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김재하,우호길 한국군사과학기술학회 2001 한국군사과학기술학회지 Vol.4 No.1
This paper considers the Maximum Pesponse Spectrum for the random vibration, sinusoidal vibration, linear sweep vibration. The random vibration quality levels and the sinusoidal vibration quality level are compared using MRS. And the severity between the vibration test specification and real environments using Maximum Response Spectrum are also compared using it.
Dynamic Modulation Transfer Function Analysis of Images Blurred by Sinusoidal Vibration
Yanlu Du,Yalin Ding,Yongsen Xu,Chongshang Sun 한국광학회 2016 Current Optics and Photonics Vol.20 No.6
The dynamic modulation transfer function (MTF) for image degradation caused by sinusoidal vibrationis formulated based on a Bessel function of the first kind. The presented method makes it possible toobtain an analytical MTF expression derived for arbitrary frequency sinusoidal vibration. The error obtainedby the use of finite order sum approximations instead of infinite sums is investigated in detail. DynamicMTF exhibits a stronger random behavior for low frequency vibration than high frequency vibration. Thecalculated MTFs agree well with the measured MTFs with the slant edge method in imaging experiments. With the proposed formula, allowable amplitudes of any frequency vibration are easily calculated. Thisis practical for the analysis and design of the line-of-sight stabilization system in the remote sensing camera.
김상락,김종훈,김풍호 경기대학교 1996 論文集 Vol.38 No.2
A simple one-dimensional dynamical system of a ball colliding with a periodically vibrating table is considered. It is assumed that the ball is a granular particle and the table is sinusoidally vibrating. The collision is characterized by a coefficient of restitution at each impact. The coefficient of restitution and the frequency of the table is fixed. For given values of initial position and velocity of a ball, we investigated the behavior from periodic to chaotic motion by changing table's amplitude A. We observed the distinct regions of period doubling, chaos, crisis and sticking.
자동차 연료 펌프용 BLDC 모터의 전자기적인 소음 저감에 관한 연구
김동기(Dong-Ki Kim),이승우(Seung-Woo Lee),윤덕용(Duck-Yong Yoon) 대한전기학회 2019 전기학회논문지 Vol.68 No.2
This paper proposes a driving method in order to reduce the electromagnetic noise of blushless DC motor for fuel pump of vehicles. In recent years, these motors have been widely employed in the electric fuel pumps because of its high-efficiency, high-reliability, compact size, light weight, and simple control method. However, despite the various advantages, brushless DC motors have realistic problems. These problems are acoustic noise and vibration, which are caused by torque ripple and sudden current fluctuation in the stator windings due to the mechanical structures and control methods. If the mechanical structures are redesigned or the control methods are improved, both cogging torque and torque ripple due to commutation can be reduced. Nevertheless, if quasi-square-wave currents are supplied to these motors by conventional methods, the stator windings may generate the electromagnetic noise and vibration within the audio frequency bands. In this paper, a sinusoidal-wave driving method is proposed to suppress the fluctuating currents. The reduction effects on noise and vibration are verified through computer simulations and experiments.
홍창섭,양홍준,강윤식,오재윤,오택열 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.12
In this paper, we study the correlation between a sinusoidal sweep durability test and a random vibration durability test through specimen tests. We compute random vibration durability test conditions having the same fatigue damage spectrum as a sinusoidal sweep durability test using the numerical analysis method. We use two kinds of specimens of different shape to perform durability tests. This paper proposes a normalization process that uses the average of the fatigue damage time caused only by a sinusoidal sweep durability test, and the average of the fatigue damage time caused only by a random vibration durability test. The normalization process makes it possible to remove the difference of fatigue life due to the difference of specimen shape. Thus, we determine one trend equation that can predict the test results of two kinds of specimen with high reliability. Through the trend equation, we can find the correlation between the fatigue life due to sinusoidal sweep vibration, and the fatigue life due to random vibration, which depends only on the specimen material and the excitation method.
