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1
Shetty, Sanath Kumar, Lawrence J. Mathias, H. Ravindranath Rai, P. Nirmal Babu, Raj Sankar N. R. i 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, nr 01 (marzec 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.
2
Pande, Chandra S., i Ramasis Goswami. "Dislocation Emission and Crack Dislocation Interactions". Metals 10, nr 4 (3.04.2020): 473. http://dx.doi.org/10.3390/met10040473.
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An understanding of the crack initiation and crack growth in metals spanning the entire spectrum of conventional and advanced has long been a major scientific challenge. It is known that dislocations are involved both in the initiation and propagation of cracks in metals and alloys. In this review, we first describe the experimental observations of dislocation emission from cracks under stress. Then the role played by these dislocations in fatigue and fracture is considered at a fundamental level by considering the interactions of crack and dislocations emitted from the crack. We obtain precise expression for the equilibrium positions of dislocations in an array ahead of crack tip. We estimate important parameters, such as plastic zone size, dislocation free zone and dislocation stress intensity factor for the analysis of crack propagation. Finally, we describe very recent novel and significant results, such as residual stresses and relatively large lattice rotations across a number of grains in front of the crack that accompanies fatigue process.
3
Gulbrandsen, Matthew T., Jill G. Putnam, J. Tracy Watson i Michael D. McKee. "Irreducible Volar DRUJ Dislocation with Distal Radius Fracture Dislocation". Journal of Wrist Surgery 09, nr 02 (12.07.2019): 156–59. http://dx.doi.org/10.1055/s-0039-1692476.
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Abstract Background Volar dislocations of the distal radioulnar joint (DRUJ) are rare and often missed during initial evaluation. Chronic dislocations and disability can occur when DRUJ dislocations are unrecognized and not reduced. DRUJ dislocations often occur with other wrist injuries, which may complicate reduction. Closed reduction can fail to reduce DRUJ dislocations, in which case open reduction is necessary. Case Description This case describes a patient who had a volar dislocation of the DRUJ with an associated dorsal distal radius fracture dislocation. Initial attempts at closed reduction were unsuccessful which prompted surgical intervention. After open reduction and internal fixation of the distal radius fracture dislocation, closed reduction of the DRUJ remained unsuccessful. This prompted an open reduction of the DRUJ. Surgical exposure demonstrated that the extensor carpi ulnaris and the distal radius had prevented closed reduction of the DRUJ. Postoperatively, a splint was placed with the wrist in supination. The patient followed-up at the 2- and 4-month intervals with persistent subluxation. However, the patient also reported minimal pain and the ability to return to work and previous level of activity. Literature Review Current literature regarding irreducible volar DRUJ dislocations with distal radius fracture dislocations includes sparse case reports, which are reviewed in this report. Clinical Relevance This case illustrates successful treatment for an uncommon volar DRUJ dislocation associated with a dorsal distal radius fracture dislocation and can be utilized to help guide future treatment of similar complex cases.
4
Wang, Xiaona, Haibin Zhang, Shinong Yan, Yongmei Zhang, Xiaolin Tian, Dunwei Peng i Yuhong Zhao. "The Response Mechanism of Crystal Orientation to Grain Boundary Dislocation under Uniaxial Strain: A Phase-Field-Crystal Study". Metals 12, nr 5 (21.04.2022): 712. http://dx.doi.org/10.3390/met12050712.
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An exploration of dislocation microstructure evolution with different misorientation angles was performed using phase field crystal method (PFC). The microcosmic evolution process of grain boundaries under external stress, as well as the corresponding energy curve and stress–strain curve, are analyzed. The relationship between the misorientation angle and the dislocations emission frequency is discussed. Three forms of dislocations reaction on the evolution process of 6°and 10° are analyzed in detail, which are respectively type I semi-annihilation, type II semi-annihilationand full-annihilation. Among them, the nature of type I semi-annihilation is a combination of dislocation and a single edge dislocation reaction with a single edge dislocation left. The essence of type II semi-annihilation is a pair of dislocation and the other pair of dislocation reaction leaving two edge dislocations. The essence of full-annihilation is that two pairs of dislocations or single edge dislocations with opposite Burger vectors react with each other and the distortion area disappears. When the misorientation angle is 10°, the dislocation reaction and the dislocation motion ability of the system are stronger than 6°. The peak of the energy curve is related to the number of dislocation proliferations in the evolution process. An emission frequency and average density of dislocations of 10° is greater than 6°. The causes of plastic deformation are revealed to a certain extent by stress–strain curves.
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Petelina, Yulia, Svetlana Kolupaeva, Konstantin A. Polosukhin i Aleksander Petelin. "Influence of the Dislocation Density on the Expansion Dynamics of the Crystallographic Slip Zone along Screw Orientations in Aluminum and Copper". Key Engineering Materials 683 (luty 2016): 136–41. http://dx.doi.org/10.4028/www.scientific.net/kem.683.136.
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Crystallographic slip is one of key mechanisms determining plastic form change of crystalline solids. Despite a large amount of works done on the subject, crystallographic slip is a very difficult subject to study. Significant progress in the study of the crystallographic slip process is possible only with the use of a set of different methods: experimental methods, methods of mathematical modeling and simulation. The paper presents a modification mathematical expansion model of closed dislocations emitted by one dislocation source with takes into account the elastic interaction force among all dislocations of the forming dislocation pile-up. The model takes into account the Peach-Koehler forces, lattice, impurity, and dislocation friction, linear tension, viscous deceleration, and the intensity of generation of point defects beyond jogs on the dislocation, as well as the elastic interaction force among all dislocations of the forming dislocation pile-up. The analysis of the study results on the expansion dynamics of the dislocation loop along the screw orientation on copper and aluminum with varying of the dislocation density from 3×1011 m−2 to 1012 m−2 is carried out. It is established that the length and the path time of the screw dislocation, as well as the number of dislocations emitted by the dislocation source, essentially depend on the density of dislocations. The dependence of the current radius, velocity, and kinetic energy of the screw dislocation on the path time and the dependence of the current velocity and the kinetic energy of the first screw dislocation emitted by the dislocation source on its current radius are described.
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Li, Yon Gan, Xiang Qian Xiu, Xue Mei Hua, Shi Ying Zhang, Shi Pu Gu, Rong Zhang, Zi Li Xie i in. "Study of Dislocation Densities of Thick GaN Films". Advanced Materials Research 989-994 (lipiec 2014): 387–90. http://dx.doi.org/10.4028/www.scientific.net/amr.989-994.387.
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The dislocation density of GaN thick films has been measured by high-resolution X-ray diffraction. The results show that both the edge dislocations and the screw dislocation reduce with increasing the GaN thickness. And the edge dislocations have a larger fraction of the total dislocation densities, and the densities for the edge dislocation with increasing thickness reduce less in contrast with those for the screw dislocation.
7
Takaki, Setsuo, Y. Fujimura, Koichi Nakashima i Toshihiro Tsuchiyama. "Effect of Dislocation Distribution on the Yielding of Highly Dislocated Iron". Materials Science Forum 539-543 (marzec 2007): 228–33. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.228.
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Yield strength of highly dislocated metals is known to be directly proportional to the square root of dislocation density (ρ), so called Bailey-Hirsch relationship. In general, the microstructure of heavily cold worked iron is characterized by cellar tangled dislocations. On the other hand, the dislocation substructure of martensite is characterized by randomly distributed dislocations although it has almost same or higher dislocation density in comparison with heavily cold worked iron. In this paper, yielding behavior of ultra low carbon martensite (Fe-18%Ni alloy) was discussed in connection with microstructural change during cold working. Originally, the elastic proportional limit and 0.2% proof stress is low in as-quenched martensite in spite of its high dislocation density. Small amount of cold rolling results in the decrease of dislocation density from 6.8x1015/m-2 to 3.4x1015/m-2 but both the elastic proportional limit and 0.2% proof stress are markedly increased by contraries. 0.2% proof stress of cold-rolled martensite could be plotted on the extended line of the Bailey-Hirsch equation obtained in cold-rolled iron. It was also confirmed that small amount of cold rolling causes a clear microstructural change from randomly distributed dislocations to cellar tangled dislocations. Martensite contains two types of dislocations; statistically stored dislocation (SS-dislocation) and geometrically necessary dislocation (GN-dislocation). In the early deformation stage, SS-dislocations easily disappear through the dislocation interaction and movement to grain boundaries or surface. This process produces a plastic strain and lowers the elastic proportional limit and 0.2% proof stress in the ultra low carbon martensite.
