Добірка наукової літератури з теми "Tapered plain tools"

The present study investigated the combined effect of friction stir processing (FSP) tool pin and shoulder profiles on particle distribution and microstructure of AA6063/SiC composites. Two strategies were used, in first strategy, plain cylindrical, tapered cylindrical, square and triangular tool pin profiles were used with flat shoulder design. In second strategy square and cylindrical pin profiles were used along with clock-wise (CW) and anti clock-wise (ACW) scrolled shoulder design. Single pass processing was performed to fabricate the composites. Microstructure examination of sample processed with various pin profiles and flat shoulder design reveals that tool with square pin profile was most effective. Among other shoulder profiles, ACW scrolled shoulder resulted in pancake shaped stir zone (SZ) and exhibited significant improvement in SZ size, out of which ACW scrolled shoulder with cylindrical pin profile produced uniform particle distribution without any defects.

Turning is one of the most widely used machining processes in the mechanical engineering industry. Thus, the choice of optimal cutting parameters (cutting speed, feed and depth of cut) is very important in order to ensure a better surface condition of the machined parts and the life of the cutting tools, which requires great relationship with the wear of the tool-part interface. The result of a good choice of cutting conditions can be seen by a reduction in this wear. During machining, the geometric shape and the physical state of the tool are modified by the combined action of the cutting forces and by the temperature reached by the cutting edge. These modifications which gradually increase with the duration of machining are commonly grouped under the term wear of the tool. They appear on the active part of the tool. In this work, we propose an optimization method allowing determining a mathematical model of the wear and tear by applying the experiment plan. This model highlights the relationship between the elements of the cutting regime (cutting speed, feed and depth of passes) and the responses studied (Wear in clearance).

This article reports an experimental investigation of the efficacy of self-flushing in the Electrical Discharge Machining (EDM) process in terms of tool wear rate (TWR), hole taper angle and material removal rate (MRR). In addition to a plain cylindrical shape, electrodes of different cross sections (slotted cylindrical, sharp-cornered triangular, round-cornered triangular, sharp-cornered square, round-cornered square, sharp-cornered hexagonal and round-cornered hexagonal) were designed as a means of inducing debris egress and then fabricated in graphite. EDM drilling trials using the rotating shaped electrodes were carried out on a Ti6Al4V workpiece. The results revealed that, although a low TWR and minimum hole taper angle were achieved using a plain cylindrical electrode, the usage of rotating shaped electrodes provided self-flushing of the dielectric fluid during the EDM process, which led to an improvement in MRR compared to that achieved with a plain cylindrical electrode. Besides, in general, the electrodes with rounded corners are associated with a lower TWR, a lower hole taper angle and a higher MRR when compared to the electrodes with sharp corners. Considering these results, it was concluded that different process attributes, i.e., TWR, hole taper angle and MRR, are all greatly affected by the electrode shape, and thus, the proper selection of the electrode shape is a precondition to attain a specific response from the EDM process.

e20608 Background: The American Society of Clinical Oncology recommends that physicians (MDs) assess the treatment goals and preferences of patients (pts) with advanced stage cancer. Available data, however, shows that pts’ values are not always well prioritized when making a treatment plan. Therefore, we iteratively developed a values tool containing 16 belief domains to inform MDs during conversations with their pts about the pts’ current priorities as they plan the next step in care. The purpose of this study was to determine the feasibility of using this values tool (defined as half of the tools having at least one value checked and half of the MDs discussing at least one value) in a phase I clinic setting. Methods: We audio-taped initial MD-pt conversations about potential enrollment in a phase I clinical trial at two academic medical centers (Emory and Mayo). The pts completed the values tool by selecting the 4 most important considerations for their next stage of care and were instructed to give the completed tool to the MD. The MDs were informed through the consent process but not specifically coached on use of the tool. The recorded conversations were coded using standard qualitative methodology to determine if a value from the tool was discussed. Results: There were 23 recorded encounters. All of the completed tools had at least one value checked and 19 of 23 (83%) completed tools were delivered to the MDs by the pts, as instructed. Of those who received the tool, 12 (63%) MDs discussed one or more of the values. The average satisfaction scores on a 5-point Likert scale were 3.9, 4.0, and 4.0, respectively, for tool clarity, ease of understanding, and benefit for pts who are offered a phase 1 trial (22/23 pts completed the evaluation). Average satisfaction scores from the 19 MDs who completed evaluations were 4.2 and 4.6, respectively, for influence of the tool on their treatment recommendation and accurate reflection of pts’ desires. Conclusions: The study met the predefined feasibility threshold and provides a strong rationale for future efficacy testing, including coaching of MDs. The tool was well accepted by both MDs and pts, and failure to deliver the completed tool by the pt was identified as a potential barrier to its effectiveness.

