• Title/Summary/Keyword: nodal force method

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Optimum Alignment of Marine Engine Shaftings by the Finite Element Method (有限要素法에 의한 舶用機關軸系裝置의 最適配置에 關한 硏究)

  • Jeon, Hio-Jung;Park, Jin-Gil;Choi, Jae-Sung
    • Journal of Advanced Marine Engineering and Technology
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    • v.2 no.1
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    • pp.3-14
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    • 1978
  • The authors have developed a calculating method of propeller shaft alignment by the finite element method. The propeller shaft is divided into finite elements which can be treated as uniform section bars. For each element, the nodal point equation is derived from the stiffness matrix, the external force vector and the section force vector. Then the overall nodal point equation is derived from the element nodal point equation. The deflection, offset, bending moment and shearing force of each nodal point are calculated from the overall nodal point equation by the digital computer. Reactions and deflections of supporting points of straight shaft are calculated and also the reaction influence number is derived. With the reaction influence number the optimum alignment condition that satisfies all conditions is calculated by the simplex method of linear programming. All results of calculation are compared with those of Det norske Veritas, which has developed a computor program based on the three-moment theorem of the strength of materials. The authors finite element method has shown good results and will be used effectively to design the propeller shaft alignment.

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A simple method of stiffness matrix formulation based on single element test

  • Mau, S.T.
    • Structural Engineering and Mechanics
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    • v.7 no.2
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    • pp.203-216
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    • 1999
  • A previously proposed finite element formulation method is refined and modified to generate a new type of elements. The method is based on selecting a set of general solution modes for element formulation. The constant strain modes and higher order modes are selected and the formulation method is designed to ensure that the element will pass the basic single element test, which in turn ensures the passage of the basic patch test. If the element is to pass the higher order patch test also, the element stiffness matrix is in general asymmetric. The element stiffness matrix depends only on a nodal displacement matrix and a nodal force matrix. A symmetric stiffness matrix can be obtained by either modifying the nodal displacement matrix or the nodal force matrix. It is shown that both modifications lead to the same new element, which is demonstrated through numerical examples to be more robust than an assumed stress hybrid element in plane stress application. The method of formulation can also be used to arrive at the conforming displacement and hybrid stress formulations. The convergence of the latter two is explained from the point of view of the proposed method.

Comparison of Force Calculation Methods in 2D and 3D Finite Element Method

  • Yan Xiuke;Koh, Chang-Seop;Ryu, Jae-Seop;Xie Dexin
    • KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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    • v.11B no.4
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    • pp.137-145
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    • 2001
  • The magnetic force calculation methods, the Maxwell's stress tensor method, virtual work method, and nodal force method, are reviewed and the equivalence of them are theoretically proved. The methods are applied to the magnetic force calculation of 2D linear and nonlinear problems, and 3D nonlinear problem. As the results, the convergence of the methods as the number of elements increases, accuracy of the methods, and integral path dependence of the methods are discussed. Finally some recommendations on the usage of the methods, including the determination of the integral path, are given.

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A Study on the Axial stiffness of Bellows (벨로즈의 종방향 강성에 관한 연구)

  • 왕지석
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.4
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    • pp.504-513
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    • 1999
  • Usually bellows are designed for the purpose of absorbing axial movement. To find out axial stiffness of bellows the axisymmetric shell theory using the finite element method is adopted in this paper. Bellows can be idealised by series of conical frustum-shaped elements because it is axisymmetric shell structure. The force required to deflect bellows axilly is a function of the dimensions of the bellows and the materials from which they are made. The displancements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to r-z cylinderical coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal dis-placements that is the step by method is used in this paper. spring constant is analyzed according to the changing geometric factors of u-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM spring constant can be predicted by input of a few factors.

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A Study on the Deformation Behaviour of Bellows Subjected to Internal Pressure (내압을 받는 벨로즈의 변형 거동에 관한 연구)

  • 왕지석
    • Journal of Advanced Marine Engineering and Technology
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    • v.23 no.5
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    • pp.702-710
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    • 1999
  • U-shaped bellows are usually used to piping system pressure sensor and controller for refriger-ator. Bellows subjected to internal pressure are designed for the purpose of absorbing deformation. Internal pressure on the convolution sidewall and end collar will be applied to an axial load tend-ing to push the collar away from the convolutions. To find out deformation behavior of bellow sub-jected to internal pressure the axisymmetric shell theory using the finite element method is adopted in this paper. U-shaped bellows can be idealized by series of conical frustum-shaped ele-ments because it is axisymmetric shell structure. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displace-ments are added to r-z cylindrical coordinates of nodal points. The new stiffness matrix of the sys-tem using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacement that is the step by step method is used in this paper. The force required to deflect bellows axially is a function of the dimensions of the bellows and the materials from which they are made. Spring constant is analyzed according to the changing geometric factors of U-shaped bellows. The FEM results were agreed with experiment. Using developed FORTRAN PROGRAM the internal pressure vs. deflection characteristics of a particu-lar bellows can be predicted by input of a few factors.