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Lauer, Kevin, Martin Herms, Anett Grochocki i Joachim Bollmann. "Iron Gettering at Slip Dislocations in Czochralski Silicon". Solid State Phenomena 178-179 (sierpień 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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Shen, Yixi, i Douglas E. Spearot. "Mobility of dislocations in FeNiCrCoCu high entropy alloys". Modelling and Simulation in Materials Science and Engineering 29, nr 8 (15.11.2021): 085017. http://dx.doi.org/10.1088/1361-651x/ac336a.
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Abstract Dislocations in high entropy alloys (HEAs) are wavy and have natural pinning points due to the variable chemical and energetic landscape surrounding the dislocation core. This can influence the critical shear stress necessary to initiate dislocation motion and the details associated with sustained dislocation glide. The objective of this work is to determine the relationship between Schmid shear stress and dislocation velocity in single phase FCC FeNiCrCoCu HEAs using molecular dynamics simulations, with comparisons made to dislocation motion in homogeneous Ni and Cu. Simulations are performed for four different dislocation character angles: 0° (screw), 30°, 60° and 90° (edge). Several key differences are reported, compared to what is previously known about dislocation motion in homogeneous FCC metals. For example, the drag coefficient B in the phonon damping regime for HEAs has a nonlinear dependence on temperature, whereas this dependence is linear in Ni. Mobility relationships between different types of dislocations common in homogeneous FCC metals, such as the velocity of screw and 60° dislocations being lower than edge and 30° dislocations at the same shear stress, do not necessarily hold in HEAs. Dislocation waviness is measured and is found to correlate with the ability of dislocations to glide under an applied shear stress, including the temperature dependence of the drag coefficient B. These results confirm that the influence of HEA chemical complexity on dislocation motion is important and this data can be used to guide development of analytical or empirical models for dislocation mobility in HEAs.
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Kang, Junyong, Shin Tsunekawa i Atsuo Kasuya. "Dislocations around precipitates in AlGaN epilayers". Journal of Materials Research 17, nr 8 (sierpień 2002): 2007–11. http://dx.doi.org/10.1557/jmr.2002.0297.
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Dislocations around precipitates in undoped AlGaN were investigated by transmission electron microscopy. The dislocation images were taken under different diffraction conditions. The dislocations are classified into two types, a pure edge dislocation loop and a close-;coiled helical dislocation. Both types of dislocations were found to depend on the shape and size of the precipitate sources. It is suggested that the pure edge dislocation loop results from homogeneous shear stress and the close-;coiled helical dislocation is caused by spherically symmetrical stress concentration at round ends of the precipitates and chemical force due to defect concentration change.
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Su, Wen, Kai Ye i Jingbo Liu. "Hydrolytic weakening of jadeite in UHP jadeite-quartzites from the Dabie Mountains, eastern China". Mineralogical Magazine 70, nr 5 (październik 2006): 509–15. http://dx.doi.org/10.1180/0026461067050354.
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AbstractDeformed jadeite grains in the UHP jadeite-quartzites from the Dabie Mountains, eastern China show evidence (by transmission electron microscopy, TEM) of plastic deformation: free dislocations, dislocation loops, dislocation networks, dislocation arrays and regularly spaced subgrain boundaries by dislocation walls. Electron energy-loss spectroscopy and TEM studies reveal the existence of water-rich bubbles within dislocations and imply a relationship with water-defect dislocation by water weakening in the jadeites. These observations suggest that the water-rich bubbles are a major weakening effect facilitating plastic deformation of jadeite by dislocation creep.
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Siddiqui, NA, i SP Sarkar. "Isolated Dorsal Dislocation of the Lunate". Open Orthopaedics Journal 6, nr 1 (30.11.2012): 531–34. http://dx.doi.org/10.2174/1874325001206010531.
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Lunate dislocations are well described in the volar direction as part of the perilunate dislocation, sometimes together with fractures of the other carpal bones or distal radius, as described by the anatomical studies of Mayfield [1]. It is a result of disruption of the complex inter-carpal and radiocarpal ligaments that hold the well conforming carpus in their normal position. Given the strength of these structures a significant trauma is required to cause them to fail. However, we present a case of a patient who not only presented with relatively trivial trauma that resulted in a lunate dislocation, but it was also in the dorsal direction and not associated with any fracture or neurological compromise. In addition, she presented several days after her injury. We treated her with closed manipulation and percutaneous K-wire fixation followed by a short period of immobilisation in a Plaster-of-Paris cast, with rapid return to full duties at work. As many volar lunate dislocations may be missed at presentation, we suggest that in patients with relatively trivial trauma there should also be a suspicion of the lunate dislocating dorsally, which may be treated successfully without the aggressive open surgery usually required in volar perilunate dislocations.
13
Hirth, John P. "Fine-scale structural defects in dislocation cores". Proceedings, annual meeting, Electron Microscopy Society of America 48, nr 4 (sierpień 1990): 446–47. http://dx.doi.org/10.1017/s0424820100175363.
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We are now entering what one might consider the third phase of study of dislocations by transmission electron microscopy (TEM). The first phase, in the 1950’s and 1960’s led to classifications of dislocation behavior, concepts of low angle boundaries, equilibrium nodes, and dislocation extension, for example. The second, with the advent of the weak-beam technique, produced improved estimates of stacking fault energy on the basis of dislocation extension, revealed more types of extended dislocation configurations, particularly in ordered intermetallic compounds and inorganic compounds, and revealed finer scale partial dislocations such as misfit dislocations and grain boundary dislocations. With improved resolution for both imaging and direct lattice resolution, we can now be thought to be entering a third phase where information on even finer scale core structure of dislocations might be revealed.The improvement in direct core structure resolution is exciting to those working on the physics of dislocation configurations or on dislocation motion and mechanical properties because of the possibility of direct confirmation of mechanisms and models that have heretofore only been tested by indirect correlations.
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Lv, Xin, i Guan-Ting Liu. "Exact Solutions for Interaction of Parallel Screw Dislocations with a Wedge Crack in One-Dimensional Hexagonal Quasicrystal with Piezoelectric Effects". Mathematical Problems in Engineering 2020 (29.05.2020): 1–15. http://dx.doi.org/10.1155/2020/4797413.
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The purpose of this paper is to consider the interaction between many parallel dislocations and a wedge-shaped crack and their collective response to the external applied generalized stress in one-dimensional hexagonal piezoelectric quasicrystal, employing the complex variable function theory and the conformal transformation method; the problem for the crack is reduced to the solution of singular integral equations, which can be further reduced to solving Riemann–Hilbert boundary value problems. The analytical solutions of the generalized stress field are obtained. The dislocations are subjected to the phonon field line force, phason field line force, and line charge at the core. The positions of the dislocations are arbitrary, but the dislocation distribution is additive. The dislocation is not only subjected to the external stress and the internal stress generated by the crack, but also to the force exerted on it by other dislocations. The closed-form solutions are obtained for field intensity factors and the image force on a screw dislocation in the presence of a wedge-shaped crack and a collection of other dislocations. Numerical examples are provided to show the effects of wedge angle, dislocation position, dislocation distribution containing symmetric configurations and dislocation quantities on the field intensity factors, energy release rate, and image force acting on the dislocation. The principal new physical results obtained here are (1) the phonon stress, phason stress, and electric displacement singularity occur at the crack tip and dislocations cores, (2) the increasing number of dislocations always accelerates the crack propagation, (3) the effect of wedge angle on crack propagation is related to the distribution of dislocations, and (4) the results of the image force on the dislocation indicate that the dislocations can either be attracted or rejected and reach stable positions eventually.
