• 제목/요약/키워드: Vibrational frequency

검색결과 349건 처리시간 0.025초

Broadband energy harvester for varied tram vibration frequency using 2-DOF mass-spring-damper system

  • Hamza Umar;Christopher Mullen;Soobum Lee;Jaeyun Lee;Jaehoon Kim
    • Smart Structures and Systems
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    • 제32권6호
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    • pp.383-391
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    • 2023
  • Energy harvesting in trams may become a prevalent source of passive energy generation due to the high density of vibrational energy, and this may help power structural health monitoring systems for the trams. This paper presents a broadband vibrational energy harvesting device design that utilizes a varied frequency from a tram vehicle using a 2 DOF vibrational system combined with electromagnetic energy conversion. This paper will demonstrate stepwise optimization processes to determine mechanical parameters for frequency tuning to adjust to the trams' operational conditions, and electromagnetic parameters for the whole system design to maximize power output. The initial optimization will determine 5 important design parameters in a 2 DOF vibrational system, namely the masses (m1, m2 (and spring constants (k1, k2, k3). The second step will use these parameters as initial guesses for the second optimization which will maintain the ratios of these parameters and present electrical parameters to maximize the power output from this system. The obtained values indicated a successful demonstration of design optimization as the average power generated increased from 1.475 mW to 17.44 mW (around 12 times).

외팔보의 동적응답과 진동모드 분석 (An Analysis of the Dynamic Response and Vibrational Mode for the Cantilevered Beam)

  • 김예현;고영준;강병용;장호경
    • 한국음향학회지
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    • 제16권1호
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    • pp.16-23
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    • 1997
  • 강제진동에 의한 외팔보의 동적응답과 진동모드를 연구하였다. Bernoulli-Euler 이론과 유한요소법을 이용하여 외팔보의 고유진동수와 진동모드를 수치해석하고 실험으로 측정하여 비교하였다. 가진주파수를 1Hz에서 70Hz까지 변화시켜 외팔보의 1차, 2차 공진주파수를 구하고, 응답위치에 따른 진동 변위를 측정하여 진동모드를 살펴보았다. 실험결과에서 외팔보의 절점(node)이 1차모드에서는 0.2차모드에서는 0,0.786으로 측정되었다. 외팔보의 공진주파수와 진동모드에 대해 이론적으로 예상했던 결과와 실험으로 측정한 결과가 거의 일치하였다.

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유체가 흐르는 가스파이프의 진동 특성 (Vibrational Characteristics of the Gas Pipelines Conveying Flow)

  • 김경태;이성수;이성우
    • 한국생산제조학회지
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    • 제21권2호
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    • pp.337-343
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    • 2012
  • This work investigates the vibrational characteristics of the underground gas pipelines. Experiments were conducted to analyze the effects of various parameters on the vibrational characteristics from the emergency detection point of view. Influences of the various types of impact exerted on the pipe, height of free fall and measuring locations were analyzed. Especially, the difference between the vibrational signal generated by the direct impact on the pipe and the ambient noise was successfully identified. To validate the experimental observation, computer simulation was also performed with constant properties(elasticity, fluid velocity and internal pressure) which are directly conjectured from the accompanying experiment with a real pipe system.

2차원 진동 미세가공을 위한 가진테이블 개발 (Development of Excitation Table for 2-dimensional Vibrational Micro Cutting)

  • 김기대;이강희
    • 한국기계가공학회지
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    • 제11권3호
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    • pp.62-67
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    • 2012
  • To realize 2-dimensional vibrational micro cutting in milling and drilling, etc. where the tools rotate, it could be a promising way to vibrate a workpiece instead of a rotating tool itself. In this study, an excitation work-table was developed using two piezoelectric materials orthogonally arranged. The trochoidal trajectory of a cutting tool which is necessary for 2D vibrational cutting is enabled in the excitation condition of higher excitation frequency and larger amplitude of vibration and the cutting condition of smaller diameter of cutting tool and lower spindle speed. The various trochoidal trajectories of a cutting tool could be generated in the excitation work-table by adjusting the input voltages to two piezoelectric materials and the phase between the two voltages and the trajectories could be readily used for the 2D vibrational micro cutting.

Dimethyldioxirane의 분자구조와 Vibrational Frequencies에 대한 양자역학적 고찰 (Quantum Mechanical Investigation for the Structure and Vibrational Frequencies of Dimethyldioxirane)

  • 강창덕;김승준
    • 대한화학회지
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    • 제42권1호
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    • pp.9-15
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    • 1998
  • Dimethyldioxirane$[(CH_3)_2CO_2]$의 분자구조, vibrational frequencies 그리고 infrared(IR) 스펙트럼의 세기(intensity)등에 대한 이론적 연구를 high level ab initio 양자역학적 방법(CISD,CCSD, CCDS(T))을 사용하여 수행하였다. 분자구조의 경우 C-O와 O-O에 대한 결합길이는 parent dixoirane$(CH_2O_2)$과 유사한 결과를 보여주었으며, electron correlation effect의 영향이 C-C나 C-H결합길이 보다 더 크게 작용하였다. 사용된 basis sets(DZ,DZP, TZP, 그리고 TZ2P)에 대해서는 polarization function의 역할이 매우 중요한 것으로 나타났으며 triple zeta(TZ)에 의한 효과는 상대적으로 나타났다. 한편 계산된 harmonic vibrational frequency들을 실험결과 및 다른 이론 계산결과와 비교, 분석하였으며 IR intencity에 근거하여 각 vibrational mode를 assign하였다.