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Study on Hot Spot Stress Calculation for Welded Joints using 3D Solid Finite Elements (3차원 솔리드 요소를 이용한 용접부 핫스팟 응력 계산에 대한 연구)

  • Oh, Jung-Sik;Kim, Yooil;Jeon, Seok-Hee
    • Journal of Ocean Engineering and Technology
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    • v.29 no.1
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    • pp.45-55
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    • 2015
  • Because of the high stress concentration near the toe of a welded joint, the calculation of local stress using the finite element method which is relevant to the fatigue strength of the weld toe crack, is a challenging task. This is mainly caused by the sensitivity of finite element analysis, which usually occurs near the area of a dramatically changing stress field. This paper presents a novel numerical method through which a less mesh-sensitive local stress calculation can be achieved based on the 3D solid finite element, strictly sticking to the original definition of hot spot stress. In order to achieve the goal, a traction stress, defined at 0.5t and 1.5t away from the weld toe, was calculated using either a force-equivalent or work-equivalent approach, both of which are based on the internal nodal forces on the imaginary cut planes. In the force-equivalent approach, the traction stress on the imaginary cut plane was calculated using the simple force and moment equilibrium, whereas the equivalence of the work done by both the nodal forces and linearized traction stress was employed in the work-equivalent approach. In order to confirm the validity of the proposed method, five typical welded joints widely used in ships and offshore structures were analyzed using five different solid element types and four different mesh sizes. Finally, the performance of the proposed method was compared with that of the traditionally used surface stress extrapolation method. It turned out that the sensitivity of the hot spot stress for the analyzed typical welded joints obtained from the proposed method outperformed the traditional extrapolation method by far.

A Study on the Stifness of Coil Spring in the Three Dimensional Space (3차원 공간에서 코일스프링의 강성에 관한 연구)

  • 이수종
    • Journal of Advanced Marine Engineering and Technology
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    • v.25 no.5
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    • pp.1130-1139
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    • 2001
  • Springs are widely utilized in machine element. To find out stiffness of coil spring, the space beam theory using the finite element method is adopted in this paper. In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculated the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants can be predicted by input of few factors.

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A Study on the Stiffness of Frustum-shaped Coil Spring (원추형 코일스프링의 강성에 대한 연구)

  • 김진훈;이수종;이경호
    • Proceedings of the Korean Society of Marine Engineers Conference
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    • 2001.11a
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    • pp.21-27
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    • 2001
  • Springs are widely utilized in machine element. To find out stiffness of frustum-shaped coil spring, the space beam theory using the finite element method is adopted in this paper In three dimensional space, a space frame element is a straight bar of uniform cross section which is capable of resisting axial forces, bending moments about two principal axes in the plane of its cross section and twisting moment about its centroidal axis. The corresponding displacement degrees of freedom are twelve. To find out load vector of coil spring subjected to distributed compression, principle of virtual work is adapted The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another increments of nodal displacements, that is, the step by step method is used in this paper. The results of the finite element method are fairly well agreed with those of various experiments. Using MATLAB program developed in this paper, spring constants and stresses can be predicted by input of few factors.

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A Study on the non -linearity of wave washer spring (웨이브 와셔 스프링의 비선형성에 관한 연구)

  • 이수종;왕지석
    • Journal of Advanced Marine Engineering and Technology
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    • v.21 no.3
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    • pp.246-255
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    • 1997
  • The wave washer springs are expected to behave non-linearly between forces and displace¬ments due to contractions of the height and due to expansions in radial direction. To find out the non -linearity of wave washer springs, the three dimensional plate analysis theory using the finite element method is adopted in this paper. The wave washer springs are considered to be three dimensional plate structures rather than frame structures, because their thickness is normally much smaller than their width. The displacements of nodal points due to small increment of force are calculated by the finite element method and the calculated nodal displacements are added to X - Y Z coordinates of nodal points. The new stiffness matrix of the system using the new coordinates of nodal points is adopted to calculate the another nodal displacements, that is, the step by step method is used in this paper. The relations between the increments of forces and displacements in each step are recorded and plotted in chart. The experimental results are compared with the calculated chart and it is shown that there are good coincidences between measured values and calculated ones.

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Numerical Modeling of Nano-powder Synthesis in a Radio-Frequency Inductively Coupled Plasma Torch

  • Hur, Min Young;Lee, Donggeun;Yang, Sangsun;Lee, Hae June
    • Applied Science and Convergence Technology
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    • v.27 no.1
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    • pp.14-18
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    • 2018
  • In order to understand the mechanism of the synthesis of particles using a plasma torch, it is necessary to understand the reaction mechanisms using a computer simulation. In this study, we have developed a simulation method to combine the Lagrangian scheme to follow microparticles and a nodal method to treat nanoparticles categorized with different particle sizes. The Lagrangian scheme includes the Coulomb force which affects the dynamics of larger particles. In contrast, the nodal method is adequate for the nanoparticles because the charge effect is negligible for nanoparticles but the number of nanoparticles is much larger than that of microparticles. This method is helpful to understand the dynamics and growth mechanism of micro- and nano-powder mixture observed in the experiment.