• 한국구조물진단유지관리공학회 논문집
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• 제26권4호
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• pp.1-10
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• 2022

이 연구에서는 강재 스프링을 감쇠 장치로써 사용 가능성을 평가하기 위해서, 강재 스프링의 인장 및 반복하중 실험을 수행하였다. 주요 실험변수는 강재의 종류(SAE9254 및 SS275), 스프링상수(700 N/mm, 1,000 N/mm 및 1,400 N/mm) 및 SAE9254의 열처리 유·무이다. 인장 실험 결과, SAE9254로 제작된 강재 스프링의 설계 스프링상수와 측정 스프링상수의 비는 1.08 ~ 1.13이며, SS275로 제작된 강재 스프링의 설계 스프링상수와 측정 스프링상수의 비는 0.86 ~ 0.97로 측정되었다. 항복 이후 열처리 유·무에 따른 SAE9254로 제작된 스프링의 하중-변위 관계 기울기는 약 240 ~ 251 kN/mm 및 92 N/mm 이었으며, SS275로 제작된 스프링의 하중-변위 관계 기울기는 거의 0이었다. 반복하중 실험 결과에서 모든 실험체는 KDS 41 17 00 (2019)에서 요구하는 변위 의존형 감쇠 장치의 적합 조건인 변위 원점에서의 하중 조건, 최대변위에서 하중 조건 그리고 에너지 소산 능력 조건을 모두 만족하였다. 그리고 열처리 안 된 SAE9254 및 SS275로 제작된 강재 스프링의 등가 감쇠비는 열처리 된 SAE9254로 제작된 스프링에 비해 각각 약 2.8배 및 1.9배 높은 수준이었다.

• Tribology and Lubricants
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• 제16권2호
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• pp.75-83
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• 2000

The present paper proposes a new type of an electro-rheological squeeze film damper (ER SFD) of which the damping capacity can be controlled by the application of electric field. The new ER .SFD- is sealed with slotted rings having electrodes at the inside of the constant gap. The ER SFD can provent the problem of electric short which might be occurred in a previous ER SFD. Reynolds lubrication equation for a Newtonian fluid and the end leakage equation for ER fluids are numerically solved to get the pressure distributions and the damping coefficients of the ER SFD. The results show that the damping coefficients greatly increase with increasing the yield shear stress of ER fluid. In addition, the unbalance response analysis of a flexible rotor supported on the new ER SFD implies that the rotor system can be operated with the minimum of rotor amplitude and force transmissibility by controlling the yield shear stress of ER fluids properly.

• 제어로봇시스템학회논문지
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• 제16권11호
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• pp.1096-1103
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• 2010

This paper proposes CDC (Continuous Damping Control) algorithm and verifies in multi-body dynamic vehicle. In order to distinguish a road profile on driving, waviness calculated by the filtered vertical-accelerations of sprung and unsprung masses is introduced. Sky-hook control is used at a low waviness road and constant damping level control is used at a high waviness road, where the hard damping level is determined by waviness, roll rate, acceleration, and deceleration. The damping levels of ride, anti-roll, anti-squat, and anti-dive modules are calculated by tuning parameters which is dependent upon vehicle velocity. Therefore this high tunable algorithm is useful to improve the ride and handling performance under various driving conditions. In the simulations, tire and dampers are modelled by SWIFT (Short Wavelength Intermediate Frequency Tire) model and 1st order delay model, and results are compared with conventional damper's.

• Journal of Biosystems Engineering
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• 제29권5호
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• pp.385-394
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• 2004

The objectives of this study were to investigate the effectiveness of rubber as an engine mount of walking-type cultivators and to determine its optimal spring constant and damping coefficient using a dynamic simulation of the engine mount system. Four different types of rubber mounts were tested to determine their spring constants and damping coefficients, and the best type was selected for the isolation of the engine vibrations transmitted to the handle. The total vibration levels transmitted to the handle when the rubber mounts weren't installed were 17.52 $m/s^2$. The total vibration levels transmitted to the handle when the rubber mounts were installed were 10.69 $m/s^2$ for Stripe 1, 11.33$m/s^2$ for Stripe 2, 10.92$m/s^2$ for Stripe 3 and 14.19$m/s^2$ for Hive, respectively, resulting in an average of $30\%$ reduction when compared with that without the engine mount. A dynamic model of the cultivator's engine-mount system and its simulation program were developed and verified. A method was proposed to determine the optimal spring constant and damping coefficient of the engine-mount system. It was found from the simulation that a spring constant of 4,100 kN/m and the largest damping coefficient were the most effective for the vibration isolation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.402-403
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• 2014

