scholarly journals Rest-to-Rest Attitude Naneuvers and Residual Vibration Reduction of a Finite Element Model of Flexible Satellite by Using Input Shaper

1999 ◽  
Vol 6 (1) ◽  
pp. 11-27 ◽  
Author(s):  
Setyamartana Parman ◽  
Hideo Koguchi
Keyword(s):  
Finite Element ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Element Model ◽  
Solar Panels ◽  
The Finite Element Method ◽  
Plate Structures ◽  
Input Shaper ◽  
Attitude Maneuver ◽  
Pointing Precision

A three-dimensional rest-to-rest attitude maneuver of flexible spacecraft equipped by on-off reaction jets is studied. Equations of motion of the spacecraft is developed by employing a hybrid system of coordinates and Lagrangian formulation. The finite element method is used to examine discrete elastic deformations of a particular model of satellite carrying flexible solar panels by modelling the panels as flat plate structures in bending. Results indicate that, under an unshaped input, the maneuvers induce undesirable attitude angle motions of the satellite as well as vibration of the solar panels. An input shaper is then applied to reduce the residual oscillation of its motion at several natural frequencies in order to get an expected pointing precision of the satellite. Once the shaped input is given to the satellite, the performance improves significantly.

Finite Element Models for Flexible Cosserat Solids

2020 ◽  
Author(s):  
Olivier A. Bauchau ◽  
Minghe Shan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Displacement Vector ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Discrete Equations ◽  
Computation Efficiency ◽  
Elasticity Problems ◽  
Element Method

Abstract The application of the finite element method to the modeling of Cosserat solids is investigated in detail. In two- and three-dimensional elasticity problems, the nodal unknowns are the components of the displacement vector, which form a linear field. In contrast, when dealing with Cosserat solids, the nodal unknowns form the special Euclidean group SE(3), a nonlinear manifold. This observation has numerous implications on the implementation of the finite element method and raises numerous questions: (1) What is the most suitable representation of this nonlinear manifold? (2) How is it interpolated over one element? (3) How is the associated strain field interpolated? (4) What is the most efficient way to obtain the discrete equations of motion? All these questions are, of course intertwined. This paper shows that reliable schemes are available for the interpolation of the motion and curvature fields. The interpolated fields depend on relative nodal motions only, and hence, are both objective and tensorial. Because these schemes depend on relative nodal motions only, only local parameterization is required, thereby avoiding the occurrence of singularities. For Cosserat solids, it is preferable to perform the discretization operation first, followed by the variation operation. This approach leads to considerable computation efficiency and simplicity.

scholarly journals New Analytical Model Used in Finite Element Analysis of Solids Mechanics

Mathematics ◽  
2020 ◽  
Vol 8 (9) ◽  
pp. 1401 ◽  
Author(s):  
Sorin Vlase ◽  
Adrian Eracle Nicolescu ◽  
Marin Marin
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Equations Of Motion ◽  
Classical Mechanics ◽  
Three Dimensional ◽  
Elastic Solid ◽  
The Finite Element Method ◽  
Governing Equations ◽  
Element Analysis ◽  
Elastic Multibody System

In classical mechanics, determining the governing equations of motion using finite element analysis (FEA) of an elastic multibody system (MBS) leads to a system of second order differential equations. To integrate this, it must be transformed into a system of first-order equations. However, this can also be achieved directly and naturally if Hamilton’s equations are used. The paper presents this useful alternative formalism used in conjunction with the finite element method for MBSs. The motion equations in the very general case of a three-dimensional motion of an elastic solid are obtained. To illustrate the method, two examples are presented. A comparison between the integration times in the two cases presents another possible advantage of applying this method.