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Huang, C. C., C. C. Yu i Sanboh Lee. "The behavior of screw dislocations dynamically emitted from the tip of a surface crack during loading and unloading". Journal of Materials Research 10, nr 1 (styczeń 1995): 183–89. http://dx.doi.org/10.1557/jmr.1995.0183.
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The behavior of screw dislocations dynamically emitted from the tip of a surface crack during loading and unloading has been investigated using a discrete dislocation model. The critical stress intensity factor at the crack tip for dislocation emission is a function of friction stress, core radius of dislocation, and dislocations near the crack tip. During motion, the velocity of dislocation is assumed to be proportional to the effective shear stress to the third power. The effect of crack length and friction stress on dislocation distributions, plastic zone, and dislocation-free zone during loading and unloading was examined.
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Lazar, Markus. "The gauge theory of dislocations: a uniformly moving screw dislocation". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 465, nr 2108 (2.06.2009): 2505–20. http://dx.doi.org/10.1098/rspa.2009.0043.
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In this paper, we present the equations of motion of a moving screw dislocation in the framework of the translation gauge theory of dislocations. In the gauge field theoretical formulation, a dislocation is a massive gauge field. We calculate the gauge field theoretical solutions of a uniformly moving screw dislocation. We give the subsonic and supersonic solutions. Thus, supersonic dislocations are not forbidden from the field theoretical point of view. We show that the elastic divergences at the dislocation core are removed. We also discuss the Mach cones produced by supersonic screw dislocations.
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Fan, Shizhao, Rong Liu, Yingnan Huang, Jianxun Liu, Xiaoning Zhan, Xiujian Sun, Meixin Feng, Yuhao Yin, Qian Sun i Hui Yang. "Observation of threading dislocations and misfit dislocation half-loops in GaN/AlGaN heterostructures grown on Si using electron channeling contrast imaging". Journal of Applied Physics 132, nr 10 (14.09.2022): 105302. http://dx.doi.org/10.1063/5.0102373.
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We implemented invisibility criterion and black–white contrast orientation analysis into low-tilt electron channeling contrast imaging (ECCI) for dislocation-type discrimination in GaN and AlGaN layers grown on a Si(111) substrate. Our ECCI and x-ray diffraction (XRD) analysis attained consistent threading dislocation densities for GaN and AlGaN grown on Si, but demonstrated drastic discrepancy in the percentage of edge-type dislocations, potentially due to the lack of appropriate consideration of mixed-type [Formula: see text] dislocations in XRD. Further ECCI analysis of GaN/AlGaN heterointerface revealed mixed-type [Formula: see text] dislocation half-loops and dislocation bending due to compressive strain relaxation, validating that not all the dislocations originated from the mosaic or columnar structure. As a result, XRD analysis based on the mosaic block model does not give reliable edge-to-screw dislocation ratio. The observation of classic van der Merwe–Matthews-type dislocation half-loop nucleation and dislocation gliding could be associated with potential GaN/AlGaN optoelectronic device degradation issues.
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Holec, David, i Antonín Dlouhý. "Stability and Motion of Low Angle Dislocation Boundaries in Precipitation Hardened Crystals". Materials Science Forum 482 (kwiecień 2005): 159–62. http://dx.doi.org/10.4028/www.scientific.net/msf.482.159.
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The present study investigates stability and motion of low angle dislocation boundaries in an array of precipitates. The model considers discrete dislocations and precipitates that are treated as impenetrable particles. Peach-Koehler forces, which originate due to the combined effect of dislocation-dislocation interactions and the applied stress, act the individual dislocations on. Both, the dislocation glide and the dislocation climb at elevated temperatures are taken into account. Results of the numerical study suggest that a critical applied shear stress (CASS) always exists which separates stable and unstable low angle boundary configurations. Varying particle size, interparticle spacing and density of dislocations in the boundary cause changes of the CASS that are systematically investigated. It is shown that the CASSs can considerably differ from the standard Orowan stress controlling the equilibrium of an isolated dislocation in a given microstructure. This result underlines the importance of long-range dislocation interactions that influence the high temperature strength of the precipitation-hardened alloys.
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Kim, Hyojung, Alexandra Zimmerman, Irene J. Beyerlein i Abigail Hunter. "Phase field modeling of dislocations and obstacles in InSb". Journal of Applied Physics 132, nr 2 (14.07.2022): 025702. http://dx.doi.org/10.1063/5.0092285.
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We present a phase-field dislocation dynamics (PFDD) model informed by first-principle calculations to elucidate the competitive dislocation nucleation and propagation between the glide and shuffle sets in InSb diamond cubic crystal. The calculations are directly informed with generalized stacking fault energy curves on the (111) slip plane for both the “glide set,” with the smaller interplanar spacing, and the “shuffle set,” with the larger interplanar spacing. The formulation also includes elastic anisotropy and the gradient term associated with the dislocation core. The PFDD calculations show that under no stress the equilibrium structure of screw glide set dislocations dissociates into Shockley partials, while those of the shuffle set dislocations do not dissociate, remaining compact. The calculated dislocation core widths of these InSb dislocations agree well with the measured values for other semiconductor materials, such as Si and GaN. We find that a shuffle set dislocation emits from a dislocation source at an applied stress about three times smaller than that needed to emit leading and trailing partials successively on the glide set plane. Once the partial dislocations in the glide set are emitted, they propagate faster than the shuffle set perfect dislocation at the same stress level.
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Xu, Ruida, Ying Li i Huichen Yu. "Creep Behavior and Deformation Mechanism of a Third-Generation Single Crystal Ni-Based Superalloy at 980 °C". Metals 13, nr 9 (1.09.2023): 1541. http://dx.doi.org/10.3390/met13091541.
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As the primary choice for aero-engine turbine blades, creep resistance is an important mechanical property for the developing third-generation single crystal Ni-based superalloys. The creep behavior of the superalloy in the [001] orientation was studied at 980 °C under a series of stress levels, accompanied with scanning electron microscope (SEM) and transmission electron microscope (TEM) observation to investigate the microstructure and deformation mechanism. The deformation mechanism of the alloy is found to be dislocation gliding, propagating and forming a dislocation network in the γ/γ′ interface. Dislocation networks could hinder the movement of dislocation and decrease the creep rate to a constant during the steady-creep stage. The formation of dislocation networks was analyzed due to the interaction of <110> {111} dislocations. Then dislocations cut into γ′ phases as individual <110> super-dislocations, anti-phase boundary dislocation pairs, and stacking faults. The <110> super-dislocation in the γ′ phase may cross-slip into the {001} plane from the {111} plane to form Kear–Wilsdorf locks, which could inhibit dislocations from gliding or cross-slipping and then enhance the creep resistance.
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Yakimov, Eugene B. "EBIC Investigations of Deformation Induced Defects in Si". Solid State Phenomena 131-133 (październik 2007): 529–34. http://dx.doi.org/10.4028/www.scientific.net/ssp.131-133.529.
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Calculation of relation between the EBIC contrast and the recombination strength for dislocations and quasi-two-dimensional dislocation trails has been carried out taking into account the real values of depletion region width. Using the relations obtained the linear defect density along dislocations and sheet density in dislocation trails are estimated. The results of EBIC investigations of dislocations and dislocation trails in plastically deformed n- and p-Si are analyzed.
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Berezin, P. A., S. V. Bragina i A. L. Petrushin. "Traumatic Hip Dislocation: Lecture". Traumatology and Orthopedics of Russia 27, nr 2 (13.07.2021): 156–69. http://dx.doi.org/10.21823/2311-2905-2021-27-2-156-169.