정용현,이은석,박순영,양창환,정진택,Chung, Yong-hyun,Lee, Eun-seok,Park, Soon-young,Yang, Chang-hwan,Jung, Jin-taeg 항공우주시스템공학회 2009 항공우주시스템공학회지 Vol.3 No.2
The structural analysis of liquid rocket engine was performed in the case of sinusoidal vibration load to verify structural safety. The finite element model is composed with main liquid rocket engine components, combustion chamber, turbopump, gas-generator, pyro-starter, main pipes, main valve, heat-exchanger, gimbal-mount and brackets. Natural vibration mode analysis and structural analysis for sinusoidal vibration load were performed. The natural mode frequency of liquid rocket engine is twice than that of launch vehicle. In the case of stress result of sinusoidal vibration load, the part of maximum stress has 1.4 margin, so the engine structure is safe for sinusoidal vibration load.
B. Rousta Navi,M. Mohammadimehr,A. Ghorbanpour Arani 국제구조공학회 2019 Steel and Composite Structures, An International J Vol.32 No.6
Vibration control in mechanical equipments is an important problem where unwanted vibrations are vanish or at least diminished. In this paper, free vibration active control of the porous sandwich piezoelectric polymeric nanocomposite microbeam with microsensor and microactuater layers are investigated. The aim of this research is to reduce amplitude of vibration in micro beam based on linear quadratic regulator (LQR). Modified couple stress theory (MCST) according to sinusoidal shear deformation theory is presented. The porous sandwich microbeam is rested on elastic foundation. The core and face sheet are made of porous and three-phase carbon nanotubes/resin/fiber nanocomposite materials. The equations of motion are extracted by Hamilton’s principle and then Navier’s type solution are employed for solving them. The governing equations of motion are written in space state form and linear quadratic regulator (LQR) is used for active control approach. The various parameters are conducted to investigate on the frequency response function (FRF) of the sandwich microbeam for vibration active control. The results indicate that the higher length scale to the thickness, the face sheet thickness to total thickness and the considering microsensor and microactutor significantly affect LQR and uncontrolled FRF. Also, the porosity coefficient increasing, Skempton coefficient and Winkler spring constant shift the frequency response to higher frequencies. The obtained results can be useful for micro-electro-mechanical (MEMS) and nano-electro-mechanical (NEMS) systems.
나경수,황인영,조기대 한국항공우주학회 2014 한국항공우주학회 학술발표회 논문집 Vol.2014 No.11
본 논문에서는 500kg 급으로 설계된 소형위성이 발사환경 하에서 구조적으로 안정한지 검증하기 위해 수행한 구조실험용모델 진동시험 결과에 대해 기술하였다. 소형위성 구조설계 요구규격은 적정 발사비용 및 발사 성공률을 가지면서 목표 궤도에 투입 가능한 중형 발사체 두 개의 요구조건을 조합하여, 최악의 조건으로 수립하였다. 진동시험 수행 시 위성체에 과도한 동적 하중이 가해지는 것을 방지하기 위해 노치 입력을 적용하였고, 노치 입력값 생성을 위해 위성체 경계하중 및 부품/구성품 설계 한계 하중을 고려하였다. 인증수준 정현파 진동시험 전·후 저수준 시험 결과 비교를 통해 구조적 문제가 없음을 확인하였고, 최종적으로 정현파 진동하중에 대한 소형위성의 구조 안정성을 확인할 수 있었다. The vibration test results of an experimental structure model are analyzed to verify the structural integrity of a 500kg class small satellite under launch environment. Two medium launch vehicles are selected as candidates considering cost, success rates and orbit, and the combined worst cases of their specifications are used to establish the structure design requirements. The notched inputs are considered to avoid inducing unrealistic dynamic loads. In order to determine the notched inputs, the satellite interface forces and design limit loads of parts/components are analyzed. The structural damage is checked by comparison of pre and post low level sinusoidal vibration test results. Finally, the structural integrity of the small satellite under sinusoidal vibration loads is verified by the qualification test results analysis.