Determine the Stress Calculating Mode of Sliding Failure of Soil Mass under the Push-Extend Multi-under-Reamed Pile

Through the analysis of the sliding failure form of soil mass under the bearing push-extend reamed of Push-extend Multi-under-reamed Pile, in the paper, the law of coulomb-Mohr is used to establish a stress function and the theory of the sliding line is used to establish Prandtl regional stress field, which determines the stress calculating mode of soil mass and provides a theoretical basis for a further study of this type of pile ultimate bearing capacity of soil mass.

Cuttings transport: Back reaming analysis based on a coupled layering-sliding mesh method via CFD

Inadequate hole cleaning is one of the main reasons for inefficient operations in extended-reach drilling.The mechanism of cuttings transport under the back reaming operation,which is frequently adopted to remove the cuttings,has been investigated in this study.To this end,a coupled layering-sliding mesh method with the Eulerian-Granular approach has been established innovatively.The dynamic layering method has been employed to simulate the axial motion of the pipe,whereas the sliding mesh method has been used to simulate the pipe rotation.The back reaming operation of a connector-furnished pipe has been simulated,and the sensitive parameter analysis has been conducted.The results thus obtained demonstrate that the increase in the initial bed height,inclination,and the diameter and length of the connector causes a significant increase in the cuttings concentration.In addition,the cuttings concentration is observed to decrease significantly with the pipe rotation speed.Furthermore,two main factors contribute towards the cuttings accumulation around the connector,namely,the difference in the cross-sectional area and the pushing effect of the connector—like a“bulldozer”.The“bulldozer”effect of the connector dominates when the tripping velocity is significant compared to the velocity of the cuttings.Conversely,the effect of the difference in the cross-sectional area becomes the leading factor for cuttings accumulation.The“bulldozer”effect of the connector causes a more severe impact on hole cleaning.In both cases,increasing the tripping velocity only mildly affects the cuttings concentration.It is therefore suggested that the tripping velocity should be slower than that of the sand during the back reaming operation.Furthermore,increased fluid velocity might lead to a higher accumulated cuttings concentration around the connector when the cuttings bed has not entirely passed through the connector.A significant flow rate can be safely applied after the cuttings have passed through the connector furnished with a large diameter,such as the bottom hole assembly.This exploration serves as an essential guide to predicting and controlling tight spots while back reaming.

Design and Fluid-Dynamic Analysis of a Flushing Nozzle for Drilling Applications

The actuator is a key component of the creaming tool in drilling applications.Its jet performances determine the effective reaming efficiency.In this work,a new selective reaming tool is proposed and the RNG k-εturbulence model is used to calculate its internal and externalflowfields.In particular,special attention is paid to the design of theflushing nozzle.The results show that the jet originating from theflushing nozzle has a significant influence on rock cutting and blade cooling effects.In turn,the jet performances depend on geometric structure of the creaming actuator.In this framework,a conical-cylindrical nozzle with a diameter of 7 mm is initially considered as a basis to implement a strategy to optimize the structural parameters of the reaming actuator,and improve the related side tracking reconstruction technology.

Rigid locked nail fixation for pediatric tibia fractures-Where are the data?

Tibial shaft fractures are common injuries among the pediatric and adolescent population. Conservative treatment remains the preferred treatment. However, over the last two decades, there has been an increasing trend of operative fixation in pediatric tibia fractures, commonly with intramedullary nail fixation (IMN). Elastic stable intramedullary nails (ESIN) are heavily used especially in skeletally immature patients as they are physeal respecting and the technique for insertion is familiar. Alternatively, reamed locked intramedullary nails (RIMN) have gained traction in adolescents and skeletally immature pre-adolescents. When identifying publications germane to intramedullary fixation of pediatric tibia fractures, the majority investigated clinical and radiographic outcomes associated with ESIN. We were able to identify only one study specifically examining RIMN in this population, albeit other studies included patients treated with RIMN. In parallel, there has been considerable progress in the field of skeletal maturity estimation with criteria based on different anatomic regions. However, little data exists for trauma purposes as no gold standard system had been accepted and proven to be precise for determination of potential growth remaining around the knee or for quantifying the risk of damage to the proximal tibial physis. Systems devised have been either unvalidated or unnecessarily complex or both. In order to achieve more informed treatment choices and optimal patient outcomes when using IMN fixation in pediatrics, simple to use, validated plain film-based methodology is needed to define skeletal maturity for the proximal tibia. Additionally, further examination of outcomes and the role of RIMN in this population are warranted.

Experimental research on characteristics of hole reaming and side cutting of one-cone bits

The hole reaming and side cutting characteristics of offset one-cone bit and conventional one- cone bit were investigated on simulated drilling experimental equipment. The borehole diameter was a little larger than the bit diameter due to side force. However, the reaming effect was not very apparent, whether drilling with an offset or conventional one-cone bit. The side cutting displacement increased gradually with increasing depth of drilling and side force. The side cutting displacement of offset onecone bits was larger than that of conventional ones under the same conditions of weight-on-bit （WOB）, rotary speed, side force and borehole depth.

