Academic literature on the topic 'Dislocations'
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Journal articles on the topic "Dislocations"
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Shetty, Sanath Kumar, Lawrence J. Mathias, H. Ravindranath Rai, P. Nirmal Babu, Raj Sankar N. R., and Vinay Kumar C. "SIMULTANEOUS BILATERAL ANTERIOR DISLOCATION OF THE SHOULDER WITH FRACTURES OF THE GREATER TUBEROSITY FOLLOWING TRAUMA- A CASE REPORT." Journal of Health and Allied Sciences NU 04, no. 01 (2014): 129–30. http://dx.doi.org/10.1055/s-0040-1703750.
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Abstract:Simultaneous bilateral shoulder dislocations are usually posterior with anterior dislocations1 being rare and simultaneous anterior shoulder dislocations with fractures of the greater tuberosity5 being even more rare usually associated with trauma or seizures2,3 . Here we present a rare case of simultaneous bilateral anterior dislocation of the shoulder with fractures of the greater tuberosity following an unusual injury mechanism which was treated surgically.
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Mohiuddin, Mohammed Jalal, Hashmi Syed Salman Hamid, and Shaik Ajaz. "SIMULTANEOUS BILATERAL SHOULDER DISLOCATION: A CASE REPORT." International Journal of Medical Sciences and Pharma Research 1, no. 1 (2015): 1–4. http://dx.doi.org/10.22270/ijmspr.v1i1.1.
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Introduction: Bilateral shoulder dislocations are relatively uncommon. Bilateral shoulder dislocationwas first described in 1902, because of muscular contractions in camphor overdose. Among thebilateral shoulder dislocation posterior are most common usually following convulsions or electricshocks. Simultaneous bilateral anterior dislocations of shoulder following trauma is a rareoccurrence. Case Report: A 28 year old male presented to emergency department with history offall on outstretched hand. He complained of pain and difficulty in moving both the shoulders. Onclinical examination, patient's both upper limbs were abducted and externally rotated. Bilaterallyshoulder contour was lost with flattening. Other classical signs of shoulder dislocation like Bryantstest, Callway sign, Hamilton's ruler test were positive. Diagnosis was confirmed on X rays. Bothshoulders were reduced in emergency operation theater under general anaesthesia by Kocher'smethod and were immobilized in sling. Conclusion: Simultaneous bilateral dislocation of theshoulder are uncommon during clinical practice but have to be diagnosed and adequately treated.Though posterior shoulder dislocations are common secondary to convulsions and electric shocksanterior shoulder dislocations should be kept in mind. The bilateral dislocations also presents withpractical problem of immobilization of both limbs and day to day care of patients. Hence thedislocations require special attention and proper care .
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Wang shumin, He Xinfu, and Dou Yankun. "Simulation Study on Edge Dislocation Motion and Its Interaction with Dislocation Loop in Pure V and TiVTa Alloy." Acta Physica Sinica 74, no. 7 (2025): 0. https://doi.org/10.7498/aps.74.20241757.
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In this paper, the motion of edge dislocations and the interaction between edge dislocations and dislocation loops in pure V and TiVTa alloy were simulated. The aim was to reveal the influence of the existence of <111> dislocation loops, which are dominant in pure V, and <100> dislocation loops, which are dominant in TiVTa alloy, on the irradiation properties of materials and the differences between the irradiation properties influenced by the two types of dislocation loops. Edge dislocations and <100> loops and <111> loops with different sizes were introduced into pure V and TiVTa alloy using molecular dynamics simulation technology. The effects of loop type, loop size, and temperature on the interaction between edge dislocations and dislocation loops in pure V and TiVTa alloy were compared and analyzed. The differences in the interaction between dislocations and dislocation loops were summarized, and the reasons were revealed.<br>The simulation results of edge dislocation motion revealed that the velocity of edge dislocations in pure V decreases with increasing temperature, while the velocity of edge dislocations in TiVTa alloy showed no obvious correlation with temperature. This is because in pure V, the motion of edge dislocations is controlled by the phonon resistance mechanism. In TiVTa alloy, due to inevitable local chemical fluctuations, the phonon resistance mechanism and the nanoscale segment detrapping mechanism simultaneously control the motion of edge dislocations.<br>The simulation results of the interaction between edge dislocations and dislocation loops showed that there are two kinds of interaction mechanisms between dislocations and loops in pure V and TiVTa alloy: for small dislocation loops, dislocations tend to absorb the loops and continue to move; for large dislocation loops, dislocations tend to cut through the loops and then move forward. With the increase in the size of dislocation loops, the stress required for dislocations to break away from the dislocation loops also increases. With the increase in temperature, the stress required for dislocations to break away from the dislocation loops decreases. This is because the larger the size of the loops, the larger the contact area between dislocations and loops, and the greater the obstacle presented by the loops. With the increase in temperature, atomic vibrations are accelerated, and the hindrance of the loops is reduced.<br>When comparing the interaction between <100> loops and <111> loops and dislocations, it is found that the hindrance of <111> loops to dislocation movement is lower than that of <100> loops, and the difference in the hindrance of <100> loops and <111> loops to dislocations is more obvious in pure V than in TiVTa alloy. This is because the mobility of <111> loops is higher than that of <100> loops, so the hindrance of <111> loops to dislocation motion is lower than that of <100> loops. However, in TiVTa alloy, significant lattice distortion reduces the mobility of <111> loops. Therefore, compared with pure V, in TiVTa alloy, although the hindrance of <111> loops is lower than that of <100> loops, the difference between them is reduced.
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Ibrahim, Halil Kafadar. "Case Report: Floating Elbow with Posterior Shoulder Dislocation." Open Journal of Orthopedics and Rheumatology 2, no. 1 (2017): 015–17. https://doi.org/10.17352/pjor.000009.
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Shoulder dislocations are the most common joint dislocations (%50). Only 2 to 4 percent of these dislocations are posterior dislocations. Posterior dislocation of the shoulder is a rare and commonly missed injury. Also, combination of the fracture of the humerus with shoulder dislocation is a very rare injury [1-6].