Damping of multi-span tube with loose supports according to the finite support clearances is investigated through the experimental modal analysis. Loose intermediate support leads to strong nonlinearity in tube dynamics, provides statistical nature, and increases tube damping through impacting and friction at the supports. Fraction of critical damping was estimated by the modal curve fitting to parameter estimation from the measured frequency response functions. Magnitude of random excitation force, which can reproduce the in-situ excitation in operating environment, was maintained as constant value with a fine tolerance during vibration testing. Range of input force was carefully selected to cover from the low magnitude excitation for linearly behaved tube motion to high magnitude of force for nonlinearly-behaved tube motion. Estimated critical damping ratio shows scatters in data and tends to increase as the magnitude of rising force and decrease with upward frequency variation. Larger size of support gap increases multi-span tube damping for high magnitude of excitation.

• Journal of Welding and Joining
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• 제14권6호
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• pp.109-118
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• 1996

Al$_2$O$_3$-TiO$_2$powders of six different compositions were plasma-sprayed on Ti substrate. The spray powders and the spray coated layers were analysed and compared using SEM and X-RD. The elastic properties (specific elastic constant and damping coefficient) of the coated specimens were measured in order to select the optimum composition range of ceramics for use in a speaker diaphragm. A correlation between the microstructure and elastic properties was also investigated. When $Al_2$O$_3$powders with 0- 13% TiO$_2$were plasma sprayed, the coated layers were composed of metastable y-Al$_2$O$_3$with small amount of $\alpha$-Al$_2$O$_3$and the content of $\alpha$-Al$_2$O$_3$was increased with TiO$_2$content. Specific elastic constant was rapidly increased with 2 and 13% TiO$_2$addition to $Al_2$O$_3$. The internal damping was nearly unchanged with TiO$_2$content The specific elastic constant seemed to be dependent on the content of $\alpha$-Al$_2$O$_3$in the coated layer.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1350-1353
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• 2007

An experimental method based on contact resonance is developed to extract the contact parameters of mechanical joints under various clamped conditions. Mechanical joint parameters of shear contact stiffness and damping were extracted for different physical joint parameters such as surface finish of the mating surfaces, the presence of lubrication, the effect of the clamping pressure, and shear load. It was found that the shear contact stiffness values decreased with increasing clamping load and increased with increasing shear loading. Contact damping ratio values were almost constant with clamping load, but decreased with increasing shear load. Moreover, rough surfaces exhibited the highest shear stiffness and contact damping compared to smooth surfaces.

• 한국정밀공학회지
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• 제19권11호
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• pp.37-45
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• 2002

This paper presents the field-dependent Bingham characteristics and damping force control of an electro-rheological (ER) fluid under squeeze mode operation. The squeeze force of the ER fluid due to the imposed electric field is analyzed and an appropriate size of the disk-type electrode is devised. On the basis of the theoretical model of the ER fluid under squeeze mode operation, the yield stress and response speed of the ER fluid are distilled from the time responses of squeeze force to the step electric potentials. Measured squeeze forces under various excitation conditions are compared with the predicted ones from Bingham model and time constant obtained at the transient response test. In addition, the controllability of the field-dependent damping force of the ER fluid under squeeze mode is experimentally demonstrated by implementing simple PID controller.

• Tribology and Lubricants
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• 제24권3호
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• pp.147-153
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• 2008

The effect of oil supply pressure on the performance of vapor cavitated short squeeze film dampers is examined. Vapor cavitation is characterized by film rupture occurring as a result of evaporating oils. The pressure of vapor cavity in the film is almost zero in absolute pressure and nearly constant. Pan's model about the shape of vapor cavity is utilized for studying the effect of vapor cavitation on the damping capability of a short squeeze film damper. As the level of oil supply pressure is increasing, vapor cavitation is suppressed so that the direct damping coefficient increases and the cross coupled damping coefficient decreases. Futhermore, the analysis of the unbalance responses of a rigid rotor supported on cavitated squeeze film dampers shows that a significant reduction in rotor amplitude and force transmissibility is possible by controlling the oil supply pressure into short squeeze film dampers.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1404-1408
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• 2006

In this paper, a hybrid-type vibration isolator which has air chamber(spring) and viscous damper in series is developed. The developed vibration isolator is designed to perform 3 following functions : spring function for normal operating conditions, damping function to reduce an impact for sudden move of upper beam, and finally leveling function. Based on the given natural frequency and damping factor, the design procedure is proposed. The performance of the developed isolator is tested by measuring stiffness and damping.