MODELING OF THE INCLUSION OF A REINFORCING SHEET WITHIN A 3D MEDIUM

2003 ◽  
Vol 13 (04) ◽  
pp. 573-595 ◽  
Author(s):  
D. CHAPELLE ◽  
A. FERENT
Keyword(s):  
Asymptotic Analysis ◽  
Variational Formulation ◽  
Degrees Of Freedom ◽  
Coupled Model ◽  
Numerical Results ◽  
Crucial Issue ◽  
Coupling Conditions ◽  
Limit Solutions

We propose a variational formulation suitable for coupling a shell and a surrounding softer 3D medium. This is intended to model the behavior of a reinforcing sheet as frequently occurs in applications. The crucial issue of the kinematical coupling conditions is addressed by taking into account the rotation degrees of freedom of the shell. We then perform an asymptotic analysis of the coupled model in which the distinction between bending-dominated and membrane-dominated shells arises. For the limit solutions we identify coupling kinematical conditions that do not involve rotations. Finally we present some numerical results that illustrate our discussions.

Best Structural Theories for Free Vibrations of Sandwich Composites via Machine Learning

2019 ◽  
Author(s):  
Marco Petrolo ◽  
Erasmo Carrera
Keyword(s):  
Degrees Of Freedom ◽  
Computational Cost ◽  
Free Vibrations ◽  
Numerical Results ◽  
Design Parameters ◽  
Sandwich Composites ◽  
Accuracy Requirement ◽  
Minimum Number ◽  
Carrera Unified Formulation ◽  
Structural Theories

Abstract This work presents a novel methodology for the development of refined structural theories for the modal analysis of sandwich composites. Such a methodology combines three well-established techniques, namely, the Carrera Unified Formulation (CUF), the Axiomatic/Asymptotic Method (AAM), and Artificial Neural Networks (NN). CUF generates structural theories and finite element arrays hierarchically. CUF provides the training set for the NN in which the structural theories are inputs and the natural frequencies targets. AAM evaluates the influence of each generalized displacement variable, and NN provides Best Theory Diagrams (BTD), i.e., curves providing the minimum number of nodal degrees of freedom required to satisfy a given accuracy requirement. The aim is to build BTD with far less computational cost than in previous works. The numerical results consider sandwich spherical shells with soft cores and different features, such as thickness and curvature to investigate their influence on the choice of generalized displacement variables. The numerical results show the importance of third-order generalized displacement variables and prove that the present framework can be of interest to evaluate the performance of any structural theory as typical design parameters change and provide guidelines to the analysts on the most convenient computational model to save computational cost without accuracy penalties.

scholarly journals Modeling and Experimental Testing of an Unmanned Surface Vehicle with Rudderless Double Thrusters

Sensors ◽  
2019 ◽  
Vol 19 (9) ◽  
pp. 2051 ◽  
Author(s):  
Chunyue Li ◽  
Jiajia Jiang ◽  
Fajie Duan ◽  
Wei Liu ◽  
Xianquan Wang ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Experimental Testing ◽  
Path Following ◽  
Model Parameters ◽  
Crucial Issue ◽  
Unknown Parameters ◽  
Path Following Control ◽  
Differential Thrust ◽  
Three Degrees Of Freedom ◽  
Propeller Thrust

Motion control of unmanned surface vehicles (USVs) is a crucial issue in sailing performance and navigation costs. The actuators of USVs currently available are mostly a combination of thrusters and rudders. The modeling for USVs with rudderless double thrusters is rarely studied. In this paper, the three degrees of freedom (DOFs) dynamic model and propeller thrust model of this kind of USV were derived and combined. The unknown parameters of the propeller thrust model were reduced from six to two. In the three-DOF model, the propulsion of the USV was completely provided by the resultant force generated by double thrusters and the rotational moment was related to the differential thrust. It combined the propeller thrust model to represent the thrust in more detail. We performed a series of tests for a 1.5 m long, 50 kg USV, in order to obtain the model parameters through system identification. Then, the accuracy of the modeling and identification results was verified by experimental testing. Finally, based on the established model and the proportional derivative+line of sight (PD+LOS) control algorithm, the path-following control of the USV was achieved through simulations and experiments. All these demonstrated the validity and practical value of the established model.

scholarly journals Nonlinear Mechanics of Beams With Partial Piezoelectric Layers

2019 ◽  
Vol 86 (10) ◽  
Author(s):  
Hamed Farokhi ◽  
Mergen H. Ghayesh
Keyword(s):  
Degrees Of Freedom ◽  
Three Dimensional ◽  
Coupled Model ◽  
Beam Theory ◽  
Internal Resonances ◽  
Element Analysis ◽  
Nonlinear Dynamical ◽  
Dimensional Finite Element ◽  
Resonant Region ◽  
Three Dimensional Finite Element

