Geometric Modeling and Simulation of Mechanical Assemblies With Elastic Components

1994 ◽  
Author(s):  
Yong Fang ◽  
F. W. Liou
Keyword(s):  
Finite Element Method ◽  
Geometric Modeling ◽  
Three Dimensional ◽  
Elastic Behavior ◽  
Elastic Analysis ◽  
Simulation Tool ◽  
Body System ◽  
Mechanical Assembly ◽  
Mechanical Assemblies ◽  
Multi Body

Abstract In this paper, the implementation of a modeling system for the simulation of three dimensional mechanical assemblies with elastic components is presented. A mechanical assembly is modeled as a multi-body system with changing topologies. The elastic behavior can be automatically modeled using finite element method. With this simulation tool, a designer can interactively create an assembly of mechanical components ready for dynamic and elastic analysis. This paper presents a prototype of the modeling system.

Computer Simulation of Three-Dimensional Mechanical Assemblies: Part I — General Formulation

1993 ◽  
Author(s):  
Yong Fang ◽  
F. W. Liou
Keyword(s):  
Computer Simulation ◽  
Dynamic Analysis ◽  
Dynamic Modeling ◽  
Collision Detection ◽  
Equations Of Motion ◽  
Three Dimensional ◽  
Simulation Tool ◽  
Geometry Modeling ◽  
Mechanical Assemblies ◽  
Multi Body

Abstract In Part I of this paper, a dynamic modeling system for the simulation of three dimensional mechanical assemblies is presented. With this simulation tool, a designer can interactively create an assembly of mechanical components ready for dynamic analysis. The modeling system presented in this paper includes the derivation of the equations of motion of spatial multi-body systems, and the formulation of the equations to model the associated collision detection and collision responses. Part II of this paper is to introduce the geometry modeling and computer simulation of 3D systems.

Advances in FEMN: The Code for Nuclear Noise Analysis Based on ICEM-CFD

2018 ◽  
Author(s):  
Baoxin Yuan ◽  
Herong Zeng ◽  
Wankui Yang ◽  
Songbao Zhang
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Geometric Modeling ◽  
Noise Analysis ◽  
Three Dimensional ◽  
Noise Spectrum ◽  
Benchmark Problem ◽  
Reactor Physics ◽  
Icem Cfd ◽  
Element Method

The finite element method based on unstructured mesh has good geometry adaptability, it has been used to solve reactor physics problems, manual description of geometric modeling and meshing makes the current finite element code very complicated, it greatly restricts the application of this method in the numerical calculation of reactor physics. Using the CAD pre-processing software ICEM-CFD, three dimensional geometry is divided into tetrahedral or hexahedral meshes, two dimensional geometry is divided into triangular or quadrilateral meshes, the main code of neutron calculation for nuclear noise analysis based on finite element method is developed. The steady state parameters are calculated and tested through benchmark problem, the test results show that the code has the corresponding computing capabilities. Finally, the neutron noise spectrum is calculated for the 3D PWR benchmark problem published by IAEA, and the noise distribution under given frequency is given.

Computer Simulation of Three-Dimensional Mechanical Assemblies: Part II — Computer Simulation

1993 ◽  
Author(s):  
T. C. Chou ◽  
F. W. Liou
Keyword(s):  
Computer Simulation ◽  
Three Dimensional ◽  
Cost Effective ◽  
Test Bed ◽  
Joint Models ◽  
Mechanical Assemblies ◽  
Final Design ◽  
Multi Body ◽  
And Control ◽  
Mating Conditions

Abstract Computer simulation of the kinematic and dynamic behaviors of mechanical assemblies has become a very important tool in design and manufacturing, because the designer can foresee how a product is going to perform before the product is actually fabricated. However, up to now, the most current simulation modules are based on analysis from another kinematic or dynamic module by specifying the mating conditions between components, and then displaying the motion on the screen. This computer simulation actually performs similarly to a movie, and can only provide visual checking. The drawback of this simulation approach is that designers are forced to use the available joint models, and may lose their creativity. In part I of this paper, general mathematical modeling of the multi-body system is presented, while part II of this paper, a prototype convex-feature modeling system is presented with which a designer can interactively create an assembly of mechanical components ready for dynamic analysis. It can provide a state-of-the-art technology for real simulation of any mechanical systems, and act as a cost-effective test bed for concepts, final design, and control algorithms.