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Traumatic hip dislocations occupy the fourth place among dislocations of various localizations and, as a rule, are the result of exposure to a high-energy traumatic agent. Such injuries are more often observed in young and middle-aged males. The main cause of hip dislocations is road accidents. The femoral head is more often dislocated posteriorly, but anterior dislocations are not casuistic and account for approximately 10%. Hip dislocations are often combined with acetabular fractures, while their fairly clear clinical picture in the presence of fractures can be leveled. Traumatic hip dislocations require urgent diagnosis and treatment. After the clinical examination of the patient, an x-ray of the pelvis and hip joints are performed. Radiographic diagnosis of hip dislocation remains relevant, but modern imaging methods allows to study the hip joint in more detail and identify concomitant injuries. The main treatment for hip dislocation is closed reduction. Early dislocation reduction and the absence of damage to the structures forming the hip joint are important for the treatment results prognosis. The further patient management tactics after the dislocation reduction is determined by the results of stress tests and the CT data. When confirming the instability and associated injuries of the hip joint anatomical structures, surgical treatment is indicated. Among the complications of hip dislocation: sciatic nerve damage, post-traumatic coxarthrosis, the femoral head avascular necrosis, heterotopic ossification. Current literature data indicates the importance of early diagnosis of dislocation-associated injuries of the hip joint and periarticular tissues. Early and comprehensive repair of all existing injuries is crucial for favorable outcomes. A number of therapeutic and diagnostic methods, primarily arthroscopy, show optimistic results, but need further study.
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Shikata, Shinichi, i Naoya Akashi. "Dislocation Vector Analysis Method of Deep Dislocation Having C-Axis Segment in Diamond". Materials Science Forum 1004 (lipiec 2020): 519–24. http://dx.doi.org/10.4028/www.scientific.net/msf.1004.519.
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X-ray topography is an effective tool to investigate dislocations in semiconductor crystals. Due to low X-ray absorption coefficients of diamond, X-rays can penetrate deep into the crystal. Thus, deep three-dimensional (3D) dislocations are projected on two-dimension (2D) film, which makes dislocation analysis particularly challenging. Dislocation vectors from the films obtained using a set of the same diffraction vectors were identified using topographical and geometrical analyses. The depth and position of the dislocations in a crystal that was projected on a film were determined using geometrical relationship. The proposed analysis method was verified by analyzing several dislocations using four <404> diffraction films. The types of dislocation were identified through Burgers vector analysis.
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Hardy, Alexandre, Vincent Sabatier, Pierre Laboudie, Bradley Schoch, Geoffroy Nourissat, Philippe Valenti, Jean Kany i in. "Outcomes After Latarjet Procedure: Patients With First-Time Versus Recurrent Dislocations". American Journal of Sports Medicine 48, nr 1 (24.10.2019): 21–26. http://dx.doi.org/10.1177/0363546519879929.
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Background: The preoperative number of dislocations has been previously proved to be a major factor influencing the results after Bankart repair with more preoperative dislocations correlated with higher recurrence rates and more reoperations. This could possibly be because of the lower quality of the tissue repaired during the procedure after multiple dislocations. On the other hand, the Latarjet procedure does not “repair” but rather reconstructs and augments the anterior glenoid. Purpose/Hypothesis: The main objective was to report the clinical outcomes of patients undergoing a Latarjet procedure after 1 dislocation versus multiple (≥2) dislocations. The hypothesis was that the preoperative number of dislocations would not influence clinical results. Study Design: Cohort study; Level of evidence, 3. Methods: Patients older than 18 years who had undergone a primary Latarjet procedure for shoulder instability with at least 2 years of follow-up were included. Three different techniques were used: a mini-open technique using 2 screws, an arthroscopic technique using 2 screws, and an arthroscopic technique using 2 cortical buttons. Patients were evaluated and answered a questionnaire to assess the number of episodes of dislocation before surgery, the time between the first dislocation and surgery, recurrence of the dislocation, revision surgery, the Walch-Duplay score, the Simple Shoulder Test score, and the visual analog scale (VAS) score for pain. Results: A total of 308 patients were included for analysis with a mean follow-up of 3.4 ± 0.8 years. Of that, 83 patients were included in the first-time dislocation group and 225 in the recurrent dislocation group. At last follow-up, the rates of recurrence and reoperation were not significantly different between groups: 4.8% in the first-time dislocation group versus 3.65% in the recurrent dislocation group and 6.1% versus 4.0%, respectively. The overall Walch-Duplay scores at last follow-up were also comparable between the 2 groups, 67.3 ± 24.85 and 71.8 ± 25.1, even though the first-time dislocation group showed a lower pain subscore (15.0 ± 8.6 vs 18.0 ± 7.5; P = .003). The VAS for pain was also significantly higher in the first-time dislocation group compared with the recurrent dislocation group (1.8 ± 2.3 vs 1.2 ± 1.7; P = .03). Conclusion: The number of episodes of dislocation before surgery does not affect postoperative instability rates and reoperation rates after the Latarjet procedure. However, patients with first-time dislocations had more postoperative pain compared with patients with recurrent dislocations before surgery.
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Lazar, Markus. "Incompatible strain gradient elasticity of Mindlin type: screw and edge dislocations". Acta Mechanica 232, nr 9 (28.06.2021): 3471–94. http://dx.doi.org/10.1007/s00707-021-02999-2.
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AbstractThe fundamental problem of dislocations in incompatible isotropic strain gradient elasticity theory of Mindlin type, unsolved for more than half a century, is solved in this work. Incompatible strain gradient elasticity of Mindlin type is the generalization of Mindlin’s compatible strain gradient elasticity including plastic fields providing in this way a proper eigenstrain framework for the study of defects like dislocations. Exact analytical solutions for the displacement fields, elastic distortions, Cauchy stresses, plastic distortions and dislocation densities of screw and edge dislocations are derived. For the numerical analysis of the dislocation fields, elastic constants and gradient elastic constants have been used taken from ab initio DFT calculations. The displacement, elastic distortion, plastic distortion and Cauchy stress fields of screw and edge dislocations are non-singular, finite, and smooth. The dislocation fields of a screw dislocation depend on one characteristic length, whereas the dislocation fields of an edge dislocation depend on up to three characteristic lengths. For a screw dislocation, the dislocation fields obtained in incompatible strain gradient elasticity of Mindlin type agree with the corresponding ones in simplified incompatible strain gradient elasticity. In the case of an edge dislocation, the dislocation fields obtained in incompatible strain gradient elasticity of Mindlin type are depicted more realistic than the corresponding ones in simplified incompatible strain gradient elasticity. Among others, the Cauchy stress of an edge dislocation obtained in incompatible isotropic strain gradient elasticity of Mindlin type looks more physical in the dislocation core region than the Cauchy stress obtained in simplified incompatible strain gradient elasticity and is in good agreement with the stress fields of an edge dislocation computed in atomistic simulations. Moreover, it is shown that the shape of the dislocation core of an edge dislocation has a more realistic asymmetric form due to its inherent asymmetry in incompatible isotropic strain gradient elasticity of Mindlin type than the dislocation core possessing a cylindrical symmetry in simplified incompatible strain gradient elasticity. It is revealed that the considered theory with the incorporation of three characteristic lengths offers a more realistic description of an edge dislocation than the simplified incompatible strain gradient elasticity with only one characteristic length.
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Sarafanov, G. F. "INSTABILITY IN A DISLOCATION ENSEMBLE AT PLASTIC DEFORMATION IN METALS". Problems of strenght and plasticity 83, nr 2 (2021): 198–206. http://dx.doi.org/10.32326/1814-9146-2021-83-2-198-206.
