Listagem por temas:
Escolhendo um título você terá acesso ao arquivo original em Post-Script.
COB101 ANALYSIS OF THE DYNAMICS OF A MICROTURBINE USING HIGH SPEED FRAMING PHOTOMICROGRAPHY
E.P. Hofer, C. Rembe, C. Witopil
Department of Measurement, Control and Microtechnology
University of Ulm, 89069 Ulm, Germany, Phone: +49 731 502 6300, Fax: +49 731 502 6301,
E-mail: mrm.office@e-technik.uni-ulm.de
As a result of the rapidly growing field of microsystem technology numerous laboratory specimens of micro devices have been developed, mainly at universities and research institutes. However, many problems still exist in order to close the gap between these prototypes and their industrial mass production. The combination of available design methods and advanced testing setups is one of the reasons. An essential step prior to introduction into the market seems to be high speed framing photomicrography for testing of dynamic phenomena in microactuators. The cinematographic image sequences allow the extraction of position, velocity, and acceleration of moving parts in micro devices. The measured data can be used for identifying material parameters of a dynamic model of the microactuator under investigation. This experimental method in combination with model analysis is demonstrated for the highly dynamic behavior of a microturbine. The rotation and sliding of a microtubine is an extremely fast non-reproducible process considering that the turbine runs with approximately 200000 revolutions per minute. Therefore, the demands on the visualization equipment are very high. The setup for testing consists of a high speed camera, a powerful light source, and a suitable microscope. The extraction of information from kinematic data allows the estimation of parameters in a dynamic model of the microturbine. This leads to the improvement of the design and, consequently, to the improvement of quality and life time of the micro device.
Keywords: Microturbine, high speed photomicrography, microscopy, dynamic model, parameter estimation.
COB212 NONLINEAR DYNAMICS OF RODS: MOMENTUM AND ENERGY CONSERVING ALGORITHMS
Fernando Alves Rochinha & Anderson Dolinski Campos
Mechanical Engineering Department, EE-COPPE/UFRJ, Cx. Postal 68503, CEP 21945-970, R. J. -BRAZIL, FARO@com.ufrj.br.
The long-term dynamics response of nonlinear geometrically rods undergoing finite bending, shearing and extension is considered in detail. The objective is the design of an unconditionally stable time-stepping algorithm which preserve fundamental constants of the motion namely the total linear and total angular momentums and, for the Hamiltonian case, the total energy. The variational form of the equations of motion is obtained through the Hamilton’s principle and its discretized spatial form is achieved by the Finite Element Method. The resulting problem is numerically solved by the new implicit time integration scheme in connection with the Newton-Raphson Method. A numerical simulation is presented in order to assess the principal features of the formulation.
Keywords: non-linear dynamics, rods, large deformations, conserving algorithms, dinâmica não-linear, grandes deformações
COB357 ANÁLISE DE IMPACTO EM UM SISTEMA MULTICORPO BI-DIMENSIONAL / IMPACT ANALYSIS OF A BI-DIMENSIONAL MUTIBODY SYSTEM
Tamotsu Hirata
Departamento Mecânica, Faculdade de Engenharia - UNESP/FEG
CEP 12.500-000 Guaratinguetá, Brasil - E-mail: tamotsu@feg.unesp.br
This work presents an impact analysis of a bi-dimensional multibody consisting of a rotating flexible multiple section beam. The impact mecanism between two steel flexible bodies was investigated and the influence of structural stiffness and non linear surface stiffness were analysed. The mathematical model for the impact mecanism is based upon the energy balance method and the equations of motion are written by the bi-dimensional flexible multibody theory with Lagrangean formulation. The numerial simulation was performed using the MATLAB software. The results are presented in terms of time-displacement of the colliding bodies.
Keywords: Impact mecanism, energy balance method, non linear surface stiffness, rotating flexible-rigid beam, bi-dimensional multibody.
COB433 ON NONLINEAR VIBRATIONS OF A NONIDEAL ‘ELECTROMOTOR-PENDULUM’
Débora Belato, José Manoel Balthazar, Hans Ingo Weber & Dean T.Mook
Faculdade de Engenharia Mecânica, UNICAMP - CEP 13803-970, Campinas - SP - Brasil. E-mail: 960474@discovery.fem.unicamp.br
Instituto de Geociências e Ciências Exatas - UNESP - Rio Claro. - CP 178. CEP 13500-230, Rio Claro - SP - Brasil.
Virginia Politechnic Institute and State University - Blacksburg, Virginia 24061-0219, USA.