Abstract This paper investigates the nonlinear static response as well as nonlinear forced dynamics of a clamped–clamped beam actuated by piezoelectric patches partially covering the beam from both sides. This study is the first to develop a high-dimensional nonlinear model for such a piezoelectric-beam configuration. The nonlinear dynamical resonance characteristics of the electromechanical system are examined under simultaneous DC and AC piezoelectric actuations, while highlighting the effects of modal energy transfer and internal resonances. A multiphysics coupled model of the beam-piezoelectric system is proposed based on the nonlinear beam theory of Bernoulli–Euler and the piezoelectric constitutive equations. The discretized model of the system is obtained with the help of the Galerkin weighted residual technique while retaining 32 degrees-of-freedom. Three-dimensional finite element analysis is conducted as well in the static regime to validate the developed model and numerical simulation. It is shown that the response of the system in the nonlinear resonant region is strongly affected by a three-to-one internal resonance.

NUCLEAR COLLISIONS MODELS WITH BOLTZMANN OPERATORS

2000 ◽  
Vol 10 (04) ◽  
pp. 479-505 ◽  
Author(s):  
S. DELLACHERIE ◽  
R. SENTIS
Keyword(s):  
Numerical Methods ◽  
Asymptotic Analysis ◽  
Numerical Results ◽  
Nuclear Collisions

We describe a model related to nuclear collisions using Boltzmann operators. An asymptotic analysis is performed concerning the gain operator for the outgoing particles. Some numerical methods related to this model are also described and numerical results are given.

scholarly journals Integrated Optimization of Floating Wind Turbine Systems

2014 ◽  
Author(s):  
Frank Sandner ◽  
David Schlipf ◽  
Denis Matha ◽  
Po Wen Cheng
Keyword(s):  
Wind Turbine ◽  
Degrees Of Freedom ◽  
Dynamic Models ◽  
Controller Design ◽  
Coupled Model ◽  
Optimal Solution ◽  
Wave Loads ◽  
Nonlinear Simulation ◽  
Floating Wind Turbine ◽  
Wind Turbine System

The purpose of this paper is to show an exemplary methodology for the integrated conceptioning of a floating wind turbine system with focus on the spar-type hull and the wind turbine blade-pitch-to-feather controller. It is a special interest to use a standard controller, which is easily implementable, even at early design stages. The optimization of the system is done with adapted static and dynamic models through a stepwise narrowing of the design space according to the requirements of floating wind turbines. After selecting three spar-type hull geometries with variable draft a simplified nonlinear simulation model with four degrees of freedom is set up and then linearized including the aerodynamics with the blade pitch controller in the closed-loop. The linear system allows conventional procedures for SISO controller design giving a theoretically suitable range of controller gains. Subsequently, the nonlinear model is used to find the optimal controller gains for each platform. Finally, a nonlinear coupled model with nine degrees of freedom gives the optimal solution under realistic wind and wave loads.

The Elastohydrodynamic Problem Expressed in Terms of Extended Variational Formulation

1986 ◽  
Vol 108 (4) ◽  
pp. 557-564 ◽  
Author(s):  
Antonio Strozzi
Keyword(s):  
Convergence Rate ◽  
Variational Formulation ◽  
Numerical Experiments ◽  
Numerical Results ◽  
Lubricated Contacts ◽  
Relaxation Scheme

The elastohydrodynamic problem is revisited in terms of an extended variational formulation, where the corresponding functional exhibits minimum properties in the solution neighborhood. Such features are exploited in the development of a relaxation-type solver. The numerical results indicate that the convergence rate of the proposed relaxation scheme becomes increasingly poor as the solution of the elastohydrodynamic problem is approached. A polyalgorithm based on a combination between relaxation-type and Newton-type schemes is proposed. The numerical experiments referred to various sealing profiles of increasing foundation compliance show that the proposed procedure is particularly advantageous in the case of soft lubricated contacts.

