• Title/Summary/Keyword: free motion

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Switched Reluctance Contact-Free Linear Actuator Using Attractive Magnetic Forces (자기 흡인력에 의한 비접촉식 SR 형 선형 구동기)

  • 이상헌;정광석;백윤수
    • Journal of the Korean Society for Precision Engineering
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    • v.20 no.10
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    • pp.47-55
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    • 2003
  • In the development of positioning device for precision manufacturing and measuring, the friction from mechanical contact causes serious decrease of performance. In this study, we studied about variable reluctance type contact-free linear actuator to overcome drawbacks from friction. In the view of electromagnetics, we analyzed and derived theoretical magnetic force equation and designed structure for generating suspension and propulsion force simultaneously. In the view of dynamics, we derived equation of motion and identified the stability of the system. Finally, we verified the feasibility of the proposed system.

An Analysis of Rolling Performance for a Barge-Type FPSO (바아지형 FPSO의 횡운동 성능에 대한 해석)

  • Choi, Yoon-Rak;Kim, Jin-Ha;Kim, Young-Su
    • Journal of Ocean Engineering and Technology
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    • v.19 no.3
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    • pp.25-30
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    • 2005
  • To predict rolling performance for a barge-type FPSO, the evaluation of correct nonlinear roll damping is critical. The square section of FPSO causes a considerable viscous damping effect. Free roll decay tests were carried out to estimate nonlinear roll damping for a barge-type FPSO, under three different conditions. The roll motion RAO was deduced from model tests in the wave condition of the wideband spectrum. In numerical calculation, the quadratic damping was considered as equivalent linear damping, using the results of free roll decay test. Tested roll performance in the JONSWAP wave spectrum was compared with numerical results. These two results shaw good agreement, in spite of the proximity of peak wave period and roll natural period.

3-D Vibration analysis of FG-MWCNTs/Phenolic sandwich sectorial plates

  • Tahouneh, Vahid
    • Steel and Composite Structures
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    • v.26 no.5
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    • pp.649-662
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    • 2018
  • In this study, based on the three-dimensional theory of elasticity, free vibration characteristics of sandwich sectorial plates with multiwalled carbon nanotube-(MWCNT)-reinforced composite core are considered. Modified Halpin-Tsai equation is used to evaluate the Young's modulus of the MWCNT/epoxy composite samples by the incorporation of an orientation as well as an exponential shape factor in the equation. The exponential shape factor modifies the Halpin-Tsai equation from expressing a straight line to a nonlinear one in the MWCNTs wt% range considered. In this paper, free vibration of thick functionally graded sandwich annular sectorial plates with simply supported radial edges and different circular edge conditions including simply supported-clamped, clamped-clamped, and free-clamped is investigated. A semi-analytical approach composed of two-dimensional differential quadrature method and series solution are adopted to solve the equations of motion. The material properties change continuously through the core thickness of the plate, which can vary according to a power-law, exponentially, or any other formulations in this direction. This study serves as a benchmark for assessing the validity of numerical methods or two-dimensional theories used to analysis of laminated sectorial plates.

Free vibration analysis of axially moving laminated beams with axial tension based on 1D refined theories using Carrera unified formulation

  • Daraei, Behnam;Shojaee, Saeed;Hamzehei-Javaran, Saleh
    • Steel and Composite Structures
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    • v.37 no.1
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    • pp.37-49
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    • 2020
  • In this paper, free vibration finite element analysis of axially moving laminated composite beams subjected to axial tension is studied. It is assumed that the beam has a constant axial velocity and is subject to uniform axial tension. The analysis is based on higher-order theories that have been presented by Carrera Unified Formulation (CUF). In the CUF technique, the three dimensional (3D) displacement fields are expressed as the approximation of the arbitrary order of the displacement unknowns over the cross-section. This higher-order expansion is considered in equivalent single layer (ESL) model. The governing equations of motion are obtained via Hamilton's principle. Finally, several numerical examples are presented and the effect of the ply-angle, travelling speed and axial tension on the natural frequencies and beam stability are demonstrated.

Magnetically levitated transport system for a controller-free carrier (제어기 무장착 운송대를 위한 선형운동 자기부상 운송시스템)

  • Son, Yeong-Uk;Park, Gi-Hwan
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.21 no.12
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    • pp.2196-2208
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    • 1997
  • In this work, a magnetic levitation (maglev) system is developed to transport a wafer between semiconductor fabrication process modules in clean rooms to take advantages of eliminating particle and oil contamination that normally exist in conventional transport systems due to contact motion of mechanical components. A main feature of the maglev system developed in this work is that a controller and power supplying part are not mounted on the moving carrier but on the stationary track, which is defined a controller-free carrier, to reduce carrier's weight. Iron-core electromagnets and irons are used for levitation, and air-core electromagnets and permanent magnets are used for stabilization. Analysis, design, and modeling of the magnetically levitated transport system are presented. The performance of the maglev system is experimentally demonstrated.

