• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.6
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• pp.70-78
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• 2000

A balanced vane pump for the use of automotive power steering systems generates a flow ripple which is imposed upon the mean flow rate. The flow ripple interacts with the characteristics of the connected pipes, valves and steering gear in a complex manner to produce a pressure ripple, also known as fluid-borne noise. In order to reduce vibration level and produce quieter and more reliable power steering systems, it is important to measure the flow ripple produced by a pump with high accuracy and fast response. In this paper, the flow ripple generated by a vane pump in automotive power steering systems is measured by the remote instantaneous flow rate measurement method (RIFM) using hydraulic pipeline dynamics. In experiment, flow and pressure ripple wave forms are measured under various operating conditions. Also, the parameters affected upon the flow and pressure ripple are investigated by the frequency analysis.

• Structural Engineering and Mechanics
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• v.53 no.5
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• pp.1031-1049
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• 2015

This paper highlights the role of innovative vibration control system based on two promising properties in a parallel configuration. Hybrid device consists of two main components; recentering wires of shape memory alloy (SMA) and steel pipe section as an energy dissipater element. This approach concentrates damage in the steel pipe and prevents the main structural members from yielding. By regulation of the main adjustable design parameter, an optimum performance of the device is obtained. The effectiveness of the device in passive control of structures is evaluated through nonlinear time history analyses of a five-story steel frame with and without the hybrid device. Comparing the results proves that the hybrid device has a considerable potential to mitigate the residual drift ratio, peak absolute acceleration and peak interstory drift of the structure.

• Structural Engineering and Mechanics
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• v.46 no.1
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• pp.137-151
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• 2013

In this paper, two new methods called Improved Amplitude-Frequency Formulation (IAFF) and Energy Balance Method (EBM) are applied to solve high nonlinear oscillators. Two cases are given to illustrate the effectiveness and the convenience of these methods. The results of Improved Amplitude-Frequency Formulation are compared with those of EBM. The comparison of the results obtained using these methods reveal that IAFF and EBM are very accurate and can therefore be found widely applicable in engineering and other science. Finally, to demonstrate the validity of the proposed methods, the response of the oscillators, which were obtained from analytical solutions, have been shown graphically and compared with each other.

• Interaction and multiscale mechanics
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• v.1 no.1
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• pp.53-81
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• 2008

The theory of microlocal analysis of hyperbolic partial differential equations shows that the energy density associated to their high-frequency solutions satisfies transport equations, or radiative transfer equations for randomly heterogeneous materials with correlation lengths comparable to the (small) wavelength. The main limitation to the existing developments is the consideration of boundary or interface conditions for the energy and power flow densities. This paper deals with the high-frequency transport regime in coupled heterogeneous structures. An analytical model for the derivation of high-frequency power flow reflection/transmission coefficients at a beam or a plate junction is proposed. These results may be used in subsequent computations to solve numerically the transport equations for coupled systems, including interface conditions. Applications of this research concern the prediction of the transient response of slender structures impacted by acoustic or mechanical shocks.

• Journal of the korean Society of Automotive Engineers
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• v.15 no.1
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• pp.73-80
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• 1993

In this study, 3-dimensional linear and non-linear vehicle models are proposed to improve ride quality. The simulations of a vehicle passing over a bump were performed with those two vehicle models. The dynamic responses of the models were analyzed in time-domain and frequency-domain. Then, discomforts in each vibration axis and the combined-axes were evaluated based on the vibrations of the proposed models. The actual vehicle test results in time domain and frequency domain. Also, the discomfort values were compared. Then the validity of those two models were verified. Also, the design parameters of the suspension system are proposed for improving the ride quality.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.9 no.4
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• pp.859-864
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• 2008

The dynamic interaction between the moving mass and the rotating Timoshenko shaft is investigated. The moving speed of the mass is presented by a constraint equation related to the rotating speed of the shaft. The dimensionless equations of motion for the rotating shaft with a moving mass by using the Timoshenko's beam theory. The dynamic responses of this system are studied. influences of dimensionless parameters such as the rotating speed ratio. the Rayleigh coefficient and the dimensionless axial force are discussed on the transient response and the maximum deflection of the moving system.

• Computational Structural Engineering
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• v.9 no.1
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• pp.47-54
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• 1996

The Control Element Assembly(CEA) shroud is one of the most important components in the reactor vessel internals for the nuclear power plant. Because of the severe modification from its original design the structural integrity of this component has been questioned. In an attempt to resolve this question, the response of the CEA shroud to a random loading in the actual operating condition is calculated analytically and experimentally and compared to the code allowables to show that it is structurally adequate and acceptable for the long term operation.

• Smart Structures and Systems
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• v.17 no.3
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• pp.431-444
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• 2016

This paper was written in the context of a benchmark study promoted by The Hong Kong Polytechnic University using data samples collected in an instrumented cable-stayed bridge. The main goal of the benchmark test was to study the identification of the bridge modes of vibration under different wind conditions. In this contribution, the tools developed at ViBest/FEUP for automated data processing of setups collected by dynamic monitoring systems are presented and applied to the data made available in the context of the benchmark study. The applied tools are based on parametric output only modal identification methods combined with clustering algorithms. The obtained results demonstrate that the proposed algorithms succeeded to automatically identify the modes with relevant contribution for the bridge response under different wind conditions.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.547-550
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• 1997

The dynamic behavior of rotor-bearing system has been investigated using finite element method. A procedure is presented for dynamic modeling of rotor-bearing system which consist of shaft elements, rigid disk, flexible bearing and support structures. A finite element model including the effects of rotary inertia, shear deformation, gyroscopic moments is developed. Linear stiffness and damping coefficient are calculated for 3 lobe sleeve bearing. The whirl frequency, mode shape, stability and unbalance response of rotor system included effect of bearing coefficient and support structures are calculated.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.6
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• pp.1426-1435
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• 1990

Dynamic behaviour of point tracking system mounted on flying vehicle shaking in a random manner is investigated and the system dynamic is represented by nonlinear stochastic equations. 2-D.O.F. nonlinear stochastic equations are successfully transformed to linear stochastic equations via equivalent linearization procedure in stochastic sense. Newly developed hybrid technique is used to obtain response statistics of the system under non-white random excitation, which is proved to be remarkably accurate one by performing stochastic simulation.