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Ning, X. J., and P. Pirouz. "A large angle convergent beam electron diffraction study of the core nature of dislocations in 3C-SiC." Journal of Materials Research 11, no. 4 (1996): 884–94. http://dx.doi.org/10.1557/jmr.1996.0110.
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Dislocations produced by 1300 °C indentation of the silicon-terminated (111) face of 3C-SiC were investigated by transmission electron microscopy. They were all found to be either widely separated partial dislocation pairs, or else, arrays of single partial dislocation half-loops on neighboring parallel slip planes and having the same Burgers vector. It was concluded that in the latter case, each array consisted of leading partial dislocations which had nucleated without accompanying trailing partial dislocations. The core nature of both dissociated dislocations and arrays of single partial dislocations has been determined by the technique of large angle convergent beam electron diffraction. The results indicate that the core of all single partial dislocation half-loops constituting an array consists of silicon atoms. It is concluded that, with the present deformation geometry, the Si-core partial dislocations are preferentially nucleated before the C-core partial dislocations. In the case of a dissociated dislocation, when a pair of partials was present, electron microscopy observations revealed that the morphology of the two partial dislocations was very different; while the Si-core partials were smooth, the C-core partial dislocations had a zig-zag morphology.
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Marshall, A. F., D. B. Aubertine, W. D. Nix, and P. C. McIntyre. "Misfit dislocation dissociation and Lomer formation in low mismatch SiGe/Si heterostructures." Journal of Materials Research 20, no. 2 (2005): 447–55. http://dx.doi.org/10.1557/jmr.2005.0065.
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Using transmission electron microscopy we observe the dissociation of 60° misfit dislocations at the interface of SiGe/Si multilayers, extending into the substrate for distances of 5.0–7.5 nm. Analysis using elasticity theory shows that this dissociationis the equilibrium configuration for individual 60° misfit dislocations, as it is for 60° mixed dislocations in bulk Si, and that the compressively strained multilayer film serves mainly to position the partial dislocations and stacking fault with respect to the free surface. We observe both undissociated 60° and Lomer edge dislocations after annealing, and conclude that these result from dislocation climb in the interface. Since the dislocations move off their slip plane during climb, they cannot remain dissociated. Significant climb and Lomer dislocation formation for these low misfit layers is observed at temperatures above 850 °C and for samples with a high initial dislocation density, such as found in thicker as-grown samples. The dislocation configuration formed during annealing is distinct from that reported to form during growth of higher mismatch films: the Lomer dislocations tend to be segmented, with the segments connected by perfect 60° dislocations.
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Kveder, Vitaly V., Valeri I. Orlov, M. Khorosheva, and Michael Seibt. "Influence of the Dislocation Travel Distance on the DLTS Spectra of Dislocations in Cz-Si." Solid State Phenomena 131-133 (October 2007): 175–82. http://dx.doi.org/10.4028/www.scientific.net/ssp.131-133.175.
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We investigated the development of dislocation-related DLTS spectra in n-CZ-Si crystals with small (about 7.104 cm-2) number of long individual dislocations depending on the distance L that dislocations traveled during deformation at 600oC and on the velocity of dislocations. We found that a typical dislocation-related DLTS signal appeared only when dislocations traveled a significant distance that is more than 150-200μm, and it depended strongly on dislocation velocity. The results were interpreted on the assumption that the DLTS signal corresponds to some core defects and atomic impurities accumulated on the dislocations during their slow motion. At high concentration of deep level defects on dislocations a strange “negative DLTS” signal was observed. This can be explained by electron tunneling between deep defects along dislocations.
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Misra, Devi Shanker. "Studies of Dislocations in Type Ib, Type IIa HPHT and CVD Single Crystal Diamonds." Crystals 13, no. 4 (2023): 657. http://dx.doi.org/10.3390/cryst13040657.
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In this review, the X-ray topography results of various types of single crystal diamonds (SCDs) are reported. Dislocations and dislocation bundles are present in all types of SCDs, the only exception being type IIa high-pressure, high-temperature (HPHT) SCDs. The technology of growing HPHT type IIa SCDs has advanced to a level where the samples show almost no dislocations or dislocation bundles. However, very few groups appear to have perfected the process of HPHT growth of type IIa SCDs. There appears to be a characteristic difference in the dislocations present in type Ib HPHT and chemical vapor deposited (CVD) SCDs. The dislocations in CVD SCDs are mostly in aggregate form, while in HPHT type Ib diamonds there are line dislocations which propagate in <111> or <112> directions. The CVD SCDs growth appears to be in the early stage in terms of the control of dislocations and dislocation bundles, compared to other semiconductor wafers. The dislocations and dislocation bundles and aggregates in SCDs limit their applications in electronic and optical devices. For instance, high-power laser windows must have low dislocations and dislocation bundles. For electronic devices such as high-power diodes, dislocations reduce the breakdown voltage of SCDs, limiting their applications. The knowledge of dislocations, their identification and their origin are, therefore, of utmost importance for the applications of SCDs, be they HPHT or CVD grown.
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Lauer, Kevin, Martin Herms, Anett Grochocki, and Joachim Bollmann. "Iron Gettering at Slip Dislocations in Czochralski Silicon." Solid State Phenomena 178-179 (August 2011): 211–16. http://dx.doi.org/10.4028/www.scientific.net/ssp.178-179.211.
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The impact of slip dislocations on the interstitial iron distribution in as-grown CZ silicon wafers is investigated by calibrated MWPCD excess charge carrier lifetime measurements, DLTS measurements and measurements of the dislocation density. In regions of high dislocation density low interstitial iron content as well as low lifetime is observed. A linear correlation between dislocation density and interstitial iron content is found. We explain this linear correlation by the thesis that slip dislocations are 60° dislocations, which have adsorbed one iron atom at each dangling bond along the dislocation axis. Interstitial iron is gettered by slip dislocations but iron silicide, which forms along the dislocation axis, is a very strong recombination center for excess charge carriers as well. Hence, gettering of interstitial iron at slip dislocations does not increase the electrical quality of silicon.
