• Title/Summary/Keyword: Tapered geometry

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MUTUAL COUPLING EFFECTS ON THE PERFORMANCE OF A SPACE-TAPERED RECTANGULAR PHASED ARRAY (공간체감된 구형 위상어레이의 성능에 미치는 상호결합의 영향)

  • Chang Byong-Kun
    • Journal of the Korea Institute of Information and Communication Engineering
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    • v.9 no.2
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    • pp.415-421
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    • 2005
  • The radiating or receiving characteristics of array elements (i.e., antennas) are changed from those of isolated elements due to mutual coupling effects and the array performance becomes different from those originally designed by assuming isolated elements. The effects of mutual coupling on the performance of a rectangular array with triangular grid geometry of dipoles above a ground plane are discussed with respect to element pattern. The concept of element gain function is used to examine the effects of mutual coupling on the array performance in terms of sidelobe level in the uniformly spaced and space-tapered rectangular arrays with triangular grid geometry of dipoles. It was shown that the sidelobe performance improved in the space-tapered array compared to the uniformly spaced array in the presence of mutual coupling effects. Computer simulation results are presented.

Analytical Study on Effects of Bearing Geometry on Performance of Sliding Thrust Bearings (미끄럼 스러스트베어링의 성능에 미치는 베어링 형상의 영향 해석)

  • Kim, Ho-Jong;Choi, Sung-Pil;Ha, Hyun-Cheon
    • The KSFM Journal of Fluid Machinery
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    • v.9 no.5 s.38
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    • pp.7-13
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    • 2006
  • In the present study, we develop an analysis module to be applicable to design of sliding thrust bearings. The pressure equation is solved by using the finite element method. Average lubricant temperature is obtained from using the energy balance method. The module developed has been applied to three types of thrust bearing, such as tapered-land thrust bearings of angular and diamond types, and tilting-pad thrust bearings. Effects of the dam of the tapered-lad thrust bearings have also been investigated. It has been seen that the tapered-land thrust bearings of angular type result in the highest load capacity, while the tilting pad thrust bearings result in the lowest lubricant temperature. It has also been seen that the dam in the tapered-land thrust bearings increases both the load capacity and lubricant temperature.

Tribological Approach on the Stress Distribution of Wheel-Rail Contact (차륜과 레일 사이의 접촉응력에 관한 트라이볼로지적 해석)

  • 황재용;김기환;김청균
    • Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
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    • 1997.04a
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    • pp.210-217
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    • 1997
  • This paper presents the numerical results of the stress analysis of wheel-rail contact problems. Two models which have straight and tapered(1:20) contact geometries between the wheelset and rail are analyzed using the finite element approach. From the simulation results we found that the tapered geometry of wheel-rail contact base line showed very stable contact stress distributions for a whole contact position between the wheel and rail in a curved rail section. The FEM computed results may present an optimized geometry of wheel-rail contact in a high-speed railway system.

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Finite Element Analysis on the Stress Distributions in Rail-Wheel Contacts of High Speed Trains (고속전철용 레일-휠 접촉에서 응력분포에 관한 유한요소해석)

  • 김청균;김기환
    • Tribology and Lubricants
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    • v.13 no.3
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    • pp.93-101
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    • 1997
  • The numerical results on the stress distributions of rail-wheel contact problems are presented for three models in a high-speed rail system. These models which have straight and tapered (1:40 and 1:20) contact geometries between the wheelset and rail are analyzed using the finite element approach. From the simulation results we found that the tapered geometry (1:20) of railwheel contact base line showed very stable contact stress distributions for a whole contact position between the wheel and rail in a curved rail section. The FEM computed results may present an optimized slope geometry of rail-wheel contact in a high-speed railway system.

