기계적 진동에 대한 MRS 및 MRS의 응용

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.

랜덤진동에서 군용 항공기 외부연료탱크 및 파일런 구조 강건성 평가

김현기(Hyun-Gi Kim),김성찬(Sungchan Kim) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.3

항공기는 기동 중 다양한 진동의 영향을 받게 된다. 이러한 진동들은 상황에 따라서는 항공기 생존에 치명적인 영향을 미칠 수 있으므로 항공기에 적용되는 구성품들은 랜덤 진동해석을 통해 다양한 진동 조건에 대한 안전성이 입증되어야 한다. 본 연구에서는 상용 소프트웨어인 MSC.Random을 사용하여 랜덤진동 조건에서 군용항공기 외부연료탱크와 파일런에 대한 구조 강건성을 평가하였다. 랜덤 진동해석은 경계조건 지점에 단위하중을 부과하여 주파수 응답해석을 수행한 후 파워 스펙트럼 밀도 프로파일로 가진하게 되는데, 이 과정에서 필요한 모드 데이타는 모달해석 방법을 통해 추출하였다. 그리고, 랜덤진동 조건으로 미국 국방환경규격에서 규정하고 있는 랜덤 진동 프로파일을 적용하였고, G 단위로 주어진 파워 스펙트럼 밀도 프로파일을 중력가속도 단위로 변환하여 사용하였다. 수치해석 결과로, x 축, y 축 및 z 축 방향에서의 랜덤 가진에 대해 수치해석 모델을 구성하는 빔 요소, 쉘 요소 그리고 솔리드 요소의 안전여유를 파악하여 본 논문에서 다루고 있는 군용 항공기에 장착되는 외부연료탱크와 파일런의 구조 강건성을 평가하였다. Aircraft are affected by various vibrations during maneuvering. These vibrations may have a fatal effect on the survival of aircraft in some cases, so the safety of components applied to the aircraft should be proven against various vibrations through random vibration analysis. In this study, the structural robustness of an external fuel tank and pylon for military aircraft was evaluated under random vibration conditions using commercial software, MSC Random. In the random vibration analysis, a frequency response analysis was performed by imposing a unit load on the boundary condition point, and then excitation was performed with a PSD profile. In this process, the required mode data was extracted through a modal analysis method. In addition, the random vibration profile specified in the US Defense Environment Standard was applied as random vibration conditions, and the PSD profile given in units of G"s was converted into units of gravitational acceleration. As a result of the numerical analysis, we evaluated the structural robustness of the external fuel tank and pylon by identifying the safety margins of beam elements, shell elements, and solid elements in a numerical model for random vibration in the x, y, and z directions.

Evaluation of structural design methodologies for predicting mechanical reliability of solder joint of BGA and TSSOP under launch random vibration excitation

Park, Tae-Yong,Park, Jong-Chan,Oh, Hyun-Ung Elsevier 2018 International journal of fatigue Vol.114 No.-

<P><B>Abstract</B></P> <P>The fatigue damage that accumulates on a solder joint under a launch vibration environment is a major cause of failure in spaceborne electronics. Thus, predicting the mechanical safety of the solder joint in the structural design phase is important to guarantee a successful space mission. This paper proposes a mechanical design methodology to predict and ensure more reliable mechanical safety of the solder joints of a plastic ball grid array (PBGA) and a thin-shrink small outline package (TSSOP) under launch random vibration excitation. Random vibration fatigue tests for a sample printed circuit board (PCB) assembly were performed to assess the fatigue life of BGA and TSSOP solder joints. The effectiveness of the proposed structural design methodologies was evaluated by comparing the margin of safety calculated from various analysis approaches and the random vibration fatigue test results of the PCB specimen.</P> <P><B>Highlights</B></P> <P> <UL> <LI> We propose structural design methodologies of spaceborne electronics. </LI> <LI> The methodologies are based on mechanical safety prediction on solder joint. </LI> <LI> We performed the fatigue tests of PCB specimens under random vibration. </LI> <LI> The effectiveness of the proposed methodologies were validated by the tests. </LI> </UL> </P>

진동 폭에 따른 전통목구조의 고유진동수 특성

황종국(Hwang Jong-Kook),홍성걸(Hong Sung-Gul),이영욱(Lee Young-Wook),정성진(Jung Sung-Jin) 대한건축학회 2009 大韓建築學會論文集 : 構造系 Vol.25 No.5

In this research a dynamic testis performed to evaluate vibration characteristics of the main building of Bongjeong-sa (temple) in the laboratory. For this purpose, a one-third scale model with the roof-dead load of 46,710N is designed and prepared on a steel sliding table of 5m by 4m. From the result of the vibration test, we evaluate natural frequency, transfer function between base layer and damping ratio of the building. The dimensions of this test building are 2910㎜ wide and 4450㎜ long. Although the soil walls, windows and doors exist between the columns, to exclude the effect of other variables other than the joints of columns and connecting beams, they were not contained in this test model. Also, the top part of roof was not contained in this test model and replaced by weight. In process of the random vibration experiment, we observe that the natural frequency of test building changes according to the magnitude of vibration. To confirm the variation of natural frequency, the random vibration test was performed for the RMS amplitude of different kinds. To confirm exactly the shift effect of predominant frequencies and the variation of transfer function value, sine waves that the amplitude changes from 0.2㎜ to 2.5㎜ were actuated and transfer function was calculated. A free vibration experiment is performed to determine damping ratio and verify the variation of damping ratio by the magnitude of initial impact displacement.

Modal analysis and ambient vibration measurements on Mila-Algeria cable stayed bridge

Abderrahmane Kibboua,Mohamed Naboussi Farsi,Jean-Luc Chatelain,Bertrand Guillier,Hakim Bechtoula,Youcef Mehani 국제구조공학회 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.2

The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.