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Suresh, T. V., D. Naveen, K. Harish, and Ravi M. Daddimani. "Bilateral Asymmetrical Hip Dislocation in a 70-year-old Female: A Rare Case Report." Journal of Orthopedics, Traumatology and Rehabilitation 16, no. 2 (2024): 191–94. https://doi.org/10.4103/jotr.jotr_9_23.
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Abstract Traumatic dislocation of the hip joint is a rare injury representing 2%–5% of all dislocations while bilateral hip dislocation accounts for 1.25% of all hip dislocations. Asymmetrical hip dislocations are even rarer accounting for approximately 0.01%–0.02% of all hip joint dislocations. We are reporting a case of bilateral asymmetrical hip dislocations with left-sided posterior dislocation and right anterior dislocation in a 70-year-old female following a road traffic accident. It is pertinent to thoroughly evaluate the patient on the Advanced Trauma Life Support guidelines. After evaluation, it is vital to reduce hip dislocation within 6 h from the time of injury to prevent complications like avascular necrosis of the femoral head. Relevant anatomy, injury mechanism, classification, diagnosis, associated injuries, treatment, and complications have also been discussed.
Dissertations / Theses on the topic "Dislocations"
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Bigger, James R. K. "Dislocations in semiconductors." Thesis, University of Oxford, 1992. http://ora.ox.ac.uk/objects/uuid:2be9288d-caee-4070-b535-b8fc6406b4d1.
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A set of codes with 3D periodic boundary conditions has been developed to model dislocations in semiconductors. Several schemes have been used to investigate the atomic structure of dislocations; classical potentials incorporated in a Molecular Dynamics framework, a tightbinding k-space scheme and ab initio pseudopotential codes developed at Cambridge and Edinburgh. An error has been detected in previous work that modelled dislocations using periodic boundary conditions. It is demonstrated, for the 90° and 30° Shockley partials, that a mismatch at the periodic boundaries leads to erroneous atomic and particularly electronic structures. A new approach is proposed which through its geometry obviates this problem. The Stillinger Weber potential has been found to predict a completely new type of reconstruction for the 90° partial. Recent work by other authors confirms this and predicts significantly different results to earlier work. A thorough investigation has been made into the bonding processes involved in the core of the 90° partial. This study has involved reproducing much of the earlier work to understand why there has been such poor agreement between various authors. The reconstruction of the 90° partial is found to involve a symmetry lowering displacement intimately connected to its electronic structure. The band-gap is predicted to be clear of states, except for the possibility of shallow states at both band edges, which contradicts the findings of the most recent work on this partial by other authors. The interaction of phosphorous with the 90° partial has been studied using the tightbinding model. The Hamiltonian has been parameterised by comparing the predictions to an earlier ab initio cluster method study. Good qualitative agreement with the ab initio work is obtained, including the prediction of a strong dislocation locking effect by phosphorous. Preliminary studies on the unreconstructed 30° partial show that phosphorous is strongly bound to the three-fold coordinated sites resulting in no states in the indirect band-gap. The modelling of interstitial copper at the core of the 90° partial has been initiated. The ab initio codes have been used and new silicon and copper pseudopotentials tested. The first attempt to model copper located interstitially in the core was not successful and the reasons for this have been identified. However, it is evident from this investigation that the neutral copper strongly repels and does not form bonds with the surrounding silicon atoms. A review is given of two techniques that have been developed to obtain the thermally averaged structure and concentration of vacancies at dislocations, together with a preliminary investigation on the Frank partial.
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Falkner, Aryanna M. "Dislocations: Short Stories." Bowling Green State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1586438288966435.
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Chen, Qian. "Evolution, interaction, and intrinsic properties of dislocations in intermetallics anisotropic 3D dislocation dynamics approach /." [Ames, Iowa : Iowa State University], 2008.
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Portelette, Luc. "Analyse des mécanismes de glissement des dislocations dans l'UO2 à l'aide de la modélisation multi-échelles comparée à l'expérience." Thesis, Aix-Marseille, 2018. http://www.theses.fr/2018AIXM0406/document.
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Dans l'étude des éléments combustibles des réacteurs à eau pressurisée, cette thèse s'inscrit dans la compréhension et la modélisation du comportement viscoplastique du dioxyde d'uranium (UO2) à l'échelle du polycristal. Lors de fonctionnement de type incidentel du réacteur, le combustible subit une forte élévation de la température avec un gradient thermique de la pastille engendrant des déformations viscoplastiques contrôlées par des mouvements de dislocations. D'abord, un modèle de plasticité cristalline a été développé de manière à décrire l’anisotropie viscoplastique du matériau en fonction de la température et de la vitesse de sollicitation. Des simulations par éléments finis (EF) sur monocristaux ont permis d’identifier que les trois modes de glissement généralement observés dans l'UO2 sont importants pour décrire le comportement anisotrope du matériau. Dans un second temps, les coefficients de la matrice d'interactions entre dislocations ont été déterminés spécifiquement pour l’UO2 afin d’améliorer la modélisation des polycristaux. En effet, en calculant par EF les dislocations géométriquement nécessaires, qui sont responsables d’une forte augmentation de la densité de dislocations stockées dans les polycristaux, les interactions entre dislocations permettent de simuler l’effet dé taille de grain et l’écrouissage des pastilles. Finalement, le modèle, adapté pour les polycristaux, a été validé par comparaison avec les essais expérimentaux sur pastille et par comparaison du comportement intra-granulaire simulé avec des mesures EBSD. Grâce à cette dernière comparaison, il est possible de remonter indirectement aux hétérogénéités de déformation dans les grains<br>This thesis is part of the study of fuel elements of pressurized water reactors and, more specifically, focus on the understanding and modelling of the viscoplastic behavior of uranium dioxide (UO$_2$) at polycrystalline scale. During the incidental operation of the reactor, the fuel undergoes a strong increase of temperature and thermal gradient between the center and the periphery of the pellet leading to viscoplastic strains due to dislocation movement mechanisms. First, a crystal plasticity model was developed in order to describe the viscoplastic anisotropy of the material considering the temperature and the loading rate. Finite element (FE) simulations on single crystals enabled to highlight that the three slip modes generally observed in UO$_2$ are crucial to describe the anisotropic behavior of the material. Secondly, coefficients of the interaction matrix have been identified specifically for UO$_2$ in order to improve the polycrystal modelling. Indeed, by calculating geometrically necessary dislocations (GNDs), which are responsible of the great increase of the stored dislocation density in polycrystals, the interactions between dislocations enable to simulate de grain size sensitivity and hardening of the fuel pellet. Finally, the model adapted for polycrystals, have been validated by comparing FE simulations with pellet compression tests and by comparing the simulated intra-granular behavior with EBSD measurements. Thanks to the latter comparison, it is possible to indirectly compare the strain heterogeneities in the grains
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Bourcier, Charline. "Les dislocations de l'espace pictural." Thesis, Aix-Marseille, 2015. http://www.theses.fr/2015AIXM3096.