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A problem related to the development of instability of a homogeneous state in an ensemble of screw dislocations under plastic deformation of metals is considered . The study of the development of instability and structure formation in the dislocation ensemble is carried out on the basis of the method developed for charged particles in plasma and associated with the correlation interaction of electrons and positively charged ions. Accordingly, the screw dislocation ensemble is represented as a system of dislocations with an opposite Burgers vector, i.e., as a plasma-like medium with opposite dislocation charges. The total dislocation charge of the dislocation ensemble is equal to zero due to the law of conservation of the Burgers vector. In this situation, the elastic field of dislocations is “cut off”. The stress field of a single dislocation is shielded by a uniformly distributed dislocation “background” and is characterized by a certain effective potential. It is found that at long distances it decreases exponentially. Therefore, the value in the argument of the falling potential can be considered as the radius of screening of the elastic field of dislocations. It is shown that the screening radius is equal to the correlation radius, which makes it possible to construct a two-particle correlation function and find the energy of the correlation interaction of dislocations. A system of kinetic equations for a dislocation ensemble is formulated, taking into account the elastic and correlation interaction of dislocations, as well as the processes of their generation and annihilation. The criterion of instability of the homogeneous distribution of dislocations for the formulated system of equations is established. The instability criterion is met under the condition that the dislocation density exceeds a certain critical value that depends on the square of the flow stress and material constants (such as the Burgers vector modulus and shear modulus, as well as indirectly, the packing defect energy). In the framework of linear analysis, it is shown that when one system of sliding screw dislocations is taken into account, a one – dimensional periodic dislocation dissipative structure is formed at the moment of instability occurrence, and when multiple sliding is taken into account, solutions appear in the form of various variants of polyhedral lattices (cellular structures). It is established that the characteristic size of the cellular structure coincides with the experimental dependence both qualitatively and quantitatively ( the cell size is proportional to the square root of the dislocation density, and the proportionality coefficient is about ten). It is shown that the origin of spatially inhomogeneous dislocation structures, based on correlation instability, depends mainly on the features of the elastic interaction of dislocations and is not critical to the choice of the mechanisms of their kinetics (i.e., the mechanisms of generation, annihilation, and runoff of dislocations).
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Fan, Qi, Xiaoyan Han, Xiangjia Zhu, Lei Cai, Xiaodi Qiu, Yi Lu i Jin Yang. "Clinical Characteristics of Intraocular Lens Dislocation in Chinese Han Populations". Journal of Ophthalmology 2020 (27.04.2020): 1–8. http://dx.doi.org/10.1155/2020/8053941.
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Purpose. To investigate the clinical characteristics of patients with intraocular lens (IOL) dislocation after IOL implantation in Chinese Han populations. Methods. The medical records of patients with IOL dislocation were retrospectively reviewed from January 2007 to December 2017, and a total of 312 patients (male: 231, female: 97) (328 eyes) were included in this study. The axial length (AL), IOL power, and the time interval between cataract surgery and IOL dislocation as well as the ocular conditions associated with IOL dislocation were recorded. The IOL dislocation was classified and graded based on its relationship with the capsule and the position of the dislocated IOL. Results. The mean time between original cataract surgery and IOL dislocation was 5.63 ± 5.13 years; IOL dislocation occurred in up to 56.1% (184 eyes) of the eyes within 5 years. Trauma was found in 136 eyes (41.5%); pars plana vitrectomies were performed in 61 eyes (18.6%), and high myopia was detected in 108 eyes (32.9%). A total of 243 eyes (74.1%) had out-of-the-bag IOL dislocations, while 85 eyes (25.9%) had in-the-bag IOL dislocations. There was a statistically significant difference in the constituent ratio of trauma between in-the-bag dislocation and out-of-the-bag dislocation (Pearson’s chi2 = 33.3992, P<0.001); ocular blunt traumas were significantly higher in in-the-bag dislocations, while open-globe injuries were significantly higher in out-of-the-bag dislocations. A statistically significant difference was found for the ratio of patients with AL longer than 30 mm between in-the-bag dislocation and out-of-the-bag dislocation (Pearson’s chi2 = 9.7355, P<0.002). Conclusions. In Chinese Han populations, the most common IOL dislocation is out-of-the-bag dislocation; the most common risk factors were trauma, long axial length, and eyes undergoing pars plana vitrectomy; a minimum follow-up of 5 years is suggested for IOL dislocation-predisposed eyes undergoing cataract surgery.
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Wang, Wen, Dan Wang i Fu Sheng Han. "Mechanical Behavior of Twinning Induced Plasticity Steel Processed by Warm Forging and Annealing". Defect and Diffusion Forum 385 (lipiec 2018): 21–26. http://dx.doi.org/10.4028/www.scientific.net/ddf.385.21.
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The present study shows that warmly forged and low-temperature annealed twinning induced plasticity (TWIP) steel exhibited very high dislocation density and apparent yield-point phenomenon in addition to very high yield strength. The initial density of dislocations significantly affected the evolution of dislocations during the subsequent tensile deformation. Original high dense dislocations prompted the rapid increase of dislocations, and intensified the complexity of dislocation configurations. All these effects made the twinning deformation weakened but the dislocation deformation enhanced, leading to increased strength but decreased plasticity.
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Zhang, Meng Qi, i Shan Wu Yang. "Analysis and Calculation of the Strain Field Disturbance Caused by Dislocation Migration". Applied Mechanics and Materials 481 (grudzień 2013): 212–16. http://dx.doi.org/10.4028/www.scientific.net/amm.481.212.
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In order to elucidate the different characters of elastic waves caused respectively by screw and edge dislocation movement, we calculated the stain field disturbance caused by migration of dislocation by elastic theory. Through the calculation, it was found that the strain field disturbance resulted from screw dislocation migration produces a transverse wave radiation while that resulted from edge dislocation migration produces transverse wave and longitudinal wave simultaneously. The result reveals the different energy radiation characters of screw dislocations and edge dislocations and explains the reason that edge dislocation moves faster than screw dislocation in general experiment. It also provides a theoretical basis for determining microcosmic mechanism of plastic deformation of metals by monitoring the changes of elastic waves.
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Suzuki, Ryo, Marina Abe, Kenichi Kojima i Masaru Tachibana. "Identification of grown-in dislocations in protein crystals by digital X-ray topography". Journal of Applied Crystallography 54, nr 1 (1.02.2021): 163–68. http://dx.doi.org/10.1107/s1600576720015356.
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X-ray topography is a useful and nondestructive method for direct observation of crystal defects in nearly perfect single crystals. The grown-in dislocations from the cross-linked seed crystal in tetragonal hen egg-white lysozyme crystals were successfully characterized by digital X-ray topography. Digital X-ray topographs with various reflections were easily obtained by reconstruction of sequential rocking-curve images. The Burgers vector of the dislocation is different from those reported previously. Interestingly, one of the dislocations had a bent shape. The preferred direction of the dislocation line was analysed by the estimated dislocation energy based on the dislocation theory. The dislocation energy can be estimated by the dislocation theory even in protein crystals composed of macromolecules.
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Bertoni, Mariana I., Clémence Colin i Tonio Buonassisi. "Dislocation Engineering in Multicrystalline Silicon". Solid State Phenomena 156-158 (październik 2009): 11–18. http://dx.doi.org/10.4028/www.scientific.net/ssp.156-158.11.
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Dislocations are known to be among the most deleterious performance-limiting defects in multicrystalline silicon (mc-Si) based solar cells. In this work, we propose a method to remove dislocations based on a high temperature treatment. Dislocation density reductions of >95% are achieved in commercial ribbon silicon with a double-sided silicon nitride coating via high temperature annealing under ambient conditions. The dislocation density reduction follows temperature-dependent and time-dependent models developed by Kuhlmann et al. for the annealing of dislocations in face-centered cubic metals. It is believed that higher annealing temperatures (>1170°C) allow dislocation movement unconstrained by crystallographic glide planes, leading to pairwise dislocation annihilation within minutes.
