• 한국소음진동공학회논문집
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• 제16권12호
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• pp.1215-1223
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• 2006

A leaf spring suspension has been widely used since it can carry big load and its simplicity. But one major drawback is the poor ride performance because of the friction in the system and the high stiffness coefficient. To overcome these, an air spring suspension can be used. The air spring suspension system can improve the ride of the heavy vehicle significantly and also it can adjust the height to the loading and unloading. The road tests for the truck with the leaf spring suspension and air spring suspension are performed to compare the ride quality of the two systems. To develop the air spring suspension system tailored to the target truck, chassis development procedure using CAE has been applied.

• KSTLE International Journal
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• 제6권1호
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• pp.13-16
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• 2005

Friction characteristics at nano-scale of self-assembled monolayers (SAMs) having different chain lengths and end groups were experimentally studied.51 order to understand the effect of the chain length and end group on the nano-scalefriction: (1) two different SAMs of shorter chain lengths with different end groups such as methyl and phenyl groups, and (2)four different kinds of SAMs having long chain lengths (C10) with end groups of fluorine and hydrogen were coated on siliconwafer (100) by dipping method and Chemical Vapour Deposition (CVD) technique. Their nano-scale friction was measuredusing an Atomic Force Microscopy (AFM) in the range of 0-40 nN normal loads. Measurements were conducted at the scanning speed of 2 $mu$m/s for the scan size of 1$mu$m x 1 $mu$m using a contact mode type $Si_3N_4$ tip (NPS 20) that had a nominal spring constant0.58 N/m. All experiments were conducted at anlbient temperature (24 $pm$1$circ$C) and relative humidity (45 $pm$ 5%). Results showedthat the friction force increased with applied normal load for all samples, and that the silicon wafer exhibited highest frictionwhen compared to SAMs. While friction was affected by the inherent adhesion in silicon wafer, it was influenced by the chainlength and end group in the SAMs. It was observed that the nano-friction decreased with the chain length in SAMs. In the caseof monolayers with shorter length, the one with the phenyl group exhibited higher friction owing to the presence of benBenerings that are stiffer in nature. In the case of SAMs with longer chain length, those with fluorine showed friction values relativelyhigher than those of hydrogen. The increase in friction due to the presence of fluorine group has been discussed with respect tothe siBe of the fluorine atom.

• Journal of Mechanical Science and Technology
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• 제20권10호
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• pp.1638-1645
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• 2006

This paper proposes a modeling technique which is able to not only reliably and easily represent the hysteretic characteristics but also analyze the dynamic stress of a taper leaf spring. The flexible multi-body dynamic model of the taper leaf spring is developed by interfacing the finite element model and computation model of the taper leaf spring. Rigid dummy parts are attached at the places where a finite element leaf model is in contact with an adjacent one in order to apply contact model. Friction is defined in the contact model to represent the hysteretic phenomenon of the taper leaf spring. The test of the taper leaf spring is conducted for the validation of the reliability of the flexible multi-body dynamic model of the taper leaf spring developed in this paper. The test is started at an unloaded state with the excitation amplitude of $1{\sim}2mm/sec$ and frequency of 132 mm. First, the simulation is conducted with the same condition as the test. Then, the simulations are conducted with various amplitudes in a loaded state. The hysteretic diagram from the test is compared with the ones from the simulation for the validation of the reliability of the model. The dynamic stress analysis of the taper leaf spring is also conducted with the developed flexible multi-body dynamic model under a dynamic loading condition.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 1995년도 추계학술대회 논문집
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• pp.538-541
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• 1995

Joint flexibilities and frictional uncertainties are known to be a major cause of performance degration in motion control systems. This paper investigates the modeling and compensation of these undesired effects. A hybrid controller, which consists of a predictive controller and a neural network controller, is designed to overcome these undesired effects. Also learning scheme for friction uncertainies, which don't interfere with feedback controller dynamics, is discussed. Through simulation works with two inetia-torsional spring system having Coulomb friction, the effectiveness of the proposed hybrid controller was tested. The proposed predictive & neural network hybrid controller shows better performance over one when only predictive controller used.