This work focused on the optimization of process parameters, which may result in increasing mechanical properties of copper weldments. The different tool pin profiles such as plain taper cylindrical, taper cylindrical with threaded, triangular, square, pentagonal and hexagonal having constant shoulder diameters were used to fabricate the weldments. The experiments were conducted at different levels of tool rotational speed and weld speeds using six different tool pin profiles. The experimental results revealed that the defect free weldments could be obtained by using different tool pin profiles. From the investigation, it was found the weldments made by using a square (SQ) tool pin profile resulted in better mechanical properties compared to other tool pin profiles. Objective functions are developed for the mechanical properties in terms of input parameters. The input parameters of an SQ tool pin profile were optimized using a metaheuristic optimization based algorithm named teaching learning based optimization (TLBO) technique to improve mechanical properties. The TLBO suggests a combination of 900 rpm of tool rotation speed and 40 mm/min weld speed for better properties.

This study focuses on optimization of process parameters, which may result in improved mechanical properties of the friction stir weldments of AA2014-T651. Plain taper and threaded taper cylindrical tool pin profiles were used for the study. A set of experiments was conducted at different levels of tool rotational and weld speeds using two tool pin profiles. Mechanical properties such as tensile strength, yield strength, impact strength, percentage of elongation, and hardness were measured. Objective functions are developed for the five mechanical properties in terms of input parameters. The input parameters were optimized using teaching–learning-based optimization algorithm technique to improve mechanical properties. The teaching–learning-based optimization algorithm suggested three best combinations such as combination-I (940 r/min and 32 mm/min), combination-II (1100 r/min and 40 mm/min), and combination-III (1205 r/min and 45 mm/min). The optimization is also validated with experimental results.

BACKGROUND: One of the main causes of death is cardiovascular diseases. Among cardiovascular diseases ischemic heart disease is major a cause of death. Emergency medical service and ambulance play the key role in providing timely care. AIM: This study was carried out to investigate the coverage area of calls of acute coronary syndrome (ACS) by ambulance stations in regards to the time using GIS-analyze. METHODS: This was descriptive study which contains secondary data from Semey ambulance service’s database about all 1704 ACS with and without elevation of ST segment emergency calls in Semey city (Kazakhstan) over the period from August 1, 2017 to May 30, 2018. Spatial Analyst and Network Analyst Extensions of ArcGIS 10.7 (ESRI, CA, USA) were used to define high ACS density areas and find 10, 15, and 20 min time response areas. Kernel density tool calculates a magnitude-per-unit area from point or polyline features using a kernel function to fit a smoothly tapered surface to each point or polyline. RESULTS: The distance to the patient for ambulances was from 7 to 15 km. For most calls, the response time was <10 min, which is the recommended national standard for emergency care. Density zones were divided into seven categories from white (from 0 to 3.4 cases/km2) to red (from 59.9 to 86.1 cases/km2). The largest high-density area of ACS cases was located in central part of the city on right-bank of the river. Furthermore, high density of ACS cases was identified in the areas of high rise buildings on the left bank of the river. CONCLUSION: GIS tools are useful tool that can be implemented in planning of emergency medical service. In our study, we determined that the service areas of ambulance stations cover the needs of patients with ACS. But nevertheless, it is necessary to plan the ambulance care to nearby regions and villages. In addition, it needs to consider the development of new areas of city and patterns of emergency calls in planning.

Nickel-based superalloys are gaining importance for their growing usage in aerospace industries. Amidst the various advanced machining processes, electro discharge machining (EDM) is considered to be an important one for its ability to machine materials irrespective of its intrinsic properties. In this study, Inconel 718 is considered as a work material, and an L18 orthogonal array (OA) experimental plan is utilized to machine the work material. The influential factors, which affect the EDM performance characteristics, are identified using analysis of variance (ANOVA). Not much work has been done regarding using grey-Taguchi technique for order of preference by similarity to ideal solution (TOPSIS) methods, although these methods can be easily applied for multi-objective optimization. These methods provide the best results with the available sparse data. The best combination of machining factors is determined using grey-Taguchi and TOPSIS methods. Based on the conducted experiments, voltage (V) and pulse off-time (t_off) show a notable contribution on output performance. The optimal combination of input parameter through grey-Taguchi is found to be 10 A, 30 V, 200 μs, and 20 μs respectively, for the EDM parameters: current (I), V, pulse on-time (t_on) and t_off for improved response. Moreover, the best parameter setting (I = 10 A, V = 30 V, t_on =100 μs and t_off = 20 μs) is identified using the TOPSIS method for the performance measures machining rate (MR), tool wear rate (TWR), overcut (OC), and taper overcut (TOC). Further tool wear behaviour is also studied through scanning electron microscope (SEM) images by varying the voltage.