The Application of Multi-Wedge Cross Wedge Rolling Forming Long Shaft Technology

2011 ◽  
Vol 101-102 ◽  
pp. 1002-1005 ◽  
Author(s):  
Jing Zhao ◽  
Li Qun Lu
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Finite Element Model ◽  
Rolling Mill ◽  
Three Dimensional ◽  
Element Model ◽  
Solid Model ◽  
The Finite Element Method ◽  
Cross Wedge Rolling ◽  
The Finite Element Model

The process of multi-wedge cross wedge rolling is an advanced precision technology for forming long shaft parts such as automobile semi-axes. Three-dimensional solid model and the finite element model of semi-axes on automobile and dies of its cross wedge rolling were established. The process of cross wedge rolling was simulated according to the actual dimension of semi-axes on automobile utilizing the finite element method (FEM)software ANSYS/LS-DYNA. The required force parameters for designing semi-axes mill are determined. The appropriate roller width was determined according to the length and diameter of semi-axes on automobile. The results have provided the basis for the design of specific structure of automobile semi-axes cross wedge rolling mill.

scholarly journals Energy of Accelerations Used to Obtain the Motion Equations of a Three- Dimensional Finite Element

Symmetry ◽  
2020 ◽  
Vol 12 (2) ◽  
pp. 321 ◽  
Author(s):  
Sorin Vlase ◽  
Iuliu Negrean ◽  
Marin Marin ◽  
Maria Luminița Scutaru
Keyword(s):  
Finite Element ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
The Finite Element Method ◽  
Method Of Calculation ◽  
Elastic Systems ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Multi Body ◽  
Elastic Elements

When analyzing the dynamic behavior of multi-body elastic systems, a commonly used method is the finite element method conjunctively with Lagrange’s equations. The central problem when approaching such a system is determining the equations of motion for a single finite element. The paper presents an alternative method of calculation theses using the Gibbs–Appell (GA) formulation, which requires a smaller number of calculations and, as a result, is easier to apply in practice. For this purpose, the energy of the accelerations for one single finite element is calculated, which will be used then in the GA equations. This method can have advantages in applying to the study of multi-body systems with elastic elements and in the case of robots and manipulators that have in their composition some elastic elements. The number of differentiation required when using the Gibbs–Appell method is smaller than if the Lagrange method is used which leads to a smaller number of operations to obtain the equations of motion.

A Static and Dynamic Model of Geared Transmissions by Combining Substructures and Elastic Foundations—Applications to Thin-Rimmed Gears

2006 ◽  
Vol 129 (2) ◽  
pp. 184-194 ◽  
Author(s):  
M. N. Bettaïeb ◽  
P. Velex ◽  
M. Ajmi
Keyword(s):  
Finite Element ◽  
Contact Stiffness ◽  
Equations Of Motion ◽  
Hybrid Approach ◽  
Three Dimensional ◽  
Element Model ◽  
3D Finite Element ◽  
Elastic Foundations ◽  
Beam Elements ◽  
Set Up

The present work is aimed at predicting the static and dynamic behavior of geared transmissions comprising flexible components. The proposed model adopts a hybrid approach, combining classical beam elements, elastic foundations for the simulation of tooth contacts, and substructures derived from three-dimensional (3D) finite element grids for thin-rimmed gears and their supporting shafts. The pinion shaft and body are modeled via beam elements which simulate bending, torsion and traction. Tooth contact deflections are described using time-varying elastic foundations (Pasternak foundations) connected by independent contact stiffness. In order to account for thin-rimmed gears, a 3D finite element model of the gear (excluding teeth) is set up and a pseudo-modal reduction technique is used prior to solving the equations of motion. Depending on the gear structure, the results reveal a potentially significant influence of thin rims on both quasi-static and dynamic tooth loading.

Investigation into the Effect of the Nut Thread Run-Out on the Stress Distribution in a Bolt Using the Finite Element Method

2003 ◽  
Vol 125 (3) ◽  
pp. 527-532 ◽  
Author(s):  
J. W. Hobbs ◽  
R. L. Burguete ◽  
E. A. Patterson
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Distribution ◽  
Three Dimensional ◽  
Element Model ◽  
Two Dimensional ◽  
The Finite Element Method ◽  
Element Analysis ◽  
Dimensional Models ◽  
Three Dimensional Models

By means of comparing results from finite element analysis and photoelasticity, the salient characteristics of a finite element model of a nut and bolt have been established. A number of two-dimensional and three-dimensional models were created with varying levels of complexity, and the results were compared with photoelastic results. It was found that both two-dimensional and three-dimensional models could produce accurate results provided the nut thread run-out and friction were modeled accurately. When using two-dimensional models, a number of models representing different positions around the helix of the thread were created to obtain more data for the stress distribution. This approach was found to work well and to be economical.