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Kivambe, Maulid, Gaute Stokkan, Torunn Ervik, Sergio Castellanos, Jasmin Hofstetter i Tonio Buonassisi. "The Impact of Dislocation Structure on Impurity Decoration of Dislocation Clusters in Multicrystalline Silicon". Solid State Phenomena 205-206 (październik 2013): 71–76. http://dx.doi.org/10.4028/www.scientific.net/ssp.205-206.71.
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Light microscopy, electron backscatter diffraction and transmission electron microscopy is employed to investigate dislocation structure and impurity precipitation in commonly occurring dislocation clusters as observed on defect-etched directionally solidified multicrystalline silicon wafers. The investigation shows that poligonised structures consist of parallel mostly similar, straight, well-ordered dislocations, with minimal contact-interaction and no evidence of precipitate decoration. On the other hand, disordered structures consist of various dislocation types, with interactions being common. Decoration of dislocations by second phase particles is observed in some cases. Enhanced recombination activity of dislocations may therefore be a result of dislocation interaction forming tangles, microscopic kinks and jogs, which can serve as heterogeneous nucleation sites that enhance metallic decoration.
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Myasoedov A.V., Pavlov I. S., Pechnikov A. I., Stepanov S.I. i Nikolaev V. I. "Defect structure of α-Ga-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=- film grown on a m-face sapphire substrate, according to transmission electron microscopy investigation". Technical Physics Letters 49, nr 1 (2023): 67. http://dx.doi.org/10.21883/tpl.2023.01.55353.19365.
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The results of a study by transmission electron microscopy of the structural state of α-Ga2O3 film with a thickness of about 1 micron, grown on the prismatic m-face sapphire by the method of chloride vapor phase epitaxy, are presented. The influence of the substrate orientation on the formation of the dislocation structure is discussed. Threading dislocations, including those with the Burgers vector 1/3< 1120 >, and dislocation half-loops are revealed. The inclined propagation of dislocations and the formation of dislocation half-loops result in the reduction of the threading dislocation density near the surface.. Keywords: dislocations, gallium oxide, TEM.
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Botros, K. Z., i S. S. Sheinin. "A method for avoiding errors in measurements of dislocation density in specimens with a high dislocation density". Proceedings, annual meeting, Electron Microscopy Society of America 50, nr 2 (sierpień 1992): 1458–59. http://dx.doi.org/10.1017/s0424820100131929.
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The measurement of dislocation density from electron microscope images of dislocations is an important tool in the hands of the materials scientist. Weak beam images are often chosen for this purpose. In cases where the dislocation density is high, there is a strong possibility that the imaging electrons propagating through the thin foil would encounter several dislocations before emerging from the bottom surface. A question which arises is what effect this may have on image contrast and whether this affects measurements of dislocation density.The authors of this paper have addressed this question by examining the contrast obtained in the case where two dislocations overlap so that the imaging electrons encounter two dislocations before reaching the bottom surface of the specimen. The details of these calculations are presented elsewhere and will not be repeated here. For purposes of this paper, the results can be summarized by stating that, for certain diffraction conditions and dislocation separations, the contrast exhibited by the overlapping dislocation configuration is very weak with the result that the dislocations would not be observed.
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Yuan, Shao Qiang, i Xiao Juan Zhang. "Evolution in Dislocation Configuration of Deformed Fe-40Ni-Ti Alloy during Isothermal Relaxation". Key Engineering Materials 609-610 (kwiecień 2014): 515–20. http://dx.doi.org/10.4028/www.scientific.net/kem.609-610.515.
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The thermo-simulation test and transmission electron microscopy (TEM) were applied to investigate the evolution of dislocation configuration and strain induced precipitation behavior during relaxation at 850°C in a deformed Fe-40Ni-Ti alloy. The stress relaxation curve can be divided into three stages, namely, the process of incubation, nucleation and growth, and the coarsening of strain-induced precipitates. The highly dense and twisted dislocations formed during the deformation develop into dislocation cells and finally, the sub-grains can be observed when relaxing to 1000s. The strain induced precipitates occur both onto the dispersed dislocations and dislocation cells. The precipitates pin the dislocations which results in retarding the progress of dislocation configuration evolution. As precipitates start to coarsen, the pinning effect weakens and the dislocations get rid of the pinning though bypassing mechanism. Adopting the same simulation test to bainitic steel, the optimum refinement could be obtained at 60-200s during relaxation processing, corresponding to the perfect dislocation cells formation of Fe-40Ni-Ti alloy.
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Qi, Yajuan, Hailong He i Meng Xiao. "Manipulation of acoustic vortex with topological dislocation states". Applied Physics Letters 120, nr 21 (23.05.2022): 212202. http://dx.doi.org/10.1063/5.0095543.
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Higher-order topological insulators as an exotic type of topological phases harboring fascinating topological corner or hinge states have attracted extensive attention recently. Dislocations are crystallinity-breaking defects in lattices that cannot be removed by local deformations due to nontrivial real-space topology. It is recently realized that dislocations can be used as a probe for higher-order topology. In this work, we propose a scheme to obtain acoustic dislocation states by introducing screw dislocations into higher-order topological insulators in a Kagome lattice. The topological dislocation states carry nonzero orbital angular momentum, which are locked to their propagation direction. We show that the screw dislocation states exist for both the tight binding model and the waveguide model as long as the system symmetry is preserved. By delicately designing the dislocation core, the dislocation states with selective angular momentum can be shifted into the bulk bandgap. Based on this in-gap dislocation states, filtering of acoustic vortex with a selective angular momentum is well achieved.
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Mughrabi, Haël. "On the dislocation mechanisms of dynamic strain ageing in fatigued plain carbon steels". International Journal of Materials Research 94, nr 5 (1.05.2003): 471–77. http://dx.doi.org/10.1515/ijmr-2003-0085.
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Abstract The fatigue life of plain ferritic carbon steels fatigued in stress-controlled (plastic-strain-controlled) tests exhibits a maximum (minimum) at a temperature of approx. 300 °C as a result of dynamic strain ageing (DSA). In the regime of DSA, an enhanced cyclic hardening related to an increased dislocation density is observed, and the dislocation arrangement changes from a dislocation cell structure (at intermediate stress amplitudes) at room temperature to a dense edge di-/multipolar bundle/wall/vein structure in the temperature range of DSA and back to a dislocation cell/ subgrain structure at higher temperatures. Related effects occur also in α-iron containing some carbon when fatigued at room temperature at a very low strain rate. This behaviour is considered to be typical of body-centred cubic materials. In the present study, the dislocation mechanisms responsible for this behaviour are discussed in detail, and a dislocation glide model is developed which can explain both the enhanced dislocation density and the change of the dislocation arrangement in the regime of DSA. The model is based on the different mobilities of mobile edge and less mobile screw dislocations in body-centred cubic metals and on the strong tendency towards multiple slip leading to a dislocation cell structure at lower temperatures. In the regime of DSA, it is proposed that the edge dislocations are hindered more strongly in their glide motion by the solute carbon atoms than the screw dislocations so that screws and edges are then more or less equally mobile. Taking into account that screw dislocations of opposite sign annihilate mutually by cross slip, this explains the observed dislocation arrangement of dense edge di-/multipolar bundles/ walls/veins of high dislocation density which, in turn, leads to an enhanced cyclic hardening rate. The dislocation sub-grain structure observed at higher temperatures reflects the increasing tendency for the transformation from dislocation cell to subgrain structures, as the temperature is increased.
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Kovacevic, Maksim, Marijana Kovacevic, Sanja Maric, Nenad Lalovic, Milivoje Dostic i Vjeran Saratlic. "Our results in the treatment of tarsal dislocations". Srpski arhiv za celokupno lekarstvo 148, nr 9-10 (2020): 554–59. http://dx.doi.org/10.2298/sarh191105034k.