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En 1962, Gerhard Richter peint Tisch. Dans ce tableau, une table représentée en perspective est biffée par une violente gestualité. L’espace pictural s’érige entre l’illusion de profondeur et l’affirmation matérielle de la toile et de la peinture. Impulsée par une pratique personnelle, mise en regard avec le travail actuel de jeunes artistes héritiers des altérations fécondes de Richter, tels que Adrian Ghenie, Duncan Wylie ou Stephen Bush, Les dislocations de l’espace pictural se penche sur les relations dynamiques qui animent une figuration en tension entre l’image et le pictural. Taches, semis et coulures déstabilisent les assises iconiques tout en créant des mondes ambigus. L’espace pictural oscille entre dextérité et lâcher-prise. L’inachèvement et les réserves exposent au regard les vacillements de ses strates constitutives<br>Gerhard Richter painted Tisch in 1962. In this painting, a table, which is represented in perspective, has been erased with a violent gestural brushstroke. The pictorial space stands between the illusion of depth and the emphasized materiality of the canvas and the painting. The dislocations of the pictorial space, fostered by Richter’s personal practice and supplemented with the work of current young artists, heirs to his productive alterations, such as Adrian Ghenie, Duncan Wylie or Stephen Bush, these dislocations show the dynamic relationships which animate a figuration in tension with the picture and the painting. Stains, patterns, and streaks destabilize established iconic values while creating ambiguous worlds. The pictorial space oscillates between dexterity and letting go. The incompleteness and the reserves display the wavering of its constitutive layers
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Ren, Qiang. "Dislocations in monolayers and semiconductors." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10014.
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Four different aspects of the properties of dislocations in monolayer and semiconductors have been investigated: (i) Using atomic relaxation techniques, dislocation dipoles of various sizes and orientations have been studied for monolayers with the Lennard-Jones potential (LJP) and the nearest-neighbour piecewise linear force (PLF) interactions. In the WP system the lower energy vacancy dipoles have over a wide range of angles an energy which is mainly a function of the vacancy content of the dipole. There is a competition between the elastic forces and the topological constraints which favour a five-fold coordinate vacancy (FCV) at the centre of each core. For the short range PLF system the lattice usually compresses upon the introduction of a dislocation, a consequence of the soft core of the interaction potential, and interstitial dipoles are lower in energy. For the long range LJP system the dislocations are mobile whereas for the PLF system they are pinned. The relevance of these results to existing theories of melting are discussed. (ii) Using generalized stacking-fault (GSF) energies obtained from first-principles density-functional calculations, a zero-temperature model for dislocations in silicon is constructed within the framework of a Peierls-Nabarro (PN) model. Core widths, core energies, PN pinning energies, and stresses are calculated for various possible perfect and imperfect dislocations. Both shuffle and glide sets are considered. 90$\sp\circ$ partials are shown to have a lower Peierls stress (PS) than 30$\sp\circ$ partials in accord with experiment. (iii) We have also studied by atomic relaxation techniques the properties of dislocations in silicon, modelled by the empirical potential of Stillinger and Weber. In order to compare with the preceding calculation no reconstruction is allowed. We find no evidence of dissociation in the shuffle dislocations. Within this model shuffle dislocations glide along their slipping planes. On the other hand, glide sets are shown to glide only in dissociated form. The dislocation displacement fields are essentially planar. The PS is found to be isotropic within the (111) plane. In other words the minimum stress at 0K required to move the dislocation in any direction with in that plane has the same projection unto the Burgers vector, the PS of the dislocation. Our PS are in good agreement with those from (ii). (iv) Using a simple two dimensional UP model, relaxation mechanisms of the epitaxial strain layers (ESL) have been simulated for various misfits and layer thickness. In this model, the relationship of two competing relaxation mechanisms is found. At small misfit, strain is released by nucleating misfit dislocations from the edges of system. This process is more favourable for the thicker layer. At large misfit, stress is relaxed through surface instability, allowing easy generation of misfit dislocations from the surface. Those results are qualitatively in agreement with experiments.
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Valladares, Alexander. "Modelling of dislocations in silicon." Thesis, University of Oxford, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.302400.
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Kolodzie, Annette Therese. "EELS at dislocations in diamond." Thesis, University of Cambridge, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.615749.
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Madec, Ronan. "Des intersections entre dislocations à la plasticité du monocristal CFC : étude par dynamique des dislocations." Paris 11, 2001. http://www.theses.fr/2001PA112239.
