• Title/Summary/Keyword: radius problem

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A Study on Appropriate Breadth for U-turn Setup (U-turn 설치를 위한 적정 폭원에 관한 연구)

  • Lee, Jin-Uk;Kim, Gi-Hyeok
    • Journal of Korean Society of Transportation
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    • v.27 no.3
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    • pp.39-47
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    • 2009
  • Currently, the minimum breadth as a point available for U-turn setup is designated as "over 9m for one way" in the traffic safety facilities practical manuals, and vehicles allowed to make a U-turn are limited to passenger cars. However, as passenger cars have recently become larger and SUVs (Sports Utility Vehicles) are being popularized, they fail to make a U-turn in one attempt. This causes a traffic jam and a problem with traffic safety. This study proposed, compared, and tested the measured values of actual differences in the turning radius of U-turn by actual cars with estimated values by using PC-Crash, a car accident simulation program. Then, the study forecasted the turning radius of U-turns of Korean passenger cars by using PC-Crash, and proposed appropriate breadth for U-turn setup.

The Effect of Cutting Edge on the Surface Roughness In Cutting Brittle Materials (취성재료의 가공시 절삭날이 표면거칠기에 미치는 영향)

  • Kim, Joo-Hyun
    • Journal of the Korean Society for Precision Engineering
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    • v.13 no.1
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    • pp.53-61
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    • 1996
  • A clear understanding of the surface formation mechanism due to cutting is very important to help produce a good quality surface. Much of the roughness along the length of a bar being cut in a lathe can be explained in terms of macroscopic tool shape and feed rate. However, the roughness along the direction of cutting requires a different explanation. The formation of surface roughness is a problem in flow and fracture of materials in the vicinity of the tool edge. On a microscopic scale the cutting edge is rounded because it is impossible to grind a perfectly sharp cutting edge. Even if a perfectly sharp cutting edge were obtained it would soon become dull as a result of rapid breakdown and wear of the cutting edge. A research project is proposed in which in the main object is to model the surface formation mechanism due to cutting. The tool was assumed to be dull, that is, its edge has a finite radius. In order to study the effect of the radius of cutting edge on the surface formation, tools having different cutting edges were used. For orthogonal cutting experiment, cast iron and glass were chosen as brittle materials. Plowing forces acting in the cutting edge were estimated and its effect on the surface roughness was studied by observing the machined surface using optical microscope.

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Design of Structure Corners restraining Tribological Failures: Part II - Analysis of Design Parameters and Examples (트라이볼로지 손상을 억제하기 위한 구조물 모서리부 설계: 제2부 - 설계인자 분석 및 예)

  • Kim, Hyung-Kyu
    • Tribology and Lubricants
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    • v.31 no.4
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    • pp.170-176
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    • 2015
  • As a continuation of Part I, which developed a design formula of the minimum corner radius (Rmin) for restraining tribological failures, Part II investigates design parameters such as material properties and contact force. As design examples, Al 7075-T651, SST 304 and HT-9 are chosen for the materials and 1, 10 and 100 kN are used for the forces. The results show that the difference in Rmin decreases as either the elastic modulus increases or the contact force decreases. Given the same material and force, the permissible Rmin decreases as the flat region increases and vice versa. Because the Rmin values obtained from the examples are very small, the dimensions of the corner radius normally designed in engineering structures are regarded acceptable. The von Mises stress evaluated for a typical example, which is far below the yield strength, confirms this interpretation. Nevertheless, the present work can provide a design criterion as well as a guideline for quality control in the manufacturing of, in particular, contact corners, which has not been attempted before to the best of the author’s knowledge. In addition, this paper considers the problem of a step that may be formed in the contact contour by using a similar approach. The result shows that no size of the step is permissible.

Giant Cell Tumor of the Distal Radius Treated with the Proximal Fibular Graft - A Case Report - (비골이식술로 치료한 요골 원위부의 거대세포종 - 증례 보고 -)

  • Jeong, Hak-Yeong;Yang, Seung-Wook;Shin, Seung-Joon;Song, Moo-Ho;Seung, Hyeong-Joon
    • The Journal of the Korean bone and joint tumor society
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    • v.4 no.2
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    • pp.103-106
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    • 1998
  • Giant cell tumor was described by Sir Astley Cooper in 1818. This tumor is considered to be a benign tumor but has problems of recurrence and metastatic change after treatment. Methods of operative treatment of this tumor have included currettage, currettage and bone graft, excision, resection, excision and graft and amputation. We experienced a case of giant cell tumor which involved the distal part of right radius and treated by wide excision and fibular graft. The postoperative courses have been satisfactory because of no recurrence or malignant change. After 6 years and 1 month follow up, the patient was able to return to daily life without any problem.

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Small Fatigue Crack Measurement and Crack Growth Characteristics for Smooth and Notch Specimens (평활 및 노치재의 미소피로균열측정과 성장특성)

  • 이종형
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.9
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    • pp.2145-2152
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    • 1993
  • The objective of this paper is to examine the detection limit, growth characteristics and notch curvature radius in short crack problem. Measurement techniques such as ultrasonic method and back-face strain compliance method were adopted. The fatigue crack growth rate of the short crack is slower than that of a long crack for a notched specimen. The characteristic of crack growth and crack closure is same as the case of a delay of crack growth caused by constant amplitude load for an ideal crack or single peak overload for a fatigue crack. The short crack is detected effectively by ultrasonic method. A short surface crack occurs in the middle of specimen thickness and is transient to a through crack depth is larger than the notch curvature radius.

