Types Of Dislocations Research Articles

Exploring the impact of pre-existing helium bubbles on nanoindentation in tungsten through molecular dynamics simulation

Gaining insight into the underlying mechanisms driving nanoindentation-induced behavior in tungsten is essential for comprehending its mechanical properties. Although the plasticity of conventional pure tungsten under nanocontact conditions is well understood, these theoretical constructs may become inadequate when applied to irradiated tungsten due to the interplay between helium bubbles and dislocations. Here, we employed an integrated approach, combining crystal defect theories, molecular dynamics simulations, and machine learning, to explore the initiation and progression of dislocations in tungsten containing helium bubbles during nanoindentation, focusing on elucidating the impact of helium bubbles. In contrast to the typical dislocation nucleation in pure tungsten, the presence of helium bubbles mitigates local shear strain, thereby hindering dislocation nucleation and propagation, leading to a reduction of indentation force. Additionally, we conducted a comparative analysis between samples with and without helium bubbles, examining factors such as atomic displacement, strain localization parameters, dislocation line length, and stress component distribution. More importantly, a significant outcome of our study is the establishment of a relationship between the consistent alteration in the shape of helium bubbles and their size during micro-scale nanoindentation, achieved through machine learning techniques. Our findings reveal that the area occupied by helium bubbles post-nanoindentation is inversely correlated with indentation depth and directly linked to helium bubble size. These discoveries represent a notable advancement in understanding the effects of irradiation to a certain degree.

Effects of volumetric energy density on melting modes, printability, microstructures, and mechanical properties of laser powder bed fusion (L-PBF) printed pure nickel

Volumetric energy density (VED) is a fundamental criterion for the laser powder bed fusion (L-PBF) process, influencing various forming characteristics. This study employed L-PBF to print pure nickel (Ni) using different VEDs across various melting modes. The thermodynamics in the different melt pools, obtained microstructural features, and tensile properties were characterized and investigated. The results reveal a higher likelihood of keyhole mode melt pool formation than the conduction mode due to the peak temperature exceeding 3005 K. The larger size and slower cooling rate of the keyhole mode melt pool facilitate the formation of cellular subgrains in the central zone and the overall grain coarsening. Compared to the conduction mode, the microstructure in the keyhole mode exhibits a higher dislocation density and a distinct distribution pattern for each type of dislocation. Unlike the L-PBF of commercial Ni alloys, where alloy element distribution significantly impacts tensile performance, the tensile performance of L-PBF Ni is governed by the interaction between grain morphology, dislocation density and distribution.

Interplay between dislocation type and local structure in dislocation-twin boundary reactions in Cu

Interplay between dislocation type and local structure in dislocation-twin boundary reactions in Cu

Analysis of Fault Influence on Geostress Perturbation Based on Fault Model Test

The distribution of the geostress field in reservoirs holds significant implications for the precise exploration and efficient development and utilization of oil and gas resources, especially in deep strata regions where faults are prevalent. Geological structural movements in these deep strata regions exacerbate the complexity of geostress field distributions. To elucidate the perturbation of the geostress field in deep reservoirs caused by faults, this study initially conducted a series of physical model tests on single fault dislocation, employing digital image correlation techniques to capture the displacement fields of various types of fault dislocations. Subsequently, a numerical model of the fault interface element was established, and fault element parameters were determined through sensitivity analysis and trial calculation. This study further analyzed the perturbation of the geostress field using this numerical model. Finally, a multi-fault numerical simulation model was constructed to clarify the perturbations in the regional geostress field under the influence of multiple faults. The results indicate that the geostress perturbation range under the action of multiple faults spans from 183.06 to 310.06 m.

Going Solo: Techniques for Emergency Fracture Management Without Assistance.