Multi-objective optimization of tapered tubes for crashworthiness by surrogate methodologies

  • Asgari, Masoud;Babaee, Alireza;Jamshidi, Mohammadamin
    • Steel and Composite Structures
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    • v.27 no.4
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    • pp.427-438
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    • 2018
  • In this paper, the single and multi-objective optimization of thin-walled conical tubes with different types of indentations under axial impact has been investigated using surrogate models called metamodels. The geometry of tapered thin-walled tubes has been studied in order to achieve maximum specific energy absorption (SEA) and minimum peak crushing force (PCF). The height, radius, thickness, tapered angle of the tube, and the radius of indentation have been considered as design variables. Based on the design of experiments (DOE) method, the generated sample points are computed using the explicit finite element code. Different surrogate models including Kriging, Feed Forward Neural Network (FNN), Radial Basis Neural Network (RNN), and Response Surface Modelling (RSM) comprised to evaluate the appropriation of such models. The comparison study between surrogate models and the exploration of indentation shapes have been provided. The obtained results show that the RNN method has the minimum mean squared error (MSE) in training points compared to the other methods. Meanwhile, optimization based on surrogate models with lower values of MSE does not provide optimum results. The RNN method demonstrates a lower crashworthiness performance (with a lower value of 125.7% for SEA and a higher value of 56.8% for PCF) in comparison to RSM with an error order of $10^{-3}$. The SEA values can be increased by 17.6% and PCF values can be decreased by 24.63% by different types of indentation. In a specific geometry, higher SEA and lower PCF require triangular and circular shapes of indentation, respectively.

Plastic collapse of tapered, tip-loaded cantilevered beams

  • Wilson, James F.;El-Esnawy, Nayer A.
    • Structural Engineering and Mechanics
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    • v.9 no.6
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    • pp.569-588
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    • 2000
  • The plastic collapse loads and their locations are predicted for a class of tapered, initially curved, and transversely corrugated cantilevered beams subjected to static tip loading. Results of both closed form and finite element solutions for several rigid perfectly plastic and elastic perfectly plastic beam models are evaluated. The governing equations are cast in nondimensional form for efficient studies of collapse load as it varies with beam geometry and the angle of the tip load. Static experiments for laboratory-scale configurations whose taper flared toward the tip, complemented the theory in that collapse occurred at points about 40% of the beams length from the fixed end. Experiments for low speed impact loading of these configurations showed that collapse occurred further from the fixed end, between the 61% and 71% points. The results may be applied to the design of safer highway guardrail terminal systems that collapse by design under vehicle impact.

Prediction and Verification of Lateral Joining Strength for Tapered-Hole Clinching using the Taguchi Method (다구찌 기법을 이용한 이종재료 경사 홀 클린칭 접합부 수평 방향 접합강도 예측 및 검증)

  • Kang, D.S.;Park, E.T.;Tullu, A.;Kang, B.S.;Song, W.J.
    • Transactions of Materials Processing
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    • v.25 no.1
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    • pp.36-42
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    • 2016
  • Fiber metal laminates (FMLs) are well known for improved fatigue strength, better impact resistance, superior damage tolerance and slow crack growth rate compared to traditional metallic materials. However, defects and loss of strength of a composite material can occur due to the vertical load from the punch during the joining with a dissimilar material using a conventional clinching method. In the current study, tapered-hole clinching was an alternative process used to join Al 5052 and FMLs. The tapered hole was formed in the FML before the joining. For the better understanding of static and dynamic characteristics, a clinched joining followed by a tensile-shear test was numerically simulated using the finite element analysis. The design parameters were also evaluated for the geometry of the tapered hole by the Taguchi method in order to improve and compare the lateral joining strength of the clinched joint. The influence of the neck thickness and the undercut were evaluated and the contribution of each design parameter was determined. Then, actual experiments for the joining and tensile-shear test were conducted to verify the results of the numerical simulations. In conclusion, the appropriate combination of the design parameters can improve the joining strength and the cross-sections of the tapered-hole clinched joint formed in the actual experiments were in good agreement with the results of the numerical simulations.

