• 대한조선학회지
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• 제16권2호
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• pp.1-7
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• 1979

The authors had done theoretical analysis of the vibration of rectangular elastic plates in contact with water. In this analysis, using the elliptic cylindrical coordinate system, they investigated the effects of mass density ratios, chord-length to thickness ratios, aspect ratios, boundary conditions and mode shapes on the added mass of plates. The results are reported in papers quoted as the reference [4] and [5] of this paper. In this report the results of experiments conducted to verify the above theoretical analysis are presented. It shows that numerical results derived from the theoretical analysis are generally in good agreement with the experimental results.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.276-276
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• 2003

This paper dealt with an experimental study on the free vibration of circular-tube-beam submerged in water. A circular-tube-beam is commonly founded on the nuclear fuel assembly system in nuclear reactor. The nuclear fuel assembly susceptible to flow-induced vibration in nuclear reactor. So, the nuclear fuel assembly be designed to avoid any resonance due to the vibration during the reactor operation. In the experiment, applied boundary condition is clamped-free and the effect of water height to natural frequency and damping is studied. The experiment in air and in water has been performed. Used experimental method is impact exciting method. The natural frequencies and damping ratio according to water height is presented.

• 한국소음진동공학회논문집
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• 제12권2호
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• pp.150-160
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• 2002

The free vibration characteristics of the triple cylindrical shells filled with fluid are investigated. The triple cylindrical shells are filled with compressible fluid. The boundary condition is clamped at both ends. Analytical method is developed to evaluate natural frequencies of triple cylindrical shells using Sanders' shell theory and courier series expansion by Stokes' transformation. Their results are compared with those of finite element method to verify the validation of the method developed. The modal characteristics of shells filled with fluid at region 1, 2 and 3 are evaluated.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 춘계학술대회논문집
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• pp.96-100
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• 2008

In this paper, a experimental and theoretical study is carried out on the hydroelastic vibration for a rectangular bottom and side plate of tank. It is assumed that the tank wall is clamped along the plate edges. The fluid velocity potential is used for the simulation of fluid domain and to obtain the added mass due to plate vibration. It is assumed that the fluid is imcompressible and inviscid. Assumed mode method is utilized to the plate model and hydrodynamic force is obtained by the proposed approach. The coupled natural frequencies are obtained from the relationship between kinetic energies of a wall including fluid and the potential energy of the wall. The theoretical result is compared with the three-dimensional finite element method. In order to verify the result, modal test was carried out for bottom/side plate of tank model by using impact hammer. It was found the fundamental natural frequency of bottom plate is lower than that of side plate of tank and theoretical result was in good agreement with that of commercial three-dimensional finite element program.

• 한국소음진동공학회논문집
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• 제12권3호
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• pp.195-203
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• 2002

In the engine room and the aft part areas of the ship, there exist so many tank structures contacting with fresh water or sea water or oil. If these structures exhibit excessive vibrations during the sea trials, it takes a lot of cost, time and effort to improve vibration situation because the reinforcement work requires emptying the fluid out of the tanks, additional welding and special painting. It is therefore very important to predict a precise vibration characteristics of the tank structures at the design stage, however it is not easy to estimate vibration characteristics of the structures because of difficulties for accurate evaluation of the added (or virtual) mass effect due to the fluid inside the tank. In this paper, numerical and experimental approaches have been performed to present same fundamental data necessary for anti-vibration design of tank structures contacting with fluid, by investigating vibration behaviors of rectangular tank structure for various water depths.

• 한국소음진동공학회논문집
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• 제18권1호
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• pp.123-130
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• 2008

An analytical method for the free vibration of a flexible rectangular plate in contact with water is developed by the Rayleigh-Ritz method. The plate clamped along the edges is partially contacted with water at both sides. It is assumed that the contained water is incompressible and inviscid. The wet mode shape of the plate is assumed as a combination of the dry mode shapes of a clamped beam. The liquid motion is described by using the liquid displacement potential and determined by using the compatibility conditions along the liquid interface with the plate. Minimizing the Rayleigh quotient based on the energy conservation gives an eigenvalue problem. It is found that the theoretical results can predict excellently the fluid-coupled natural frequencies comparing with the finite element analysis result.