Orthopaedic injuries represent some of the most frequent conditions treated in emergency centers worldwide. Proper reduction techniques and evaluation of radiographic parameters are paramount in treating patients effectively. Orthopaedic providers at large tertiary centers may have several assistants available but are also burdened by notable patient loads and volumes. Frequently, fracture care may necessitate procedures performed by providers without the availability of skilled assistance, both in large tertiary academic centers and small independent emergency rooms with limited resources. As providers at a busy level 1 tertiary trauma center with only one primary orthopaedic resident responsible for the performance of most fracture reductions, we present both novel techniques and refined published approaches that allow the safe, efficient, and reliable reduction and stabilization of several different types of fracture dislocations with limited or no assistance, and only commonly found supplies.

Hydrogen isotope population near dislocations in zirconium from molecular dynamics

Performance of zirconium tritides used for hydrogen isotope storage is significantly changed under reactor environments. This can be attributed to the formation of various radiation-induced dislocations. To help gain insight, molecular dynamics simulations have been employed to investigate hydrogen isotope population in zirconium containing different types of edge dislocations. Our studies reveal that hydrogen isotope concentration is highest near the tensile side of dislocation cores and varies based on dislocation type. This increase in hydrogen isotope concentration can be explained by the Boltzmann equation based on calculations using swelling volume and pressure field, with significantly reduced computational cost. Strikingly, because hydrogen isotope in the compressive regions of dislocations is depleted, the overall hydrogen isotope content is found to be unchanged by dislocation formation. These results counter the previous view that the dislocation trapping effect increases hydrogen isotope solubility and provide an understanding of changes in hydrogen isotope pressure under reactor conditions. By elucidating the impact of dislocations on hydrogen isotope storage performance, this research offers insights for optimizing zirconium tritides in nuclear applications. and contributes to the advancement of hydrogen isotope storage materials.

Anterior shoulder dislocation: A bibliometric analysis in the past two decades (2003–2022)

BackgroundAnterior shoulder dislocation is the most common type of shoulder dislocation and is easy to develop into recurrent type, causing economic burden to society. This study uses the bibliometric method to analyze the global research status, hotspots and trends of anterior shoulder dislocation, aiming to promote the exploration of anterior shoulder dislocation. MethodsThe literature on anterior shoulder dislocation in the past two decades were retrieved and downloaded from the Web of Science Core Collection (WOSCC) database. CiteSpace, VOSviewer and bibliometrix package of R software were used to conduct scientific bibliometric analysis of the literature. Finally, some statistical graphics were performed in Graphpad Prism. ResultsA total of 3914 publications related to anterior shoulder dislocation from 2003 to 2022 were retrieved and screened from the WOSCC database. The ranking of the analysis results showed that Provencher MT was the author with the highest frequency of occurrence. Rush University was the most notable contributor. The American Journal of Sports Medicine was the most comprehensive journal. The United States was the most prominent country. Keywords related to surgical treatment were more significant than others. ConclusionIn the past two decades, the research output on anterior shoulder dislocation have been increasing year by year. The focus has gradually shifted to surgical treatment. Surgical treatment may continue to be the research hotspots in this field in the future.

Superior strength and wear resistance of mechanically deformed High-Mn TWIP steel

In the present study, the mechanical and wear behaviour of the surface-mechanically treated high-manganese (high-Mn) twinning-induced plasticity (TWIP) steel were investigated. The TWIP alloy was first designed and fabricated via surface-mechanical attrition treatment (SMAT) system and the mechanical properties including strength, wear behaviour as well as the microstructural evolution were thereafter determined. Transmission electron microscopy (TEM) characterization revealed a typical dislocation as a result of the surface treatment as well as the formation of twin layers with a reduced stacking fault energy (SFE). Due to the ultra-fine grain refinement caused by plastic deformation during surface treatment, a microhardness value of 489 HV can be obtained after treatment. Likewise, the yield strength of the high-Mn TWIP steel could be enhanced from 360 MPa to 813 MPa and a reduction in elongation to failure of about 20 % can be achieved. The wear test showed that the treated TWIP steel possessed a reduced friction coefficient and improved wear resistance at different testing loads, attributed to the nanoscale refinement of grains induced during treatment. The strength, hardness, and wear resistance of the fabricated TWIP alloy improves significantly, thanks to surface treatment by SMAT.

