• International Journal of Precision Engineering and Manufacturing
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• 제4권5호
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• pp.15-21
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• 2003

In order to improve the quality of a spindle unit it is important to increase its rotational accuracy. The rotational accuracy of a spindle unit can be defined as the stability or immobility of its spindle axis while rotating. Spindle rotation in the rolling bearings causes the disturbing influence, which leads to the oscillation of a rotation axis. The purpose of this study is to investigate the oscillation sources and find a way to decrease the runout without additional expenses. The main source of oscillation is the interaction between rolling bodies and ring races. The first oscillation source was the out-of-shape imperfection of inner bearing ring. The mutual compensation of oscillation by proper rings orientation was proposed, which sometimes allow to decrease the radial runout of spindle rotation axis by approximate 40％ down. Also the outer ring harmonics were explored as the second oscillation source. The analysis shows the dependency between the number of rolling bodies and the outer ring race harmonics. The conclusion on the orientation of bearing cages and the bearing rings was made, which makes possible to obtain the optimal variant of their mounting in the spindle unit when the rotational accuracy of the spindle is maximal, and the spindle runout considerably less.

• Tribology and Lubricants
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• 제7권1호
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• pp.28-34
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• 1991

The performance of the counterrotating floating ring journal bearing is analysed with isothermal finite bearing theory. The effect of counterrotating speed of the sleeve on the performance of the bearing is investigated. It is shown that counterrotating floating ring journal bearings properly designed can have considerable load capacity at the same counterrotating speed, while conventional circular journal bearing with one fluid film cannot. Investigating the relationship between the frictional torques on the ring due to the inner and outer films and the rotational speed of the ring, the stability of the equilibrium state is identified and the operating characteristics of the counterrotating floating ring journal bearing according to the method of acceleration or deceleration of the rotational speeds of the journal and sleeve are clarified. It is theoretically confirmed that floating ring journal bearings can be used in counterrotating journal-bearing system and become good substitutes for rolling bearings in counterrotating systems.

• 오토저널
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• 제6권2호
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• pp.39-46
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• 1984

There are various ringshaped automotive and machine parts and the study about the characteristics of ring are the important basis of the quality control and performance improvement of outer race of ball bearing, railwheel, ring gear, piston ring, and other ringshaped seals, etc. In this study, the effect of prestress which arise inevitably during the fitting of the ring shape parts and the effect of central line extension/contraction on the vibrational characteristics of ring are verified. Although many studies are made on the vibration of ring, the study about prestress and extension were rather scarce and rare. As a result of the study, a series of frequency formulas are derived. The result of this study can be utilized in the improvement of design as well as in the quality control during the fitting work.

• 한국가스학회지
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• 제12권1호
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• pp.36-41
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• 2008

본 논문에서는 완전밀폐식 LNG 저장탱크의 외부탱크 측벽면과 지붕 구조물에 대한 강도안전성을 유한요소법으로 해석하였다. 예응력 콘크리트 구조물로 건설된 외부탱크는 내부탱크의 붕괴로 인해 발생하는 LNG 유체정압과 유체동압, 그리고 태풍을 포함한 외부의 풍압하중을 받는다. FEM 해석결과에 의하면, 외부탱크의 측벽면과 지붕 구조물이 서로 연결되는 링빔 구조물은 저장탱크에 작용하는 대부분의 내 외부 하중을 담당하고 있다. 이러한 해석결과는 외부탱크의 설계 포인트를 링빔에 두고, 그 다음은 지붕구조물의 중심부에 대한 설계 안전성을 검토하는 것이다. 완전밀폐식 LNG 저장탱크 해석에서 사용한 해석모델은 LNG 누설에 의한 내부압력 및 태풍과 같은 외부압력이 결합된 복합하중에서도 안전한 강도안전성을 유지하고 있음을 알 수 있다.

• Tribology and Lubricants
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• 제19권1호
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• pp.9-14
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• 2003

The sealing performance of an elastomeric O-ring using the double layered material has been analyzed fer the contact stress behaviors that develop between the O-ring seal and the surfaces with which it comes into contact. The leakage of an O-ring will occur when the pressure differential across the seal Just exceeds the initial (or static) peak contact stress. The contact stress behaviors that develop in compressed O-rings, in common case of dovetail grooved geometry, are investigated using the finite element method. The FE analysis includes material hyperelasticity and axisymmetry. The computed FEM results show that the contact stress behaviors are related to the ratio of diameter between the inner ring and the outer ring, and the temperature of vacuum chamber.