• 대한조선학회지
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• 제21권1호
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• pp.21-34
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• 1984

This paper is concerned with the experimental investigation of transverse vibration characteristics in water of rectangular plates having an inner free cutout. Systematic experiments are carried out to investigate effects of the surrounding water on the added mass and the natural frequency of the plates due to the changes of the aspect ratio, hole size and eccentricity. The main subject is the clamped rectangular plate with a circular hole. For the purpose of comparative evaluations, some other common-type boundary conditions and hole shapes such as ellipses and rectangles are also investigated. Some of the results obtain are as follows; 1) For each given aspect ratio of the plate, there is a hole area ratio which gives a minimum value of the nondimensional frequency parameter for each mode. The hole area ratio increases as the order number of the mode increases. 2) The nondimensinal mass-increment parameter decreases as the aspect ration or the order number of the mode increases. For each given aspect ratio, the parameter the fundamental mode decreases monotonically as the hole area ratio increase. In cases of the second and higher order modes, however, each mode has a hole area ratio which gives a maximum value of the parameter for each aspect ratio more then 2/3. 3) Comparing elliptic holes with rectangular ones with same hole area ratio, nondimensional frequency parameters are almost same for each given ratio of the shorter axises to the longer one. 4) The influences of difference in boundary condion on nondimensional frequency parameters in water are similar to those in air.

• Journal of Biosystems Engineering
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• 제24권3호
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• pp.217-224
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• 1999

우리나라의 경우 각종 장해와 주년 수요의 증가에 따른 불시재배의 증가로 인하여 저온신장성, 병해저항성 등과 같이 작물의 내성증진을 목적으로 접목묘의 이용이 급속도로 신장되고 있다. 특시 연작장해가 심한 박과형 채소류는 대부분 접목재배가 필요한 실정이다. 그러나 국내의 경우, 접목작업은 거의 수작업으로 행해지며 세밀한 조작과 숙련성 그리고 많은 노력을 필요로 한다. 따라서, 접목 생산성을 높일 수 있는 저가의 자동화 시스템 개발이 요구된다. 다양한 접목법들 중 현재 농가에서 가장 광범위하게 이용되고 있는 호접은 삽접 및 절단접에 비하여 자동화가 어렵고 활착 후 절단작업이 부가적으로 필요하나 접목 후 순화공정이 간단하고 활착률이 높다. 본 논문에서는 호접과 삽접에 대하여 접목 후의 활착률 및 접목에 소요되는 작업시간을 비교하였고, 호접법에 의거하여 작업공정을 생력화한 육묘 자동접목 시작기를 개발하였다. 시작기는 농가조합 및 중규모 육묘장의 설비를 지향하여, 묘판 및 접목묘의 취급을 제외하고 1인 접목작업 형태의 자동화 시스템으로 개발하였다. 시작기는 크게 버퍼기능을 부착한 배치형 육묘장치부, 2세트에 공압 매니퓰레이터, 대목과 접수의 원할한 접목을 위해 설계한 특수 그리퍼, 각고 조절형 절단부, 진동형 클립공급부 그리고 자동 클립 장착장치로 구성하였다. 접목 작업시간은 대략 4ch 정도이나 작업시간의 조정이 가능하도록 하였다. 실험실에서 수행한 간이접목 시험 결과, 절단날이 대목과 접수의 접촉부위를 관통할 때 접촉면이 서로 어긋나는 경우가 발생하였으나 육묘들이 호접에 적정한 기하학적 물성 요건을 갖춘다면 80% 이상의 접목 육묘의 기하학적 물성에 따른 체계적인 접목시험이 필요하다.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 춘계학술대회
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• pp.839-844
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• 2003

The effect of water level on the free vibration of a partially water-filled two rectangular plates structure was investigated by experimental modal analysis and finite element analysis using ANSYS computer program. Modal parameters of two rectangular plates coupled with water were obtained by means of experiment and the FEM solutions were compared with the experimental solutions to verify the finite element model. As a result, the comparison between the experiment and FEM results showed excellent agreement. The transverse vibration modes, in-phase and out-of-phase, were observed alternately in the fluid-coupled system. The effect of water level and water gap size on the fluid-coupled natural frequency were investigated. It was found that the natural frequency of the partially water-filled two rectangular plates are not proportional to the water level, but depend on mode number of plates.

• 대한조선학회지
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• 제13권4호
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• pp.1-10
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• 1976

It is a well-known phenomenon that, in the case of vibrations of an elastic body in a fluid such as water, the presence of the surrounding fluid has the effect of lowering the natural frequencies of the vibration as compared with those in air or vacuum on account of the increased inertia, i.e. added mass. In this report, defining the mass increase factor as the ratio of added mass to vibration mass of the body in air, the author investigated the mass increased factor of an elastic plate vibrating in the fluid. It is assumed that the edges of the plate are simply supported, and that the surrounding fluid is an infinite ideal one. For the problem formulation the elliptical cylindrical coordinate system is adopted, so that a rectangular plate may be represented by a sheet degenerated from an elliptical cylinder. By virtue of the coordinate system adopted, plates which are chordwisely finite and lengthwisely contineous could directly be treated, but plates which are chordwisely finite in both directions could not be treated directly. For the latter, hence, plates which are chordwisely finite and lengthwisely semi-finite are investigated as an appropriate approximation. Some examples of the mass increase factor are numerically calculated for the fundamental mode and modes of zero or one nodal line in each direction with the range of the aspect ratio from 1 to 10 or more.