Bilateral Asymmetrical Hip Dislocations after Falling from Height: A Case Report and Literature Review

Background: Hip dislocations, constituting 2-5 percent of all joint dislocations, predominantly present as posterior dislocations. Bilateral hip dislocations are rare, accounting for 1.25% of cases. Associated fractures often involve the proximal femur and acetabulum. Case Report: A 60-year-old man with no prior hip trauma history sustained bilateral hip dislocations after a 6-meter fall. Initial assessments and a hip computed tomography (CT) scan confirmed posterior dislocation of the right hip and anterior dislocation of the left hip. The patient underwent a successful closed pelvic reduction operation four hours post-injury, as confirmed by a post-reduction CT scan. Conclusion: The study, encompassing 11 relevant studies and 208 patients, predominantly men (81%), revealed that asymmetrical bilateral hip dislocations were exceptionally rare (0.01-0.02 percent). Contrary to expectations, this study challenges the presumed stronger association of traffic accidents with bilateral dislocations, presenting a statistically significant association between the type of dislocation and trauma mechanism. Associated fractures, such as acetabulum fractures in unilateral cases and posterior edge fractures in bilateral cases, varied. Avascular necrosis (AVN), a common complication, was not observed in the current case, where reduction occurred within the critical 6-hour timeframe. This report contributes valuable insights into the characteristics and associations of asymmetric bilateral hip dislocations, emphasizing the importance of prompt intervention to mitigate complications. Further research is needed to validate these findings and explore underlying patterns in this rare clinical scenario.

More severe surface relief but stronger fatigue resistance at small scales: Vacancy-assisted fatigue damage mechanism

Surface relief in forms of extrusions and intrusions as the substantial feature of early fatigue damage is one of the most important phenomena studied in metal fatigue. The most common surface relief models in bulk metals are agreed to be correlated with the formation of typical dislocation patterns as persistent slip bands (PSBs), while little is known about the fundamental mechanisms at submicron and even nanometer scales where dislocation pattern formation is fully inhibited. Here, as exampled with thin Au films, the underlying fatigue damage mechanism at small scales is investigated through the quantitative characterization of fatigue damages. Continuous generation and migration of vacancies is found to be crucial for the shape of extrusion/intrusions and kinetics of their growth at submicron and even nanometer scales. Due to the degraded dislocation interaction and intensified vacancy diffusion, the delayed vacancy accumulation in the small-scale metal interior suppresses the extrusion and interface void formation in thinner films, which finally leads to the superior ability to support tremendous surface relief and strong fatigue resistance. The finding of the vacancy-dominated fatigue mechanism at small scales extends our understanding of the metal fatigue mechanisms down to the submicron and even nanometer scales and suggests a novel interface engineering strategy by vacancy behavior modulation for fatigue-tolerance material design.

The ISAKOS subclassification of Rockwood type III AC joint dislocations in a stable type A and an unstable type B is not clinically relevant.

The treatment of Rockwood type III AC joint dislocations has been debated for decades. In 2014, theInternational Society of Arthroscopy, Knee Surgery and Orthopaedic Sports Medicine (ISAKOS) Upper Extremity Committee suggested a subclassification of the injury into type A, considered stable and best treated nonsurgically, and type B, considered unstable and best treated surgically. Type B is defined by the presence of scapular dyskinesis and overriding of the clavicle to the acromion on a modified lateral radiograph. The objective of the study was to investigate if this subclassification is clinically relevant. This was a prospective cohort study. Inclusion criteria were patients aged 18-60 years with acute AC joint dislocation and a baseline Zanca radiograph with an increase in the CC distance of >25% compared to the uninjured side. All patients were treated nonsurgically with 3 months of home-based training and with the option of delayed surgical intervention. Patients were assessed at baseline and at follow-ups 6 weeks, 3 months, 6 months and 1 year after the injury. At the 6-weekfollow-up, patients were graded as stable and unstable according to the ISAKOS criteria. Outcomes were the Western Ontario Shoulder Instability Index (WOSI) and referral for surgery. At 6 weeks of follow-up,20 patients were classified as stable type A and 69 were classified as unstable type B. The ISAKOS subclassification was not clinically relevant, but patients graded as stable had statistically significantly better WOSI scores at 6 months compared to the unstable group (p = 0.03)but not at 3 months or 1 year. Nine patients (9.5%), all from the unstable group, were referred for surgery. No patients from the stable group underwent surgery (n.s). The ISAKOS subclassification of Rockwood type III in a stable type A and an unstable type B is not clinically applicable. Level II.