Deformations and Stresses in Soft Body Tissues of a Sitting Person

1978 ◽  
Vol 100 (2) ◽  
pp. 79-87 ◽  
Author(s):  
W. W. Chow ◽  
E. I. Odell
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Surface Friction ◽  
Element Model ◽  
The Finite Element Method ◽  
Decubitus Ulcers ◽  
Surface Pressure Distribution ◽  
Body Tissues ◽  
Von Mises ◽  
Von Mises Stresses

This paper investigates the deformations and stresses in the buttocks of a person when he sits on a cushion. The study is motivated by the need for a better understanding of the design of wheelchair cushions and the prevention of decubitus ulcers. The finite element method is used on an axisymmetric model. Surface pressure distribution, surface friction, hydrostatic pressures and von Mises stresses are obtained. The finite element model reveals the three-dimensional state of stress at all internal locations for a typical human body. Thus the study complements the experimental measurements performed by many physicians and bioengineers.

Experimental and Analytical Evaluation of Buckling Forces of a Spiral Wound Flexible Gasket

2005 ◽  
Author(s):  
Reid A. Larson ◽  
George Bibel
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Three Dimensional ◽  
Element Model ◽  
The Finite Element Method ◽  
Original Experiment ◽  
Series Of Experiments ◽  
Metallic Rings ◽  
The Finite Element Model ◽  
Spiral Wound

Inward buckling forces of spiral wound flexible gaskets is studied experimentally and analytically using the finite element method. A series of experiments was conducted utilizing an NPS 16 Class 300 weld-neck pipe and flange conforming to specification ASME B16.5. Strain gauges were mounted on the inner and outer metallic rings of the spiral wound sealing gasket and strain data was recorded during initial bolt pre-loading. Using this particular experiment as a pattern, a finite element model was developed to simulate the flange, bolt, and nonlinear gasket response under identical loading conditions. The computer-generated solid model consists of a quarter-symmetry, three-dimensional assembly constructed to the specifications of the pipe, flange, bolts, and gaskets used in the hardware trials. The finite element model was loaded to simulate the initial bolt pre-loading through the same range as in the original experiment. Solutions obtained from the finite element model are compared with the experimental results, and conclusions are drawn.

scholarly journals Dynamic analysis of complex spacial frame systems by the finite element method

1986 ◽  
Vol 8 (2) ◽  
pp. 21-26
Author(s):  
Nguyen Ngoc Ve
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Static Load ◽  
Equations Of Motion ◽  
Element Model ◽  
Superposition Method ◽  
Direct Integration ◽  
The Finite Element Method ◽  
Mode Superposition Method ◽  
Frame Systems

Numerical simula1ion of complex special frame systems subjected to static load dynamic load and base acceleration is formulated. A finite element model is applied therein the, complex nodes and the foundation influence are considered. Equations of motion are soviet afterontively by step-by-step direct integration and mode superposition method. A number of illustrated  example are computed by the numerical superpose FRADYN), which can be used directly in the field of staeciural design.

Dynamic stiffness formulation for the vibrations of stiffened plate structures with consideration of in-plane deformation

2017 ◽  
Vol 24 (20) ◽  
pp. 4825-4838 ◽  
Author(s):  
Xuewen Yin ◽  
Wenwei Wu ◽  
Kuikui Zhong ◽  
Hui Li
Keyword(s):  
Finite Element ◽  
Dynamic Stiffness ◽  
Plane Deformation ◽  
Element Model ◽  
The Finite Element Method ◽  
Plate Structures ◽  
Beam Elements ◽  
Stiffness Model ◽  
Out Of Plane ◽  
The Relationship

A dynamic stiffness method is presented for the vibrations of plate structures that are reinforced by eccentric stiffeners. The model incorporates both out-of-plane and in-plane deformations of the plates and the stiffeners. Based on the relationship between the forces and displacements along the common edges of the plate or beam elements, the dynamic stiffness formulae for the plate and the beam elements are derived, respectively. The globally assembled dynamic stiffness matrix is then obtained using the finite element method so that the dynamics of built-up stiffened plates can be readily addressed by using the present method. Compared to the conventional finite element model, the dynamic stiffness model can provide very accurate solutions using only one element over each uniform plate and beam member, regardless of its geometry.

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