A Numerical Investigation Into Hydrodynamic Interaction Coefficients for Multiple Freely Floating Bodies in Waves

2020 ◽  
Author(s):  
Mir Tareque Ali
Keyword(s):  
Hydrodynamic Interaction ◽  
Three Dimensional ◽  
Computer Code ◽  
Source Distribution ◽  
Hydrodynamic Coefficients ◽  
Body System ◽  
Regular Waves ◽  
Floating Bodies ◽  
Interaction Coefficients ◽  
Multi Body

Abstract When two or more bodies are floating in waves in each other’s vicinity, the fluid loading on the separate bodies will be influenced by the presence of the neighboring bodies. The wave loads on each body are affected, because of sheltering or wave-reflection effects due to the presence of surrounding floating body, while additional loads are exerted by the radiated waves, which are produced by the motions of the neighboring bodies. For a multi-body system, it is important to accurately compute the hydrodynamic coefficients and interaction coefficients, since these parameters will be used later to solve the 6xN simultaneous equations to predict the motion responses (where N is the number of freely floating bodies in the multi-body system). This paper aims to investigate the hydrodynamic interaction coefficients for two three dimensional (3-D) bodies floating freely in each other’s vicinity. Since the nature of hydrodynamic interaction is rather complex, it is usually recommended to study this complicated phenomenon using numerically accurate scheme. A computer code developed using 3-D source distribution method which is based on linear three-dimensional potential theory is used and the validation of the computer code has been justified by comparing the present results with that of the published ones for hydrodynamic coefficients and interaction coefficients of two bodies closely floating in regular waves. The calculated results for box-cylinder model are compared with the published results and the agreement is quite satisfactory. Numerical simulations are further conducted for two closely floating rectangular barges of side-by-side position in regular waves. During the computations of hydrodynamic coefficients and interaction coefficients for multi-body model, the separation distance between the floating bodies have been varied. Finally, some conclusions are drawn on the basis of the present analysis.

Geometric Modeling and Robust Control of a Gyroscopic System

2015 ◽  
Author(s):  
Diego Colón ◽  
Bruno A. Angelico ◽  
Fabio Y. Toriumi ◽  
Paulo U. M. Liduário ◽  
José M. Balthazar
Keyword(s):  
Geometric Modeling ◽  
Three Dimensional ◽  
Control Technique ◽  
Loop Control ◽  
Control Moment Gyroscope ◽  
Differentiable Manifolds ◽  
Control Moment ◽  
Geometric Concepts ◽  
Multi Body ◽  
Gyroscopic Systems

Gyroscopic systems are multi-body systems which present coupled three dimensional motion. The configuration space and the state space are differentiable manifolds, and differential geometric concepts are frequently useful in the process of modeling. This paper deals with a Control Moment Gyroscope (CMG), which is not asymptotically stable, so it needs a stabilizing control law. We apply a new methodology of modeling kinematics and dynamics of rigid multi-body systems, based in the concept of Cartan’s connection and covariant derivative. The systems has two inputs (torques) and two outputs (angles) that will be controlled by a robust linear closed-loop control technique (LQG/LTR). Experimental results are presented in order to validate the proposal.

An Evaluation of ASME’s “Design by Analysis” Guidelines

2013 ◽  
Author(s):  
Kotur S. Raghavan
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Stress Analysis ◽  
Three Dimensional ◽  
Limit Load ◽  
Point Of View ◽  
Elastic Analysis ◽  
The Finite Element Method ◽  
Elastic Stresses ◽  
Element Method

ASME’s Boiler and Pressure Vessel Codes have a history of over one hundred years. The codes have been evolving over time with continuous revisions, improvements and refinements. A major milestone has been the incorporation of “Design by Analysis (DBA)” guidelines about fifty years back (for instance Sec. VIII, Division 2). These were introduced as it was recognized that the prevailing Design by Rules (Section VIII, Division 1) tended to be somewhat over-conservative. The essence of DBA guidelines consists of evaluating the elastic stresses at critical locations and checking the same against the allowable. The allowable happen to functions of the nature of stress distribution and the nature of load. A given stress could be of membrane, bending or peak category and also be either primary or secondary. At the time of appearance of the DBA guidelines, the state of the art of stress analysis was not well advanced and the finite element method was just getting developed. As of today, however, the finite element method has reached a high level of maturity and is very widely used. The latest edition (2010) has recognized this and it contains modeling and post-processing guidelines applicable to FE analysis. This edition also recommends the use of one of three possible approaches. The first is the elastic analysis and classification and categorization of stresses with guidelines regarding how to deal with two- and three-dimensional situations. The other two options are provided to take care of situations wherein the categorization process may lead to either uncertainty or ambiguity. These involve nonlinear analysis either by way of Limit-Load method or Elastic-Plastic Stress Analysis. In either approach the analyst will look for the loads at which there is an onset of gross plastic flow. In the present paper an attempt is made to evaluate the latest DBA guidelines from design application point of view. The purpose is to assess the limitations of the elastic analysis approach. Studies are undertaken to focus typically on the following aspects: 1. Two dimensional problems involving symmetry or axisymmetry. There are situations in which the “bending” stresses are liable to be misinterpreted. 2. Three dimensional problems with emphasis on the assessment of bending stress as categorization in 3D situations is a real challenge 3. General situations involving the secondary stresses. The allowable stress limit for secondary stress is somewhat arbitrary and perhaps very conservative. The studies tend to suggest that the nonlinear route is to be adopted as it is reliable and accounts for many uncertainties associated with the elastic approach.

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