• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.998-999
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• 2014

This paper proposes a method for damping force modeling of magnetorheological (MR) damper featuring bypass hole. After describing configuration and of the MR damper, a damping force modeling of the MR damper is derived based on Bingham model of MR fluid. MR damper consists of piston, accumulator, gap, bypass hole and coil. Damping force is consists of spring force induced by accumulator, viscous force induced at gap and bypass hole, and controllable force induced at gap.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2014년도 추계학술대회 논문집
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• pp.712-712
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• 2014

본 논문에서는 지연-가중-합 빔형성 방법이 적용된 지향성 헤드폰의 마이크로폰 배치 설계를 설명한다. 마이크로폰의 갯수, 마이크로폰 간의 간격 등이 헤드폰 지향성에 영향을 미치는 설계 변수가 된다. 본 논문에서는 현실성을 고려하여 4개 이하의 마이크로폰을 포함한 10cm 길이의 배열을 타겟으로 한다. 전방으로부터의 소리를 증폭하고 후방으로부터의 소리를 감쇠하여, 전-후방 음압차를 최대화하는 것을 목표로 하였다. 구형 머리전달 함수를 이용한 시뮬레이션을 통해 최적의 마이크로폰 배치를 결정하였다. 설계된 헤드폰은 3개의 마이크로폰을 이용하여 300~3000Hz의 주파수 대역에서 평균 34.6dB의 전-후방 음압차를 보였다. 이 결과는 선행 연구에서 수행된 지연-합 빔형성 방법을 이용한 결과에 비해 8.8dB 뛰어난 성능이다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.418-422
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• 1997

A numerical computation and experimental test have been performed for the investigation of dynamic behavior of composite beams with bonded piezo ceramics. The present finite element method based on layerwise approach can effectively evaluate the characteristics of the composite beams with bonded piezo ceramics. The natural frequencies and damping values were measured by fitting the frequency response function obtained from FFT analyzer. The frequency-dependent damping properties of composite material were measured to utilize them for the finite element analysis of the composite beams with bonded piezo ceramics. The experimental results are in good agreement with those of finite element analysis.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1997년도 춘계학술대회논문집; 경주코오롱호텔; 22-23 May 1997
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• pp.95-101
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• 1997

A general method is presented for the analysis of the damping effectiveness of viscoelastic layer applied to elastic beam. The damping is attributed to the shear deformations of the treatment. Specific results are then given for sandwich beams with dissipative cores. The calculated results by this method are validated by comparison with the experimental results. Optimum design of a viscoelastic damping layer which is constrainedly cohered on a steel beam is discussed from the viewpoint of the modal loss factor. An object function is a loss factor of 3-layered beam and design variable is the thickness of constraining layer and viscoelastic layer. Optimum thickness can be obtained when 3-layered beam has a maximum loss factor.

• 한국소음진동공학회논문집
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• 제15권12호
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• pp.1361-1369
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• 2005

Based on a full layerwise displacement shell theory, the nitration and damping characteristics of cylindrical sandwiched panels with viscoelastic layers are investigated. The transverse shear deformation and the normal strain of the cylindrical hybrid panels are fully taken into account for the structural damping modelling. The present finite element model Is formulated by using Hamilton's virtual work principle and the cylindrical curvature of hybrid panels is exactly modeled. Modal loss factors and frequency response functions are analyzed for various structural parameters of cylindrical sandwich panels. Present results show that the full layerwise finite element method can accurately predict the vibration and damping characteristics of the cylindrical hybrid panels with surface damping treatments and constrained layer damping.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.411-414
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• 2006

In this paper, the forced vibration of damped composite beam with arbitrary section was analyzed. The damping material was assumed to have either complex shear modulus or complex Young???smodulus. Damped composite beam could be modeled using beam elements with less D.O.F. rather than solid elements. Finite element method for these methods was formulated and programmed using complex values. The results of frequency responses revealed good agreement with those of NASTRAN in several beam structures.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.831-836
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• 2006

In the process of accurate manufacture and measurement, it is necessarily required to isolate external or internal vibration due to external disturbance and internal actuators. The higher vibration isolation system gets damping around resonance, the better it is generally. This paper analyzes the performance of an existing passive air-spring for vibration isolation table by using experiment and simulation. Optimal design for a passive air spring can be obtained by tuning the size of the orifice. Also design for an active isolation system is carried out by applying PID controller and considering non-linearity of pneumatic characteristics with help of look-up table. We have developed the active vibration isolation table with the better isolation performance.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.81-85
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• 2006

The motion of a system composed of a plate, constant springs and varying dampers is considered when the system is subject to harmonic force. Letting the frequencies of harmonic force and damper variation ${\Large f}_1\;and\;{\Large f}_2$, respectively, the displacement at the center of the plate has the strongest component at frequency ${\Large f}_1$. The angular displacement of the plate has strong components at ${\Large f}_1-{\Large f}_2$, and the natural frequency of the rotational mode of the system. If these two frequencies coincide, the plate oscillates with almost single frequency and a large amplitude. These results can be applied to development of a moment shatter with low frequencies.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1404-1408
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• 2006

In this paper, a hybrid-type vibration isolator which has air chamber(spring) and viscous damper in series is developed. The developed vibration isolator is designed to perform 3 following functions : spring function for normal operating conditions, damping function to reduce an impact for sudden move of upper beam, and finally leveling function. Based on the given natural frequency and damping factor, the design procedure is proposed. The performance of the developed isolator is tested by measuring stiffness and damping.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.224-231
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• 2006

A six-degree-of-freedom dynamic model with time-varying mesh stiffness/damping and friction has been developed for the dynamic analysis of a gear driving system. This model includes a spur gear pair, bearing, friction and prime mover. Using Newton???s method, equations of motion for the gear driving system were derived. Two computer programs are developed to calculate mesh stiffness, transmission error and friction force and analyze the dynamics of the modeled system using a time integration method. The influences of mesh stiffness/damping, bearing, and friction affecting the system were investigated by performing eigenvalue analysis and time response analysis. It is found that the reduction of the maximum peak magnitude by friction is decided according to designing the positions of pitch point and maximum peak in the responses.