at strains less than 0.5% in a wide range of temperatures: the lower the applied stress the steeper the minimum, referred to as incubation period.
23 citations
31 Oct 2016-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, a molecular dynamics simulation of nanoindentation on single crystal copper with coherent twin boundary (CTB) has been presented, where Thompson's tetrahedron notation has been adopted to scrutinize the process of PDL's formation without cross-slip and release from the indented place.
Abstract: Despite the intense interest in coherent twin boundary (CTB) of nanotwinned materials, many details of interactions between the complex dislocation (prismatic dislocation loop (PDL)) and CTB in a single crystal remain mysteries. In this study, molecular dynamics (MD) simulation of the nanoindentation on single crystal copper with CTBs has been presented. At the initial stage of nanoindentation, indenter moves downward and PDLs form. Thompson's tetrahedron notation has been adopted to scrutinize the process of PDL's formation without cross-slip and release from the indented place. Dislocations at PDLs' side edge are stair-rod partial dislocations, including two Lomer-Cottrell locks and two Hirth Locks. Then the interactions between PDL and CTB drive the migration of CTB. As a result, a parallelogram step which is bounded by Frank partial dislocations has been left, implying the formation of twinning dislocations. When the indenter moves further, the interactions repeat and twinning dislocations multiply. Our simulation results shed light on the interactions between PDL and CTB and would provide a new insight into understanding the role CTB plays during mechanical deformation.
23 citations
TL;DR: In this article, the effect of pre-existing dislocations and interstitial carbon on the initiation of plastic deformation in interstitial free (IF) steel and ultra low carbon (ULC) steel were investigated by the nanoindentation technique.
Abstract: The effect of pre-existing dislocations and interstitial carbon on the initiation of plastic deformation in interstitial free (IF) steel and ultra low carbon (ULC) steel were investigated by the nanoindentation technique. The critical load, Pc, of the pop-in phenomenon, which corresponds to plasticity initiation, appeared clearly on the loading curve. The Pc in high dislocation density materials was smaller than that in low dislocation density materials with no difference between IF and ULC while the Pc in low dislocation density materials was remarkably higher in ULC than in IF. These results indicate that the interstitial carbon in the matrix does not affect the pop-in phenomenon when there are pre-existing dislocations or dislocation sources, and we discuss the reason for their occurrence occurs in high dislocation density materials.
23 citations