• 한국자동차공학회논문집
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• 제3권4호
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• pp.19-29
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• 1995

This paper discusses the stick-slip phenomenon of the driveline system of a vehicle in consideration of friction. Friction is operated on the between of flywheel and clutch disk. The expressions for obtaining the results have been derived from the equation of motion of a three degree of freedom frictional torsion vibration system which is made up driving part(engine, flywheel), driven part(clutch, transmission) and dynamic load part(vehicle body) by applying forth-order Rungekutta method. It was found that the great affect parameters of the stick-slip or stick motion were surface pressure force between flywheel and clutch disk, time decay parameter of surface pressure force and 1st torsional spring constant of clutch disk when driveline system had been affected by friction force. The results of this study can be used as basic design data of the clutch system for the ride quality improvement of a car.

• Tribology and Lubricants
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• 제32권4호
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• pp.107-112
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• 2016

This paper presents a rotordynamic analysis of the reduction gear system applied to the 250 kW super critical CO₂ cycle. The reduction gear system consists of an input shaft, intermediate shaft, and output shaft. Because of the high rotating speed of the input shaft, we install tilting pad bearings, rolloer bearings support the intermediate and output shafts. To predict the tilting pad bearing performance, we calculate the applied loads to the tilting pad bearings by considering the reaction forces from the gear. In the rotordynamic analysis, gear mesh stiffness results in a coupling effect between the lateral and torsional vibrations. The predicted Campbell diagram shows that there is not a critical speed lower than the rated speed of 30,000 rpm of the input shaft. The predicted modes on the critical speeds are the combined bending modes of the intermediate and output shaft, and the lateral vibrations dominate when compared to the torsional vibrations. The damped natural frequency does not strongly depend on the rotating speeds, owing to the relatively low rotating speed of the intermediate and output shaft and constant stiffness of the roller bearing. In addition, the logarithmic decrements of all the modes are positive; therefore all modes are stable.

• 대한기계학회논문집
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• 제10권5호
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• pp.593-600
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• 1986

본 연구에서는 베어링과 같은 기계 회전부품의 정밀진동분석을 위한 구동장치 로서 평판 자기결합기를 갖는 회전장치를 제작하였다. 이 회전장치의 진동특성을 고 찰하기 위해 Weinmann 등의 연구결과에 따라 자기 결합기의 전달 토오크가 그대로 피 동축에 전달됨을 이용하여 이론전개를 하였으며 이 결과를 실험치와 비교하였다.

• Geomechanics and Engineering
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• 제5권1호
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• pp.71-86
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• 2013

For rock materials, a transversely isotropic failure criterion established through the extended Lade-Duncan failure criterion incorporating an anisotropic state scalar parameter, which is a joint invariant of deviatoric microstructure fabric tensor and normalized deviatoric stress tensor, is verified with the results of triaxial compressive data on Tournemire shale. For torsional shear mode with $0{\leq}b{\leq}0.75$, rock shear strengths decrease with ${\alpha}$ increasing until the rock shear strength approaches minimum value at ${\alpha}{\approx}40^{\circ}$, and after this point, the rock shear strengths increase as ${\alpha}$ increases further. For the torsional shear mode with b > 0.75, rock shear strengths are almost constant for ${\alpha}{\leq}40^{\circ}$, but it increases with increase in ${\alpha}$ afterwards. The rock shear strength variation against ${\alpha}$ agrees with shear strength changing tendency of heavily OCR natural London Clays tested before. Prediction results show that the transversely isotropic failure criterion proposed in the paper is reasonable.

• 동력기계공학회지
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• 제12권2호
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• pp.23-28
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• 2008

The primary objective of this study is to truly understand reaction force be due to engine exciting force. Exciting forces of the engine apply a source of the vehicle NVH(Noise, Vibration, Harshness). To understand reaction force was applied MSC.Nastran software. Analyzed frequency response analysis of powertrain mount system. First, engine exciting force was applied field function. Also nonlinear characteristics was applied field function : such as dynamic spring constant and loss factor. And nonlinear characteristics was applied CBUSH. Generally characteristics of rubber mount is constant frequency. But characteristics of hydraulic mount depend to frequency. Therefore nonlinear characteristics was applied. Powertrain mounting system be influenced by powertrain specification, mount position, mount angle and mount characteristics etc. In this study, we was analyzed effects of powertrain mounting system. And we was varied dynamics spring constant and loss factor of mounts.