The origin of exceptionally large ductility in molybdenum alloys dispersed with irregular-shaped La2O3 nano-particles

Molybdenum and its alloys are known for their superior strength among body-centered cubic materials. However, their widespread application is hindered by a significant decrease in ductility at lower temperatures. In this study, we demonstrate the achievement of exceptional ductility in a Mo alloy containing rare-earth La2O3 nanoparticles through rotary-swaging, a rarity in Mo-based materials. Our analysis reveals that the large ductility originates from substantial variations in the electronic density of states, a characteristic intrinsic to rare-earth elements. This characteristic can accelerate the generation of oxygen vacancies, facilitating the amorphization of the oxide-matrix interface. This process promotes vacancy absorption and modification of dislocation configurations. Furthermore, by inducing irregular shapes in the La2O3 nanoparticles through rotary-swaging, incoming dislocations interact with them, creating multiple dislocation sources near the interface. These dislocation sources act as potent initiators at even reduced temperatures, fostering diverse dislocation types and intricate networks, ultimately enhancing dislocation plasticity.

Synergistic effects of chemical composition on precipitates, dislocations, and mechanical properties of precipitation-strengthened alloys

The properties of materials are intricately dependent on their chemical composition, and microstructures. Achieving a precise modulation in the composition and microstructure of materials to enhance properties significantly is a huge challenge. In this work, we uncovered the effects of nickel and silicon composition on the precipitates, dislocations, and properties of Cu–Ni–Si alloys. The results show that the volume fraction of precipitates increased from 0.84 % to 4.80 % with the increase of Ni and Si contents. The average diameter of the precipitates increased from 6.20 nm to 20.21 nm, and the dislocation density increased from 2.16 × 1013 m−2 to 4.08 × 1015 m−2 concerning the Ni and Si contents. In addition, the dislocation type changes from half-edge dislocation and half-screw dislocation to screw dislocation. The modified WHWA (Williamson Hall-Warren Averbach) method was proved to be the most accurate way of calculating dislocation density. As anisotropy was present in the alloy, adding a dislocation contrast factor and removing some lower-intensity diffraction peaks could further correct the obtained results and reduce the calculation error. Furthermore, the above analysis and findings were employed to design a Cu-3.21Ni-0.66Si alloy with a high yield strength (814 MPa), high ultimate tensile strength (970 MPa), and comparable electrical conductivity of 42.4 % IACS. This work offers a meaningful way to develop precipitation-strengthening alloys.

Comparison of ultrasound-guided closed reduction and percutaneous pinning fixation for unstable humeral lateral condylar fractures.

Ultrasound-guided techniques have become popular in severe humeral lateral condylar fractures (HLCFs). This study compared the results of ultrasound-guided closed reduction and percutaneous pinning (UG-CRPP) for Song types 4 and 5 and dislocation type of HLCFs. This retrospective study was conducted in patients with HLCFs treated between January 2021 and October 2022 at three hospitals. The patients were divided into three groups according to Song's classification and elbow dislocation. The surgical time, reduction failure rate, and outcomes of the three groups were compared. The mean surgical time of the 94 patients across the three groups (Song 4 group, 42 cases; Song 5 group, 38 cases; and dislocation group, 14 cases) was the longest for Song 4 (66.14 ± 23.05 min), followed by the dislocation group (59.71 ± 21.07 min) and Song 5 (52.16 ± 14.94 min) (for all, P = 0.009). The failure rate decreased in the following order: dislocation group (5/14), Song 4 group (7/42), and Song 5 group (2/38). The failure rate of closed reduction in Song 4 was 3.2-fold higher than that in Song 5, and for the dislocation group, it was 7.6-fold higher than that in Song 5. Significant differences were observed between the Song 4, Song 5, and dislocation groups in terms of shaft-condylar angle and supination (P = 0.015, P = 0.043). No significant differences (P > 0.05) were observed in the carry angle, flexion, extension, or pronation of the three groups. Two cases of delayed healing, four cases of superficial infection, one case of trochlear necrosis, and 39 cases of lateral spur in the Song 4 group were observed. In the Song 5 group, five had a superficial infection, one had re-displacement, and 26 had a lateral spur. In the dislocation group, there were two cases of superficial infection and 10 of lateral spurs. Song 4 HLCFs require longer surgical time and present more postoperative complications than Song 5 and dislocation-type HLCFs and can easily lead to lateral spurs. The failure rates of closed reduction in Song 4 and the dislocation type were higher than those in Song 5. Thus, UG-CRPP can be used to treat patients with unstable HLCFs.

