• 소음진동
• /
• 제9권4호
• /
• pp.806-812
• /
• 1999

Dynamic behaviors are analyzed for a flexble spinning disk with angular acceleration, considering geometric nonlinearity. Based upon the Kirchhoff plate theory and the von Karman strain theory, the nonlinear governing equations are derived which are coupled equations with the in-plane and out-of-planedisplacements. The governing equations are discretized by using the Galerkin approximation. With the discretized nonlinear equations, the time responses are computed by using the generalized-$\alpha$ method and the Newton-Raphson method. The analysis shows that the existence of angular acceleration increases the displacements of the spinning disk and makes the disk unstable.

• 전자공학회논문지D
• /
• 제34D권12호
• /
• pp.22-30
• /
• 1997

The design procedure for direct coupled combline filter with tapped line in/out was summarized on Ku-band satellite frequency downconverter for stellite application. We calculated the resonator dimensions, spacing between successive resonators, ground plane spacing and tapping position of in/output lines in accordance with the given procedure. Partitions wer eemployed between adjacent resonators by inserting irises to improve filter response characteristis. The designed filter was manufactued with aluminum alloy package to reduce mass, and resonators wer machined from the filter body and in/output lines wer fixed on resonators with epoxy to survive in vibration conditon during launch.

• 전산구조공학
• /
• 제11권3호
• /
• pp.155-164
• /
• 1998

이 논문은 변단면을 고려한 수평 곡선보의 자유진동에 관한 연구이다. 진동시 곡선보 요소에 작용하는 합응력과 관성력의 동적평형방정식을 이용하여 변단면 원호형 수평 곡선보의 자유진동을 지배하는 상미분방정식을 유도하였다. 이 미분방정식을 원형 단면을 갖는 선형변변단면에 적용하여 고유진동수, 진동형 및 합응력을 산출하였다. 수치 해석예에서는 양단고정 및 양단회전 곡선보를 채택하였으며, 수치해석 결과로서 고유진동수와 단면비, 세장비 및 중심각 사이의 관계를 그림에 나타내었다. 또한 실험실 규모의 실험을 통하여 본 연구결과의 타당성을 보였다.

• 한국재료학회지
• /
• 제4권1호
• /
• pp.3-8
• /
• 1994

최근 중요하게 된 진동 흡수를 위해서 $BaTiO_{3}$ 세라믹의 흡진 특성을 측정하고 미세구조와의 연관을 조사했다.$BaTiO_{3}$ 세라믹은 비교적 물리적 화학적으로 안정하여 좋은 흡진재로 기대된다.BaTiO$_{3}$ 세라믹은 흡진 특성을 강화시키기 위해서 섬유상 분말을 소결하여 만들었다. KDC법으로 직경이 0.2$\mu\textrm{m}$, 1.2$\mu\textrm{m}$, 2.0$\mu\textrm{m}$인 각각 다른 섬유상 $K_2Ti_4O_9$을 만들고 이온교환해서 섬유상 $BaTiO_{3}$ 을 만들었다. 면상으로 배향시킨 소결체의 흡진 특성과 전기적 물성을 조사하여 미세구조와 의 관계를 밝혔다. 소결체의 입경과 등가회로, 전기기계합계수($K_{t}$), 발생 전압(V)을 조사한 결과, 사용한 섬유의 직경이 클수록 소결체의 입경은 작아졌다. 따라서 입계가 많아졌다. 흡진 특성은 입계가 많을수록 커진다. 즉 입계의 내무마찰이 클수록 흡진률은 커지며 이때의 내부마찰은 등가회로를 조사함으로써 확인되었다.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 2005년도 춘계 학술발표회 논문집
• /
• pp.548-555
• /
• 2005

Since soil-structure interactions are one of the most important subjects in the structural/foundation engineering, much study concerning the soil-structure interactions had been carried out. One of typical structures related to the soil-structure interactions is the strip foundation which is basically defined as the beam or strip rested on or supported by the soils. At the present time, lack of studies on dynamic problems related to the strip foundations is still found in the literature. From these viewpoint, this paper aims to theoretically investigate dynamics of the elliptic strip foundations and also to present the practical engineering data for the design purpose. Differential equations governing the free, out-of-plane vibrations of such sap foundations we derived, in which effects of the rotatory and torsional inertias and also shear deformation are included although the warping of the cross-section is excluded. Governing differential equations subjected to the boundary conditions of free-free end constraints are numerically solved for obtaining the natural frequencies and mode shapes by using the numerical integration technique and the numerical method of non-linear equation.

• Advances in aircraft and spacecraft science
• /
• 제10권1호
• /
• pp.51-65
• /
• 2023

In this paper, the effect of deepness on in-plane free vibration behavior of a curved functionally graded (FG) nanobeam based on nonlocal elasticity theory has been investigated. Differential equations and boundary conditions have been developed based on Hamilton's principle. In order to figure out the size effect, nonlocal theory has been adopted. Properties of material vary in radial direction. By using Navier solution technique, the amount of natural frequencies has been obtained. Also, to take into account the deepness effect on vibrations, thickness to radius ratio has been considered. Differences percentage between results of cases in which deepness effect is included and excluded are obtained and influences of power-law exponent, nonlocal parameter and arc angle on these differences percentage are studied. Results show that arc angle and power law exponent parameters have the most influences on the amount of the differences percentage due to deepness effect. It has been observed that the inclusion of geometrical deep term and material distribution results in an increase in sensitivity of dimensionless natural frequency about variation of aforementioned parameters and a change in variation range of natural frequency. Finally, several numerical results of deep and shallow curved functionally graded nanobeams with different geometry dimensions are presented, which may serve as benchmark solutions for the future research in this field.