Cette étude vise le développement d’un outil d’évaluation ludique, valide et fiable (le Ludo-Tdc) capable d’investiguer de manière quantitative et qualitative la coordination des enfants atteints du trouble développemental de la coordination (TDC) âgés de 5 à 12 ans. La version expérimentale du questionnaire était composée de 49 tâches, nommées items, sélectionnées à partir d’échelles de mesure existantes et de la littérature. L’outil, présenté sous la forme d’un plateau de jeu, a été soumis à 20 enfants atteints de TDC (moyenne d’âge : 9 ± 2 ans ; sex ratio : 3 garçons/2 filles). Chaque session de jeu était filmée, puis analysée par l’expérimentateur qui attribuait, sur une échelle à 4 catégories de réponse, des scores à chaque tâche réalisée par les enfants pour évaluer quantitativement leur niveau de coordination et des scores à 10 critères qualitatifs utilisés pour évaluer les qualités avec lesquelles les enfants réalisaient l’ensemble des tâches du jeu. Les réponses ont été analysées avec le logiciel RUMM2020 qui utilise le modèle de Rasch, un modèle statistique permettant de vérifier que l’outil satisfait aux conditions d’une mesure objective. La capacité du Ludo-Tdc à discriminer les enfants ayant un TDC des enfants sains du même âge et du même sexe a également été investiguée. L’analyse a montré que les deux premières catégories de réponse n’étaient pas bien discriminées et ont dû être regroupées ensemble, résultant ainsi en une échelle à 3 catégories de réponse. La version finale du Ludo-Tdc, constituée de 32 items et de 8 critères qualitatifs, possède une très bonne précision de mesure (coefficient de fiabilité de 0,94 pour l’échelle quantitative et de 0,90 pour l’échelle qualitative). Le Ludo-Tdc est également capable de discriminer de manière significative les enfants ayant un TDC des enfants sains du même âge (p<0,001). Cette étude a donc permis de développer un outil d’évaluation unidimensionnel et fiable, le Ludo-Tdc, capable d’évaluer la coordination des enfants atteints de TDC âgés de 5 à 12 ans. Les propriétés métriques de l’outil devraient permettre aux cliniciens travaillant avec des enfants atteints de TDC de faire un état des lieux du niveau de coordination de ces enfants, ainsi que de personnaliser le plan de rééducation et d’en vérifier son efficacité. * * * This study aims to develop an enjoyable, valid and reliable assessment tool (the Fun-Dcd) capable of quantitatively and qualitatively assessing the coordination of children between the ages of 5 and 12 with Developmental Coordination Disorder (DCD). The experimental version of the questionnaire was composed of 49 tasks, called items, selected from existing measurement scales and from the relevant literature. This tool, presented in the form of a board game, was submitted to 20 children with DCD (mean age of 9 ± 2 years; sex ratio of 3 boys to 2 girls). Each game session was video-taped and then analysed by the examiner. Scores were then attributed, on a scale with 4 response categories, for each task performed by the children in order to quantitatively evaluate their level of coordination. Additionally, scores were also attributed on a scale with 4 response categories, for 10 qualitative criteria used to assess the qualities with which the children completed the entire set of game tasks. The responses were analysed with Rumm2020 software which uses the Rasch model, a statistical model able to verify that the tool satisfies the criteria of an objective measurement. The capacity of the Fun-Dcd to discriminate between children with DCD and healthy children of the same age and sex was also investigated. Analysis showed that the first two response categories were not well discriminated and should have been grouped together, thus resulting in a scale with 3 response categories. The final version of the Fun-Dcd, consisting of 32 items and 8 qualitative criteria, displays a very high level of measurement precision (reliability coefficient of 0.94 for the quantitative scale, and 0.90 for the qualitative scale). The Fun-Dcd was also able to discriminate children with DCD from healthy children of the same age (p<0.001). This study has therefore enabled the elaboration of a reliable, unidimensional assessment tool, the Fun-Dcd, capable of assessing the coordination level of children between the ages of 5 and 12 with DCD. The metric properties of the tool should allow clinicians working with children suffering from DCD to obtain an overview of the level of coordination of these children, as well as to customize their rehabilitation program and verify its efficiency.