• 오토저널
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• 제6권1호
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• pp.56-62
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• 1984

Various automotive and machine parts are having the shape of circular ring and the study and the verification of its dynamic characteristics can be the important basis of quality control and improvement of performance of inner and outer race of ball and roller radial bearing, ring gear, seal, etc. In this study, three separate sets of governing equations on the flexural vibration of circular ring were formulated each considering the effects of viscous damping, rotatory inertia and shear deformation, and three frequency formulas were derived. Numerical values of frequencies of circular and rectangular cross section ring were tabulated and compared with experimental value. Some important parameters were found in the ring vibration characteristics.

• KSTLE International Journal
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• 제4권1호
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• pp.1-7
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• 2003

A turbo pump unit provides high pressure oxygen and fuel in a space shuttle main engine (SSME). This paper focused on rotordynamics, investigating its characteristics based on a numerical simulation of turbo pump finite element model. Speeds up to 50,000 rpm are considered, as well as the special problems related to elastic-ring, seal hydrodynamic force, shroud force and clearance-excitation farce. The rotordynamic prediction shows that the elastic-ring which is inserted between the casing and the outer race of ball bearing allows far an acceptable separate margin of first critical speed. Additionally, the results show that the floating ring seal, which have a peculiar ring, adds substantial stiffness and damping to the system as well as exhibits superior performance in terms of rotordynamic stability of system compared to the plain seal.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제52권10호
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• pp.484-490
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• 2003

This paper describes with the stator analysis and design of a ring type ultrasonic motor. The design for piezoelectric ceramic and elastic body of stator were calculated by using the finite element method (FEM) that consider the resonance frequency, vibration mode and coupling efficiency. Namely, such results were acquired the calculation result of the piezoelectric ceramic thickness 0.5[mm], elastic body thickness 2.0[mm], resonance frequency 51.8[kHz], vibration mode 7 order and coupling efficient 12.5[%], the outer and inner diameter of vibrator 50[mm], 38[m]. On the basis of such result, the ring type ultrasonic motor was manufactured. Also for driving characteristics of ring type ultrasonic motor, 2-phase inverter was constructed. Then the propriety of this paper was established from comparision of the simulation and an experiment results of the ring type ultrasonic motor.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2009년도 제40회 하계학술대회
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• pp.1159_1160
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• 2009

본 논문에서는 초고속 자기부상열차의 유력한 후보가 될 수 있는 초전도 반발식 자기부상의 특성을 연구하기 위한 반발력을 3차원 유한요소 자기 해석을 통하여 계산하고 분석하였다. 본 해석의 결과에 따르면 움직이는 부분이 없는 정지형 시험기는 반발식 자기부상시험기로써 적용될 수 있다.

• 한국초전도ㆍ저온공학회논문지
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• 제11권1호
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• pp.49-54
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• 2009

This paper presents the numerical simulation results on the moving type electrodynamic suspension (EDS) simulator and static type EDS simulator using high-Tc superconducting (HTS) levitation magnet. The levitation force of the EDS system is formed by the reaction between the moving magnet and the fixed ground conductor. The possible two ways to simulate the EDS system were simulated in this paper by using finite element method (FEM). The first way was the moving type simulator which consists of the fixed HTS magnet and the moving ground conductor. The second way was the static type simulator which consists of the fixed magnet, the fixed ground conductor and the ac current supply system. To verify the characteristics of high speed EDS system with the moving type simulator heavy, large and fast moving ground conductor is needed. The static type simulator can get the characteristics of the high speed EDS system by applying equivalent ac current to velocity, therefore it does not need large moving part. The static type EDS simulator, which can consist of an HTS magnet, the fixed ground conductor(s), an AC power supply and the measuring devices, also test the effect of the shape of the ground conductor easily. The plate type ground conductor made stronger levitation force than ring type ground conductor. Although the outer diameter 335 mm ring type ground conductor (Ring3) was larger than the outer diameter 235 mm ground conductor (Ring2), the levitation force by Ring2 was stronger than that by Ring3. From the calculation results on this paper, the consideration of the magnetic flux distribution according to the levitation height should be included in the process of the ground conductor design.