• Computers and Concrete
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• 제26권3호
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• pp.285-292
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• 2020

In engineering structures, to having the projected structure to serve all the engineering purposes, the theory to be used during the modeling stage is also of great importance. In the present work, an analytical solution of the free vibration of the beam composed of functionally graded materials (FGMs) is presented utilizing different beam theories. The comparison of supposed beam theory for free vibration of functionally graded (FG) beam is examined. For this aim, Euler-Bernoulli, Rayleigh, Shear, and Timoshenko beam theories are employed. The functionally graded material properties are assumed to vary continuously through the thickness direction of the beam with respect to the volume fraction of constituents. The governing equations of free vibration of FG beams are derived in the frameworks of four beam theories. Resulting equations are solved versus simply supported boundary conditions, analytically. To verify the results, comparisons are carried out with the available results. Parametrical studies are performed for discussing the effects of supposed beam theory, the variation of beam characteristics, and FGM properties on the free vibration of beams. In conclusion, it is found that the interaction between FGM properties and the supposed beam theory is of significance in terms of free vibration of the beams and that different beam theories need to be used depending on the characteristics of the beam in question.

• 한국기계가공학회지
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• 제12권2호
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• pp.91-99
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• 2013

Car cross beam made by aluminium for new car is designed for the substitution of steel and it can be verified the performance by computer simulations. The parts of car cross beam are designed to replace steel parts according to their manufacturing processes. At the first stage, the weight of the aluminium car cross beam can be reduced to 75% by comparing with that of steel car cross beam. But NVH performance of the aluminium car cross beam becomes slightly insufficient as compared with that of steel car cross beam. Taguchi method is adopted to optimize the design variables affecting NVH characteristics of car cross beam. New car cross beam is designed at the second stage by using these analysis results. Weight reduction can be obtained to 31.7% by design modification and material change of car cross beam in comparison with the original steel one. NVH characteristics of aluminium car cross beam become on an equal level with the steel car cross beam. By side impact analysis results, new car cross beam has higher performance as compared with the steel car cross beam.

• Applied Science and Convergence Technology
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• 제27권4호
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• pp.65-69
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• 2018

We studied the critical pressure characteristics of an anode type ion beam source driven by both charge repulsion and diffusion mechanism. The critical pressure $P_{crit}$ of the diffusion type ion beam source was linearly decreased from 2.5 mTorr to 0.5 mTorr when the gas injection was varied in 3~10 sccm, while the $P_{crit}$ of the charge repulsion ion beam source was remained at 3.5 mTorr. At the gas injection of 10 sccm, the range of having normal beam shape in the charge repulsion ion beam source was about 6.4 times wider than that in the diffusion type ion beam source. An impurity of Fe 2p (KE = 776.68 eV) of 12.88 at. % was observed from the glass surface treated with the abnormal beam of the charge repulsion type ion beam source. The body temperature of the diffusion type ion beam source was observed to increase rapidly at the rate of $1.9^{\circ}C/min$ for 30 minutes and to vary slowly at the rate of $0.1^{\circ}C/min$ for 200 minutes for an abnormal beam and normal beam, respectively.

• Geomechanics and Engineering
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• 제11권1호
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• pp.95-116
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• 2016

A novel higher order shear-deformable beam model, which provides linear variation of transversal normal strain and quadratic variation of shearing strain, is proposed to describe the beam resting on foundation. Then, the traditional two-parameter Pasternak foundation model is modified to capture the effects of the axial deformation of beam. The Masing's friction law is incorporated to deal with nonlinear interaction between the foundation and the beam bottom, and the nonlinear properties of the beam material are also considered. To solve the mathematical problem, a displacement-based finite element is formulated, and the reliability of the proposed model is verified. Finally, numerical examples are presented to study the effects of the interfacial friction between the beam and foundation, and the mechanical behavior due to the tensionless characteristics of the foundation is also examined. Numerical results indicate that the effects of tensionless characteristics of foundation and the interfacial friction have significant influences on the mechanical behavior of the beam-foundation system.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.950-953
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• 2006