A Study on Structural Safety of the Solid Fuel Grain by Hot Flow inside a Hybrid Rocket Combustor (Multi-port 하이브리드 로켓 연소기에서 고온 산화제 유동에 의한 고체연료의 구조적 안전성에 대한 연구)

  • Do, Gyu-Sung;Yoon, Chang-Jin;Kim, Jin-Kon;Moon, Hee-Jang
    • Journal of the Korean Society for Aviation and Aeronautics
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    • v.15 no.4
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    • pp.38-44
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    • 2007
  • This paper describes the structural safety of solid fuel in the Hybrid Rocket Motor (HRM). Hybrid rocket combustion has the distinct regression characteristics which include the process of thermal pyrolysis and fuel vaporization. Most of all, this regression characteristics would structurally affect the strength of the fuel having a multi-port configuration, and even may cause the breaking from the fuel grain. This problem would probably influence the performance and operating safety of HRM. Therefore, for the safe operation of HRM, the critical port radius which determines the structurally safe region was discussed from the heat analysis of the solid fuel.

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A Study on the Flow Friction Loss of a Shrouded Rotating Disk (밀폐된 단일 회전 원판 주위의 유동손실에 관한 연구)

  • 조성욱;임윤철
    • Tribology and Lubricants
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    • v.19 no.5
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    • pp.292-297
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    • 2003
  • The fundamental fluid mechanics associated with the rotation of a smooth plane disk enclosed within a cylindrical chamber have been studied experimentally. In order to acquire systematic information pertinent to this problem torque and friction loss data were obtained over a wide range of disk Reynolds numbers for axial clearance-disk radius ratio H/R from 0.025 to 0.2 and radial tip gap-disk radius ratio s/R from 0.021 to 0.105. Loss analysis of hard disk drive (HDD) is presented to describe the contribution of windage loss of a rotating disk. The minimum loss form factor of HDD can be obtained from this analysis at each operation conditions.

Buckling of Composite Cylindrical Shells Sugjected ot Torsion of Lateral Pressure (비틀림 및 횡압럭을 받고 있는 복합재 원통쉘의 좌굴)

  • Han, Byeong-Gi;Lee, Seong-Hui;Yu, Taek-In
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.20 no.5
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    • pp.1436-1444
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    • 1996
  • The problem ofinstability of laminated circular cylindrical shell under the action of torsio or lateral pressure is investigated. The analysis is based on the Sander's theory for finite deformations of thin shell. The buckling is elastic for thin compoisite shell nad the geometry is assumed to be free of initial imperfections. The equilibrium equations are obrained by usitn the p[erturbation technique. Solution procedure is based on the Galerkin mehtod. The computer program for numerical results is made for several stacking sequence, length-to-radius ratio, and radius-to-thickness ratio. The numerical results of buckling load are present.

Solution of the Inverse Electromagnetic Scattering Problem for Cylindrical Objects by Using the Resonance Scattering Ttheory (공진산란이론을 이용한 원통형 산란체에 대한 전자기파문제의 역산란 이론)

  • Jung, Yong-Hwa;Jeon, Sang-Bong;Ahn, Chang-Hoi
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.55 no.3
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    • pp.142-148
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    • 2006
  • The resonances that contain the information on the properties of the scattering target can be used for target reconstruction approaches. The inverse scattering theory for the resonances has been applied to the problems of the scattering for a spherical, cylindrical dielectric objects and dielectrically coated conductors, shown reasonable results. Though by using this method the thickness and the dielectric constants of the target can be obtained from a determination of the spacing and of the widths of the scattering resonances, the radius of the target should be given. In this paper, we suggest the improved inverse theory combined with the resonance scattering theory to obtain the radius in addition to the dielectric constant of the target. The applications of this method for scattering problems of electromagnetic waves from cylindrical targets were accomplished, and it shows its validity.

The Effect of Die Design and Process Condition in Precision Forging for AI7075 Alloy(l) (AI7075합금의 정밀단조시 금형설계와 단조조건의 영향(l)-실험과 상계해석을 중심으로-)

  • 이영선;이정환;정형식;이상용;이동원
    • Proceedings of the Korean Society for Technology of Plasticity Conference
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    • 1996.10a
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    • pp.105-112
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    • 1996
  • Aluminium alloy have been used extensively as forging materials for aircraft components due to their high specific strength and corrosion resistance. A large portions of these materials are used as airframe components consisted of various combination of such Rib-Web structure. But the problem of high forging pressure and defect which were caused by narrow Rib thickness prevented from the favorable developments and laboratory scaled trials. In this study, optimization of forging variables such as corner radius and temperature in Rib-Wed structure were established. The 2 mm of corner radius minimized the forging pressure to get the fixed Rib height, which well coincided with theoretical result according to Upper-Bound analysis. And optimum workpiece temperature was below 450$^{\circ}C$ in consideration of grain growth and forging defects by local melting.

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