• Title/Summary/Keyword: Optimal taper angle

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The Optimum Shape of Taper HTS Current Lead Having Partial Current Sharing Region (일부 전류분류 영역을 갖는 테이퍼 형상 전류도입선의 최적 형상에 대한 연구)

  • 허광수;설승윤
    • Proceedings of the Korea Institute of Applied Superconductivity and Cryogenics Conference
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    • 2003.10a
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    • pp.185-189
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    • 2003
  • The purpose of this study is to obtain the optimal operating condition of conduction cooled taper shape high-temperature superconductor (HTS) current lead operated in current sharing mode. In our previous study, we discovered that the optimal operating condition of constant cross-section area HTS current lead is in the current sharing state, and in optimal condition, the temperature gradient at warm end is not zero. The analysis result of taper HTS current lead is quiet similar to the constant area HTS current lead. The minimum dissipation of taper HTS current lead is not influenced by taper angle, however the optimal operation condition is varied with taper angle.

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Research on Optimal Taper Stud Bolts for Steam Turbines Using the FEM (유한요소법을 이용한 증기터빈용 최적 테이퍼 스터드 볼트에 관한 연구)

  • 이부윤;김태완
    • Journal of Advanced Marine Engineering and Technology
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    • v.24 no.2
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    • pp.8-16
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    • 2000
  • The thread load distribution as applied to large stud bolts for steam turbines is investigated using the finite element method. The stress concentration in tapered threads is studied with varying prestress and taper angle. Based upon the thread load distribution, the optimal taper angles to reduce the stress concentration are determined for various prestresses. The presented finite element model is validated by comparing results of the calculated thread load with analytic ones. The optimal taper angles obtained from this research can be used in designing tapered threads of large stud bolts for steam turbines.

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Machining Characteristics of Micro-EDMed Holes According to Dielectric Fluid, Capacitance and Ultrasonic Vibrations (방전가공을 이용한 미세구멍 가공 시 절연액, 축전용량과 초음파 부가에 따른 가공특성)

  • Seo, Dong-Woo;Yi, Sang-Min;Chu, Chong-Nam;Park, Min-Soo
    • Journal of the Korean Society for Precision Engineering
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    • v.24 no.12
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    • pp.42-49
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    • 2007
  • When micro holes are machined by EDM, machining characteristics of machined holes are changed according to the machining conditions. Typical machining conditions are the kind of dielectric fluids, capacitance and ultrasonic vibrations. They influence electrode wear, machining time, radial clearance and taper angle. In this paper, machined holes whose depths are 300, 500, $1000\;{\mu}m$ are observed for each machining conditions. Using deionized water as a dielectric fluid makes electrode wear small, machining time short, radial clearance large and taper angle small. High capacitance makes electrode wear high. Ultrasonic vibrations make electrode wear large, machining time short, radial clearance small and taper angle small. From the results of experiments, the optimal machining conditions were obtained to machine highly qualified micro holes.

Transient Response of The Optimal Taper-Flat Head Slider in Magnetic Storage Devices

  • Arayavongkul, R.;Mongkolwongrojn, M.
    • 제어로봇시스템학회:학술대회논문집
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    • 2004.08a
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    • pp.990-994
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    • 2004
  • This paper presents a method to predict the transient characteristic of the air lubricated slider head in a hard disk drive by using optimization technique. The time dependent modified Reynolds equation based on the molecular slip flow approximation equations was used to describe the fluid flow within the air bearing and the implicit finite difference scheme is applied to calculate the pressure distribution under the slider head. The exhaustive search combined with the Broyden-Fletcher-Goldfarb-Shanno method were employed to obtain optimum design variables which are taper angle, rail width and taper length in order to keep the forces and moments acting on the slider head in dynamic equilibrium. The results show that the optimal head slider of the magnetic head has good stability characteristic that can reach the steady state within 0.5 microsecond.

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CFD Analysis on the Flow Characteristics of Diffuser/Nozzles for Micro-pumps (마이크로 펌프용 디퓨져/노즐의 유동 특성에 관한 CFD 해석)

  • Kim Donghwan;Han Dong-Seok;Jeong Siyoung;Hur Nahmkeon;Yoon Seok-Jin
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.17 no.6
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    • pp.544-551
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    • 2005
  • The flow characteristics have been numerically investigated for various shapes of the diffuser/nozzles which are used for a valveless micro-pump. The important parameters considered in this study are the throat width ($15\~120\mu$m), the taper angle ($3.15\~25.2^{\circ}$), and the diffuser length ( $600\~4,800\mu$m), and the size of the middle chamber ($1\~16mm^2$). To find the optimal values for these parameters, steady state calculations have been performed assuming the constant pressure difference between the inlet and exit of the flow For the taper angle and the throat width, it is found that there exists an optimum at which the net flow rate is the greatest. The optimal taper angle is in the range of $10\~20^{\circ}$ for all the pressure differences; and the throat width indicates an optimal value near $75\mu$m for the case of 35 kPa pressure difference. The net flow rate is also influenced by the size of the middle chamber. With decreasing chamber size, the net flow rate is reduced because of the interference between two streams flowing into the middle chamber. The unsteady pulsating flow characteristics for a micro-pump with a given diffuser/nozzle shape have been also investigated to show the validity of the steady state parametric study.