Direct Kinematic Singularities of 3-3 Stewart-Gough Platforms

2005 ◽  
Vol 219 (4) ◽  
pp. 311-324 ◽  
Author(s):  
C H Liu ◽  
J Chiu
Keyword(s):  
Parallel Manipulator ◽  
Degrees Of Freedom ◽  
Polynomial Equation ◽  
Numerical Results ◽  
Polynomial Equations ◽  
Kinematic Singularity ◽  
Cubic Polynomial ◽  
Singular Configuration ◽  
Kinematic Singularities ◽  
Stewart Gough Platform

In this article, a method to locate direct kinematic singularities of a 3-3 Stewart-Gough parallel manipulator (called a Stewart manipulator henceforth) is proposed. The Stewart manipulator is first replaced by an analogous manipulator, the 3PRPS parallel manipulator, and as the first three active joints of this manipulator remain fixed, this manipulator reduces to an asymmetric 3RPS parallel manipulator. With all moving platform's degrees of freedom, except its height, properly specified, there exists at least one height that gives rise to direct kinematic singularity of the asymmetric 3RPS manipulator and this height is a root of a cubic polynomial equation. The procedure to locate direct kinematic singularities thus reduces to solving cubic polynomial equations. Numerical results show that every singular configuration of the asymmetric 3RPS manipulator thus-determined is also a singular configuration of the 3-3 Stewart-Gough platform.

The Vibration Analysis of Five Degrees of Freedom Man-Vehicle-Road Coupled Model

2013 ◽  
Vol 765-767 ◽  
pp. 361-365
Author(s):  
Pei Cheng Shi ◽  
Wen Chen Xie
Keyword(s):  
Degrees Of Freedom ◽  
Ride Comfort ◽  
Coupled Model ◽  
Reference Value ◽  
Response Characteristics ◽  
Vibration Model ◽  
Study Results ◽  
Road Surface Roughness ◽  
The Mathematical Model ◽  
The Relationship

The 5-DOF man-vehicle-road coupled vibration model is established by the relationship among three interactions of man-vehicle-road and the vibration differential equation of the 5-DOF man-vehicle-road model is obtained by Newtons method. The mathematical model is conversed into the derived simulation model based on MATLAB/SIMULINK software. The vibration characteristics of the 5-DOF couple model are analyzed by the excitations of ride speed and random road surface roughness time series since the corresponding parameters have been set. The paper demonstrates the acceleration curves and their response characteristics of the bodywork and man-chair system. The study results have a guiding significance and reference value to analyze the vehicle ride comfort.

scholarly journals THE INFLUENCE OF FOUNDATION MASS ON DYNAMIC RESPONSE OF TRACK-VEHICLE INTERACTION

2018 ◽  
Author(s):  
Pham Dinh Trung
Keyword(s):  
Dynamic Response ◽  
Degrees Of Freedom ◽  
Dynamic Balance ◽  
Mass Parameter ◽  
Numerical Results ◽  
Integrated System ◽  
Railway Track ◽  
Moving Vehicle ◽  
Balance Principle ◽  
Foundation Model

The influence of foundation mass on the dynamic response of track-vehicle interaction is studied in this paper. The moving vehicle is modeled as a two-axle mass-spring-damper system having four degrees of freedom. The new foundation model, called “Dynamic foundation model” including linear elastic spring, shear layer, viscous damping and special consideration of foundation mass parameter, is used to analyze dynamic response of the track-vehicle interaction. Then, the railway track on dynamic foundation model subjected to a moving vehicle is regarded as an integrated system. By means of finite element method and dynamic balance principle, the governing equation of motion for railway track-vehicle-foundation interaction is derived and solved by step-by-step integration method. The accuracy of the algorithm is also verified by comparing the numerical results with the other numerical results in the literature. The influence of foundation mass parameter on the dynamic response of railway track-vehicle interaction is investigated. The numerical results show that the foundation mass effects significantly on the dynamic response of track-vehicle interaction and it is more increasing dynamic displacements than others without foundation mass. The study has meaning practice and the foundation quite agrees to describe true behavior of soil in the problems of the analyzing dynamic response of structures on the foundation.

scholarly journals Vibration Protection of Mechanical Systems Consisting of Solid And Deformable Bodies

2018 ◽  
Vol 3 (9) ◽  
pp. 18
Author(s):  
Ismail Ibrahimovich Safarov ◽  
Teshaev Muhsin Khudoyberdiyevich
Keyword(s):  
Finite Number ◽  
Degrees Of Freedom ◽  
Mechanical Systems ◽  
Numerical Results ◽  
Constructive Method ◽  
Vibration Protection ◽  
Deformable Bodies ◽  
Reaction Forces ◽  
Active Vibration ◽  
Servo Constraints

In this  paper active vibration protection of mechanical systems consisting of solid and deformable bodies is considered. To actively control the oscillations of dissipative mechanical systems, a constructive method is used to determine the structure of the reaction forces of servo constraints. As an example, we consider the system with a finite number of degrees of freedom. Numerical results for various harmonic are also given.

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