• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.481-482
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• 2008

This investigation presents a method to design an optimal shape of a matching waveguide connecting two waveguides having different impedances. The design objective is to maximize power transmission through the waveguide system. When an incident wave impinges on an elastic waveguide system consisting of waveguides of different impedances, all of the incident wave power may not pass through due to the mechanical impedance. Therefore, the maximization of the transmitted power through a waveguide difficult to achieve without a systematic design method. In this work, the optimal shape design of a matching waveguide connecting two waveguides of different impedances is formulated as a shape optimization problem. If the material of the matching waveguide is given, its shape is the only parameter controlling the transmission power. Relatively simple one dimensional elastic wave transmission problems will be considered in this work, but the underlying methodology and the related physics can be clearly demonstrated. The influences of initial configurations as well as the target frequencies on the optimized shapes will be also investigated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1998년도 춘계학술대회논문집; 용평리조트 타워콘도, 21-22 May 1998
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• pp.34-39
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• 1998

In order to compute the forces which are transmitted through rubber bushings with a commercial multibody dynamic analysis (MBDA) program, a rubber bushing model is needed. The rubber bushing model of MBDA programs such as DADS or ADAMS is the Voigt model which is simply a parallel spring-viscous damper system, meaning that the damping force of the Voigt model is proportional to the frequency. However, experiments do not necessarily support this proportionality. Alternatively, the viscoelastic characteristics of rubber bushings can be better represented by the complex stiffness. The purpose of this paper is to develop a viscoelastic rubber bushing model for the MBDA programs. Firstly, a methodology is proposed to calculate the complex stiffness of rubber bushings considering static and dynamic load conditions. Secondly, a viscoelastic rubber bushing model developed which uses standard elements provided by DADS. The proposed methods are applied to the rubber bushings of the lower control arms of a rear suspension of a 1994 Ford Taurus model. Then, the forces computed for the rubber bushing model are analyzed and compared with the Voigt model in time and frequency domains.

• 한국자동차공학회논문집
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• 제6권1호
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• pp.163-181
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• 1998

In this study, the objective is determine the optimal design variable of engine mount system using the rubber mount of bush-type which is usually utilized in passive control to minimize vibrations of vehicle body or transmission from engine into body. The engine model adopted in this study is 4-cylinder, 4-stroke gasoline engine support- ed by 4-points. The system is modelled in 10 d.o.f.-rigid body motion of the engine & transmission in 6 d.o.f., elastic motion of vehicle body in 4 d.o.f.(1st torsional, 1st vertical and 1st & 2nd lateral bending vibration mode). To consider the elastic motion of vehicle body, find the eigenvalues and mode shapes of vehicle body by nodal testing and then determine the modal masses and stiffnesses of the body. The design variables of the engine mount system are locations, stiffness and damping coefficients of the rubber mounts(28 design variables). In case of considering the torque-roll axis for the engine, the design variables of the mount system are reduced to 22 design variables. The objective functions in optimal design process are considered by three cases, that is, 1) transmitted forces through engine mounts, 2) acceleration components of generalized coordinates for the vibration of vehicle body, 3) acceleration of specified location(where gear box) of body. three case are analyzed and compared with each other.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2009년도 춘계학술대회 논문집
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• pp.280-281
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• 2009

Piezoelectric vibrators can be good replacements of electric motors to excite touch screen of a mobile device owing to small volume and low power consumption. One problem to be solved yet for real application is larger excitation force or moment than available currently. More efficient excitation by a piezoelectric vibrator could be achieved by operating at one of resonance frequencies of the system, which must also be as close as possible to frequency range where index finger is most sensitive and increasing transmission force or moment at that frequency. In this study, dynamic models are derived for the piezoelectric exciter and an adhesive viscoelastic layer, which connect the exciter to the screen. The adhesive layer is modeled as distributed stiffness by considering its geometric shape to relative to the piezoelectric exciter. Then, equations of motion for the piezoelectric exciter and the adhesive layer are derived using Hamilton's principle. Based on this model, dynamic characteristics of the exciter will be designed to maximize the force or moment transmitted onto the screen structure.

• 한국소음진동공학회논문집
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• 제16권7호
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• pp.729-738
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• 2006

Knowledge of acoustic transmission loss of acoustic window material has a great importance for the sonar performance in ship. The purpose of this study was to investigate the measurement and analysis method for the acoustic transmission loss of the acoustic window materials for sonar dome. The measurement and analysis were carried out in water with GRP material. Transmission losses were calculated based on integrated direct and transmitted signals. The experimental setup enabled to vary the angle of incidence. Thus the transmission loss data could be expressed as the function of frequency and angle of rotation. In this paper, diffraction effect of incident angle, size of specimen with test material, transmission analysis method and multiple waves as incident acoustic signal were discussed.