Vigorous Endosteal Reaming across Fracture Site to Aid Union in Atypical Femur Fractures

Background: Bisphosphonate abuse is associated with atypical femur fractures, which despite different fixation methods have increased non-union, delayed union, and re-operation rates. Therefore, there is a need for a surgical technique that may enhance union in such cases. Herein we are introducing a novel technique of sequential multiple vigorous reaming across the fracture site to introduce reaming debris/endosteal bone graft around the fracture site. Materials and Methods: We present a retrospective analysis of five prospectively treated patients with atypical diaphyseal femur fracture who presented to us from January 2015 to August 2019. All the patients were followed up at regular intervals and assessed both clinically and radiologically. Results: All 5 cases operated with our technique showed union at a mean follow-up of 16 weeks (12 - 20 weeks). There were no complications reported in our study at the last mean follow-up of 25 months (12 - 51 months). Conclusion: This technique of multiple vigorous reaming at and around the fracture site provides a new paradigm in the management of AFF. The autograft around the outer cortex promotes the formation of bridging callus and results in the early union.

Fracture Union in Closed Interlocking Nail in Humera Shaft Fractures

Background： Fracture shaft humerus is a major cause of morbidity in patients with upper extremity injuries. The aim of this study was to evaluate the outcome of interlocking nail in humeral shaft fractures. Methods： This study was conducted in the Department of Orthopedic Surgery in SMS and R Sharda University from January 2010 to November 2013. Seventy-eight patients were recruited from emergency and out-patient department having a close fracture of humerus shaft. All patients were operated under general anesthesia and closed reamed interlocking nailing was done. All patients were followed for 9 months. Results： Out of 78 patients, 69 patients underwent union in 90-150 days with a mean of I 10.68 days. Complications found in four patients who had nonunion, and five patients had delayed union, which was treated with bone grafting. All the patients were assessed clinically and radiologically for fracture healing joint movements and implant thilure. The results were excellent in 88.46% and good in 6.41% patients. Complete subjective, functional, and clinical recovery had occurred in almost 100% of the patients. ConcLusions： The results of the present study indicates that in the presence of proper indications, reamed antegrade intramedullary interlocked nailing appears to be a method of choice for internal fixation ofosteoporotic and pathologic fractures.

Improvement of machining accuracy in EDCM by enhanced electrochemical reaming based on a non-metallic backing layer

Electrochemical Discharge Machining(ECDM)is potentially applicable for the fabrication of film-cooling holes.However,It is extremely difficult for the holes to achieve higher precision and machining quality owing to the working liquid diminish in the lateral machining gap.In this study,a non-metallic backing layer was proposed to overcome the diminish of working liquid,and the electrochemical reaming,as a post-processing method for ECDM,was used to further improve the machining accuracy and quality of the holes.First,the three-dimensional morphology of the melted pit of a paraffin backing layer was scanned to obtain the geometric parameters.Then,simulation analysis and experimental verification of auxiliary flushing by using the non-metallic backing layer were performed.The machining performance of the holes machined with electrochemical reaming based on non-metallic backing layer was confirmed by the observations of the surface topography of the hole wall and orifice,measurement of the orifice precision,and analysis of the element composition on the surface of the orifice wall.Finally,an optimum combination of machining parameters for electrochemical reaming is obtained through a process parameter optimization experiment.

Study on the reaming process of aluminum alloy 7050-T7451 under different cooling conditions

Aluminum alloy 7050 is widely used in the aeronautical industries.However,owing to their highly ductile property,chips created during high-speed machining cannot be naturally broken,and long continuous chips are unavoidably formed,impacting the machining stability and quality of the parts.Because a smaller cutting allowance is required compared with conventional machining operations,the behavior of the chips during reaming operation may be more complex and different from those determined in previous investigations.Therefore,studying the characteristics of chip formation and hole quality during the reaming process is essential to improve the machinability of aluminum alloy 7050.In this study,three different cooling conditions were applied to reaming aluminum alloy 7050-T7451 with polycrystalline diamond(PCD)reamers.The finite element models(FEMs)were established to simulate the chip formation.The macro-and micro-morphologies of chips under the three cooling conditions were compared to analyze the chip behaviors.The diameter,surface roughness,and micro-morphologies of the reamed holes were also analyzed to evaluate the hole quality.The results showed that the chip morphology was strongly influenced by the cutting parameters and cooling strategies.It was found that the desired chip morphologies satisfactory geometrical accuracy and surface quality during the reaming of aluminum alloy 7050-T7451 could be achieved using internal cooling at a spindle speed of 8000 r/min and a feed rate of 0.0l mm/z.This study also demonstrates the feasibility of an internal cooling strategy for breaking chips when reaming aluminum alloy 7050-T7451,which opens new possibilities for improving the chip-snarling that occurs during hole machining.