• 한국윤활학회:학술대회논문집
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• 한국윤활학회 1996년도 제23회 학술대회
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• pp.30-35
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• 1996

An elastohydrodynamic lubrication (EHL) analysis for an axially crown profiled cylindrical roller is carried out using a finite difference method and the Newton-Raphson method. Variations of the minimum film thickness with dimensionless parameters show considerably different from those of infinite solutions.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2007년도 춘계학술대회 논문집
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• pp.147-148
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• 2007

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.370-371
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• 2012

• 기계저널
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• 제22권4호
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• pp.262-270
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• 1982

머지않은 장래에는 이러한 초컴퓨터와 신기술들이 유체역학의 주요한 발전을 주도하고, 오랫동안 취급하지 못하였던 난류유통도 해석할 수 있을 것이며, 복잡한 비행기 형상의 외부 유통도 발 전된 형체막형화 기법과 격자발생법 및 그래픽 기술을 이용하여 손쉽게 계산될 것이다. 금세기 말까지의 공기역학의 발전은 주로 공기의 탄성효과를 고려한 비정상압축성 공기역학에서 이루 어질 것이다.

• 대한기계학회논문집
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• 제15권6호
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• pp.1975-1981
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• 1991

본 연구에서는 완전히 불균일한 격자계를 사용하여 프로파일링을 한 원통형로 울러의 프로파일링 시작점 부근에서의 압력분포 및 유막형상과 함께 무차원변수의 변 화에 따른 최소유막의 거동을 상세히 조사하고자 한다. 이 결과에서 실제 로울리 베 어링의 로울러 프로파일의 설계시에 적용할 수 있는 새로운 기준을 제시하고자 한다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 추계학술대회논문집B
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• pp.318-323
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• 2001

Characteristics of the pulsatile flow in a 3-dimensional elastic blood vessel are investigated to understand the blood flow phenomena in the human body arteries. In this study, a model for the elastic blood vessel is proposed. The finite volume prediction is used to analyse the pulsatile flow in the elastic blood vessel. Variations of the pressure, velocity and wall shear stress of the pulsatile flow in the elastic blood vessel are obtained. The magnitudes of the velocity waveforms in the elastic blood vessel model are larger than those in the rigid blood vessel model. The wall shear stresses on the elastic vessel vary with the blood vessel motions. Amplitude indices of the wall shear stress for blood in the elastic blood vessel are $4\sim5$ times larger than those of the Newtonian fluid. As the phase angle increased, point of the phase angle is are moved forward and the wall shear stresses are increased for blood and the Newtonian fluid.

• 한국소음진동공학회논문집
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• 제18권2호
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• pp.177-184
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• 2008

The dynamic stability of elastically restrained cantilever pipe conveying fluid with crack is investigated in this paper. The pipe, which is fixed at one end, is assumed to rest on an intermediate spring support. Based on the Euler-Bernoulli beam theory, the equation of motion is derived by the energy expressions using extended Hamilton's Principle. The crack section is represented by a local flexibility matrix connecting two undamaged pipe segments. The influence of a crack severity and position, mass ratio and the velocity of fluid flow on the stability of a cantilever pipe by the numerical method are studied. Also, the critical flow velocity for the flutter and divergence due to variation in the support location and the stiffness of the spring support is presented. The stability maps of the pipe system are obtained as a function of mass ratios and effect of crack.

• Tribology and Lubricants
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• 제31권4호
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• pp.177-182
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• 2015

Tapered roller bearings are widely used in equipment where high combined thrust and radial loads are experienced. A certain amount of tilting between the tapered rollers and the races always occurs because of bending moment load conditions and shaft deflection. It is now well understood that a coherent elastohydrodynamic lubrication (EHL) film separates the rollers and races. In spite of extensive study on EHL problems for over half a century, relatively few studies have focused on the finite line contacts problem. This study presents a complete numerical analysis of the effects of roller tilting on the EHL characteristics in a tapered roller bearing. We systematically analyze this highly nonlinear problem using finite differences with fully non-uniform grids and the Newton-Raphson method. Detailed EHL pressure distributions and film shapes are presented under moderate loads and material parameters. A very small roller tilting significantly affects the pressure distributions and film shapes near both ends of the roller. Moreover, the effect of tilting on the EHL characteristics at the small end is much greater than that at the large end. Therefore, in designing optimum profiles for tapered roller bearings, the profile radius should be larger at the small end.

• Tribology and Lubricants
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• 제23권5호
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• pp.187-194
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• 2007

The profile of the roller in the axial direction is the main design factor in order to increase endurance life against the contact fatigue due to the stress concentration along the edge of the roller. Even under the elas-tohydrodynamic lubrication (ehl) conditions, the stress concentration along the edge of the roller greatly worsens the fatigue life both for the roller and contacting body. In this study, roller contacts of finite axial length are studied for the film thickness and pressure of ehl. For the real contact behaviors under the ehl conditions, multigrid and multi-level method is applied so that much higher loading conditions can be investigated. Several axial profiles of roller are investigated to verify how both ehl film and pressure are generated and some of them are recommended for the ehl contact condition.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2010년도 제35회 추계학술대회논문집
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• pp.519-522
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• 2010

블레이드 구조변형 효과를 고려한 스테이터-로터의 케스케이드 모델의 상호간섭의 평가를 위하여 유체-구조 연계 해석 시스템을 수행하였다. 고정된 스테이트와 회전하는 로터는 상호 간섭 영향이 유동해석에 고려되었다. 또한 정적인 유체-구조 연게해석과 수렴률 증진을 효과적으로 수행하기 위하여 큰 인공감쇠를 가지는 Newmark 시간 적분 기법을 적용하였다. 수치 실험을 통해 탄성축 위치에 따른 구조 변형 효과가 케스케이드 성능에 미치는 영향을 파악하였다. 구조 변형 효과가 고려된 경우 일반적인 강체 블레이드모델에 대한 성능 예측 결과와 다소 차이가 유발될 수 있음을 보였으며 공력 탄성학적 영향을 확인하였다.