• Journal of the Korean Society of Safety
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• v.17 no.3
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• pp.1-6
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• 2002

A dynamic characteristics of shock absorber in the various excitation is investigated experimentally. Work diagrams and characteristic curves are used as a experimental standard. The various excitation conditions temperature and noise are very important factors in associated with the reduction of damping force. It is found that the heat occurrence from shock absorber, the gas shock absorber is much higher than oil shock absorber and increased in high speed. As to the variation of damping force, there are no change when the speed is low but we fixed amount of variation by increasing speed and change of new and old decrease. The sound pressure of the swash noise from cycle of shock absorber, we compared with theory sound pressure by experiment.

• Wind and Structures
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• v.30 no.3
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• pp.245-260
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• 2020

Wind load and responses are the major factors which govern the design norms of tall buildings. Corner modification is one of the most commonly used minor shape modification measure which significantly reduces the wind load and responses. This study presents a comparison of wind load and pressure distribution on different corner modified (chamfered and rounded) Y plan shaped buildings. The numerical study is done by ANSYS CFX. Two turbulence models, k-epsilon and Shear Stress Transport (SST), are used in the simulation of the building and the data are compared with the previous experimental results in a similar flow condition. The variation of the flow patterns, distribution of pressure over the surfaces, force and moment coefficients are evaluated and the results are represented graphically to understand the extent of nonconformities due to corner modifications. Rounded corner shape is proving out to be more efficient in comparing to chamfered corner for wind load reduction. The maximum reduction in the maximum force and moment coefficient is about 21.1% and 19.2% for 50% rounded corner cut.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1111-1115
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• 2008

The relative magnitudes of the individual terms of the momentum equation are analyzed and compared by the analytical methods in open channel flow. The temporal variations of each term(local acceleration term, convective acceleration term, pressure force term, gravity force term, and friction force term) are analyzed for the influence factors to runoff expressed by the parameters of the momentum equation, stream slopes and roughness coefficients. The magnitudes of each term vary with the channel characteristics, especially when the roughness coefficients are dominant or for the mild stream slopes the pressure term can not be negligible. As a result of the characteristics of momentum equation in open channel flow, the acceleration terms are very small compared with the other terms. The magnitudes of local acceleration and convective acceleration offsets each other. The peak time of each term except the gravity term coincides with inflection point of the hydrograph rising limb each other.

• Tribology and Lubricants
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• v.6 no.2
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• pp.43-49
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• 1990

The Dynamic Behavior in line contacts between the vane tip and camring in an oil hydraulic vane pump with intravanes has been investigated. Variations of the radial acting force of a vane were calculated from previously measured results of dynamic infernal pressure in four chambers surrounding a vane, and variations of the behavior were estimated in both the rotational speed range from 1200 to 2700 rpm and in the delivery pressure range from 10 to 21Mpa. The results indicate the variations of the radial acting force. Under the standard operating condition (to 14 Mpa, 1800 rpm), the radial acting force on the vane is governed by internal dynamic pressures, but it is more influenced by rotating speed at higher than 2000 rpm relatively.

• Transactions of the Korean Society of Mechanical Engineers
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• v.18 no.6
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• pp.1510-1519
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• 1994

It is important to understand the friction characteristics between piston-ring assembly and cylinder wall for the friction loss reduction as well as the solution of problem such as scuffing wear and oil consumption. A new system was developed for the piston-ring assembly friction force measurement. This system was applied to the friction force measurement to find its functional relationship with variables such as engine speed, oil viscosity, and engine load. The friction mean effective pressure(fmep) was found to have a linear relationship with$(\vpsilon{U})^{0.42}$ under motering and with$(\vpsilon{U})^{0.45}$ under firing operations, where $\vpsilon$ is the kinematic oil viscosity and U is mean piston speed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.498-501
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• 2000

Air dynamic bearings are inherently unstable in dynamic behavior due to the varying angle of a force produced and the nonlinear characteristics of stiffness. In this study, such dynamic behavior is obtained and compared with experimental results. A body axis coordinate system is employed to avoid the change of a moment of inertia. FDM is used to calculate the pressure distribution on the bearing surface and then the force acting on the rotor was calculated by integrating the pressure distribution. By integrating accelerations which are calculated from the equations of motion using the 4th order Runge-Kutta method, the pose of the bearing at each time step is obtained.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.04a
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• pp.140-144
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• 1997

Although the cone type venturi flow meter is superior to another differential pressure type flow meter in precision, the venturi is installed at the pipe as an L beam, so that the dynamic load due to drag force and flow-induced force is generated in the flow meter. In this paper we propose a methodology to evaluate this dynamic load directly by using stain-gages attached on the venturi and we discuss about the dynamic characteristics on the basis of flow-induced vibration theory.

• Proceedings of the KSR Conference
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• 2005.05a
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• pp.103-108
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• 2005

Since the braking system of rolling stock is directly linked to it's safety, ensuring reliability of braking system and evaluation of performance of it are very important. To develope the performance of braking system, it is required advanced technology and gradually various factors in the field test result. This study is designed to analyze the air pressure control about braking force in rolling stock, also, by comparing braking force of KTX with that of high speed train. This paper suggests to establish a method of computation of braking force form the air pressure control. And The high speed train researches into patterns of braking system such as the train of speed up and introduction of electric and pneumatic braking system.

• Journal of Drive and Control
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• v.9 no.2
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• pp.8-14
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• 2012

Electro-hydraulic spring return actuator(ESRA) is utilized for air conditioning facilities in a nuclear power plant. It features self-contained, hydraulic power that is integrally coupled to a single acting hydraulic cylinder and provides efficient and precise linear control of valves as well as return of the actuator to the de-energized position upon loss of power. In this paper, the algebraic equations of ESRA at steady-state have been developed for the analysis of static characteristics that includes control pressure and valve displacement of pressure reducing valve, flow force on flapper as well as its displacement over the entire operating range. Also, the effect of external load on piston deviation is investigated in terms of linear system analysis. The results of static characteristics show the unique feature of force balance mechanism and can be applied to the stable self-controlled mechanical system design of ESAR.

• International Journal of Naval Architecture and Ocean Engineering
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• v.11 no.2
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• pp.648-661
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• 2019

Thin fabric-based yacht sails have a cambered shape to generate lift force; however, their shape can be easily deformed by wind pressure and also affected by the deformation of the mast. These deformations can change the airflow characteristics over the sail. Therefore, Fluid-Structure Interaction (FSI) analysis is needed to evaluate the sail force precisely. In this study, airflow over the deformed sail and rig was studied using FSI. Elastic deformation of the sail and rig was obtained by an aerodynamic calculation under dynamic pressure loading on the sail surface. The effects of rig deformation on the aerodynamic performance of the sail were examined according to the rig type and mast flexibilities. As a result, the changes of lift force for a fractional type rig with a thin mast section were more significant than with a masthead rig.