• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2007년도 추계학술대회논문집
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• pp.1042-1048
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• 2007

This work analytically investigated the radiated noise of a helical gear-housing system due to the excitation of helical gears. The helical gears were modeled as a 12-degree of freedom mass-spring-damper system; the shaft was modeled as a rod, a beam, and a torsional shaft; and the gear housing was modeled as a clamped circular plate with viscous damping. The modeling of this system used transfer matrices for helical gears, shafts, and bearings. Damping for both the bearings and the plate were obtained by modal testing. For the evaluation of noise, sound pressure from the plate due to the force and the moment in both radial and tangential directions was analytically derived by the Rayleigh integral. The analytical derivation and parameters from the experiment were applied to an analysis of noise for the two sets of helical gears with differing gear ratios. The analysis showed that the moment excitation in both helical gears contributed more to the noise of the plate than axial force excitation.

• 대한기계학회논문집
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• 제1권3호
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• pp.141-145
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• 1977

In this paper, approximate solutions of the von Karman equations for the free flexural vibration of a transversely isotropic thin rectangular plate with two simply supported edges and two clamped edges are obtained. Applying one term Ritz-Galerkin procedure, the spatial dependent part of the equation is separated and time dependent function is found to be the Duffing's equation. Then the relation between nonlinear period and amplitude of the vibration is obtained by using averaging method which is a method of the perturbation procedure. It can be seen that averaging method is easy and agrees well with prior results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1994년도 추계학술대회논문집; 한국종합전시장, 18 Nov. 1994
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• pp.244-249
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• 1994

The dynamic characteristics of mechanical structure are strongly affected by the properties of joint parameters. In this study, the test structures are constructed with two beam structures which are clamped by bolts, and a bolted joint which is modelled as a lumped stiffness element. To identify the dynamic joint parameters with variance of clamping torque of bolts, the sensitivity analysis and the mode energy analysis methods are investigated experimentally. As a result of these two methods, stiffnesses of bolted joint are experimentally found to increase as the clamping torque increases. These stiffnesses identified from the sensitivity analysis and the mode energy analysis method have some difference.

• Journal of Mechanical Science and Technology
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• 제19권9호
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• pp.1711-1719
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• 2005

In an electro statically actuated nanoelectromechanical system (NEMS) resonator, it is shown that both the resonance frequency and the resonance quality (Q) factor can be manipulated. How much the frequency and quality factor can be tuned by excitation voltage and resistance on a doubly-clamped beam resonator is addressed. A mathematical model for investigating the tuning effects is presented. All results are shown based on the feasible dimension of the nanoresonator and appropriate external driving voltage, yielding up to 20 MHz resonance frequency. Such parameter tuning could prove to be a very convenient scheme to actively control the response of NEMS for a variety of applications.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2006년도 정기 학술대회 논문집
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• pp.949-954
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• 2006

The purpose of this paper is to investigate the stability of tapered columns with clamped one end and carrying a tip mass of rotatory inertia with translational elastic support at the other end. The linearly tapered columns with the solid rectangular cross-section is adopted as the column taper. The differential equation governing free vibrations of such Beck columns is derived using the Bernoulli-Euler beam theory. Both the divergence and flutter critical loads are calculated from the load-frequency curves which are obtained by solving the differential equation. The critical loads are presented as functions of various non-dimensional system parameters: the taper type, the subtangential parameter, mass ratio and spring stiffness.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.1939-1944
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• 2000

Different test methods were used to measure and compare the loss factor of a steel beam. They are free vibration logarithmic decay method, half-power bandwidth method using narrow-band analysis, wide-band analysis method with inverse FFT. In these tests, specimens are clamped at one end. Free vibration method and half-power bandwidth method gave good results. Effect of vibration pick-ups were tested. We also tried center excitation method but could not obtain loss factor.

• 한국농공학회지
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• 제41권5호
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• pp.112-122
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• 1999

이 논문은 일정체적을 갖는 양단고정 변단면 기둥의 좌굴하중 및 후좌굴 거동에 관한 연구이다. 기둥의 변단면으로는 직선형, 포물선형, 정현의 선형을 갖는세 가지 변단면을 채택하였다. Bernoulli-Euler 보 이론을 이용하여 압축하중이 작용하여 좌굴된 기둥이 정확탄성곡선을 지배하는 미분방정식을 유도하였다. 유도된 미분방정식을 Runge-Kutta 법과 REgula-Falsi법을 이용하여 수치해석하였다. 수치해석의 결과로 좌굴하중, 좌굴기둥의 평형경로 및 정확탄성곡선을 산출하였다. 또한 좌굴하중-단면비 곡선으로부터 최강기둥의 좌굴하중과 단면비를 산출하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2002년도 가을 학술발표회 논문집
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• pp.11-16
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• 2002

The differential equations governing free vibrations of the elastic, horizontally curved beams with unsymmetric axis are derived in Cartesian coordinates rather than in polar coordinates, in which the effect of torsional inertia is included. Frequencies are computed numerically for the sinusoidal curved beams with both clamped ends and both hinged ends. Comparisons of natural frequencies between this study and SAP 2000 are made to validate theories and numerical methods developed herein. The convergent efficiency is highly improved under the newly derived differential equations in Cartesian coordinates. The lowest four natural frequency parameters are reported, with and without torsional inertia, as functions of three non-dimensional system parameters: the horizontal rise to chord length ratio, the span length to chord length ratio, and the slenderness ratio.

• Structural Engineering and Mechanics
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• 제55권4호
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• pp.785-799
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• 2015

A three-dimensional (3-D) method of analysis is presented for determining the free vibration frequencies of hyperboloidal shells free at the top edge and clamped at the bottom edge like a hyperboloidal cooling tower by the Ritz method based upon the circular cylindrical coordinate system instead of related 3-D shell coordinates which are normal and tangent to the shell midsurface. The Legendre polynomials are used as admissible displacements. Convergence to four-digit exactitude is demonstrated. Natural frequencies from the present 3-D analysis are also compared with those of straight beams with circular cross section, complete (not truncated) conical shells, and circular cylindrical shells as special cases of hyperboloidal shells from the classical beam theory, 2-D thin shell theory, and other 3-D methods.

• 한국군사과학기술학회지
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• 제7권1호
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• pp.47-58
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• 2004

Loss factors of A356, Mn-Cu alloy and aluminum matrix composites reinforced with $SiC_p$ and Ni-coated graphite particles at various contents have been investigated using clamped-free cantilever beam method. The loss factors of half-power bandwidth of the specimens were measured over a wide range of frequencies from 50 to 3300Hz. Among the specimens, Al-10%$SiC_p$-10%$C_p$ showed the highest loss factor at the mode I, while Mn-Cu alloy showed the highest loss factors at the modes II and III. Consequently, at the mode I the Al-10%$SiC_p$--10%$C_p$ showed the loss factor of 0.00093, which is 2.64 and 1.58 times higher than those of A356 and Mn-Cu alloy, respectively.