• Transactions of the Korean Society of Mechanical Engineers A
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• v.32 no.11
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• pp.930-936
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• 2008

This paper studies the effect of pad at initial stage and wear during braking on the dynamic contact pressure distribution. Wear is influenced by variable factor (contact pressure, sliding speed, radius, temperature) during dynamic braking and variation in contact pressure distribution. Many researchers have conducted complex eigenvalue analysis considering wear characteristic with Lim and Ashby wear map. The conventional analysis method is assumed the pad has smooth and flat surfaces. The purpose of this paper is to validate that wear rate induced by braking is considered for the precise squeal prediction. After obtaining pad wear from experiment, it is incorporated with FE model of brake system. Finally, the comparisons in fugitive nature of squeal will be carried out between the complex eigenvalue analysis and noise dynamometer experiment.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.05a
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• pp.460-465
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• 2002

The nonlinear vibration of the CRT shadow mask is analyzed in consideration of the V-shaped tension distribution and the effect of wire impact damping. The reduced order FEM model of the shadow mask is obtained from dynamic condensation for the mass and stiffness matrices. Damping wire is modeled using the lumped parameter method to effectively describe its contact interactions with the shadow mask. The nonlinear contact-impact model is composed of spring and damper elements, of which parameters are determined from the Hertzian contact theory and the restitution coefficient, respectively. The analysis model of the shadow mask with damping wires is experimentally verified through impact tests of shadow masks performed in a vacuum chamber. Using the validated analysis model of the shadow mask with damping wires, the‘design of experiments’technique is applied to search fur the optimal damping wire configuration so that the vibration attenuation of the shadow mask is maximized.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.05a
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• pp.1343-1347
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• 2006

Non-contact modal testing for longitudinal modes of a pipe is discussed in this work. The suggested method can generate and measure longitudinal vibrations without mechanical contact by using the coupling phenomenon between deformation and magnetic field, known as the magnetostrictive effect. This effect has been used to generate and measure ultrasonic waves, but seldom used to deal with audible vibrations. In this investigation, the validity of the developed method in a typical vibration frequency range is checked with an inconel pipe being used in nuclear power plants.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.9
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• pp.731-737
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• 2002

Nonlinear vibration of the CRT shadow mask with impact damping wires is analyzed in consideration of the mask tension distribution and the effect of wire impact damping. A reduced order FEM model of the shadow mask is obtained from dynamic condensation of the mass and stiffness matrices, and damping wire is modeled using the lumped parameter method to effectively describe its contact interactions with the shadow mask. The nonlinear contact-impact model is composed of spring and damper elements, of which parameters are determined from the Hertzian contact theory and the restitution coefficient, respectively. The analysis model of the shadow mask with damping wires is experimentally verified through impact tests of shadow masks performed in a vacuum chamber.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.2 s.119
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• pp.177-184
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• 2007

The purpose of this study is to investigate experimentally the characteristics of rotational, radial, and axial vibration for helical gears with different contact ratios. For this purpose, the gear box is specially designed and manufactured. Two helical gears with different face widths and reduction ratios are investigated. The gear vibration in each direction is measured by accelerometers attached to the gear body. Rotational vibration is the highest and radial vibration is the lowest in the gear frequencies. While the increase of rotational speed increases gear vibration, it does not always increase with torque. It is not also linearly related to the contact ratio. In addition, axial vibration is not proportional to rotational vibration.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.12 no.8
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• pp.639-647
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• 2002

The nonlinear vibration of the thin perforated plate is analyzed in consideration of the V-shaped tension distribution and the effect of wire impact damping. The reduced order FEM model of the tension plate is obtained from dynamic condensation for the mass and stiffness matrices. Tension wire is modeled using the lumped parameter method to effectively describe its contact interactions with the plate. The nonlinear contact-impact model is composed of spring and damper elements, of which parameters are determined from the Hertzian contact theory and the restitution coefficient, respectively. From the evaluation of the computational accuracy and computation time for the deduced impact stiffness and damping coefficient, we determined proper values for the simulation works, accounting for the computational accuracy as well as the computational efficiency. Finally we discussed the results of nonlinear nitration analysis for variations of their design parameters.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.1089-1092
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• 2004

This paper deals with the development of a contact-type counting device using a piezoelectric polymer film as a sensor. The piezoelectric and vibration characteristics of the film under a bending vibration were investigated theoretically and experimentally. A counting device, which includes filters, an amplifier, an analog-digital converter, and a display, was designed and fabricated. The performance of the piezoelectric polymer sensor was evaluated in the sense of the responses to contact force, contact frequency, and contact speed. The life and the temperature effect were also investigated for the piezoelectric film sensor.

• Journal of KSNVE
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• v.7 no.3
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• pp.499-509
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• 1997

During the process of oxide removal from work rolls in sheet metal manufacture, filamentary brushes frequently exhibit a bouncing or chatter behavior. The dynamics of this phenomenon is investigated through the development of expressions for the non-linear contact stiffness between the brush and the roll. With formulation of simple structural models, the time responses in the presence and absence of friction under random excitation are investigated. Possible solutions for the minimization or avoidance of this bouncing or chatter problem are also suggested.

• Proceedings of the KSME Conference
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• 2001.06b
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• pp.454-458
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• 2001

In this paper, contact between the coupler-roller and guide in elevator door mechanism is modeled and analyzed with DADS 3D program. The contact force of coupler-roller is an important factor for impact and noise reduction when doors of elevator are opened or closed. To minimize the maximum contact force, an optimal cam profile for the door guide is suggested. To find an optimal shape of the guide, several types of motion curve are tested with DADS contact module.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.4
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• pp.280-287
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• 2008

For the reduction of common-mode noise level in Indirect-contact ECG (IDC-ECG) measurement a driven-right-leg grounding method was a lied to the IDC-ECG. Because the IDC-ECG does not require any direct contact between the electrodes and the human skin. it is adequate for un-constraining long-term ECG measurement at home and its various applications are now under development. However, larger 60 Hz noise induced by power line a ears in IDC-BCG than in conventional ECG, that is a restriction of IDC-ECG a application. In this study, the driven-right-leg ground which has been used in conventional direct-contact ECG, was adapted to the IDC-ECG measurement by feedback of the inversion of amplified common-mode noise to the body through the conductive fertile laid on the chair seat By this study, indirect-contact driven-right-leg ground was developed and it was shown to work stably. It was shown that the level of 60Hz power line noise was reduced to about -40 dB when the driven-right-leg gain was 1000. This study shows that we can extend the upper limit of the frequency band of IDC-ECG to 100Hz from 30Hz which is conventional upper limit in IDC-ECG, and we can raise the ground impedance between the body and conductive textile. So it is expected that the application area of the IDC-ECG will be extended by the results of this study.