• Journal of Theoretical and Applied Mechanics
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• 제3권1호
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• pp.34-44
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• 2002

Theoretical analysis Is carried out to identify the modal coupling effect between some particular acoustic modes of a vehicle compartment cavity and vibration modes of body panels like side doors, roof or floor. A simplified panel-cavity coupled model is investigated on the coupled resonance frequencies, modes and frequency response characteristics. Through parametric study, It Is possible to explain how the acoustic response of a coupled system will be determined by the vibration and acoustic property of the individual panel and cavity system. Full coupled system shows some interesting features different from those of the semi-coupled system In frequency, mode and acoustic response.

• 대한기계학회논문집A
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• 제25권12호
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• pp.2002-2008
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• 2001

Nonlinear vibration characteristics of a piezoelectric-type micro actuator used for hard disk drives are experimentally studied. The nonlinear characterisitics include hysteresis, superharmonic resonance, jump phenomenon, and shifting of natural frequencies. The vibration modes and frequencies of the commercial actuator of the Hutchinson's Magnum series are measured using a laser vibrometer. From harmonic excitation to the PZT acturator, we observe interesting hysteresis patterns with 3 times input frequency. It is shown that the micro actuator has the typical 3 times superhamonic resonances coupled to the first torsional and sway modes of the suspension.

• 제어로봇시스템학회논문지
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• 제5권5호
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• pp.540-549
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• 1999

In this paper, the vibration suppression scheme based on a model referece approach is proposed. The vibration results from the coupling of the system and its frequency are given by the mechanical factors. In the proposed scheme, a low frequency vibration mode is transferred to high one. And also its damping ratio can be increased without any mechanical redesign. Therefore, bandwidth and open loop gain of the plant are increased and the performance of the system can be improved. This paper analyzes the proposed vibration suppression scheme, which is compared with the conventional control scheme for mechanical resonance suppression. For proving the realistic validity, we apply the proposed scheme to a LOS(Line Of Sight) stabilization system which has vibration effect. Finally, the proposed scheme is verified through simulations and experiments.

• 대한기계학회논문집A
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• 제24권9호
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• pp.2220-2227
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• 2000

In this paper, dynamic photoelastic hybrid method is developed and its validity is certified. The dynamic photoelastic hybrid method can be used on the obtaining of dynamic stress intensity factors and dynamic stress components. The effect of crack length on the dynamic stress intensity factors is less than those on the static stress intensity factors. When structures are under the dynamic mixed mode load, dynamic stress intensity factor of mode I is almost produced. Dynamic loading device manufactured in this research can be used on the research of dynamic behavior when mechanical resonance is produced and when crack is propagated with the constant velocity.

• 대한기계학회논문집A
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• 제21권2호
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• pp.337-345
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• 1997

An analysis is presented for the response of a beam constrained by a nonlinear spring to a harmonic excitation. The system is governed by a linear partial differential equation with a nonlinear boundary condition. The method of multiple scales is used to reduce the nonlinear boundary value problem to a system of autonomous ordinary differential equations of the amplitudes and phases. The case of the third-order subharmonic resonance is considered in this study. The autonomous system is used to determine the steady-state responses and their stability.

• International Journal of Reliability and Applications
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• 제5권2호
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• pp.59-74
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• 2004

There are many uncertain parameters associated with vibration components. Their physical parameters, the machining quality of vibration components, and the applied load acting on them are all uncertain. As a result, the natural frequency and the fatigue limits are also uncertain variables. In this paper, we express these parameters of vibration components and the frequency zone of resonance through interval models; this way, the robust reliability of the vibration components is defined. The robust reliability model measures and assesses the reliability of vibration components. The robust reliability of a cantilever beam is evaluated as an example. The results show that this method is reasonable for robust reliability analysis of vibration components because it does not require a large amount of failure data, it avoids the evaluation of the probability density function, and the computation is simple.

• Journal of the Korean Physical Society
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• 제73권9호
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• pp.1399-1404
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• 2018

This study used an inductively coupled plasma (ICP) dry etching process with a metal amplitude mask to fabricate a double-side notched long-period fiber grating (DNLPFG) for loading sensing. The DNLPFG exhibited increasing resonance attenuation loss for a particular wavelength when subjected to loading. When the DNLPFG was subjected to force loading, the transmission spectra were changed, showing a with wavelength shift and resonance attenuation loss. The experimental results showed that the resonant dip of the DNLPFG increased with increasing loading. The maximum resonant dip of the $40-{\mu}m$ DNLPFG sensor was -26.522 dB under 0.049-N loading, and the largest force sensitivity was -436.664 dB/N. The results demonstrate that the proposed DNLPFG has potential for force sensing applications.

• 한국자동차공학회논문집
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• 제15권6호
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• pp.44-49
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• 2007

It is well known that the acoustic cavity inside the tire-wheel assembly contributes to vehicle interior noise. In this paper, we have performed acoustic and structural modal testings to investigate the influences of the acoustic cavity resonance on structural vibration characteristics for the tire in free-suspension and for the loaded tire. The testings have given us some findings, which are reported in this paper.

• 대한기계학회논문집
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• 제18권6호
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• pp.1439-1447
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• 1994

Test results of friction-factor for the flow of air in a narrow channel lined with various honeycomb geometries show that, generally, the friction-factor is nearly constant or slightly decreases as the Reynolds number(or Mach number) increases, a characteristic common to turbulent flow in pipes. However, in some test geometries this trend is remarkably different. The friction factor dramatically drops and then rises as the Mach number increases. This phenomenon can be characterized as a "friction-factor jump." Further investigations of the acoustic spectrum indicate that the "friction-factor jump" phenomenon is accompanied by an onset of a normal mode resonance excited coherent flow fluctuation structure, which occurs at Reynolds number of the order of $10^4$. New empirical friction-factor model for "friction-factor jump" cases is developed as a function of Mach number and local pressure.ach number and local pressure.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 춘계학술대회논문집
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• pp.496-503
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• 2001

The suspension of the optical pickup actuator is damped by the presence of silicone rubber damper bond at its termination. In spite of the presence of it, the actuator still exhibits a strong mechanical resonance which affects its settling time and vibrational characteristics. This resonance can cause errors in reading information from the disk, particularly in high speed CD-ROM and DVD-ROM drives. Ferrofluids are stable colloidal suspensions of sub-micron sized magnetic particles in a carrier liquid. In the actuator design, ferrofluid is applied to the surface of the magnets until the quantity is sufficient to maintain intimate contact with the bobbin/carrier assembly. The fluid is retained in the magnetic field and its viscosity provides the desired mechanical damping to the moving assembly, improving the actuators settling time and vibrational characteristics. Access time is also improved, particularly on warped or eccentric discs.