• KIEAE Journal
• /
• 제7권4호
• /
• pp.147-152
• /
• 2007

Numerous non-destructive tests(NDT) to assess the safety of real structures have been developed. System identification(SI) techniques using dynamic responses and behaviors of structural systems become an outstanding issue of researchers. However the conventional SI techniques are identified to be non-practical to the complex and tall buildings, due to limitation of the availability of an accurate data that is magnitude or location of external loads. In most SI approaches, the information on input loading and output responses must be known. In many cases, measuring the input information may take most of the resources, and it is very difficult to accurately measure the input information during actual vibrations of practical importance, e.g., earthquakes, winds, micro seismic tremors, and mechanical vibration. However, the desirability and application potential of SI to real structures could be highly improved if an algorithm is available that can estimate structural parameters based on the response data alone without the input information. Thus a technique to estimate structural properties of building without input measurement data and using limited response is essential in structural health monitoring. In this study, shaking table tests on three-story plane frame steel structures were performed. Out-put only model analysis on the measured data was performed, and the dynamic properties were inverse analyzed using least square method in time domain. In results damage detection was performed in each member level, which was performed at story level in conventional SI techniques of frequency domain.

• Smart Structures and Systems
• /
• 제4권2호
• /
• pp.209-220
• /
• 2008

A methodology for the seismic vulnerability assessment of historical monuments is presented in this paper. The ongoing work has been conducted in Tunisia within the framework of the FP6 European Union project (WIND-CHIME) on the use of appropriate modern seismic protective systems in the conservation of Mediterranean historical buildings in earthquake-prone areas. The case study is the five-century-old Zaouia of Sidi Kassem Djilizi, located downtown Tunis, the capital of Tunisia. Ambient vibration tests were conducted on the case study using a number of force-balance accelerometers placed at selected locations. The Enhanced Frequency Domain Decomposition (EFDD) technique was applied to extract the dynamic characteristics of the monument. A 3-D finite element model was developed and updated to obtain reasonable correlation between experimental and numerical modal properties. The set of parameters selected for the updating consists of the modulus of elasticity in each wall element of the finite element model. Seismic vulnerability assessment of the case study was carried out via three-dimensional time-history dynamic analyses of the structure. Dynamic stresses were computed and damage was evaluated according to a masonry specific plane failure criterion. Statistics on the occurrence, location and type of failure provide a general view for the probable damage level and mode. Results indicate a high vulnerability that confirms the need for intervention and retrofit.

• 한국공간구조학회논문집
• /
• 제9권1호
• /
• pp.79-85
• /
• 2009

최근의 대공간구조물은 장스팬화 됨은 물론이고 경량화되면서 면외 방향의 강성이 매우 작아지고 있다. 이로 인하여 공력불안정 진동의 발생 여부는 물론이고 연성구조물의 판단시에도 고유진동수의 정확한 산정이 필요하다. 그러나 국내외 대공간구조물의 고유진동수 제안식에 대한 연구는 매우 미흡한 실정이다. 따라서 국내 7개 공간구조물의 고유치해석에서 얻은 근사식을 일본건축학회 고유치해석에 근거한 2가지 제안식과 일본의 28개 공간구조물의 계측치에서 얻은 고유진동수 근사식을 비교하였다. 지붕의 고유진동수는 스팬이 증가함에 따라서 작아지는 경향을 확인하였다. 국내의 고유진동수 값은 전반적으로 일본의 공간구조물의 해석과 계측에 근거한 고유진동수보다 동일한 스팬에서 작은 경향을 보임을 알 수 있었다. 따라서 국내 공간구조물의 지붕은 일본의 경우보다 비교적 연성구조물인 것을 확인할 수 있다.

• 센서학회지
• /
• 제27권5호
• /
• pp.300-305
• /
• 2018

The uncooled microbolometer thermal sensor for low cost and mass volume was designed to target the new infrared market that includes smart device, automotive, energy management, and so on. The microbolometer sensor features 80x60 pixels low-resolution format and enables the use of wafer-level vacuum packaging (WLVP) technology. Read-out IC (ROIC) implements infrared signal detection and offset correction for fixed pattern noise (FPN) using an internal digital to analog convertor (DAC) value control function. A reliable WLVP thermal sensor was obtained with the design of lid wafer, the formation of Au80%wtSn20% eutectic solder, outgassing control and wafer to wafer bonding condition. The measurement of thermal conductance enables us to inspect the internal atmosphere condition of WLVP microbolometer sensor. The difference between the measurement value and design one is $3.6{\times}10-9$ [W/K] which indicates that thermal loss is mainly on account of floating legs. The mean time to failure (MTTF) of a WLVP thermal sensor is estimated to be about 10.2 years with a confidence level of 95 %. Reliability tests such as high temperature/low temperature, bump, vibration, etc. were also conducted. Devices were found to work properly after accelerated stress tests. A thermal camera with visible camera was developed. The thermal camera is available for non-contact temperature measurement providing an image that merged the thermal image and the visible image.