• KSTLE International Journal
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• 제2권1호
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• pp.75-79
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• 2001

This paper is a report on the parametric study of the friction characteristics on the direct acting type OHC valve train system. The numerical simulation was performed by using the IV-TAP. Dynamic analysis by using the lumped mass method was previously performed to define the acting load. The friction characteristics were analyzed by using the partial asperity contact model. The effects of operating conditions and major design parameters on the total driving torque were investigated. From the analytical prediction, it is found that valve spring stillness, surface roughness, and base circle radius are the main factors to reduce the frictional loss on the valve train system.

• 대한기계학회논문집
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• 제16권8호
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• pp.1513-1518
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• 1992

본 연구에서는 참고문헌 8의 해법을 응용하여 다발 보의 마찰 접촉 문제를 푸는 방법에 대하여 설명한다. 각 보 요소의 변형은 미소변형 및 Bernoulli-Euler이 론을 이용하여 계산하며, 마찰력 계산을 위하여는 Coulomb 마찰 법칙을 이용한다. 보의 종류와 형상 및 보를 묶는 클램프(clamp)의 종류에 따라서 수 많은 종류의 스프 링이 얻어 질 수 있다. 여기에서는 편의상 보 다발이 클램프에 의하여 강하게 묶여 있으며, 그 묶인 점에서는 각 보의 법선 방향(normal direction) 상대 운동은 없는 것 으로 간주한다.

• 한국음향학회지
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• 제15권2호
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• pp.33-39
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• 1996

비선형 건마찰 감쇠를 가진 외팔보의 강제진동 응답을 건마찰 감쇠기와 가진력의 위치변화에 대하여 미끄러진 변위와 힘레벨을 수치해석하였다. 구성모드의 분석은 비선형 감쇠를 가진 계를 해석하기 위해 구속조건과 Lagrange 승수에 기초를 두고 분석하였다. 외팔보의 진동분석 결과 건마찰 감쇠기가 부착된 단순 지지된 보(beam)에서 보여진 응답특성과 유사한 특성이 나타났다.

• 한국자동차공학회논문집
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• 제12권4호
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• pp.146-153
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• 2004

This paper presents a discrete analysis approach to investigate the performance of dual mass flywheel (DMF). In the discrete analysis, arcspring installed between the flywheels is modeled as N- discrete elements. Each element consists of mass, spring and nonlinear friction element. LuGre friction model is used to describe nonlinear friction characteristic. Based on the dynamic models of the DMF, clutch, engine, manual transmission and vehicle, a DMF performance simulator is developed using MATLAB Simulink. Simulation results of the engine speed, driveshaft torque and vehicle velocity are compared with test results. It is found that the discrete DMF model describes the vehicle behavior closely, especially during the clutch actuation period.

• 소음진동
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• 제9권2호
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• pp.258-264
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• 1999

The purpose of this paper is to investigate the damping behavior of a flexible joint. The slip at a structrual joint is selected at the tips of two identical cantilever beams adjoining each other. Both the direction of normal force and its magnitude varies due to the global deformation of the structure from mode to mode in the friction model. The friction dependent on vibration displacements resultsin the same functional behavior of the hysteretic material damping. Linearized energy loss factors are obtained as functions of both linear and torsional spring stiffness for their groups of symmetric and anti-symmetric modes, respectively. Experimental measurements as made for comparisons with analytical estimations by controlling the magnitude of fastening torque in the fastener, Hi-Lite. Trends on damping levelsmeasured in a very common vibration test method make an excellent agreement on the estimated damping levels.

• 한국자동차공학회논문집
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• 제16권2호
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• pp.99-105
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• 2008

Multi-leaf springs are widely used for a major suspension component in many commercial vehicles. The modeling technique of multi-leaf springs is one of the most difficult problems in suspension modeling as the elements have complicated nonlinear characteristics such as a hysteresis behavior due to the friction. In this paper, hysteretic characteristics with the static and dynamic test are modeled and are simulated with three links and joints in MSC.ADAMS. Simulation results showed good agreements with test results. Using this methodology, it is expected that dynamic characteristics of suspension system with multi-leaf spring can be more accurately evaluated in vehicle dynamics.