• Journal of the Korean Society of Industry Convergence
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• v.15 no.1
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• pp.13-19
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• 2012

Due to a low stiffness of cranktrain and a failure experience from a history within short development time, a viscous torsional vibration damper was applied in order to reduce the torsional vibration and keep the high reliability for the durability of cranktrain system in the direct injection diesel engine. As an improvement of the crankshaft stiffness by increasing the diameter of main and pin journal, a rubber type damper could be considered. In this study, the control factors of rubber damper, the moment of inertia ring, stiffness of damper and damping coefficient of ring, were investigated by DFSS method through the analysis work and the measurement in the real engine condition.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.15 no.2
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• pp.57-65
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• 2016

The suspension system of a subway vehicle is composed of $1^{st}$ and $2^{nd}$ springs. The suspension system is the most important parameter in determining the vibration ride comfort. If the $1^{st}$ suspension spring is designed as a spring with strong stiffness to improve the running stability at high speed, it causes vehicle vibrations. In this paper, by testing and analyzing changes of the characteristics of Chevron springs, which have been the primary suspension springs used for about 20 years, we study how changing the characteristics affects vehicle acceleration and ride comfort. The lateral and longitudinal vibrational ride comfort index levels were lower than the vertical ones. Therefore, as increasing the stiffness of Chevron springs has the greatest effect on the vertical vibrational ride comfort index level, a countermeasure for vertical vibration reduction is needed when the stiffness increases owing to aging. Finally, maintenance guidelines, including the replacement time for the Chevron rubber, were proposed based on these findings.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.6
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• pp.17-23
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• 2006

Rubber materials have the nonlinear, large deformation and viscoelastic behavior. W.D. Kim et al. studied these characteristics through the static, fatigue, dynamic, aging and viscoelastic test. This paper discussed that the properties of engine mounting rubber, such as static stiffness, fatigue life and damping factor, are predicted based on CAE by using material properties acquired by the report of Kim et al. In result, the static stiffness of engine mounting rubber is predicted approximately in comparison with test value. Also, it was confirmed that the relationship of fatigue life and Green-Lagrange strain in specimen was the valid tool to predict the fatigue life of engine mounting rubber. From the results of transient viscoelastic analysis the damping factor changed rapidly at the range less than 8hz.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2002.03a
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• pp.373-382
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• 2002

In this paper, the characteristic dependencies of LRB(lead rubber bearing) were studied by various prototype tests on LRB for buildings. The characteristics of LRB were dependent on displacements, repeated cycles, frequencies, vertical pressures and temperatures. The prototype test showed that the displacement was the most governing factor influencing on characteristics of LRB. The effective stiffness and equivalent damping of LRB were decreased with large displacement, and increased with high frequency. After the repeated cyclic test with 50 cycles, the effective stiffness and equivalent damping of LRB were reduced by approximately 20% compared with those of the 1$^{st}$ cycle. The effective stiffness was decreased with high vertical pressure, while the equivalent damping was increased. In which, the equivalent damping was more dependent on the vertical pressure than the effective stiffness.s.

• Proceedings of the KSR Conference
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• 2009.05a
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• pp.599-605
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• 2009

The aim of the present study is the characteristics of bridge rubber pads and suggested how to determine the stiffness the pads. A disk bearing is operated as an elastic bearing in the vertical direction and is composed of a Polyether Urethane (polyurethane) disk for elastic support and Polytetrafluoroethylene (PTFE) to accommodate movement. Static tests are conducted in a laboratory to determine the static behavior of a Polyurethane disk. Finite Element (FE) analysis is also performed to verify the static performance. For dynamic behavior, four disk bearings having the identical Polyurethane disk used in the static tests are installed in a full size railway bridge and tested under a running locomotive. From the tests results, the static and dynamic stiffness of disk bearings are estimated and compared with each other. In the procedure to estimate the stiffness of a pad, the dead load(pre-load) of a bridge and live load of a vehicle are considered.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.4
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• pp.939-952
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• 1998