Modal analysis and ambient vibration measurements on Mila-Algeria cable stayed bridge

Kibboua, Abderrahmane,Farsi, Mohamed Naboussi,Chatelain, Jean-Luc,Guillier, Bertrand,Bechtoula, Hakim,Mehani, Youcef Techno-Press 2008 Structural Engineering and Mechanics, An Int'l Jou Vol.29 No.2

The seismic response analysis of an existing bridge needs a mathematical model that can be calibrated with measured dynamic characteristics. These characteristics are the periods and the associated mode shapes of vibration and the modal damping coefficients. This paper deals with the measurements and the interpretation of the results of ambient vibration tests done on a newly erected cable stayed bridge across the Oued Dib River at Mila city in Algeria. The signal analysis of ambient vibration records will permit to determine the dynamic characteristics of the bridge. On the other hand, a 3-D model of the bridge is developed in order to assess the frequencies and the associated modes of vibration. This information will be necessary in the planning of the test on the site (locations of the sensors, frequencies to be measured and the associated mode shapes of vibration). The frequencies predicted by the finite element model are compared with those measured during full-scale ambient vibration measurements of the bridge. In the same way, the modal damping coefficients obtained by the random decrement method are compared to those of similar bridges.

Stochastic modeling and vibration analysis of rotating beams considering geometric random fields

Choi, C.K.,Yoo, H.H. Elsevier [etc.] 2017 Journal of Sound and Vibration Vol.388 No.-

<P>Geometric parameters such as the thickness and width of a beam are random for various reasons including manufacturing tolerance and operation wear. Due to these random parameter properties, the vibration characteristics of the structure are also random. In this paper, we derive equations of motion to conduct stochastic vibration analysis of a rotating beam using the assumed mode method and stochastic spectral method. The accuracy of the proposed method is first verified by comparing analysis results to those obtained with Monte-Carlo simulation (MCS). The efficiency of the proposed method is then compared to that of MCS. Finally, probability densities of various modal and transient response characteristics of rotating beams are obtained with the proposed method. (C) 2016 Elsevier Ltd. All rights reserved.</P>

Response-only modal identification using random decrement algorithm with time-varying threshold level

Chang-Sheng Lin,Tse-Chuan Tseng 대한기계학회 2014 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.28 No.6

Modal Identification from response data only is studied for structural systems under nonstationary ambient vibration. The topic of thispaper is the estimation of modal parameters from nonstationary ambient vibration data by applying the random decrement algorithm withtime-varying threshold level. In the conventional random decrement algorithm, the threshold level for evaluating randomdec signatures isdefined as the standard deviation value of response data of the reference channel. The distortion of randomdec signatures may be, however,induced by the error involved in noise from the original response data in practice. To improve the accuracy of identification, amodification of the sampling procedure in random decrement algorithm is proposed for modal-parameter identification from the nonstationaryambient response data. The time-varying threshold level is presented for the acquisition of available sample time history to performaveraging analysis, and defined as the temporal root-mean-square function of structural response, which can appropriately describea wide variety of nonstationary behaviors in reality, such as the time-varying amplitude (variance) of a nonstationary process in a seismicrecord. Numerical simulations confirm the validity and robustness of the proposed modal-identification method from nonstationary ambientresponse data under noisy conditions.

건설중장비 제품개발 초기 단계에서의 라디에이터 진동 설계

강현석(Hyunseok Kang),김성환(Sunghwan Kim),강종민(Jongmin Kang) 한국소음진동공학회 2011 한국소음진동공학회 학술대회논문집 Vol.2011 No.10

The working conditions of construction equipments such as excavators, wheel loaders and haulers are very tough and severe in fact. To design main components of construction equipment under the severe environment, it’s important for engineers to consider design for vibration durability point of view at the early stage of product development process. Radiator as a cooling unit of construction equipment is one of critical components to apply design for vibration. We present a design for vibration process and methodology on the radiator system in construction equipment industries. From the natural frequency and the random vibration analysis based on field vibration test data, we could find current status of radiator layout design to develop and made best layout specification of radiator design to decide for product development process at the early stage.

비정상 랜덤 진동 조건에서 압전 에너지 수확 장치의 시변 상관 다변량 응답 특성 분석

윤헌준(Heonjun Yoon),김미소(Miso Kim),박춘수(Choon-Su Park),윤병동(Byeng D. Youn) 대한기계학회 2014 대한기계학회 춘추학술대회 Vol.2014 No.11

The output performances, such as the tip displacement and electric power, of a piezoelectric energy harvester (PEH) are produced as a correlated multivariate response due to the electromechanical coupling. Furthermore, since most ambient vibrations in nature are inherently random and non-stationary, the tip displacement and electric power may also randomly change with time. However, there has been no attempt to investigate the temporal correlated multivariate response of the PEH under a non-stationary random vibration. Therefore, this study aims at statistically comparing the stochastic analytical predictions and experimental observations on the tip displacement and electric power under a nonstationary random vibration. In the stochastic analytical prediction, the output performances were calculated based on the time-varying power spectral density estimated by the smoothed pseudo Wigner-Ville distribution. In the experimental setup, the input acceleration signal was induced by an electrostatic shaker and its amplitude and excitation frequency were randomly modulated. The weighted integrated factor was used as a correlation metric for the temporal response, which calculates an error between stochastic analytical predictions and experimental observations under one experimental setting. Finally, T-pooling metric was used to integrate the evidence from all relevant data of the correlated multivariate response under various experimental settings into a single aggregate measure for assessing the global agreement.