• Title/Summary/Keyword: Dynamic equation

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An Analysis of Dynamic Characteristics of Air-Lubricated Slider Bearing by Using Perturbation Method (섭동법을 이용한 공기윤활 슬라이더 베어링의 동특성 해석)

  • Gang, Tae-Sik;Choe, Dong-Hun;Jeong, Tae-Geon
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.24 no.6
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    • pp.1520-1528
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    • 2000
  • This study presents a method for determining bearing stiffness and damping coefficients of air-lubricated slider bearing, and shows influences of air-bearing surface geometry(recess depth, crown an d pivot location) on flying attitude and dynamic characteristics. To derive the dynamic lubrication equation, the perturbation method is applied to the generalized lubrication equation which based on linearized Boltzmann equation. The generalized lubrication equation and the dynamic lubrication equation are converted to a control volume formulation, and then, the static and dynamic pressure distributions are calculated by finite difference method. The recess depth and crown of the slider show significantly influence on flying attitude and dynamic characteristics comparing with those of pivot location.

Dynamic characteristics of the compressor-combined condenser system (압축기 계가 결합된 응축기의 동특성)

  • Kim, Jae-Dol
    • Transactions of the Korean Society of Mechanical Engineers B
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    • v.22 no.7
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    • pp.1001-1012
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    • 1998
  • This paper reports the analysis of dynamic characteristics of air-cooled condenser. At first, there is an assumption that the superheated vapor flows into the condenser inlet. And in order to consider the effect of pressure change in the dynamic characteristics of the condenser the combined system of condenser and compressor was used. By using the equation of energy balance and the equation of mass balance, the basic equation for describing the dynamic characteristics of condenser can be derived. The transfer function for describing dynamic response of the condenser to flow rate change outlet can be obtained from using linearizations and Laplace transformations of the equation. From this transfer function, analytical investigation which affects the frequency responses of condenser has been made. Through this study, it became possible that the information about the dynamic characteristics of air-cooled condenser is offered. While the average heat transfer coefficient of the refrigerant side necessary for the theoretical calculation of the dynamic characteristics is given by calculation method for the tube length and pressure drop of air-cooled condenser.

Dynamic visco-hyperelastic behavior of elastomeric hollow cylinder by developing a constitutive equation

  • Asgari, Masoud;Hashemi, Sanaz S.
    • Structural Engineering and Mechanics
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    • v.59 no.4
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    • pp.601-619
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    • 2016
  • In this study, developments of an efficient visco-hyperelastic constitutive equation for describing the time dependent material behavior accurately in dynamic and impact loading and finding related materials constants are considered. Based on proposed constitutive model, behaviour of a hollow cylinder elastomer bushing under different dynamic and impact loading conditions is studied. By implementing the developed visco-hyperelastic constitutive equation to LS-DYNA explicit dynamic finite element software a three dimensional model of the bushing is developed and dynamic behaviour of that in axial and torsional dynamic deformation modes are studied. Dynamic response and induced stress under different impact loadings which is rarely studied in previous researches have been also investigated. Effects of hyperelastic and visco-hyperelastic parameters on deformation and induced stresses as well as strain rate are considered.

Development of Curve Fitted Equation for the Dynamic Response of a Buried Concrete Pipelines with Various End Boundary Conditions (여러 단부경계조건을 가진 콘크리트 매설관의 동적응답에 대한 곡선적합식의 개발)

  • Jeong, Jin-Ho;Kim, Sung-Ban;Joeng, Du-Hwoe
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.572-581
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    • 2006
  • This study is to investigate dynamic response of concrete buried pipelines with various end boundary conditions and develop a curve fitted equation to ensure practicality and convenience for the use at the actual field for the test of resistance of earthquake. Dynamic response under the various end boundary conditions is calculated with analysis on values and computing programs. However, such a method of analysis requires skillfulness in using computing programs for dynamic movement of buried pipelines with dynamic analysis formula and has lower efficiency and practicality because, in the nature of analysis program of values, it needs much time to conduct repeated calculations. Therefore, the study is intended to develop a curve fitted equation to ensure more efficient and practical analysis. This paper tests various degrees of equation with non-linear least square method and developments a curve fitted equation based on the transmission speed with the best results. In the use of curve fitted equation, degree of polynomial and determining coefficient are influenced by the speed of transmission.

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Control of an stochastic nonlinear system by the method of dynamic programming

  • Choi, Wan-Sik
    • 제어로봇시스템학회:학술대회논문집
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    • pp.156-161
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    • 1994
  • In this paper, we consider an optimal control problem of a nonlinear stochastic system. Dynamic programming approach is employed for the formulation of a stochastic optimal control problem. As an optimality condition, dynamic programming equation so called the Bellman equation is obtained, which seldom yields an analytical solution, even very difficult to solve numerically. We obtain the numerical solution of the Bellman equation using an algorithm based on the finite difference approximation and the contraction mapping method. Optimal controls are constructed through the solution process of the Bellman equation. We also construct a test case in order to investigate the actual performance of the algorithm.

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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 responses of a riser under combined excitation of internal waves and background currents

  • Lou, Min;Yu, Chenglong
    • International Journal of Naval Architecture and Ocean Engineering
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    • v.6 no.3
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    • pp.685-699
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    • 2014
  • In this study, the dynamic responses of a riser under the combined excitation of internal waves and background currents are studied. A modified Taylor-Goldstein equation is used to calculate the internal waves vertical structures when background currents exist. By imposing rigid-lid boundary condition, the equation is solved by Thompson-Haskell method. Based on the principle of virtual work, a nonlinear differential equation for riser motions is established combined with the modified Morison formula. Using Newmark-${\beta}$ method, the motion equation is solved in time domain. It is observed that the internal waves without currents exhibit dominated effect on dynamic response of a riser in the first two modes. With the effects of the background currents, the motion displacements of the riser will increase significantly in both cases that wave goes along and against the currents. This phenomenon is most obviously observed at the motions in the first mode.

Classes of exact solutions for several static and dynamic problems of non-uniform beams

  • Li, Q.S.
    • Structural Engineering and Mechanics
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    • v.12 no.1
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    • pp.85-100
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    • 2001
  • In this paper, an analytical procedure for solving several static and dynamic problems of non-uniform beams is proposed. It is shown that the governing differential equations for several stability, free vibration and static problems of non-uniform beams can be written in the from of a unified self-conjugate differential equation of the second-order. There are two functions in the unified equation, unlike most previous researches dealing with this problem, one of the functions is selected as an arbitrary expression in this paper, while the other one is expressed as a functional relation with the arbitrary function. Using appropriate functional transformation, the self-conjugate equation is reduced to Bessel's equation or to other solvable ordinary differential equations for several cases that are important in engineering practice. Thus, classes of exact solutions of the self-conjugate equation for several static and dynamic problems are derived. Numerical examples demonstrate that the results calculated by the proposed method and solutions are in good agreement with the corresponding experimental data, and the proposed procedure is a simple, efficient and exact method.

Prediction of the dynamic flow stress

  • Alves, Marcilio
    • Structural Engineering and Mechanics
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    • v.20 no.5
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    • pp.495-504
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    • 2005
  • This article explores a constitutive equation that is able to correlate stress, strain and strain rate. In order to show the advantages of the constitutive equation here proposed and how its material parameters are obtained, data extracted from the literature, for materials as different as polymers and metallic alloys, are used. Finite element simulation of the impact behaviour of a beam is presented to highlight the care one needs to exercise when using the more traditional Cowper-Symonds equation. The present constitutive equation has shown to be accurate for a wide range of strains, stresses and strain rates.