• Title, Summary, Keyword: Dynamic Analysis

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A Study on the Dynamic Stress Analysis of an Engine Block using Flexible-body Dynamic Analysis (유연체 동역학적 해석을 이용한 엔진블록의 동응력 해석에 관한 연구)

  • Son, Chang-Su;Cheon, Ho-Jeong;Seong, Hwal-Gyeong;Yoon, Keon-Sik
    • Journal of the Korean Society for Precision Engineering
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    • v.28 no.7
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    • pp.805-813
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    • 2011
  • The dynamic stress of the diesel engine block is analyzed by using flexible-body dynamic analysis. Multiple loadings including the pressure load due to gas combustion, thermal load, and dynamic load are considered. Thermal load is assumed constant, however, pressure load and dynamic load are treated as time dependent. The present work is focused on the dynamic stress analysis, especially on finding critical points of the engine block. The analysis model includes four parts - engine block, generator, bed, and mounts. On the other hand, crank shaft, pistons, and main bearings are excluded from the model. However, their dynamic effects are applied by dynamic forces, obtained in the separate analysis. Dynamic stress is found by using flexible body dynamic analysis, and compared to the measured data.

An Investigation of Dynamic Characteristics of Structures in Optimization (동하중을 고려한 설계의 필요성에 관한 고찰)

  • Kang, B.S.;Kim, J.S.;Park, G.J
    • Proceedings of the KSME Conference
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    • pp.1011-1016
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    • 2004
  • All the loads in the real world are dynamic loads and it is well known that structural optimization under dynamic loads is very difficult. Thus the dynamic loads are often transformed to the static loads using dynamic factors. However, due to the difference of load characters, there can be considerable differences between the results from static and dynamic analyses. When the natural frequency of a structure is high, the dynamic analysis result is similar to that of static analysis due to the small inertia effect on the behavior of the structure. However, if the natural frequency is low, the inertia effect should not be ignored. Then, the behavior of the dynamic system is different from that of the static system. The difference of the two cases can be explained from the relationship between the homogeneous and the particular solutions of the differential equation that governs the behavior of the structure. Through various examples, the difference between the dynamic analysis and the static analysis are shown. Also the optimization results considering dynamic loads are compared with static loads.

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Seismic Analysis of Tunnel in Transverse Direction Part II: Evaluation of Seismic Tunnel Response via Dynamic Analysis (터널 횡방향 지진해석 Part II: 동적해석을 통한 터널의 지진응답 예측)

  • Park, Du-Hee;Shin, Jong-Ho;Yun, Se-Ung
    • Journal of the Korean Geotechnical Society
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    • v.26 no.6
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    • pp.71-85
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    • 2010
  • Dynamic analyses of tunnels are widely performed in practice in Korea. Accurate performance of a dynamic analysis is very difficult, requiring appropriate application of lower and lateral boundary conditions, deconvolution, constitutive model, and selection of dynamic soil properties etc. Lack of a systematic guideline on how to perform the dynamic analysis makes it even more difficult to perform an analysis. In addition, dynamic analyses are not needed in most cases and pseudo-static analyses are more than adequate. However, they are performed without a clear understanding on the need for the dynamic analysis and differences between the two methods. In this study, firstly, a guideline for correctly performing a 2D dynamic analysis is developed. Secondly, the differences in the tunnel responses using dynamic and pseudo-static analyses are discussed and compared. The results show that the discrepancies between the dynamic and static analyses are not significant for most cases. It is therefore recommended that the dynamic analyses be performed at tunnel portal, very soft ground, or in cases where spatial variation of the ground motion needs to be considered in the seismic analysis of tunnels in transverse direction.

Dynamic fracture instability in brittle materials: Insights from DEM simulations

  • Kou, Miaomiao;Han, Dongchen;Xiao, Congcong;Wang, Yunteng
    • Structural Engineering and Mechanics
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    • v.71 no.1
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    • pp.65-75
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    • 2019
  • In this article, the dynamic fracture instability characteristics, including dynamic crack propagation and crack branching, in PMMA brittle solids under dynamic loading are investigated using the discrete element method (DEM) simulations. The microscopic parameters in DEM are first calibrated using the comparison with the previous experimental results not only in the field of qualitative analysis, but also in the field of quantitative analysis. The calibrating process illustrates that the selected microscopic parameters in DEM are suitable to effectively and accurately simulate dynamic fracture process in PMMA brittle solids subjected to dynamic loads. The typical dynamic fracture behaviors of solids under dynamic loading are then reproduced by DEM. Compared with the previous experimental and numerical results, the present numerical results are in good agreement with the existing ones not only in the field of qualitative analysis, but also in the field of quantitative analysis. Furthermore, effects of dynamic loading magnitude, offset distance of the initial crack and initial crack length on dynamic fracture behaviors are numerically discussed.

A Study on the Dynamic Analysis of Railway Vehicle by Using Track Coordinate System (트랙좌표계를 이용한 철도차량의 동역학 해석에 관한 연구)

  • Kang, Juseok
    • Transactions of the Korean Society of Automotive Engineers
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    • v.21 no.2
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    • pp.122-130
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    • 2013
  • Rail geometries such as cant, grade and curvature can be easily represented by means of a track coordinate system. In this analysis, in order to derive a dynamic and constraint equation of a wheelset, the track coordinate system is used as an intermediate stage. Dynamic and constraint equations of railway vehicle bodies except the wheelset are written in the Cartesian coordinate system as a conventional method. Therefore, whole dynamic equations of a railway vehicle are derived by combining wheelset dynamic equations and dynamic equations of railway vehicle bodies. Constraint equations and constraint Jacobians are newly derived for the track coordinate system. A process for numerical analysis is suggested for the derived dynamic and constraint equations of a railway vehicle. The proposed dynamic analysis of a railway vehicle is validated by comparison against results obtained from VI-RAIL analysis.

