• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.8
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• pp.773-778
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• 2009

Chevron rubber springs are used in primary suspensions for rail vehicle. Chevron rubber spring have function which reduce vibration and noise, support load carried in operation of rail vehicle. Prediction and evaluation of characteristics are very important in design procedure to assure the safety and reliability of the rubber spring. The computer simulation using the nonlinear finite element analysis program executed to predict and evaluate the load capacity and stiffness for the chevron spring. The non-linear properties of rubber which are described as strain energy functions are important parameters. These are determined by material tests which are uniaxial tension, equi-biaxial tension and shear test. The appropriate shape and material properties are proposed to adjust the required characteristics of rubber springs in the three modes of flexibility.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.6 no.3
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• pp.82-88
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• 1997

This paper derives the generalized stiffness to find dynamic characteristics and its derivatives of a continuous system. And a new sensitivity analysis method is presented by using the amount of change of generalized stiffness and vibrational mode caused by the variation of stiffness. In this paper, to get or detect appropriate results, cantilever beam and stepped beam and stepped beam are used. Deviations of sensitivity coefficient, natural frequency, and vibrational mode are calculated as result, and compared with the theoretical exact values.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.1643-1646
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• 2008

In this study, an elastic network model is established in order to find dominant factors which reflect thermostability of protein structures. The connections in the elastic network model are selected with respect to the free energy between alpha-carbons, which is representatives of residues in the elastic network model. We carried out normal mode analysis and compared eigenvalues of the stiffness matrix from the elastic network model. In most cases, thermophilic proteins are observed to have higher values of lowest natural frequency than mesophiles and psychrophiles have. As a result, the thermophiles are calculated to be stiffer than other proteins in view of dynamic vibration.

• 한국전산유체공학회:학술대회논문집
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• 1998.05a
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• pp.82-89
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• 1998

There are many moving-body problems to be solved, the solution of which necessary for proper design of flight vehicles in aerospace industry. Since a body moves relative to other bodies in the category of these problems, difficulty arises regarding both generation of computational grid around the body in motion and conservation of flow properties in the moving grid system. A few example could be store separation from the aircraft and relative vibration of multiple bodies in the high-speed flow passage. In this paper we report on the progress made in computing moving-body aerodynamics related with sabot separation characteristics. Conservative overlapping grid together with cell-merging-unmerging technique is used to solve the Euler equations for a body in high-speed motion. Carbuncle errors has to be removed before we obtain physically adequate solution. Two-dimensional application is reported here.

• Transactions of the Society of Information Storage Systems
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• v.1 no.1
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• pp.23-28
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• 2005

This paper investigates the effects of disk thickness and Pemto slider on PES(position error signal) for high TPI(track per inch) drives above 150kTPI at early stage of their development. In order to reduce the disk flutter which becomes a dominant contributor to the TMR, the thicker disks with both 63 and 69mi1 have been used. Also, PES of a Pemto slider with thinner thickness than Pico slider has been estimated to decrease the conversion factor of disk motion in axial direction to head off-track motion. A frequency-domain PES estimation and prediction tool has been developed via measurement of disk flutter and HSA(head stack assembly) forced vibration. It has been validated by the measured PES in drive level. Based on the model and measurement of disk flutter, PES of a drive with the thicker disk and Pemto slider is predicted and their impact is investigated.

• International Journal of Fluid Machinery and Systems
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• v.10 no.3
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• pp.307-317
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• 2017

In liquid-propellant rockets, POGO instability can occur, in which a fluctuation of propellant supply to the engine, a thrust fluctuation, and a structural vibration are coupled. For the prediction of this instability, it is required to provide dynamic characteristics of the pump represented as the transfer matrix correlating the upstream and downstream pressure and flow rate fluctuations. In the present study, the flow rate fluctuation is evaluated from the fluctuation of pressure difference at the different locations assuming that the fluctuation is caused by the inertia of the flow rate fluctuation. The experiments were performed in some flow conditions, and it was shown that the tendencies of dynamic characteristics are related to excitation frequencies, cavitation numbers and flow rate coefficients.

• Journal of the Korean Society for Precision Engineering
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• v.25 no.12
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• pp.20-26
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• 2008

• Journal of the Korean Society for Precision Engineering
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• v.25 no.4
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• pp.86-92
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• 2008

This paper is to investigate the behavior of linear static structure stress, the fatigue and experimental shock fracture far engine base in the Auxiliary Power Unit to resolve its restricted electrical power problem. The shock fracture test was experimentally made under MIL standard criteria. The numerical results by finite element method had a good agreement with those from the shock test. The design data of predicting the fracture at the initial crack and the damage behavior of structure with shock and vibration load in the battle field can be obtained from shock test. In the functional shock test, the crack at the side parts of the engine base was found at peak acceleration of 40g.

• Journal of KSNVE
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• v.7 no.5
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• pp.827-836
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• 1997

To suggest the standard of railroad noise and its measures and grasp its status 15 open sites of the Jungang. Taeback and Youngdong line in which the background noise level is very low and the railroad is at grade and 7 urban sites of the Kyungboo and Honam line were selected and the sound level which 373 trains passing through the former and 271 trains passing through the latter emitted was investigated. The community response of railroad noise was surveyed for apartment near wayside. Noise reduction of wall for apartment at the wayside was investigated. The prediction of electric train subway noise is derived for the environment impact assessment.

• Transactions of the Korean Society of Mechanical Engineers
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• v.13 no.1
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• pp.20-28
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• 1989

SEA(Statistical Energy Analysis) method has been applied to predict the sound radiation power from vibrating machinery. In this study, sound radiation power was predicted from coupled structures by transmission of vibration, which composed of two plates welded into an L shape. The predicted sound radiation power is in agreement within 2 or 3 dB on octave band comparing with values obtained from direct measurements. Also, in order to prove the validity of this method in changes of sound radiation power associated with modifications to structures, rubber pad was stuck on a plate. The results agree approximately within 3 or 5 dB. And SEA method is valuable for the optimal design to reduce the noise. Additionally, this paper suggests that the logarithmic decrement method is valid as the one for finding the loss factor.