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Nous avons mis au point une simulation tridimensionnelle de la dynamique des dislocations et de leurs interactions. L'objectif est d'étudier la plasticité du monocristal CFC à partir d'une description réaliste des mécanismes physiques élémentaires qui la gouvernent. La simulation Mixte est une dynamique des dislocations à caractère de ligne discrétisé, qui permet de traiter de façon parfaitement rigoureuse les jonctions entre dislocations. En outre, elle est pourvue de conditions aux limites périodiques qui permettent d'équilibrer automatiquement les flux de dislocations entrant et sortant du volume simulé et de définir sans ambigui͏̈té la densité de dislocations. Une première application nous a conduits à étudier l'écoulement plastique dans les monocristaux CFC. Sans aucun paramètre ajustable, on retrouve la loi d'échelle de la forêt et la force globale des obstacles sécants. Nous avons ensuite cherché à dégager la contribution des différentes interactions entre systèmes de glissement. Leur force est très variable. Les interactions dipolaires sont faibles, tandis que les jonctions constituent bien, globalement, des obstacles durs. L'interaction entre systèmes primaire et dévié, qui a jusqu'ici soulevé peu d'intérêt, apparaît enfin comme étant la plus forte de toutes. Ce résultat surprenant mérite d'être étudié en détail car il est susceptible d'apporter de nouvelles réponses à des problèmes mal compris comme la formation de microstructures de dislocations organisées et le poids relatif des termes diagonaux et non-diagonaux dans les matrices d'écrouissage<br>A new three-dimensional simulation of dislocation dynamics and interactions bas been designed with the objective of investigating the plasticity of FCC single crystals from a physical viewpoint. In this "Mixed model" the line character is discretised into screw, edge and mixed orientations, which allows in particular to perform an accurate description of the formation and destruction of junctions between dislocations. In addition, periodic boundary conditions are included, which allows to obtain a balance of dislocation fluxes in the simulated volume and a realistic description of the dislocation densities. The first applications were concerned with plastic flow in FCC single crystals. The scaling law of the forest model and the average strength of secant obstacles were obtained without any fitting parameter. Then, the specific contribution of each different interaction between glide systems was measured. The corresponding strengths are rather uneven. Dipolar interactions are weak, while junctions constitute on the whole strong obstacles as expected. The interaction between one slip system and its cross-slipped system, which bas been largely ignored until now, appears to be the strongest. This surprising result calls for an exhaustive study. Indeed, it may bring new answers to pending questions related to the formation of patterned microstructures and the relative contribution of diagonal and cross coefficients in the hardening matrix
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Landeiro, dos Reis Marie. "Étude de l'interaction dislocation - amas de lacunes par simulations numériques." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS311/document.
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Des amas de lacunes ont été observés et caractérisés expérimentalement dans les métaux de haute pureté après déformation plastique ou après une suite de traitements thermiques particuliers. Ces amas sont des obstacles à la propagation des dislocations et peuvent par conséquent induire un durcissement du métal.Cette étude par simulations numériques a permis d'explorer différents mécanismes de propagation de dislocations dans une concentration d'amas en fonction de la contrainte de cisaillement appliquée et de la température. À haute contrainte, la force appliquée sur la dislocation devient supérieure aux forces d'ancrage s’exerçant sur la ligne. La dislocation franchit la distribution d'amas en glissant et en cisaillant les amas. La dépendance de la force d'ancrage en fonction de la taille de l'amas est ajustée sur nos simulations de statique moléculaire. Dans ce domaine de contrainte, les configurations d'amas ancrant la dislocation sont rares et l'activation thermique suffit à désancrer la ligne. La probabilité de désancrer la ligne dépend de l'enthalpie d'activation, un paramètre que nous avons également estimé à l'aide d'un modèle analytique ajusté sur nos résultats atomistiques. À plus faible contrainte, lorsque la force appliquée est inférieure aux forces d'ancrage induites par les amas, la probabilité que la dislocation se désancre uniquement par glissement devient faible. La diffusion des lacunes, émises préférentiellement des amas, intervient alors et favorise la formation de crans. Cela contribue au désancrage de la ligne. Ce mécanisme est le glissement assisté par la montée. Les barrières d'émission, d'absorption et de migration de lacunes ont été déterminées par statique moléculaire et sont fortement dépendantes du champ élastique et de la distorsion du réseau atomique générés par la présence de la dislocation. Cela induit une forte anisotropie de diffusion au voisinage des dislocations qui conduit notamment au mécanisme de 'pipe diffusion'. L'évolution au cours du temps de l'ensemble de ces mécanismes a été étudiée à l'aide d'un modèle de ligne élastique couplé à un algorithme de Monte Carlo cinétique dont l'ensemble des barrières d'énergie provient de nos simulations atomistiques. Moyennant les hypothèses du modèle, nous avons alors obtenu une estimation de la vitesse des dislocations en fonction de la contrainte et de la température appliquée. Nous avons ensuite utilisé la loi d'Orowan pour estimer la vitesse de déformation liée à ces mécanismes<br>Vacancy clusters have been observed and characterized experimentally in highly pure metals after plastic deformation or after a particular sequence of heat treatments. These clusters hinder the dislocation propagation and can therefore harden the metal.Using numerical simulations we have explored different mecanisms of dislocation propagation through a vacancy-cluster distribution, for several applied shear stress and temperature. At high stresses, the force applied on the dislocation becomes greater than the pinning forces acting on the line. The dislocation gets through the cluster distribution by gliding and shearing the clusters. The dependence of the pinning force with the cluster size is adjusted on our molecular static simulations. In this stress range, the pinning configurations are rare and the thermal activation is sufficient to unpin the line. The probability for the line to pass the pinning configuration depends on the activation enthalpy, a parameter that we have also estimated using an analytical model adjusted on our atomistic results. At lower stresses, when the applied force is below the pinning forces induced by the cluster, the probability that the dislocation unpins by pure glide becomes negligeable. The diffusion of vacancies, emitted preferentially from the vacancy clusters, intervenes and promotes the formation of jogs that contributes to the unpinning of the line. Such a mecanism is the glide assisted by climb. The emission, the absorption and the vacancy migration barriers have been determined by molecular static and are highly dependent on the elastic field and the atomic network distortion induced by the dislocation. This promotes a strong diffusion anisotropy in the vicinity of the dislocations which leads in particular to the pipe diffusion mechanism. The evolution with time of all these mechanisms has been studied using an elastic line model coupled to a kinetic Monte Carlo algorithm in which the parameters come from our atomistic simulations. According to the model assumptions, we obtained an estimation of dislocation velocity as a function of the applied shear stress and the temperature. We used the Orowan's law to estimate the strain rate related to such mechanisms
Books on the topic "Dislocations"
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1955-, Hébert Gilles, Gagnon Monika, Winnipeg Film Group, and Dunlop Art Gallery, eds. Dislocations. Winnipeg Film Group, 1995.