Insertion of twisted tapes in smooth channels is one of the passive methods used for enhancing heat transfer. Flow and associated heat transfer characteristics of these channels are very complex. Understanding this complex flow is helpful while designing new passive methods. Numerical methods like computational fluid dynamics (CFD) are gaining much popularity for analyzing and designing these heat transfer enhancement techniques. This paper focuses on such a numerical study. The preliminary study is focused on development of numerical methodology through validation. Successive studies are aimed at development of an innovative design for twisted tape. Twisted tapes with taper angle (tapered twisted tapes, i.e., tape width decreases along the flow direction) are developed and evaluated on the basis of the performance of these tapes with those of conventional tapes. A circular tube with tapered twisted tape with a twist ratio of 3 and taper angles of 0.3, 0.4, 0.5, 0.6, and 0.7 is considered for this study along with a plain tube. Three Reynolds numbers (Re) of 8545, 11393, and 13333 are considered to examine the sensitivity of the performance. Simulations are performed with a commercially available CFD tool, ansys fluent (v14.0). Heat transfer and pressure drop results are presented in the form of Nusselt number (Nu), friction factor (f), and overall enhancement ratio (η). An increase of 17% in overall enhancement is predicted with taper angle of 0.5.

Aluminium-copper joints are widely used in electrical applications due to their unique properties. However, joining of these metals by conventional welding techniques is restricted due to the formation of brittle (bulk size) intermetallic phases.As the other solid-state welding techniques are restricted to a particular joint geometry and they are time-consuming, Friction Stir Welding (FSW) technique is used in the present work to join AA2024 and pure Cu, which resulted in distribution of Cu particles in the stir zone. The nature and distribution of these particles, along with the nature and thickness of the intermetallic layer at the interface, would dictate the strength of the joint. However, they depend on the various process parameters. Therefore, the objective of the current work was to optimize the various FSW parameters to obtain better properties by controlling the size of particles in the SZ. For the given purpose, the experiments are done with AA2024 on advancing side and Cu on retreating side and vice versa. Then the other parameters such as tool rotation speed and tool traverse speed are also optimized. These experiments are performed for varying interface positions by using a tapered plain tool and tapered threaded tool. The optimum weld was achieved by a plain tool when the tool was offset towards the advancing side i.e.AA2024 side of the weld. The weld contains a thin continuous intermetallic layer at the interface,due to which maximum joint strength was achieved. From three-point bend test; it was found that the root of this weld was the weakest region. The weakest region of the optimum weld (single side weld) was eliminated by double side weld, where the weld was repeated from the backside of the previous weld. As the intrinsic microstructure of the AA2024-pure Cu weld can change due to heating when the weld is used as a current carrying system, the effects of heating on the optimum weld were also studied. In case of the threaded tool also the optimum weld was obtained, whentool was offset towards the advancing side i.e AA2024 side of the weld. This weld contained high volume fraction of fine Cu particles in AA2024 matrix. This lead to increase in ductility of joint as compared to plain tool weld. Further, Zn and Ni interlayers were used to modify the composition of the particles formed in eth weld nugget. This further increased the ductility of the joint due to the formation of binary/ternary intermetallics. From this work, it is concluded that the expected desirable morphology of metallic and intermetallic particles can be achieved by optimum tool geometry and tool offset position. Due to this optimization considerable improvement in the mechanical properties of the AA2024-pure Cu welds was observed.