Algebra of optical dislocations with plasmonic nanostructures.

Plasmonic structures with physical and Berry-type dislocations are shown to produce vortices with phase singularity according to the system and illumination parameters. We demonstrate that, by combining the two types of dislocations in one structure, the manipulation with the topological charge of the emerging vortex beams can be controlled in an intriguing way. As a result, the plasmonic field distribution can be conveniently modified and selectively excited.

Traumatic Hip Dislocation: Pediatric and Adult Evaluation and Management.

Traumatic hip dislocation of a native hip joint represents an orthopaedic emergency that should be treated promptly. Dislocations can be classified based on the associated injuries and the direction of dislocation. Expeditious evaluation, reduction, and management of associated injuries are required to optimize short and long-term function of the hip. There are several important differences between the blood supply and ossification of the pediatric hip that necessitate different strategies for the evaluation and management of traumatic hip dislocations in pediatric patients. Appropriate treatment is dictated by the direction and type of dislocation as well as associated injuries. In addition to closed reduction, arthroscopy, open reduction (potentially with fracture fixation and/or soft-tissue repair), osteotomy, and total hip arthroplasty all have roles in treatment. Consensus on optimal postreduction activity protocols after simple hip dislocation remain unestablished. Short and long-term outcomes are largely driven by the amount of time from injury to reduction and associated injuries.

Three-Part Fracture Dislocation and Four-Part Fracture Dislocation of the Proximal Humerus: How Different are the Glenoid Labrum and Capsular Injuries Between Them?

Anterior fracture dislocation of the shoulder may have associated injury to the glenoid labrum and/or capsule. There is a need to look at the possible patterns of capsulo-labral injuries intra-operatively and correlate them with pre-operative radiographs and CT scans. It can enable surgeons to predict the patterns of soft-tissue injuries in a specific fracture type. Patients operated for ORIF of 3- and 4-part anterior fracture dislocation between January 2017 and December 2022 were included in the study. The following data were collected: demographic details, fracture morphology and classification on radiograph and CT scan, neurovascular injury, the subtype of anterior dislocation, and intra-operative identifiable injury to glenoid labrum and/or capsule. A total of 24 cases (mean age 40 ± 10years) of anterior fracture dislocation of the shoulder were included in the study and were grouped based on Neer's classification. 12 patients had 3-part anterior fracture dislocation (3-part Group) with a mean age of 34 ± 9years, while 12 patients had 4-part anterior fracture dislocation (4-part Group) with a mean age of 46 ± 7years (p = 0.001). 10 out of 12 patients in the 3-part Group had the subcoracoid position of the dislocated head, whereas the head was present in 9 out of 12 patients of the 4-part Group at the preglenoid position (p = 0.003). The head position was at a mean distance of 1.85cm from the anterior glenoid rim in the 4-part Group, whereas the head was engaged at the anterior rim of the glenoid in the 3-part Group. The medial metaphyseal beak was present in 11 out of 12 patients in the 3-part Group, whereas it was absent in all the cases of the 4-part Group (p = 0.001). 92% of the included patients in our study had capsulo-labral injury. 11 out of 12 patients in the 3-part Group had labral injury compared to 10 out of 12 patients in the 4-part Group with severe capsular stripping (p = 0.001). The 3-part fracture dislocation with radiological findings such as the long medial metaphyseal beak and subcoracoid position of the dislocated head had a strong association with a glenoid labral injury, whereas the 4-part fracture dislocation type had a widely displaced preglenoid position of the dislocated head with an absent metaphyseal beak and had a strong association with a capsular type of soft-tissue injury. III.

