• Advances in concrete construction
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• 제14권1호
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• pp.35-43
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• 2022

Based on novel Galerkin's technique, the theoretical study gives a prediction to estimate the vibrations of FG rotating cylindrical shell. Terms of ring supports have been introduced by a polynomial function. Three different laws of volume fraction are utilized for the vibration of cylindrical shells. Variation frequencies with the locations of ring supports have been analyzed and these ring supports are placed round the circumferential direction. The base of this approach is an approximate estimation of eigenvalues of proper functions which are the results of solutions of vibrating equation. Each longitudinal wave number corresponds to a particular boundary condition. The results are given in tabular and graphical forms. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. There is a new form of frequencies is obtained for different positions of ring supports, which is bell shaped. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases.

• Advances in concrete construction
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• 제13권5호
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• pp.367-376
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• 2022

Theoretical study of vibration distinctiveness of rotating cylindrical are examined for three volume fraction laws viz.: polynomial, exponential and trigonometric. These laws control functionally graded material composition in the shell radius direction. Functionally graded materials are controlled from two or more materials. In practice functionally graded material comprised of two constituent materials is used to form a cylindrical shell. For the current shell problem stainless steel and nickel are used for the shell structure. A functionally graded cylindrical shell is sanctioned into two types by interchanging order of constituent materials from inner and outer side for Type I and Type II cylindrical shell arrangement. Fabric composition of a functionally graded material in a shell thickness direction is controlled by volume fraction law. Variation of power law exponent brings change in frequency values. Influence of this physical change is investigated to evade future complications. This procedure is capable to cater any boundary condition by changing the axial wave number. But for simplicity, numerical results have been evaluated for clamped- simply supported rotating cylindrical shells. It has been observed from these results that shell frequency is bifurcated into two parts: one is related to the backward wave and other with forward wave. It is concluded that the value of backward frequency is some bit higher than that forward frequency. Influence of volume fraction laws have been examined on shell frequencies. Backward and forward frequency curves for a volume fraction law are upper than those related to two other volume fraction laws. The results generated furnish the evidence regarding applicability of present shell model and also verified by earlier published literature.

• Advances in concrete construction
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• 제10권6호
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• pp.499-507
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• 2020

In current study, utilizing the Kelvin's theory with polynomial, exponential and trigonometric volume fraction laws for functionally graded cylindrical shell vibrations. Effects of different parameters for ratios of length- and height-to-radius and angular speed versus fundamental natural frequencies been determined for two categories of cylindrical shells with clamped-free edge condition. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The frequencies are same when the cylinder is stationary. The frequencies increases and decreases on changing the constituent materials. The frequency results are verified with the earlier literature for the applicability of present model.

• Earthquakes and Structures
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• 제24권4호
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• pp.237-245
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• 2023

Based on novel Galerkin's technique, the theoretical study gives a prediction to estimate the vibrations of FG rotating cylindrical shell. Terms of ring supports have been introduced by a polynomial function. Three different laws of volume fraction are utilized for the vibration of cylindrical shells. Variation frequencies with the locations of ring supports have been analyzed and these ring supports are placed round the circumferential direction. The base of this approach is an approximate estimation of eigenvalues of proper functions which are the results of solutions of vibrating equation. Each longitudinal wave number corresponds to a particular boundary condition. The results are given in tabular and graphical forms. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing length-to-radius ratio. There is a new form of frequencies is obtained for different positions of ring supports, which is bell shaped. Moreover, on increasing the rotating speed, the backward frequencies increase and forward frequencies decreases.

• Advances in concrete construction
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• 제13권3호
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• pp.223-231
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• 2022

The problem is formulated by applying the Kirchhoff's conception for shell theory. The longitudinal modal displacement functions are assessed by characteristic beam ones meet clamped-clamped end conditions applied at the shell edges. The fundamental natural frequency of rotating functionally graded cylindrical shells of different parameter versus ratios of length-to-diameter and height-to-diameter for a wide range has been reported and investigated through the study with fractions laws. The frequency first increases and gain maximum value with the increase of circumferential wave mode. By increasing different value of height-to-radius ratio, the resulting backward and forward frequencies increase and frequencies decrease on increasing height-to-radius ratio. Moreover, on increasing the rotating speed, the backward frequencies increases and forward frequencies decreases. The trigonometric frequencies are lower than that of exponential and polynomial frequencies. Stability of a cylindrical shell depends highly on these aspects of material. More the shell material sustains a load due to physical situations, the more the shell is stable. Any predicted fatigue due to burden of vibrations is evaded by estimating their dynamical aspects.