• 한국소음진동공학회논문집
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• 제16권7호
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• pp.754-761
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• 2006

This paper presents the dynamic characteristics of MR impact damper for vehicle collision system. Various types of mechanism have been proposed to reduce force transmitted to the vehicle chassis and finally to protect occupants from injury. In the case of head-on collision, the bumper makes main role of isolation material for collision attenuation. In this study, the proposed bumper system consists of MR impact damper and structures. The MR impact damper utilizes MR fluid which has reversible properties with applied magnetic field. The MR fluid operates under flow mode. The bellows is used for generation of fluid flow. A mathematical model of the MR impact damper is derived incorporating with Bingham model of the MR fluid. Field dependent damping force is investigated with time and frequency domain. The MR impact damper is then incorporated with vehicle crash system. The governing equation of motion of vehicle model is formulated considering occupant model. Dynamic characteristics of vehicle collision system investigated with computer simulation.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1549-1554
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• 2000

HDD structure is excited by the dynamic motion of disk-spindle motor components. Those excitations which are generated at stator and magnet rotor, at bearings and from disk dynamics, are transmitted through motor spindle and flange to HDD cover and base. The operational deflection shape measurement can show the structural excitation patterns at the most influent frequency on the acoustic noise level. One of those components is the axial excitation along spindle, and the other is the local orbital excitation at contact area of motor flange and base. To make a reduction of those structural transmission excitations, the structure of spindle motor is modified to the direction of reinforcement at transmission path without change of bearings, magnet and coil. Some excitation of spindle motor component carrying out essential function is unavoidable. So it is the efficient way of HDD noise improvement to control the structural transmission of excitation.

• 한국소음진동공학회논문집
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• 제23권3호
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• pp.282-290
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• 2013

A new method is presented that uses guided wave techniques for sludge and blockages detection in long-range pipelines. Existing techniques have the limitations that the sludge position needs to be known a priori and the area to be inspected needs to be accessible. Two guided wave techniques have been developed which allow the sludge or blockages to be detected remotely without the need to access the specific location where the pipe is blocked, nor to open the pipe. The first technique measures the reflection of guided waves by sludge which can be used to accurately locate the blocked region; the second technique detects sludge by revealing the changes to the transmitted guided waves propagating in the blocked region or after it. The two techniques complement each other and their combination leads to a reliable sludge or blockage detection. Various types of realistic sludge have been considered in the study and the practical capabilities of the two techniques have been demonstrated.

• Journal of Advanced Marine Engineering and Technology
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• 제34권8호
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• pp.1057-1067
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• 2010

다단 기어연쇄, 베어링, 축, 로터로 구성되는 함포용 synchro system의 구동장치를 개발하기 위하여, AGMA규격에 의한 기어 굽힘강도, 면압강도해석, 기어치형설계를 포함한 정적설계를 수행하였다. 또한 전달행렬법을 효과적으로 적용시킬 수 있는 Hibner's branch법과 자유도가 큰 경우에도 계산 오차 없이 고유특성치를 빠뜨리지 않고 산출할 수 있는 ${\lambda}$-matrix법을 도입하여 함포용 Synchro system의 좌우 선회용과 상하 고각형의 위험속도 해석 및 평가를 하였고, 운전속도 범위 내에 위험속도가 존재하지 않았다.

• 한국기계가공학회지
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• 제19권7호
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• pp.98-105
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• 2020

This study deals with the passive control of the dynamic characteristics of a theoretical model which is a string with fixed ends and loaded by two point masses - a main mass (M_o) and a secondary mass (M_s). It has been controlled passively by means of a relocation of a secondary mass. A main mass placed on the string is considered as a vibrating receiver which be forced to vibrate by a vibrating source being positioned on the string. By analyzing the motion of a string, the equation of motion for a string was derived by using a method of variation of parameters. To define the optimal conditions for the vibration reduction, the governing equation, which denotes the dynamic response of a string was derived in the closed form and then evaluated numerically. The possibility of reduction of an amplitude and a power being transmitted to a main mass were found to depend on the location and the magnitude of a secondary mass as well as the range of a forcing frequency.