Rubber dampers are widely used to damp out vibrations generated in many mechanical elements because of the excellent damping characteristics of rubber. The damping characteristics of rubber is much dependent on temperature and frequency, which, in some cases, limit the effectiveness of rubber dampers. In this study, in order to increase the damping properties and axial and cross stiffnesses of rubber vibration dampers which are used in recording and regenerating devices, solid cores were inserted with interference tolerance in the rubber dampers. The damping characteristics of the rubber dampers with cores were investigated by experimentally and numerically using finite element method with respect to the interference tolerance, the core roughness, the materials of the core and the environmental temperature. From the experimental and theoretical investigations, it was found that the core in the rubber increased both the damping and stiffness of the damper. Also, it was found that the damping and stiffness of the rubber damper were much dependent on the temperature and frequency. Using the results of the experimental and theoretical investigations, the optimum design method for the cored rubber damper for recording and regenerating devices was developed.

• Journal of the Korean Society for Railway
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• v.17 no.4
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• pp.281-288
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• 2014

The objective of this study was to estimate the vibration reduction capacities of a floating track system using a resilient rubber mat, and to compare the results with the track support stiffness and track impact factor of a conventional slab track system by performing field tests using actual vehicles running along a service line. The theoretically designed track support stiffness and track impact factor were compared with the measured track support stiffness and track impact factor for each tested track. The calculated and measured track support stiffness of the floating track system were found to be similar, and the floating track system satisfied the design specifications of the track impact factor. The overall vibration level and track support stiffness of the floating track system were thereupon found to be significantly lower than those of the conventional slab track system. The experimental results thus showed that the vibration reduction effect of the floating track system is greater than that of the conventional slab track.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2A
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• pp.121-129
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• 2010

In this paper, the characteristics of high damping rubber bearing were studied through various prototype test. The characteristics of HDRB were dependent on displacements, repeated cycles, frequencies, vertical pressure, temperature, the capability of shear deformation and the vertical stiffness. The prototype test showed that the displacement was the most governing factor influencing on characteristics of HDRB. The effective stiffness and equivalent damping of HDRB were decreased with displacement, and increased with frequency. The effective stiffness was decreased with high vertical pressure, while the equivalent damping was increased. In which, the equivalent damping was more dependent on the vertical pressure than the effective stiffness. According to the results of this study, more careful examination is required to design the effective stiffness and equivalent damping ratio considering the dependencies of design displacement and exciting velocity.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.4
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• pp.39-49
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• 2002

In this paper, the characteristics of RB(rubber bearing) were studied by various prototype tests on RB with low hardness rubber. The characteristics of RB were tested on displacements, repeated cycles, frequencies, vertical pressures, temperature, vertical stiffness and the capability of shear deformation. The prototype test showed that the displacement and vertical pressures were the most governing factors influencing on characteristics of RB. The effective stiffness and equivalent damping of RB showed small increment in high frequency range. After the repeated cyclic test with 50's cycles, the effective stiffness and equivalent damping of RB were almost constant compared with those of the 1st cycles due to low hysteretic damping. The shear modulus of RB was reduced after large deformation, and this value of RB was partly recovered after 40 days. Finally, the shear failure test of RB was conducted, the prototype was failed over 490% of shear strain, and real size RB was failed over 430% of shear strain.

• Journal of the Korean Society for Railway
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• v.10 no.2 s.39
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• pp.211-216
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• 2007

Rubber components are widely used in many application such as vibration isolators, damping, ride quality. Rubber spring is used in primary suspension system for railway vehicle. Characteristics and useful life prediction of rubber spring was very important in design procedure to assure the safety and reliability. Non-linear properties of rubber material which are described as strain energy function are important parameter to design and evaluate of rubber spring. These are determined by physical tests which are uniaxial tension, equi-biaxial tension and pure shear test. The computer simulation was executed to predict and evaluate the load capacity and stiffness for rubber spring. In order to investigate the useful life, the acceleration test were carried out. Acceleration test results changes as the threshold are used for assessment of the useful life and time to threshold value were plotted against reciprocal of absolute temperature to give the Arrhenius plot. By using the acceleration test, several useful life prediction for rubber spring were proposed.