Numerical Study for the Improvement of Tapered-hole Clinching Joint Strength of Fiber Metal Laminates and Aluminum 5052 using the Taguchi Method (다구찌 기법을 이용한 섬유금속적층판과 Al 5052 합금의 경사 홀 클린칭 접합력 향상을 위한 수치적 연구)

  • Kang, D.S.;Lee, B.E.;Park, E.T.;Kim, J.;Kang, B.S.;Song, W.J.
    • Transactions of Materials Processing
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    • v.24 no.1
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    • pp.37-43
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    • 2015
  • The purpose of the current study is to improve the clinching joint strength of aluminum and fiber metal laminates (FMLs) comprised of three layers. The joining of FML and Al 5052 by a conventional clinching joint has some disadvantages such as necking of the upper sheet, lack of interlocking, defects caused by the vertical load, and especially loss of strength of the composite material due to the low ductility. In the current study, a tapered-hole clinching method is proposed as an alternative for the joining of Al 5052 and FMLs. A hole with a tapered shape is formed before the joining process. The design parameters were evaluated using the Taguchi method for the geometry of the tapered hole in order to determine the maximum separation load. The diameter of the punch corner, clearance, punch stroke and the tapered length were used as the main variables in the Taguchi method. In conclusion, the contribution ratio for each of the fours variable examined was 35.07%, 22.44%, 21.32% and 14.11%, respectively. In addition, the appropriate combination of the design parameters can make a 5% improvement in the vertical direction joint strength.

Role of network geometry on fluid displacement in microfluidic color-changing windows

  • Ucar, Ahmet Burak;Velev, Orlin D.;Koo, Hyung-Jun
    • Smart Structures and Systems
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    • v.18 no.5
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    • pp.865-884
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    • 2016
  • We have previously demonstrated a microfluidic elastomer, which changes apparent color and could have potential applications in smart windows. The practical use of such functional microfluidic systems requires rapid and uniform fluid displacement throughout the channel network with minimal amount of liquid supply. The goal of this simulation study is to design various microfluidic networks for similar applications including, but not limited to, the color-switching windows and compare the liquid displacement speed and efficiency of the designs. We numerically simulate and analyze the liquid displacement in the microfluidic networks with serpentine, parallel and lattice channel configurations, as well as their modified versions with wide or tapered distributor and collector channels. The data are analyzed on the basis of numerical criteria defined to evaluate the performance of the corresponding functional systems. We found that the lattice channel network geometry with the tapered distributors and collectors provides most rapid and uniform fluid displacement with minimum liquid waste. The simulation results could give an important guideline for efficient liquid supply/displacement in emerging functional systems with embedded microfluidic networks.

THREE-DIMENSIONAL FINI6E ELEMENT ANALYSIS OF THE ENDOSSEOUS IMPLANT DESIGNS (삼차원 유한요소 해석에 의한 골내 임프란트의 구조에 관한 연구)

  • Hyun, Young-Keun;Kwon, Jong-Jin
    • The Journal of Korean Academy of Prosthodontics
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    • v.35 no.1
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    • pp.181-210
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    • 1997
  • The stress distribution generated in the surrounding bone was calculated and compared for various geometry of the dental implants by means of the finite element methods. The models were designed to represent the screw type endosseous implants(varing the size, shape, direction of the screw thread and the angle of the body) with supporting bone and the cylinder type endosseous implants(varing the lower portion-Round type, tapered type) with supporting bone. Static mean bite forces were applied 100N vertically and 25N horizontally on the center of the implant and three dimensional finite analysis was undertaken using software ANSYS 5.1 Version. The result demonstrated that different implant shape leads to significant variations in stress distribution in the bone. In the case of variation of the screw size, direction and shape the implant model with normally directional and triangular screw implied lower stress than with upper directional or lower directional and quadrangular screw but among models a different screw size, within a variation of 0.2mm there was no meaningful difference in maximum stress. In the case of variation of angle of body the straight implied lower stress than the tapered. As a result of analysis of cylinder type, the implants with larger radius of curvature of the round form and larger diameter of the tapered form implied lower stress.

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