The floor impact noise of concrete structures in apartments buildings is affected from the flexural wave propagation characteristics. Accordingly, the measurement of wave propagation characteristics is required for suggestion of efficient method to reduce the impact noise. The purpose of this article is to propose an experimental technique to measure dynamic properties of concrete structures. The method was proposed using the flexural wave propagation characteristics. Wave speeds, bending stiffness and their loss factors are estimated from which the vibration dissipation capabilities are investigated. Several different concrete beam structures were custom-built for measurement. The damping treatments using viscoelastic materials for reducing noise generation are also tested. The beam transfer function of the damped beam is predicted using the compressional damping model from which the mechanism of the vibration energy dissipation is investigated.

• 대한전자공학회논문지TC
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• 제39권4호
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• pp.209-215
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• 2002

본 논문에서는 수평편파용 EMCD 어레이 안테나의 빔 틸트 특성을 기술하고 있다. 소자하나에 대하여 설계를 한 후, 이를 어레이 설계에 적용하여 어레이 안테나의 특성을 평가하였다. FDTD법에 의해 해석된 수평편파용 EMCD 어레이 안테나의 이론적 주파수특성과 지향성 패턴 결과는 실제 제작한 안테나의 측정치와 잘 일치하였다. 제작된 20 소자 어레이 안테나의 주빔의 앙각 틸트 각도는 무궁화위성이 위치한 47°였고, 반치폭은 약 ±7.5°정도로 양호한 지향성 특성을 보였다.

• 한국소음진동공학회논문집
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• 제18권10호
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• pp.1024-1032
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• 2008

The vibration characteristics of a rotating cantilever beam undergoing impulsive force are investigated using wavelet transformation. The transient response induced by the impulsive force and the rigid body motion of the beam are calculated using hybrid deformation variable modeling along with the Rayleigh-Ritz assumed mode methods. The vibration characteristics of the beam can be analyzed in time-frequency domain with the wavelet transform method. Therefore, the effects of the impulsive force on the transient vibration characteristics of the beam can be investigated more effectively.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.400-406
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• 2008

The vibration characteristics of a rotating cantilever beam undergoing impulsive force are investigated using wavelet transformation. The transient response induced by the impulsive force and the rigid body motion of the beam are calculated using hybrid deformation variable modeling along with the Rayleigh-Ritz assumed mode methods. The vibration characteristics of the beam can be analyzed in time-frequency domain with the wavelet transform method. Therefore, the effects of the impulsive force on the transient vibration characteristics of the beam can be investigated more effectively.

• 비파괴검사학회지
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• 제32권4호
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• pp.347-354
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• 2012

Using a single-line pulsed laser beam is well known as a useful noncontact method to generate a directional surface acoustic wave. In this method, different laser beam energy profiles produce different waveforms and frequency characteristics. In this paper, we considered two typical kinds of laser beam energy profiles, Gaussian and square-like, to find out a difference in the frequency characteristics. To achieve this, mathematical models were proposed first for Gaussian laser beam profile and square-like respectively, both of which depended on the laser beam width. To verify the theoretical models, experimental setups with a cylindrical lens and a line-slit mask were respectively designed to produce a line laser beam with Gaussian spatial energy profile and square-like. The frequency responses of the theoretical models showed good agreement with experimental results in terms of the existence of harmonic frequency components and the shift of the first peak frequencies to low.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 추계학술대회논문집
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• pp.252-257
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• 2006

Low vibration characteristics of a vehicle are mainly influenced by the local stiffness of the joint structure beam section. The method of substituting equivalent beam element to spring element for the joint is presented. Formation process of the equivalent beam joint modeling is described in terms of key section properties. To get required dynamic characteristics section properties of the equivalent beam element are set to design variables. The study shows that the equivalent beam joint model can be effectively used for low frequency vibration analysis of a vehicle.