A Doubly Asymptotic, Nonreflecting Boundary for Ground-Shock Analysis

1987 ◽  
Vol 54 (3) ◽  
pp. 489-497 ◽  
Author(s):  
I. C. Mathews ◽  
T. L. Geers
Keyword(s):  
Finite Element ◽  
Mass Matrix ◽  
Equations Of Motion ◽  
Element Model ◽  
Solution Procedure ◽  
Buried Structures ◽  
Soil Medium ◽  
First Order ◽  
Ground Shock ◽  
Limiting Value

This paper desribes the formulation and implementation of a nonreflecting boundary for use with existing finite-element codes to perform nonlinear ground-shock analyses of buried structures. The boundary is based on a first-order doubly asymptotic approximation (DAA1) for disturbances propagating outward from a selected portion of the soil medium surrounding the structure of interest. The resulting set of first-order ordinary differential equations is then combined with the second-order equations of motion for the finite-element model so as to facilitate solution by a staggered solution procedure. This procedure is shown to be computationally stable as long as the time increment is smaller than a limiting value based on the finite-element mass matrix and the DAA-boundary stiffness matrix. Computational results produced by the boundary are compared with exact results for linear canonical problems pertaining to infinite-cylindrical and spherical shells.

scholarly journals Design optimization of vehicle asynchronous motors based on fractional harmonic response analysis

2021 ◽  
Vol 12 (1) ◽  
pp. 689-700
Author(s):  
Ao Lei ◽  
Chuan-Xue Song ◽  
Yu-Long Lei ◽  
Yao Fu
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Natural Frequency ◽  
Asynchronous Motor ◽  
Element Model ◽  
Design Parameters ◽  
Response Analysis ◽  
Harmonic Response ◽  
First Order ◽  
Harmonic Response Analysis

Abstract. To make vehicles more reliable and efficient, many researchers have tried to improve the rotor performance. Although certain achievements have been made, the previous finite element model did not reflect the historical process of the motor rotor well, and the rigidity and mass in rotor optimization are less discussed together. This paper firstly introduces fractional order into a finite element model to conduct the harmonic response analysis. Then, we propose an optimal design framework of a rotor. In the framework, objective functions of rigidity and mass are defined, and the relationship between high rigidity and the first-order frequency is discussed. In order to find the optimal values, an accelerated optimization method based on response surface (ARSO) is proposed to find the suitable design parameters of rigidity and mass. Because the higher rigidity can be transformed into the first-order natural frequency by objective function, this paper analyzes the first-order frequency and mass of a motor rotor in the experiment. The results proved that not only is the fractional model effective, but also the ARSO can optimize the rotor structure. The first-order natural frequency of asynchronous motor rotor is increased by 11.2 %, and the mass is reduced by 13.8 %, which can realize high stiffness and light mass of asynchronous motor rotors.

Self-Vibration Characteristics of Plane Gate in Inverted Siphon Project

2012 ◽  
Vol 160 ◽  
pp. 64-68
Author(s):  
Hui Fang Xue ◽  
You Wang
Keyword(s):  
Finite Element ◽  
Large Scale ◽  
Element Model ◽  
Vibration Characteristics ◽  
The Self ◽  
Vibration Modes ◽  
Vibration Frequencies ◽  
Small Opening ◽  
First Order ◽  
Inverted Siphon

Based on the vibration problem of the plane gate in the inverted siphon exit of a large-scale hydraulic project in northern Xinjiang, the software ANSYS is used to build the entity model and finite element model. Considering the influence of fluid-solid coupling, the self-vibration characteristics of the gate in the water and without water are analyzed. The first six self-vibration frequencies and vibration modes of the gate are calculated. The results show that the height of water has a significant impact on the self-vibration frequencies of the plane gate. The first order natural frequency on the condition of small opening is decreased by 28.5%. It shows that the structure of the plane gate must be improved.

scholarly journals Linear Vibration Analysis of Shells Using a Seven-Parameter Spectral/hp Finite Element Model

2020 ◽  
Vol 10 (15) ◽  
pp. 5102
Author(s):  
Carlos Valencia Murillo ◽  
Miguel Gutierrez Rivera ◽  
Junuthula N. Reddy
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Variable Thickness ◽  
Equations Of Motion ◽  
Shear Deformation Theory ◽  
Element Model ◽  
Linear Elastic ◽  
Commercial Code ◽  
The Finite Element Model ◽  
Hp Finite Element

In this paper, a seven-parameter spectral/hp finite element model to obtain natural frequencies in shell type structures is presented. This model accounts for constant and variable thickness of shell structures. The finite element model is based on a Higher-order Shear Deformation Theory, and the equations of motion are obtained by means of Hamilton’s principle. Analysis is performed for isotropic linear elastic shells. A validation of the formulation is made by comparing the present results with those reported in the literature and with simulations in the commercial code ANSYS. Finally, results for shell like structures with variable thickness are presented, and their behavior for different ratios r/h and L/r is studied.