This paper presents results from the application of the genetic algorithm (GA) technique to the design optimization of hydrofoil and marine propeller incorporating the potential-based boundary element method (BEM). Although larger population size as implemented by simple genetic algorithm (SGA) could find the optimal individual after a fewer number of generations than smaller population size, it is penalized by a longer amount of time to evaluate fitness in every generation. An investigation is, therefore, conducted in this research to implement micro genetic algorithm (μGA) with a very small population, and with simple genetic parameters, in order to achieve faster convergence to better solutions from generation to generation. The technique is applied here to optimize hydrofoils of different plan forms, e.g., rectangular, elliptical, trapezoidal etc. Firstly, the hydrofoil design parameters, such as angle of incidence, maximum thickness, and camber ratios, aspect ratio, taper ratio, angle of sweep, etc. are initialized randomly and the generated hydrofoil is analyzed by potential based boundary element method. GA then updates the design parameters over generation after generation and finally, finds an improved hydrofoil of maximum lift-drag ratio or minimum drag coefficient satisfying some design constraints. An improved blade or hydrofoil section is also designed by GA satisfying some design constraints. Finally, the technique is applied to the optimum design of marine propeller. In this study, μGA is found a useful and prospective tool for the design optimization of hydrofoil due to its faster convergence.

Abstract Great efforts are invested in improving oil and gas reservoir recovery to meet the rise in local energy consumption and global demand. To improve the production and ultimate recovery of a major oil field in the Middle East, extended-reach drilling (ERD) is executed in wells with long horizontal multilaterals to achieve maximum reservoir contact (MRC), the increase in ERD wells demand led to many drilling challenges and difficulties. The challenges in designing ERD wells are multiple, such as trajectory control, well collision avoidance, hole cleaning efficiency, high torque & drag, differential sticking, wellbore stability, Logging-while-drilling (LWD) log quality and long circulating hours. In recognition of this, the dedicated operator and service team developed a drilling optimization roadmap that addresses the drilling challenges at the greatest performance impact. The optimization roadmap comprises enhanced trajectory design, drillstring design, drilling fluids and system hydraulics design, and subsurface geomechanical modelling in the planning phase, in addition to realtime formation evaluation, hole cleaning and torque and drag monitoring, and drillstring vibrations management in the execution phase. The exploitation of 4 inch and 5 inch tapered drillstring as opposed to complete 5 inch drillstring for drilling torque reduction and its related tripping behavior was explored on the first Optimization stage of the optimization plan, using this approach successfully reduced drilling torque, but the tripability out of hole became problematic and more difficult. The first stage outcome called for utilizing complete 5 inch drillpipe string in addition to oil-based mud (OBM) lubricant (OMNI-LUBETM) that resulted in 20-25% reduction of the drilling torque. Tripability improved compared to 4 inch drill pipe in the second optimization stage, but still facing some issues in few laterals. On the final optimization stage, the engineering & operations team introduced the Dog Leg Reamer tool on top of the drilling bottomhole assembly (BHA) which resulted in a significant improvement in the tripping behavior in addition to a smoother hookload along in the drilled interval. The implementation of the holistic drilling system design and optimization methodologies helped achieving new performance records, lateral after lateral. The optimization roadmap delivered a proven performance in the most challenging drilling environments. The key technical challenges, performance optimization roadmap, job execution, and post well evaluation of the drilling performance are presented in this paper.

Abstract Drilling low-pressure formations represent challenges. In the present paper, an operational situation became an issue when during the drilling of a deviated well, the circulation was lost, and the BHA got stuck, followed by a gas inflow observed in the return line. After a well control procedure and several failed attempts to control the well and recover the drilling BHA, another problem occurred when the drill pipe got plugged, making it impossible to continue pumping control pills. The scenario described above was presented to the Coiled Tubing and Thru Tubing companies with the request of a proposal to help solve three specific goals to achieve remove the plug in the inner of the drill pipe, getting communication between the drill pipe and the open hole to be able to pump Lost Control Material (LCM) and control de well, perform a cut of the drill pipe in case the pipe couldn't be recover after control the gas inflow. With an interdisciplinary group, the problem was analyzed, and a proposal was submitted, including three runs with Coiled Tubing and Thru Tubing tools. The first run a cleanout of the drill pipe with a downhole motor and taper mill. The second run will be with an abrasive punching BHA to establish communication with the annuls, and the third run will be for an abrasive cutting that will allow the recovery of the drill pipe above the free point. The job preparation includes the engineering program with the operational parameters and flow chart and the logistic preparation with the resources such as coiled tubing equipment, thru-tubing BHAs, chemicals, and fluids, among others. During the operation, other discussions and revisions forced a change in the plan from the initial proposal, performing two of the three runs for the cleanout and abrasive cutting, which represented a benefit by controlling the well with the slurry pumped working as a LCM that helped control the gas inflow. With a conclusion of a successful cut and drill pipe recovery, the operation data and analysis of the preparation vs. the execution are presented in the paper.