Optimal Machining Condition of WC-Microshaft Using Electrochemical Machining (텅스텐카바이드 미세축의 전해가공 시 최적가공조건 선정)

  • 최세환;류시형;최덕기;주종남
    • Proceedings of the Korean Society of Precision Engineering Conference
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    • 2002.10a
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    • pp.245-249
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    • 2002
  • Tungsten carbide microshaft is used as various micro-tools in MEMS because it has high hardness and good rigidity. In this study, experiments were performed to produce tungsten carbide microshaft using electrochemical machining. $H_2SO_4$solution was used as electrolyte because it can dissolve tungsten and cobalt simultaneously. Optimal electrolyte concentration and machining voltage satisfying uniform shape and large MRR of workpiece were found. For one-step machining, the immersion depth over 1 mm was selected for avoidance of concentration of electric charge at the tip of the microshaft. The limit diameter with good straightness was shown and an empirical formula for WC-microshaft machining was suggested. By controlling the various machining parameters, a straight microshaft with 30 $\mu\textrm{m}$ diameter, over 1 mm length and under 0.5$^{\circ}$ taper angle was obtained.

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Effects of Mixing Chamber Shape on Cutting Performance in AWJ (AWJ에서 혼합챔버 형상이 절단성능에 미치는 영향)

  • Lee, Hyo-Ryeol;Kwak, Yong-Kil;Kim, Hwa-Young;Ahn, Jung-Hwan;Yeo, Myeong-Heon
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.20 no.5
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    • pp.535-540
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    • 2011
  • It is well known that abrasive waterjet (AWJ) was developed as a kind of high-density energy processing technologies. AWJ is used to obtain cutting quality of various materials such as metal, ceramics, glass and composite materials within a short manufacturing time because of the characteristics of heatless and noncontact processing. However, surface roughness and dimension error like round, burr, taper vary severely according to the processing conditions such as pressure, cutting speed, orifice diameter, stand off distance and abrasive flow rate. In this paper, the effect of the shape of mixing chamber on surface quality is studied. Three types of mixing chamber - round, parabolic, elliptical - are suggested and each performance is compared to that of cylindrical mixing chamber experimentally. From the result, is proved to be the optimal mixing chamber in the aspect of surface quality the parabolic one.

WC Micro-shaft Fabrication Using Electrochemical Etching (전해 가공을 이용한 WC 미세축 제작)

  • 최세환;류시형;최덕기;주종남
    • Journal of the Korean Society for Precision Engineering
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    • v.21 no.6
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    • pp.172-178
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    • 2004
  • Tungsten carbide microshaft can be used as various micro-tools for MEMS because it has high hardness and high rigidity. In this study, experiments are performed to produce tungsten carbide micro-shaft using electrochemical etching. H$_2$SO$_4$ solution is used as electrolyte because it can dissolve tungsten and cobalt simultaneously. Optimal electrolyte concentration and machining voltage satisfying uniform shape, good surface quality, and high MRR of workpiece are experimentally found. By controlling the various machining parameters, a straight micro-shaft with 5 ${\mu}{\textrm}{m}$ diameter, 3 mm length, and 0.2$^{\circ}$taper angle was obtained.

Flutter characteristics of axially functional graded composite wing system

  • Prabhu, L.;Srinivas, J.
    • Advances in aircraft and spacecraft science
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    • v.7 no.4
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    • pp.353-369
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    • 2020
  • This paper presents the flutter analysis and optimum design of axially functionally graded box beam cantilever wing section by considering various geometric and material parameters. The coupled dynamic equations of the continuous model of wing system in terms of material and cross-sectional properties are formulated based on extended Hamilton's principle. By expressing the lift and pitching moment in terms of plunge and pitch displacements, the resultant two continuous equations are simplified using Galerkin's reduced order model. The flutter velocity is predicted from the solution of resultant damped eigenvalue problem. Parametric studies are conducted to know the effects of geometric factors such as taper ratio, thickness, sweep angle as well as material volume fractions and functional grading index on the flutter velocity. A generalized surrogate model is constructed by training the radial basis function network with the parametric data. The optimized material and geometric parameters of the section are predicted by solving the constrained optimal problem using firefly metaheuristics algorithm that employs the developed surrogate model for the function evaluations. The trapezoidal hollow box beam section design with axial functional grading concept is illustrated with combination of aluminium alloy and aluminium with silicon carbide particulates. A good improvement in flutter velocity is noticed by the optimization.

Design Optimization of QTP-UAV Prop-Rotor Blade Using ModelCenter (ModelCenter를 이용한 QTP-UAV 프롭로터 블레이드 형상 최적설계)

  • Kang, Hee Jung
    • Journal of Aerospace System Engineering
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    • v.11 no.4
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    • pp.36-43
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    • 2017
  • Blade design optimization of QTP-UAV prop-rotor was conducted using ModelCenter(R). Performance efficiency of the blade in hover and forward flight were adopted as the multi-objective function. Required power and pitch link force applied to constraint in each flight mode and limited lower than the value of the baseline blade. Design variables of root chord length of the blade, taper ratio, twist slope, twist angle at 0.5R of the blade, anhedral angle, parabolic coefficient of a tip shape and location of airfoil were used to generate the blade planform. CAMRAD-II, the comprehensive analysis program of rotorcraft, was used for performance analysis of prop-rotor blade in design process. Performance of the optimized blade improved 1.6% of figure of merit in hover and 13.6% of propulsive efficiency in forward flight. Pitch link force also reduced approximately 30% less than that of the baseline blade.