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셸 구조물의 중고주파 진동 파워흐름해석 (Power Flow Analysis for Medium-to-High Frequency Vibration of Shell Structures)

  • 박도현;김일환;홍석윤;길현권
    • 한국소음진동공학회:학술대회논문집
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    • 한국소음진동공학회 2002년도 춘계학술대회논문집
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    • pp.1177-1184
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    • 2002
  • In this paper, power flow analysis method on the various types of thin shell has been developed to solve vibrational Problems in the medium to high frequency ranges. Energy governing equations have been derived both for out-of plane and in-plane waves in thin shell. These results have been numerically applied to predict the vibrational energy density and intensity distributions of cylindrical, spherical and doubly-curved shells.

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고유진동수의 간이 추정식을 이용한 보강판 구조물의 동특성의 최적변경에 관한 연구 (A Study on Optimum Modification of Dynamic Characteristics of Stiffened Plate Using Simplified Equation of Natural Frequency)

  • 박성현;남정길
    • Journal of Advanced Marine Engineering and Technology
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    • 제26권1호
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    • pp.48-58
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    • 2002
  • There is a purpose of this study for the proposal of the optimum technique utilized for the vibration design initial step. The stiffened plate structure for the ship hull is made for analysis model. To begin with, dynamic characteristics of stiffened plate structure is analysed using FEM. Main vibrational mode of the structure is decided in the analytical result of FEM. The simplified equation on the natural frequency of the main vibrational mode is induced. Next, sensitivity analysis is carried out using the simplified equation, and rate of change of dynamic characteristics is calculated. Then, amount of design variable is calculated using this sensitivity value and optimum structural modification method. The change of natural frequency is made to be an objective function. Thickness of panel, cross section moment of stiffener and girder become a design variable. The validity of the optimization method using simplified equation is examined. It is shown that the result effective in the optimum modification for natural frequency of the stiffened plate structure.

Energetics of In-plane Motions in Coupled Plate Structures

  • Park, Young-Ho;Park, Chang Hyun
    • 한국해양공학회지
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    • 제34권6호
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    • pp.428-435
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    • 2020
  • Energy flow analysis (EFA) has been used to predict the frequency-averaged vibrational responses of built-up structures at high frequencies. In this study, the frequency-averaged exact energetics of the in-plane motions of the plate were derived for the first time by solving coupled partial differential equations. To verify the EFA for the in-plane waves of the plate, numerical analyses were performed on various coupled plate structures. The prediction results of the EFA for coupled plate structures were shown to be accurate approximations of the frequency-averaged exact energetics, which were obtained from classical displacement solutions. The accuracy of the results predicted via the EFA increased with an increase in the modal density, regardless of various structural parameters. Therefore, EFA is an effective technique for predicting the frequency-averaged vibrational responses of built-up structures in the high frequency range.

질량변경에 따른 연속계의 동특성변화 예측 (Prediction of Dynamic Characteristics of Continuous Systems Due to the Mass Modification)

  • 이정윤;최상렬;박천권;오재응;정석주
    • 대한기계학회논문집
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    • 제17권2호
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    • pp.248-256
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    • 1993
  • 본 연구에서는 연속계의 진동모드를 구하여 일반질량(generalize mass)을 유 동하였으며 집중, 분포질량 변경에 따른 일반질량 변화량을 산출하여 감도계수를 구하 는 새로운 연속계 감도해석 방법을 제안하였고, 타당성을 검증하기 위해 외팔보, 계단 보에 적용하여 감도계수, 고유진동수, 진동모드, 전달함수의 변화량을 예측하고 이론 치와 비교하였다. Fig.1은 본 연구의 흐름도를 나타낸다.

MO Study of CO Chemisorption and Oxidation on a Pt(100) Surface

  • Choe, Sang-Joon;Park, Dong-Ho;Huh, Do-Sung
    • Bulletin of the Korean Chemical Society
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    • 제15권11호
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    • pp.933-939
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    • 1994
  • Using an atom superposition and electron delocalization molecular orbital (ASED-MO) method, we have investigated the vibrational and chemisorptive properties of adsorbates on a Pt(100) surface during CO oxidation. The calculated vibrational stretching frequency for a predicted structure of $[CO{\cdot}{\cdot}{\cdot}O]^*$ complex is 1642 $cm^{-1}$. The CO bond stretches by 0.05 ${\AA}$ when adsorbed on one-fold site, and is tilted by 30 ${\AA}$ from the surface normal. We find the decrease in CO vibrational frequency on going from the one-fold to the high coordination sites. Binding at the two-fold site is predicted to be favored for $Pt_{18}(100)$ and at the 1-fold site for $Pt_{23}(100)$. From the calculations of the steric interactions, we have found that pre-adsorbed oxygen modifies the surface so that CO is adsorbed on the one-fold site ordered in a $(\sqrt{2}{\times}{\sqrt}{2})R45^{\circ}$. Our results are in good agreement with recent experimental findings of Hong et al. [J.Phys. Chem. 1993, 97, 1258].