• 예술인문사회 융합 멀티미디어 논문지
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• 제7권3호
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• pp.411-419
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• 2017

기하학적으로 급격히 변화되는 부분의 응력집중은 봉에 작용하는 평균응력 보다 큰 응력이 작용하여, 봉의 파손을 발생시키는 원인 중 하나이다. 구멍과 단이 있는 봉이 비틀림 하중을 받았을 경우, 응력집중 변화에 대해 구멍의 위치에 따른 관계를 규명하였다. 본 논문에서는 범용 유한요소 소프트웨어인 ANSYS Workbench를 통해 구멍의 위치가 다른 봉의 응력을 해석하였다. 해석된 결과, 필렛과 구멍이 서로 가까울수록 응력이 증가되는 것으로 나타났다. 또한, 본 해석에 사용된 모델에서는 구멍이 필렛으로부터 특정거리(L : -100 mm ~ 300 mm) 이상에서는 구멍과 필렛에서 발생한 최대 등가응력이 거의 일정하였다. 반면에, 구멍이 필렛으로부터 특정거리(L : -100 mm ~ 300 mm) 이하에서는 구멍과 필렛에서 발생한 최대 등가응력이 급격하게 증가 및 감소하는 변화를 보였다. 그리고 특정거리(L : -100 mm ~ 300 mm) 이하에서 구멍과 필렛에서 발생한 등가응력의 차이가 발생하는 지점을 확인할 수 있었다. 본 논문의 해석 결과는 비틀림을 받는 단이 있는 봉에서 구멍 위치를 선정할 때, 사용 될 수 있다.

• 산업경영시스템학회지
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• 제20권44호
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• pp.497-506
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• 1997

In this paper described is the software developed to calculate the physical properties of arbitrary section shape. The software consists of arbitrary section display module(ASDM) and section property calculation module(SPCM). ASDM defines and displays the shape of arbitrary section and SPCM calculates its properties such as area, centroid, moment of inertia, torsional constant, etc.. In many cases, calculation of section properties is not easy because user has to define the vertex coordinates which are difficult to do so in the case of arbitrary section. In the developed software, however, since user is asked to define only points of central lines and thickness of arbitrary section, the calculattion task of arbitrary section is very effective.

• The Journal of the Acoustical Society of Korea
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• 제21권2E호
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• pp.63-70
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• 2002

In this paper, an optimization technique for thin walled beams of vehicle body structure is proposed. Stiffness of thin walled beam structure is characterized by the thickness and typical section shape of the beam structure. Approximate functions for the section properties such as area, area moment of inertia, and torsional constant are derived by using the response surface method. The approximate functions can be used for the optimal design of the vehicle body that consists of complicated thin walled beams. A passenger car body structure is optimized to demonstrate the proposed technique.

• Macromolecular Research
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• 제15권6호
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• pp.491-497
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• 2007

NPT Monte Carlo simulations were performed to calculate the molecular properties of syndiotactic poly(vinyl chloride) (PVC) and syndiotactic poly(vinyl alcohol) (PVA) melts using the configurational bias Monte Carlo move, concerted rotation, reptation, and volume fluctuation. The density, mean square backbone end-to-end distance, mean square radius of gyration, fractional free-volume distribution, distribution of torsional angles, small molecule solubility constant, and radial distribution function of PVC at 0.1 MPa and above the glass transition temperature were calculated/measured, and those of PVA were calculated. The calculated results were compared with the corresponding experimental data and discussed. The calculated densities of PVC and PVA were smaller than the experimental values, probably due to the very low molecular weight of the model polymer used in the simulation. The fractional free-volume distribution and radial distribution function for PVC and PVA were nearly independent of temperature.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 1999년도 봄 학술발표회 논문집
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• pp.327-334
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• 1999

Steel box girders are popular to the Practicing engineers for the its large Pure torsional constant. But closed box girders at-e susceptible to the eccentric loading due to the distortion of the cross section. Distorton of the box girder develops the warping normal stress and transverse flexural stress in the cross section and their magnitudes can be large unless internal diaphragms are installed sufficiently. In this study, stiffness matrix and equivalent nodal force vector are formulated on the basis of displacement method. Shape functions are directly derived from the homogeneous solution of the governing differential equation of the distortion. New finite element formulations were coded into a computer program. Several numerical examples were presented to show the validity of developed program.