Squeal Analysis of a Disc Brake Considering Damping between a Disc and a Pad Lining

2012 ◽  
Vol 157-158 ◽  
pp. 1000-1003
Author(s):  
Ke Wei Zhou ◽  
Cheol Kim ◽  
Min Ok Yun ◽  
Ju Young Kim
Keyword(s):  
Finite Element ◽  
Equations Of Motion ◽  
Element Model ◽  
Disc Brake ◽  
Vibration Modes ◽  
Assumed Mode Method ◽  
Frictional Damping ◽  
System Components ◽  
Mode Method ◽  
Assumed Mode

The improved equations of motion for a friction-engaged brake system have been newly derived on the basis of the assumed mode method and frictional damping. The equations of motion with a finite element model were constructed by a set of vibration modes found from FE modal analysis on all system components. Consequently, the modal information of system components are combined with equations of motion derived from the analytical model. Numerical analysis showed the mode which was unstable in an undamped case became stable in a damped case.

Three-Dimensional Solid Brick Element Using Slopes in the Absolute Nodal Coordinate Formulation

2013 ◽  
Vol 9 (2) ◽  
Author(s):  
Alexander Olshevskiy ◽  
Oleg Dmitrochenko ◽  
Chang-Wan Kim
Keyword(s):  
Finite Element ◽  
Finite Elements ◽  
Absolute Nodal Coordinate Formulation ◽  
Mass Matrix ◽  
Equations Of Motion ◽  
Test Problems ◽  
Absolute Nodal Coordinate ◽  
Highly Nonlinear ◽  
Brick Element ◽  
The Absolute

The present paper contributes to the field of flexible multibody systems dynamics. Two new solid finite elements employing the absolute nodal coordinate formulation are presented. In this formulation, the equations of motion contain a constant mass matrix and a vector of generalized gravity forces, but the vector of elastic forces is highly nonlinear. The proposed solid eight node brick element with 96 degrees of freedom uses translations of nodes and finite slopes as sets of nodal coordinates. The displacement field is interpolated using incomplete cubic polynomials providing the absence of shear locking effect. The use of finite slopes describes the deformed shape of the finite element more exactly and, therefore, minimizes the number of finite elements required for accurate simulations. Accuracy and convergence of the finite element is demonstrated in nonlinear test problems of statics and dynamics.

Performance Characteristics of a Smart Flexible Beam With Distributed ACLD Elements

2002 ◽  
Author(s):  
L. C. Hau ◽  
Eric H. K. Fung
Keyword(s):  
Finite Element ◽  
Degrees Of Freedom ◽  
Equations Of Motion ◽  
Viscoelastic Model ◽  
Element Model ◽  
Flexible Beam ◽  
Constrained Layer Damping ◽  
Optimal Output ◽  
Modes Of Vibration ◽  
Original Size

The finite element method, in conjunction with the Golla-Hughes-McTavish (GHM) viscoelastic model, is employed to model a clamped-free beam partially treated with active constrained layer damping (ACLD) elements. The governing equations of motion are converted to a state-space form for control system design. Prior to this, since the resultant finite element model has too many degrees of freedom due to the addition of dissipative coordinates, a model reduction is performed to revert the system back to its original size. Finally, optimal output feedback gains are designed based on the reduced models. Numerical simulations are performed to study the effect of different element configurations, with various spacing and locations, on the vibration control performance of a “smart” flexible ACLD treated beam. Results are presented for the damping ratios of the first two modes of vibration. It is found that improvement on the second mode damping can be achieved by splitting a single ACLD element into two and placing them at appropriate positions of the beam.

Vibration Analysis of Reissner-Mindlin Plates Using Quadrilateral Heterosis Element

2010 ◽  
Vol 163-167 ◽  
pp. 1793-1796
Author(s):  
Zhong Liang Ru ◽  
Hong Bo Zhao ◽  
Chuan Rui Zhu
Keyword(s):  
Finite Element ◽  
Free Vibration ◽  
Mass Matrix ◽  
Element Model ◽  
Mindlin Plate ◽  
Integration Scheme ◽  
Transverse Shear Locking ◽  
Locking Phenomena ◽  
Selective Reduced Integration ◽  
The Finite Element Model

The free vibration of the eigenfrequencies and models of a rectangular p1ate with simply supported comp1eted clamped supported were calculated by finite element method using the quadrilateral heterosis element. Firstly, the basic Governing equations of Reissner-Mindlin plate for elastodynamics was introduced, And then the finite element model of the plate vibration was established, nine nodes heterosis element was adopted, the stiffness matrix and mass matrix were obtained. Selective-reduced integration scheme was carried out to eliminatethe curvature thickness and the transverse shear locking phenomena in the plate bending. Numerical experiments of plate free vibration using heterosis element with quadrilateral linear shape functions for the displacements was studied, eight models ware obtained which were closely to the closed solutions, the results show that the method successfully yields a stabilized element.

A Parallel h-Adaptive Finite Element Model for Wind Energy Assessment in Nevada

2003 ◽  
Author(s):  
Darrell W. Pepper ◽  
Yitung Chen ◽  
Joseph M. Lombardo
Keyword(s):  
Finite Element ◽  
Wind Energy ◽  
Finite Element Model ◽  
Initial Conditions ◽  
Meteorological Data ◽  
Equations Of Motion ◽  
Element Model ◽  
Adaptive Finite Element ◽  
Galerkin Finite Element ◽  
Energy Assessment

A Petrov-Galerkin finite element model that employs local mesh adaptation is being developed to determine potential wind energy sites within the state of Nevada. Meteorological data collected from various private, county, city, and government agencies are used to generate diagnostic flow fields, which subsequently provide initial conditions for the prognostic solution of the time-dependent equations of motion and species transport. The model runs on a multiprocessor SGI Onyx 3800. Results of the data collection, including wind energy site forecasts, will be made available on the web when the assessment for the entire state is completed.

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