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Introduction/Objective. Tarsal dislocations are rare injuries. Usually, they are caused by high-energy trauma. Depending on the type of dislocation, surgical treatment or closed reduction is used. In this study, 13 patients are presented with the aim to analyze the type of feet dislocations, their treatment, and outcome. Methods. Tarsal dislocation cases treated in the University Hospital in Foca were analyzed during the period 2009?2016. All the cases were clinically and radiographically examined and monitored on control examinations at least three years. The mobility of joints was measured and pain existence was estimated by visual analogue scale. Results. All 13 patients with tarsal dislocation were male. Four patients were treated surgically (two patients with tarsometatarsal and one with cuboid and navicular dislocation) and other patients had non-surgical treatment. In 10 patients, an excellent functional result has been achieved and in two patients with tarsometatarsal dislocation a good functional result. In one patient with cuboidal dislocation satisfactory functional result has been achieved. Conclusion. Out of the 13 reviewed patients with tarsal dislocations, functional results were rated as excellent in 10 dislocations, good in two, and satisfactory in one. Diagnosis and treatment of foot dislocations are demanding, but a favorable functional outcome can be expected with an adequate treatment of these injuries.
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Christensen, Tyson C., Thomas L. Sanders, Ayoosh Pareek, Rohith Mohan, Diane L. Dahm i Aaron J. Krych. "Risk Factors and Time to Recurrent Ipsilateral and Contralateral Patellar Dislocations". American Journal of Sports Medicine 45, nr 9 (2.05.2017): 2105–10. http://dx.doi.org/10.1177/0363546517704178.
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Background: Previous studies have reported variable rates of recurrent lateral patellar instability mainly because of limited cohort sizes. In addition, there is currently a lack of information on contralateral patellar instability. Purpose: To evaluate the rate of recurrent ipsilateral patellar dislocations and contralateral patellar dislocations after a first-time lateral patellar dislocation. Additionally, risk factors associated with recurrent dislocations (ipsilateral or contralateral) and time to recurrence were investigated. Study Design: Cohort study; Level of evidence, 3. Methods: This population-based study included 584 patients with a first-time lateral patellar dislocation occurring between 1990 and 2010. A retrospective review was conducted to gather information about the injury, subsequent dislocations (ipsilateral or contralateral), and structural characteristics including trochlear dysplasia, patella alta, and tibial tubercle to trochlear groove (TT-TG) distance. Risk factors were assessed to delineate associations with subsequent dislocations and time to recurrence. Results: At a mean follow-up of 12.4 years, 173 patients had ipsilateral recurrence, and 25 patients had a subsequent contralateral dislocation. At 20 years, the cumulative incidence of ipsilateral recurrence was 36.0%, while the cumulative incidence of contralateral dislocations was 5.4%. Trochlear dysplasia (odds ratio [OR], 18.1), patella alta (OR, 10.4), age <18 years at the time of the first dislocation (OR, 2.4), elevated TT-TG distance (OR, 2.1), and female sex (OR, 1.5) were associated with recurrent ipsilateral dislocations. Time to recurrence was significantly decreased in patients with trochlear dysplasia (23.0 months earlier time to recurrence; P < .001), elevated TT-TG distance (18.5 months; P < .001), patella alta (16.4 months; P = .001), and age <18 years at the time of the first dislocation (15.4 months; P < .001). Risk factors for subsequent contralateral dislocations included patella alta and trochlear dysplasia. Conclusion: At 20 years after a first-time lateral patellar dislocation, the cumulative incidence of recurrent ipsilateral patellar dislocations was 36.0%, compared with 5.4% for contralateral dislocations. Trochlear dysplasia, elevated TT-TG distance, patella alta, age <18 years at the time of the first dislocation, and female sex were associated with ipsilateral recurrence. Trochlear dysplasia, elevated TT-TG distance, patella alta, and age <18 years at the time of the first dislocation were predictive of a statistically significant decrease in time to recurrence.
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Marshall, A. F., D. B. Aubertine, W. D. Nix i P. C. McIntyre. "Misfit dislocation dissociation and Lomer formation in low mismatch SiGe/Si heterostructures". Journal of Materials Research 20, nr 2 (luty 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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Cai, Minglei, Tedi Kujofsa, Xinkang Chen, Md Tanvirul Islam i John E. Ayers. "Interaction Length for Dislocations in Compositionally-Graded Heterostructures". International Journal of High Speed Electronics and Systems 27, nr 03n04 (wrzesień 2018): 1840022. http://dx.doi.org/10.1142/s0129156418400220.
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Several simple models have been developed for the threading dislocation behavior in heteroepitaxial semiconductor materials. Tachikawa and Yamaguchi [Appl. Phys. Lett., 56, 484 (1990)] and Romanov et al. [Appl. Phys. Lett., 69, 3342 (1996)] described models for the annihilation and coalescence of threading dislocations in uniform-composition layers, and Kujofsa et al. [J. Electron. Mater., 41, 2993 (2013)] extended the annihilation and coalescence model to compositionally-graded and multilayered structures by including the misfit dislocation-threading dislocation interactions. However, an important limitation of these previous models is that they involve empirical parameters. The goal of this work is to develop a predictive model for annihilation and coalescence of threading dislocations which is based on the dislocation interaction length Lint. In the first case if only in-plane glide is considered the interaction length is equal to the length of misfit dislocation segments while in the second case glide and climb are considered and the interaction length is a function of the distance from the interface, the length of misfit dislocations, and the density of the misfit dislocations. In either case the interaction length may be calculated using a model for dislocation flow. Knowledge of the dislocation interaction length allows predictive calculations of the threading dislocation densities in metamorphic device structures and is of great practical importance. Here we demonstrate the latter model based on glide and climb. Future work should compare the two models to determine which is more relevant to typical device heterostructures.
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Trushin, Maxim, O. F. Vyvenko, Teimuraz Mchedlidze, Oleg Kononchuk i Martin Kittler. "Electronic States of Oxygen-Free Dislocation Networks Produced by Direct Bonding of Silicon Wafers". Solid State Phenomena 156-158 (październik 2009): 283–88. http://dx.doi.org/10.4028/www.scientific.net/ssp.156-158.283.
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The results of experimental investigations of the dislocation-related DLTS-peaks originated from the dislocation networks (DN) are presented. Samples with DNs were produced by direct bonding of p-type silicon wafers and no enhancement of oxygen concentration was detected near the DN plane. Origins of the DLTS peaks were proposed and a correlation with the dislocation-related photoluminescence data was established based on known dislocation structure of the samples. Two types of shallow DLTS peaks exhibited Pool-Frenkel effect, which could be linked to the dislocation deformation potential. One of the shallow DLTS peaks was related to straight parts of screw dislocations and another - to the intersections of the dislocations.
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Lyu, Dandan, i Shaofan Li. "Recent developments in dislocation pattern dynamics: Current opinions and perspectives". Journal of Micromechanics and Molecular Physics 03, nr 03n04 (wrzesień 2018): 1840002. http://dx.doi.org/10.1142/s2424913018400027.
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The development of crystal plasticity theory based on dislocation patterns dynamics has been an outstanding problem in materials science and condensed matter of physics. Dislocation is the origin of crystal plasticity, and it is both the individual dislocation behavior as well as the aggregated dislocations behaviors that govern the plastic flow. The interactions among dislocations are complex statistical and stochastic events, in which the spontaneous emergence of organized dislocation patterns formations is the most critical and intriguing events. Dislocation patterns consist of quasi-periodic dislocation-rich and dislocation poor regions, e.g. cells, veins, labyrinths, ladders structures, etc. during cyclic loadings. Dislocation patterns have prominent and decisive effects on work hardening and plastic strain localization, and thus these dislocation micro-structures are responsible to material properties at macroscale. This paper reviews the recent developments of experimental observation, physical modeling, and computer modeling on dislocation microstructure. In particular, we focus on examining the mechanism towards plastic deformation. The progress and limitations of different experiments and modeling approaches are discussed and compared. Finally, we share our perspectives on current issues and future challenges in both experimental, analytical modeling, and computational aspects of dislocation pattern dynamics.