Dynamic Deformation Analysis of Cylinder Bore considering Forced Vibration (강제 진동을 고려한 실린더 보어의 동적 변형 해석)

  • 윤성호;조덕형
    • Transactions of the Korean Society of Automotive Engineers
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    • v.10 no.5
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    • pp.174-181
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    • 2002
  • Dynamic deformation of the cylinder bore during actual engine operation has an important effect on the combustion gas sealing, oil consumption, friction and so on. The dynamic analysis using the finite element method is performed to investigate the dynamic deformation of the cylinder bore subjected to forced vibration under excitation of the combustion gas pressure. However, this analysis requires large computer memory and tremendous solving time. The pseudo-static analysis can be an alternative to the dynamic analysis at the expense of accuracy. Dynamic analysis and static analysis results are presented for both closed-deck block and open-deck block that are respectively combined with the cylinder block, cylinder head, transmission, and oil pan.

Effects of damping ratio on dynamic increase factor in progressive collapse

  • Mashhadi, Javad;Saffari, Hamed
    • Steel and Composite Structures
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    • v.22 no.3
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    • pp.677-690
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    • 2016
  • In this paper, the effect of damping ratio on nonlinear dynamic analysis response and dynamic increase factor (DIF) in nonlinear static analysis of structures against column removal are investigated and a modified empirical DIF is presented. To this end, series of low and mid-rise moment frame structures with different span lengths and number of storeys are designed and the effect of damping ratio in DIF is investigated, performing several nonlinear static and dynamic analyses. For each damping ratio, a nonlinear dynamic analysis and a step by step nonlinear static analysis are carried out and the modified empirical DIF formulas are derived. The results of the analysis reveal that DIF is decreased with increasing damping ratio. Finally, an empirical formula is recommended that relates to damping ratio. Therefore, the new modified DIF can be used with nonlinear static analysis instead of nonlinear dynamic analysis to assess the progressive collapse potential of moment frame buildings with different damping ratios.

Integrated Dynamic Simulation of a Magnetic Bearing Stage and Control Design (자기베어링 스테이지의 동적 거동 통합 시뮬레이션을 통한 제어 설계)

  • Kim, Byung-Sub
    • Journal of The Korean Society of Manufacturing Technology Engineers
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    • v.22 no.4
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    • pp.730-734
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    • 2013
  • The dynamic simulation of machine tools and motion control systems has been widely used for optimization, design verification, control design, etc. There are three main streams in dynamic simulation: structural dynamic analysis based onthe finite element method, dynamic motion analysis based on equations of motion, and control system analysis based on transfer functions. Generally, one of these dynamic simulation methods is chosen and employed for specific purposes. In this study, an integrated dynamic simulation is introduced, in which the structure, motion, and control dynamics are combined together. Commercially well-known software is used in the integrated dynamic simulation: ANSYS, ADAMS, and Matlab/Simulink. Using the integrated dynamic simulation, the dynamics of a magnetic bearing stage is analyzed and the causes of oscillation and noise are identified. A controller design for suppressing a flexible dynamic mode is carried out and verified through the integrated dynamic simulation.

Efficient Vibration Analysis of Stadium Structure (경기장 구조물의 효율적인 진동해석)

  • 김기철;이동근
    • Proceedings of the Computational Structural Engineering Institute Conference
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    • pp.475-482
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    • 2001
  • Stadium stand could be led to significant dynamic response due to rhythmical activities of spectator. The dynamic loads induced by spectators movements are considered as static loads in design standard of many countries but these loads have dynamic characteristics. So, it is desirable to apply measured dynamic loads created by spectator activities and to analyze the dynamic behavior of stadium system. The precise investigation of the dynamic loads on stadium structures and the accurate analysis of dynamic behavior of stadium systems are demanded for effective design. As the floor mesh of stadium stand is refined, the number of nodes increase in numerical analysis. So it is difficult to analyze entire stadium structures and much more computer memory are necessary for vibration analysis of stadium system. In this study, the various dynamic loads induced by spectator movements are measured and analyzed. And new modeling method that reduce the nodal points of stadium systems are introduced. Vibration analysis of stadium system is executed to inspect the accuracy and the efficiency of proposed method in this paper.

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Analysis of the Static and Dynamic Stability Properties of the Unmaned Airship

  • Lee, Hae Chang
    • International Journal of Aeronautical and Space Sciences
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    • v.2 no.2
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    • pp.82-94
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    • 2001
  • The purpose of this paper is to analyze the static and dynamic stability-of the unmanned airship under development ; the target airship's over-all length of hull is 50m and the maximum diameter is 12.5m. For the analysis, the dynamic model of an airship was defined and both the nonlinear and linear dynamic equations of motion were derived. Two different configuration models (KA002Y and KA003Y) of the airship were used for the target model of the static stability analysis and the dynamic stability analysis. From the result of analyses, though the airship is unstable in static stability, dynamic characteristics of the airship can provide the stable dynamic stability. All of the results, airship models and dynamic flight equations will be an important basement and basic information for the next step of developing the automatic flight control system(AFCS) and the stability augmentation system(SAS) for the unmanned airship as well as for the stratospheric airship in the future.

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