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Museum of Modern Art (New York, N.Y.), ed. Dislocations. Museum of Modern Art, 1991.
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Hospital, Janette Turner. Dislocations: Stories. Louisiana State University Press, 1987.
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J, Bacon D., ed. Introduction to dislocations. 4th ed. Butterworth-Heinemann, 2001.
Find full textBook chapters on the topic "Dislocations"
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Ohmura, Takahito. "Nanomechanical Characterization of Metallic Materials." In The Plaston Concept. Springer Nature Singapore, 2022. http://dx.doi.org/10.1007/978-981-16-7715-1_8.
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AbstractMechanical behavior of metallic materials on nanoscale is characterized by using Nanoindentation and Transmission Electron Microscope (TEM) to understand the fundamental plasticity mechanisms associated with microstructural factors including dislocations. The advanced characterization techniques enable us to grasp the behavior on the nanoscale in detail. New knowledges are obtained for the plasticity initiation under the extremely high stress close to the theoretical strength in regions with defect-free matrix and pre-existing defects such as grain boundaries, in-solution elements, and dislocations. The grain boundaries act as an effective dislocation source, the in-solution elements retard a nucleation of dislocation, and the pre-existing dislocations assist a plasticity initiation. The deformation behavior associated with microstructures is also described. The dislocation structure with a certain density was observed right after indentation-induced strain burst, which is so-called “pop-in,” suggesting a dislocation avalanche upon the pop-in. It has been directly observed that the lower mobility screw dislocation causes the higher flow stress in a bcc metal. A remarkable strain softening can be understood by an increase in dislocation density based on conventional physical models. Phase stability for indentation-induced transformation depends on a constraint effect by inter-phase boundary and grain boundary.
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Henry, Mark. "Perilunate Dislocations and Fracture Dislocations/Radiocarpal Dislocations and Fracture Dislocations." In Arthroscopic Management of Distal Radius Fractures. Springer Berlin Heidelberg, 2010. http://dx.doi.org/10.1007/978-3-642-05354-2_11.
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Lawyer, Tracye J., and Patrick F. Bergin. "Dislocations." In Orthopedic Surgery Clerkship. Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-52567-9_4.
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Mura, Toshio. "Dislocations." In Micromechanics of defects in solids. Springer Netherlands, 1987. http://dx.doi.org/10.1007/978-94-009-3489-4_6.
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Saffar, Docteur Philippe. "Dislocations." In Carpal injuries. Springer Paris, 1990. http://dx.doi.org/10.1007/978-2-8178-0777-5_10.
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Guerin, Frances. "Dislocations." In A Companion to German Cinema. Wiley-Blackwell, 2012. http://dx.doi.org/10.1002/9781444345605.ch19.
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Swinburne, Thomas D. "Dislocations." In Stochastic Dynamics of Crystal Defects. Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-20019-4_2.
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Babu, Jacob. "Dislocations." In Essential Orthopedic Review. Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-78387-1_4.
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Jackson, A. G. "Dislocations." In Handbook of Crystallography. Springer New York, 1991. http://dx.doi.org/10.1007/978-1-4612-3052-6_13.
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Sutton, Adrian P. "Dislocations." In Physics of Elasticity and Crystal Defects. Oxford University Press, 2020. http://dx.doi.org/10.1093/oso/9780198860785.003.0006.
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Plastic deformation involves planes of atoms sliding over each other. The sliding happens through the movement of linear defects called dislocations. The phenomenology of dislocations and their characterisation by the Burgers circuit and line direction are described. The Green’s function plays a central role in Volterra’s formula for the displacement field of a dislocation and Mura’s formula for the strain and stress fields. The isotropic elastic fields of edge and screw dislocations are derived. The field of an infinitesimal dislocation loop and its dipole tensor are also derived. The elastic energy of interaction between a dislocation and another source of stress is derived, and leads to force on a dislocation. The elastic energy of a dislocation and the Frank-Read source of dislocations are also discussed. Problem set 6 extends the content of the chapter in several directions including grain boundaries and faults.
Conference papers on the topic "Dislocations"
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Siegl, Wolfgang, Gregor Mori, Werner Ecker, et al. "Hydrogen Trapping in Heat Treated and Deformed Armco Iron." In CORROSION 2019. NACE International, 2019. https://doi.org/10.5006/c2019-13083.
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Abstract The purpose of this research was to investigate the influence of microstructure of Armco iron on hydrogen trapping by analyzing the trapping ability of grain boundaries and dislocations. Hydrogen traps were introduced into the material by systematically subjecting it to various grades of heat treatment and mechanical deformation. By combining different treatment steps (annealing at different temperatures, cold rolling at various deformation degrees, severe plastic deformation), a wide range of different grain sizes and dislocation densities was created. Microstructural characterization and electrochemical permeation experiments were performed to gain information on the diffusivity of hydrogen in the material and the influence of traps on the diffusivity. An experimental setup according to Devanathan and Stachurski was used. By combining the information on the microstructure obtained from the material characterization with the experimental results, the trapping ability of microstructural features were evaluated. Dislocations have a strong impact on diffusion and hydrogen trapping, while grain boundaries only show this effect in small grain size regions. In specimens with grain sizes in the micrometer range and above, no influence of grain boundaries on diffusion was observed.