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Starenchenko, Vladimir, Dmitrii Cherepanov, Raisa Kurinnaya, Marina Zgolich i Olga Selivanikova. "The Influence of Dislocation Junctions on Accumulation of Dislocations in Strained FCC – Single Crystals". Advanced Materials Research 1013 (październik 2014): 272–79. http://dx.doi.org/10.4028/www.scientific.net/amr.1013.272.
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Dislocation junctions, formed as a result of dislocation reactions, affect the plastic strain process, at least, for two reasons. First of all, junctions serve as barriers to shear-forming dislocations and restrict their path, therefore, the size of the shear zone. Sizes of the shear zone are determined by the density of reacting dislocations in non-coplanar slip systems, forming long enough barriers in the form of dislocation junctions. Secondly, non-breaking dislocation junctions are accumulated inside the shear zone, which leads to an increase in the intensity of the dislocation density accumulation.The present work is devoted to the study of the influence of dislocation junctions on accumulation of the density of dislocation debris (debris junctions) due to formation of stable junctions. For this purpose, the probability density function of lengths in non-breaking junctions is calculated. The model of dislocation interactions, built by the authors of the paper for FCC single crystals, is used.
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Katagiri, Kento, Tatiana Pikuz, Lichao Fang, Bruno Albertazzi, Shunsuke Egashira, Yuichi Inubushi, Genki Kamimura i in. "Transonic dislocation propagation in diamond". Science 382, nr 6666 (6.10.2023): 69–72. http://dx.doi.org/10.1126/science.adh5563.
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The motion of line defects (dislocations) has been studied for more than 60 years, but the maximum speed at which they can move is unresolved. Recent models and atomistic simulations predict the existence of a limiting velocity of dislocation motion between the transonic and subsonic ranges at which the self-energy of dislocation diverges, though they do not deny the possibility of the transonic dislocations. We used femtosecond x-ray radiography to track ultrafast dislocation motion in shock-compressed single-crystal diamond. By visualizing stacking faults extending faster than the slowest sound wave speed of diamond, we show the evidence of partial dislocations at their leading edge moving transonically. Understanding the upper limit of dislocation mobility in crystals is essential to accurately model, predict, and control the mechanical properties of materials under extreme conditions.
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Misra, Devi Shanker. "Studies of Dislocations in Type Ib, Type IIa HPHT and CVD Single Crystal Diamonds". Crystals 13, nr 4 (11.04.2023): 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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Hiratani, Masato, i Hussein M. Zbib. "Stochastic Dislocation Dynamics for Dislocation-Defects Interaction: A Multiscale Modeling Approach". Journal of Engineering Materials and Technology 124, nr 3 (10.06.2002): 335–41. http://dx.doi.org/10.1115/1.1479693.
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A stochastic dislocation dynamics (SDD) model is developed to investigate dislocation glide through dispersed obstacles. The model accounts for: 1) the dynamics of the flight process between successive meta-stable dislocations under various drag mechanism using discrete dislocation dynamics, and 2) thermal activation processes for meta-stable pinned dislocations using a stochastic force. The integration of the two processes allows one to examine the transient regime of dislocation motion between obstacle-controlled motion and drag-controlled motion. Result pertaining to the stress-strain rate behavior in copper are obtained. The stress and temperature dependence of the average dislocation velocity show obstacle-controlled region below the critical resolved shear stress (CRSS) and drag controlled region above the CRSS, which is in good qualitative agreement with experimental data. In the transient region right below the CRSS, negative temperature sensitivity is observed due to the competition between the drag effects in dislocation flight process and thermal activation process.
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liu, F. X., A. C. F. Cocks i E. Tarleton. "Dislocation dynamics modelling of the creep behaviour of particle-strengthened materials". Proceedings of the Royal Society A: Mathematical, Physical and Engineering Sciences 477, nr 2250 (czerwiec 2021): 20210083. http://dx.doi.org/10.1098/rspa.2021.0083.
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Plastic deformation in crystalline materials occurs through dislocation slip and strengthening is achieved with obstacles that hinder the motion of dislocations. At relatively low temperatures, dislocations bypass the particles by Orowan looping, particle shearing, cross-slip or a combination of these mechanisms. At elevated temperatures, atomic diffusivity becomes appreciable, so that dislocations can bypass the particles by climb processes. Climb plays a crucial role in the long-term durability or creep resistance of many structural materials, particularly under extreme conditions of load, temperature and radiation. Here we systematically examine dislocation-particle interaction mechanisms. The analysis is based on three-dimensional discrete dislocation dynamics simulations incorporating impenetrable particles, elastic interactions, dislocation self-climb, cross-slip and glide. The core diffusion dominated dislocation self-climb process is modelled based on a variational principle for the evolution of microstructures, and is coupled with dislocation glide and cross-slip by an adaptive time-stepping scheme to bridge the time scale separation. The stress field caused by particles is implemented based on the particle–matrix mismatch. This model is helpful for understanding the fundamental particle bypass mechanisms and clarifying the effects of dislocation glide, climb and cross-slip on creep deformation.
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Luo, Shichao, i Yinan Cui. "Elastodynamics Field of Non-Uniformly Moving Dislocation: From 3D to 2D". Crystals 12, nr 3 (8.03.2022): 363. http://dx.doi.org/10.3390/cryst12030363.
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Molecular dynamics (MD) and experiments indicate that the high-speed dislocations dominate the plasticity properties of crystal materials under high strain rate. New physical features arise accompanied with the increase in dislocation speed, such as the “Lorentz contraction” effect of moving screw dislocation, anomalous nucleation, and annihilation in dislocation interaction. The static description of the dislocation is no longer applicable. The elastodynamics fields of non-uniformly moving dislocation are significantly temporal and spatially coupled. The corresponding mathematical formulas of the stress fields of three-dimensional (3D) and two-dimensional (2D) dislocations look quite different. To clarify these differences, we disclose the physical origin of their connections, which is inherently associated with different temporal and spatial decoupling strategies through the 2D and 3D elastodynamics Green tensor. In this work, the fundamental relationship between 2D and 3D dislocation elastodynamics is established, which has enlightening significance for establishing general high-speed dislocation theory, developing a numerical calculation method based on dislocation elastodynamics, and revealing more influences of dislocation on the macroscopic properties of materials.
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Arnaya, Agung K., Made B. Karna, Anak A. G. Y. Asmara i Putu F. Meregawa. "Irreducible second and third metatarsophalangeal dislocation: a rare case report". International Journal of Research in Medical Sciences 9, nr 2 (29.01.2021): 587. http://dx.doi.org/10.18203/2320-6012.ijrms20210448.
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Metatarsophalangeal (MTP) articulations are complex structures that are prone to sprains, subluxations, and dislocations. MTP dislocations are an uncommon but well documented and problematic orthopaedic injury. Once the diagnosis is certain, the dislocation should be reduced as soon as possible. Immediate reduction of the dislocation can limit numerous complications. A 24-year-old male patients came to emergency department of Sanglah Hospital with 2nd and 3rd MTP joint dislocation. Patient treated with open reduction and immobilization with pinning for 2nd and 3rd metatarsal. After several attempt of closed reduction, the dislocation can be reduce with open reduction and immobilization with k wire, after 4 weeks k wire was removed without any complication and patient can walk normally. Irreducible metatarsophalangeal dislocation of the lesser toes is unusual with third toe was the most commonly affected, followed by the second, fourth, and fifth toes. Radiographs are very useful for diagnose. Multiple procedures have been created to attempt to reduce and stabilize the MP joint. According to other studies, Kirschner wires were also only used in unstable dislocations. In this case, dorsal surgical approach is the most commonly chosen method to reduce the irreducible metatarsophalangeal joint dislocations of the lesser toes. When irreducible dislocation found and closed reduction is initially unsuccessful, we recommend a dorsal surgical approach to open reduction and using Kirschner wires for unstable dislocations.