Modeling free vibration analysis of osteon as bone unite

  • Ebrahimi, Farzad;Zokaee, Farin
    • Biomaterials and Biomechanics in Bioengineering
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    • v.5 no.1
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    • pp.1-10
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    • 2020
  • This paper investigated vibrational behavior of the osteon as bone unit in the different situations. This study can lead to increase our knowledge of our body. In this paper free vibration of the osteon with considering it as composite material has been studied. The effect of numbers of lamellae and radius of those on natural frequency of osteon are subtle; while thickness of lamellae have decreasing trend on natural frequency of osteon. The presence of nerve and blood in haversian canal change trend of natural frequency, absolutely. Using the nonlocal strain gradient theory(NSGT) leads to effectiveness of scale parameter on equations of motion and the obtained results. The governing equations are derived by Hamilton's principles. A parametric study is presented to examine the effect of various parameters on vibrational behaviour of osteon. The results can also be regarded as a benchmark in vibration analysis behavior of osteon as bone unite.

Dynamic analysis of gradient elastic flexural beams

  • Papargyri-Beskou, S.;Polyzos, D.;Beskos, D.E.
    • Structural Engineering and Mechanics
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    • v.15 no.6
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    • pp.705-716
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    • 2003
  • Gradient elastic flexural beams are dynamically analysed by analytic means. The governing equation of flexural beam motion is obtained by combining the Bernoulli-Euler beam theory and the simple gradient elasticity theory due to Aifantis. All possible boundary conditions (classical and non-classical or gradient type) are obtained with the aid of a variational statement. A wave propagation analysis reveals the existence of wave dispersion in gradient elastic beams. Free vibrations of gradient elastic beams are analysed and natural frequencies and modal shapes are obtained. Forced vibrations of these beams are also analysed with the aid of the Laplace transform with respect to time and their response to loads with any time variation is obtained. Numerical examples are presented for both free and forced vibrations of a simply supported and a cantilever beam, respectively, in order to assess the gradient effect on the natural frequencies, modal shapes and beam response.

New Launching Concept for Free-Fall Lifeboats and Validation by Model Experiments and Numerical Simulations

  • Arai, Makoto
    • Journal of Ship and Ocean Technology
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    • v.6 no.1
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    • pp.1-15
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    • 2002
  • A new concept for launching free-fall lifeboats, proposed by Yokohama National University is described in this paper. It has been pointed out that, using the conventional single-skid free-fall system, the potential for dangerous lifeboat motions (in which the lifeboat moves backward or jerks on the surface after entering the water) increases with the fall height of the lifeboat. One of the principal causes of this undesirable motion is vertical rotation of the lifeboat during its restricted fall at the edge of the launching skid. Thus a new "double-skid"launching concept is proposed to effectively eliminate the rotation of the lifeboat at the skid end and to enable the lifeboat to move smoothly after entering the water. In order to evaluate the performance of the proposed method, a series of model experiments and numerical simulations is carried out in which two lifeboat models with overall lengths of 1 meter and 6 meters are used. The effects of design parameters such as skid angle and skid height are investigated, and an example of the implementation of this new system at the stern of a large merchant ship is illustrated.

Fourier Series Expansion Method for Free Vibration Analysis of a Fully Liquid-Filled Circular Cylindrical Shell (Fourier 급수전개를 이용한 유체로 가득 채워진 원통형 셸의 고유진동 해석)

  • 정경훈;이성철
    • Journal of KSNVE
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    • v.4 no.2
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    • pp.137-146
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    • 1994
  • An analytical method for linear free vibration of fully liquid-filled circular cylindrical shell with various boundary conditions is developed by the Fourier series expansion based on the Stokes' transformation. A set of modal displacement functions and their derivatives of a circular cylindrical shell is substituted into the Sanders' shell equations in order to explicitily represent the Fourier coefficients as functions of the end point displacements, forces, and moments. For the vibration relevant to the liquid motion, the velocity potential of liquid is assumed as a sum of linear combination of suitable harmonic functions in the axial directions. The unknown parameter of the velocity potential is selected to satisfy the boundary condition along the wetted shell surface. An explicit expression of the natural frequency equation can be obtained for any kind of classical boundary conditions. The natural frequencies of the liquid-filled cylindrical shells with the clamped-free, the clamped-clamped, and the simply supported-simply supported boundary conditions examined in the previous works, are obtained by the analytical method. The results are compared with the previous works, and excellent agreement is found for the natural frequencies of the shells.

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An analytical method for free vibration analysis of functionally graded sandwich beams

  • Bouakkaz, K.;Hadji, L.;Zouatnia, N.;Adda Bedia, E.A.
    • Wind and Structures
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    • v.23 no.1
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    • pp.59-73
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    • 2016
  • In this paper, a hyperbolic shear deformation beam theory is developed for free vibration analysis of functionally graded (FG) sandwich beams. The theory account for higher-order variation of transverse shear strain through the depth of the beam and satisfies the zero traction boundary conditions on the surfaces of the beam without using shear correction factors. The material properties of the functionally graded sandwich beam are assumed to vary according to power law distribution of the volume fraction of the constituents. The core layer is still homogeneous and made of an isotropic material. Based on the present refined beam theory, the equations of motion are derived from Hamilton's principle. Navier type solution method was used to obtain frequencies. Illustrative examples are given to show the effects of varying gradients and thickness to length ratios on free vibration of functionally graded sandwich beams.