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Bruemmer, S. M., L. A. Chariot, and C. H. Henager. "Microstructure and Microdeformation Effects on IGSCC of Alloy 600 Steam Generator Tubing." In CORROSION 1987. NACE International, 1987. https://doi.org/10.5006/c1987-87088.
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Abstract Microdeformation characteristics in Alloy 600 tubing have been examined after various tensile deformations. Microstructure developed during processing was found to control subsequent microdeformation behavior. Grain boundary carbides were the most effective source of dislocations, activating at lower macro-strains and continuing to operate at higher macrostrains than other sources. Ledges within grain boundaries, twin boundaries and matrix carbides also acted as dislocation sources. Most dislocation activity at low strains was confined to planar arrays. A conceptual model is presented to account for the effects of interfacial and matrix microstructure on microdeformation and primary-side SCC of Alloy 600 tubing. Microstructure is linked to IGSCC resistance through its influence on microdeformation behavior and the resultant crack-tip stress state. Dislocation source activity at grain interfaces is proposed to be a critical aspect controlling IGSCC susceptibility. Effective sources such as grain boundary carbides promote crack blunting, decrease the crack-tip stress state and increase resistance to cracking.
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Browe, Daniel P., Carrie A. Voycheck, Patrick J. McMahon, and Richard E. Debski. "Injury to the Glenohumeral Capsule During Anterior Dislocation Results in Damage to the Anteroinferior Capsule." In ASME 2011 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2011. http://dx.doi.org/10.1115/sbc2011-53840.
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The glenohumeral joint is the most frequently dislocated major joint in the body with about 2% of the population dislocating their shoulders between the ages of 18 and 70 [1]. About 80% of these shoulder dislocations occur in the anterior direction, and they most commonly occur in the apprehension position, which is characterized by 60° of glenohumeral abduction and 60° of external rotation [2]. The most common pathology associated with dislocation is instability due to permanent deformation [3]. Current surgical repair techniques for shoulder dislocations are inadequate with about 25% of patients still experiencing pain and instability after surgery [4]. By assessing the strain distribution, it is possible to determine the stabilizing function of the various capsular regions. In addition, surgeons could benefit from knowing the location and extent of tissue damage when placating the capsule during repair procedures. Therefore, the objective of this study was to determine the location and extent of injury to the anteroinferior capsule during anterior dislocation by quantifying the strain at dislocation and the non-recoverable strain following dislocation.
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Shao, S., and S. N. Medyanik. "Interaction of Dislocations With Interfaces in Nanoscale Multilayered Metallic Composites." In ASME 2008 International Mechanical Engineering Congress and Exposition. ASMEDC, 2008. http://dx.doi.org/10.1115/imece2008-67523.
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Atomistic simulation studies of dislocation nucleation and propagation in nanoscale multilayered metallic systems (Cu-Ni and Cu-Nb) are performed. Nanoindentation model is used to generate dislocations at and near the surface. Interaction of the propagating dislocations with two types of interfaces (coherent and incoherent) is analyzed. In the case of coherent interface, Cu(111)-Ni(111), dislocations that initiate in Cu layer propagate through the interface into Ni. However, the interface acts as an obstacle for dislocation propagation and leads to a higher dislocation density near the interface. In the case of incoherent interface, Cu(111)-Nb(110), dislocations that initiate in Cu do not propagate into Nb and tend to accumulate in copper near the interface. In both cases, the interfaces provide mechanisms for strengthening the nanoscale multilayered metallic systems.
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Oyinbo, Sunday Temitope, and Tien-Chien Jen. "Molecular Dynamics Simulation of the Effect of Hydrogen on the Interaction Between Dislocations in Alpha-Iron." In ASME 2022 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/imece2022-94722.
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Abstract In this study, we use extensive molecular dynamics (MD) calculations based on a highly-accurate interatomic potential to examine how hydrogen atoms impact the mechanisms behind the mobilities of edge and screw dislocations in alpha-iron (α-Fe) at a temperature ranging from 300 K to 500 K. The dislocation mobility in α-Fe is shown to be temperature and hydrogen concentration-dependent in this MD investigation. It is demonstrated from the results that hydrogen impurities that are efficient in locking dislocations exist in the form of complexes that are scattered discretely along the dislocation line and that these complexes operate as extremely effective impediments to the mobility of dislocations. The hydrogen impact on the edge dislocation motion from the dislocation velocities versus shear stress reveals that the movement of edge dislocations in α-Fe with hydrogen is much damped as the hydrogen concentration increases. Furthermore, the motion of screw dislocations in the α-Fe is by the process of kink-pair nucleation and migration. according to the simulation results, the locking mechanism of the cross-slip seen along the dislocation path is due to the strong-feature energy landscape and inherent energy fluctuation in the system, resulting in jogs formation.
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Zhou, Yongkai, and Luyang Han. "Failure Analysis Work Flow for Dislocation Identification and Characterization by Electron Channeling Contrast Imaging Using SEM and FIB." In ISTFA 2016. ASM International, 2016. http://dx.doi.org/10.31399/asm.cp.istfa2016p0476.
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Abstract A failure analysis work flow is presented demonstrating dislocation visualization, site isolation, TEM lamella preparation and defect characterization. A novel beam control technique allows visualizing dislocations with significantly improved spatial resolution in SEM using Electron Channeling Contrast Imaging. Site-specific TEM preparation on dislocations is therefore possible. The prepared thin lamella can be inspected in the SEM using STEM to study dislocations. This is a cost effective work flow without using TEM.
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Banerjee, Sauvik, Mutasem Shehadeh, Gang Lu, Nicholas Kioussis, and Nasr Ghoniem. "A Multiscale Approach for the Determination of Nonsingular Elastic Fields of Dislocations in Bulk and Nano-Layered Materials." In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-42058.