Complex Axial Carpal Dislocation with Scapholunate Ligament Injury

Abstract Background Axial carpal dislocations (ACDs) are high-impact injuries, involving both proximal and distal carpal rows, adding complexity to the diagnostic and treatment challenges. This article explores a distinctive case of axial radial carpal dislocation, highlighting an irreducible second carpometacarpal joint (CMCJ) and concomitant scapholunate (SL) ligament injury. Understanding the background of axial carpal injuries is crucial for recognizing and addressing these complex cases effectively. Description A 27-year-old man presented with a left wrist injury following a motorcycle accident, revealing an irreducible second CMCJ with a unique ligamentous injury pattern. Despite unsuccessful closed reduction attempts, the surgical intervention involved a dorsal midline incision, fixation of the second CMCJ and SL interval, and ligament repair. Postoperative assessment demonstrated proper alignment with a mild gap in the SL interval, revealing the intricate nature of the injury. Literature Review Existing studies describe a type of axial dislocation starting at the third webspace, traveling through capitate–hamate intervals leading to scaphoid dislocation. However, in the article, we describe a variant of ACD through second CMCJ causing an SL interval instability. Clinical Relevance Recognizing and comprehensively addressing axial radial carpal dislocations are crucial for optimal patient outcomes. The case report contributes valuable insights into the rare pattern of ACD involving SL instability that was missed on initial radiographs but detected through computed tomography scan and thereby managed appropriately. Any CMCJ dislocation should raise a suspicion of axial dislocation unless proved otherwise.

Effects of Ti content on the tensile ductility, lattice distortion and mechanical properties of VNbTaTix refractory high-entropy alloys

Refractory high-entropy alloys (RHEAs) have remarkable properties like high strength and thermal stability at high temperatures. Their practical application is hindered by ambient brittleness and inferior formability. Titanium (Ti) is recognized as a crucial element in improving the ductility and oxidation resistance of RHEAs, but its plasticizing mechanism is still unclear. To address this, a series of body-centered cubic (BCC) single-phase VNbTaTix alloys were designed. The alloys exhibited exceptional ductility and cold-rolling formability at room temperature. Remarkably, the tensile fracture elongation of VNbTaTi alloy was about 26.9%, which surpassed most RHEAs. The major plastic mechanisms of the alloys are a/2<1 1 1>-type dislocation and {1 1 2}<1 1 1>-type twinning. Solid solution strengthening was identified as the primary strengthening mechanism. Although Ti reduced the solid solution strengthening effect, it contributed to weight reduction and enhanced local lattice distortion. This study not only designed several RHEAs with ductility but also provided insights into the effect of Ti content on their phase stability, lattice distortion, and strength mechanisms. These findings have significant implications for designing new RHEAs with ambient ductility.

Molecular dynamics simulation study of void collapse mechanisms in cubic metals under shock compression

Molecular dynamics simulations have revealed the collapse mechanism of a void in cubic metals under shock compression along [100] direction. The results show that the void collapse is caused by emitting dislocations from its surface. The type of cubic metal plays a decisive role in the subsequent microstructural evolution around the void. Void in face-centered-cubic metals collapses by emitting Shockley dislocations from its surface when piston velocity exceeds the threshold; while void in body-centered-cubic metals collapses by emitting prismatic dislocation loops, which are formed by the reaction of edge dislocations. Simulation results also reveal that the type of dislocation that induces void collapse is independent of void size. Finally, based on the elastic theory, we find that the maximum resolved shear stress along the slip direction determines the types of dislocation emitted from the voids.