• Advances in nano research
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• 제10권2호
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• pp.129-138
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• 2021

In present article, utilizing the Love shell theory with volume fraction laws for the cylindrical shells vibrations provides a governing equation for the distribution of material composition of material. Isotopic materials are the constituents of these rings. The position of a ring support has been taken along the radial direction. The Rayleigh-Ritz method with three different fraction laws gives birth to the shell frequency equation. Moreover, the effect of height- and length-to-radius ratio and angular speed is investigated. The results are depicted for circumferential wave number, length- and height-radius ratios with three laws. It is found that the backward and forward frequencies of exponential fraction law are sandwich between polynomial and trigonometric laws. It is examined that the backward and forward frequencies increase and decrease on increasing the ratio of height- and length-to-radius ratio. As the position of ring is enhanced for clamped simply supported and simply supported-simply supported boundary conditions, the frequencies go up. At mid-point, all the frequencies are higher and after that the frequencies decreases. The frequencies are same at initial and final stage and rust itself a bell shape. The shell is stabilized by ring supports to increase the stiffness and strength. Comparison is made for non-rotating and rotating cylindrical shell for the efficiency of the model. The results generated by computer software MATLAB.

• 대한기계학회논문집
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• 제9권4호
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• pp.487-496
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• 1985

회전하는 축대칭 얇은 셸구조물의 진동 특성을 유한요소법에 의하여 해석하였다. 2개의 절점을 가진 Conical Frustrm 형태의 축대칭 요소를 사용하였으며 원주방향의 변위는 Fourier Series로 분해하여서 방정식의 수를 상당히 줄일 수 있었다. Sanders-Koiter의 셸이론을 사용하였으며 진 동 모우드는 회전의 영향을 설명하기 위하여 대칭 및 비대칭 모우드를 모두 고려하였다. Coriolis 행렬을 포함하는 운동방정식에서 고유 진동수를 계산하기 위해서 질량, 강성 및 Coriolis 행렬로 이루어지는 Hermitian 행렬의 Sturm Sequence Property를 이용하였으며, 좁은 밴드를 갖는 대형 행렬에 알맞는 Determinant Search 방법을 확장하여 고유진동수 및 벡터를 구하였다. 원통형 셸에 대하여 정지한 경우 계산한 고유진동수를 실험치 및 이론치와 비교한 결과 잘 일치됨을 알 수 있었다. 여러 가지 회전 속도에 대해서 얻어진 고유진동스를 이론치와 비교한 결과 잘 일치 됨을 알 수 있어\ulcorner며 회전의 영향으로 traveling wave진동의 현상이 나타남을 알 수 있었다.

• 한국자기학회지
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• 제25권3호
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• pp.83-86
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• 2015

무기체계가 첨단, 고도화되면서 탄약을 정밀 제어하여 목표를 타격하기 위하여 공중폭발탄(ABM)이 개발되어 전장에서 운용되고 있다. 이러한 공중폭발탄의 시한정밀도를 향상시키기 위하여 총구를 이탈하는 탄의 속도를 측정하여 표적까지의 정확한 비행시간을 계산한 후 탄에 입력하여야 한다. 본 연구에서는 K4 기관총의 소염기 부분에 탄을 감지할 수 있는 장치를 도입하였다. 탄약의 주요 금속 부품은 신관 부분의 알루미늄과 파편 효과를 발휘하는 탄체의 철 부분, 총열의 강선부를 통과할 때 직진운동을 회전운동으로 전환시키는 회전탄대의 구리로 구성되어 있는데 알루미늄 부분을 탐지하기 위하여 와전류 탐촉자의 원리를 도입하였다. 탄이 총구를 벗어나는 수십 us 동안 탄속을 측정하기 위하여 U 자형의 MnZn Ferrite 코어에 코일을 권선하여 200 kHz의 교류 전류를 인가하여 탄의 총구 이탈 속도를 측정하였으며, 도플러 레이더와 병행 계측한 결과 ${\pm}1%$ 이내에서 잘 일치하였다.