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The traditional description of elastic field and energies of dislocations is based on continuum theory of linear elasticity that suffers from the long-standing problem of singularities at the dislocation core. Singular solutions are often circumvented by introducing an artificial core-cutoff radius. This limits the applicability of the theory to describe situations where it is important to know the strained state and nanoscopic details within a few atomic spacings surrounding the dislocation center, known as the dislocation core. In this paper, a computationally tractable multiscale approach is developed to calculate the nonsingular elastic fields of dislocations in both bulk and nano-layered materials. The approach is an extension of Peierls-Nabarro (PN) model, with the following features: (1) all three components of the displacement vector for atoms within the dislocation core are included; (2) the entire generalized stacking fault energy (GSFE or gamma-γ) surface obtained from ab initio calculations is utilized; and (3) the method can be generalized to treat curved dislocations. We combine the parametric dislocation dynamics (DD) approach for the interaction and motion of dislocations with the ab initio calculations of the lattice restoring forces, which are extracted from the γ surface. The method is used to study two important problems: (a) dislocation dissociation in bulk crystals (b) dislocation transmission across interfaces in elastic bimaterials. Dislocation core structures in bulk aluminum and silver are determined. The results from the model are shown to be in excellent agreement with experiments for both Al and Ag. For bi-materials system, the effects of the mismatch in the elastic properties, γ surface and lattice parameters on the spreading of the dislocation onto the interface(s) and the transmission across the interface(s) are studied in detail.
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Bow, Jong-Shing, and Speed Yu. "Depth Measurement of Dislocations in Si Substrate by Stereo TEM." In ISTFA 2005. ASM International, 2005. http://dx.doi.org/10.31399/asm.cp.istfa2005p0233.
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Abstract Traditional plane-view TEM images, which have large fields of view and are usually used to check the existence of dislocations, cannot tell whether a dislocation goes through the p-n junction or not. While XTEM images tell the local depth of a small part of a dislocation only, other methods have to be developed to explore how a dislocation goes in the substrate. In this article, the authors have modified the technique of stereo TEM, which was used to study the 3D shapes of precipitates, to study how a dislocation runs in the Si substrate. Three images recorded after tilting the TEM sample were used for measuring the dislocation depth profile. The distances between a few chosen points on the dislocation and the reference line were measured from above three images. Results suggested that the depth profiles of dislocations in the Si substrate can be accurately determined by stereo TEM.
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Robison, Andrew, Lei Lei, Sowmya Ramarapu, and Marisol Koslowski. "Interface Effects in Strained Thin Films." In ASME 2009 International Mechanical Engineering Congress and Exposition. ASMEDC, 2009. http://dx.doi.org/10.1115/imece2009-12539.
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Crystalline films grown epitaxially on a substrate consisting of a different crystalline material are of considerable interest in optoelectronic devices and the semiconductor industry. The film and substrate have in general different lattice parameters. This lattice mismatch affects the quality of interfaces and can lead to very high densities of misfit dislocations. Here we study the evolution of these misfit dislocations in a single crystal thin film. In particular, we consider the motion of a dislocation gliding on its slip plane within the film and its interaction with multiple obstacles and sources. Our results show the effect of obstacles such as precipitates and other dislocations on the evolution of a threading dislocation in a metallic thin film. We also show that the material becomes harder as the film thickness decreases in excellent agreement with experiments.
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Selberg, Lars A., and Thomas E. Hoge. "Interferometric slope measurement technique for detection and measurement of silicon crystal lattice defects." In OSA Annual Meeting. Optica Publishing Group, 1988. http://dx.doi.org/10.1364/oam.1988.mgg1.
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An ac heterodyne interferometric technique for detecting crystal lattice dislocations and measuring their heights is presented. Preliminary laboratory data indicate the sensitivity of the technique for defect detection to be in the nanometer range. Crystal lattice dislocations in semiconductor wafers (sliplines) can render useless any device through which a dislocation passes. These dislocations are caused by the release of latent stresses in the lattice. The release of these stresses is brought about by the processing of wafers for device fabrication. Detection of the sliplines at an early stage is important to process efficiency.
Reports on the topic "Dislocations"
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Chen, Qian. Evolution, Interaction, and Intrinsic Properties of Dislocations in Intermetallics: Anisotropic 3D Dislocation Dynamics Approach. Office of Scientific and Technical Information (OSTI), 2008. http://dx.doi.org/10.2172/939374.
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Thomson, Robb, Emeritus. Small angle scattering by dislocations. National Institute of Standards and Technology, 1998. http://dx.doi.org/10.6028/nist.ir.
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Thomson, Robb Emeritus, L. E. Levine, and G. G. Long. Small angle scattering by dislocations. National Institute of Standards and Technology, 1998. http://dx.doi.org/10.6028/nist.ir.6117.
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Tan, A. M. Chapter 5: Dislocations in Cadmium Telluride. Office of Scientific and Technical Information (OSTI), 2018. http://dx.doi.org/10.2172/1440720.
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Wolfer, W. G. Phonon Drag Dislocations at High Pressures. Office of Scientific and Technical Information (OSTI), 1999. http://dx.doi.org/10.2172/793838.
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Altan, B., and A. C. Eringen. Interactions of Four Edge Dislocations with Crack. Defense Technical Information Center, 1988. http://dx.doi.org/10.21236/ada201408.
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Levine, L. E., and Robb Emeritus Thomson. X-ray scattering by dislocations in crystals:. National Institute of Standards and Technology, 1996. http://dx.doi.org/10.6028/nist.ir.5931.
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Clayton, J. D., D. L. McDowell, and D. J. Bammann. Modeling Dislocations and Disclinations with Finite Micropolar Elastoplasticity. Defense Technical Information Center, 2001. http://dx.doi.org/10.21236/ada417830.
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Maloy, S. A., F. Chu, J. J. Petrovic, and T. E. Mitchell. Dislocations and mechanical properties of single crystal niobium disilicide. Office of Scientific and Technical Information (OSTI), 1996. http://dx.doi.org/10.2172/378865.
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Pilania, Ghanshyam. Misfit dislocations at metal-ceramic and ceramic-ceramic interfaces. Office of Scientific and Technical Information (OSTI), 2015. http://dx.doi.org/10.2172/1184608.
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