A system consisting of a pendulum with a support-point that is vibrated in a horizontal plane by a DC motor considered as a limited power source, is considered. For low velocities of the motor this system is nonideal, because the speed of the motor is influenced by the response of the system. In this condition, the planar oscillation of the pendulum is analysed as a control parameter is varied. The distinct regions of operation are defined and discussed in its nonlinear characteristics.
Keywords: Nonideal system; Non-linear Dynamics; Pendulum / Sistema não ideal; Dinâmica não linear; Pêndulo.
COB455 ESTUDO PRELIMINAR DE TRAJETÓRIAS DE REENTRADA DE UM MICROSATÉLITE RECUPERÁVEL / PRELIMINARY STUDY OF RE-ENTRY TRAJECTORIES FOR A RECOVERABLE MICROSATELLITE
Hanfried Schlingloff, Marcelo Curvo & Jaime Augusto Silva
CTA/Instituto de Aeronáutica e Espaço/ASE, CEP - 12228-904 São José dos Campos - SP, Brasil - E-mail: jaime@ase2.iae.cta.br
This work deals with reentry trajectory simulation of a small satellite intended for microgravity experiments. The satellite is considered to be orbiting at an altitude of 300 kilometers above the Earth on a circular orbit with small inclination (2.317o). Conditions at the deorbit point are specified and several trajectory simulations are made. A parametric study for preliminary design analysis is presented. It is seen that the reentry trajectory is very sensitive to the initial conditions established at the deorbit point. Dispersion minimization at impact point and vehicle’s total range are considered. Final results are presented as well as a comprehensive analysis of the results obtained.
Keywords: Fator de Carga, Microsatélite, Órbita, Pré Pára-quedas, Reentrada, Trajetória. / Load Factor, Microsatellite, Orbit, Pre-Parachute, Reentry, Trajectory.
COB463 INFLUÊNCIA DE PALHETAS FLEXÍVEIS NA DINÂMICA DE SISTEMAS ROTATIVOS - TEORIA E EXPERIMENTO / INFLUENCE OF FLEXIBLE BLADES ON THE DYNAMICS OF ROTATING SYSTEMS -- THEORY & EXPERIMENT
Ilmar Ferreira Santos & Gustavo Coutinho Colla
Dep. de Projeto Mecânico, Fac. de Engenharia Mecânica - UNICAMP, CEP 13083-970 Campinas, Brasil - E-mail: ilmar@dpm.fem.unicamp.br
This paper gives a theoretical and experimental contribution to the problem of coupled vibrations among rotor and long flexible blades. The design of a special test rig is presented, which enables a experimental validation of di#erent mathematical models (unidimensional, bidimensional and tridimensional), normally used to describe the flexible blades' behavior in a rotating reference system. The blades are modeled as a particle (concentrated mass) connected to the rotor by means of flexible beams (without mass), using the Newton-Euler's Method. Comparing the results obtained with help of the mentioned test rig, the mathematical model could be validated in the frequency range of 0 to 40 Hz.
Keywords: rotor dynamics, flexible blades' models, rotor-blades coupled vibrations, test rig/ dinâmica de rotores, modelagem de palhetas flexíveis, acoplamento vibratório, bancada de testes.
COB666 MÉTODO DE OTIMIZAÇÃO DE PARÂMETROS DE ATRASO PARA ANÁLISE DE FLUTTER / LAG PARAMETERS OPTIMIZATION METHOD FOR FLUTTER ANALYSIS
Maria Amélia Lima Rodrigues, Eduardo Morgado Belo & Hugo Borelli Resende
Escola de Engenharia de São Carlos - EESC-USP - CEP 13560-970 São Carlos - SP - E-mail: amelia@sc.usp.br - E-mail: belo@sc.usp.br
EMBRAER - DTE/GEE/PCD 204 - CEP 12227-901 São José dos Campos - SP - E-mail: cademb@ns01.embraer.com.br
The equations of motion for the aeroelastic analysis of an aircraft contain unsteady aerodynamic terms which must be approximated by algebraic forms if they are to be written in the Laplace domain. The most common approximation involves rational functions, and several authors have used the so-called Padé functions. In most of the aerodynamic applications in literature, the numerator coefficients, i.e. the lag parameters, have been a priori specified over the desired reduced frequency limit, based on the engineer’s own judgement. An alternative is to optimize these non-linear parameters, via non-linear programming techniques, to improve the approximations. In this work, the lag parameters of the approximating function were optimised using the Nelder&Mead simplex method. This optimization was implemented in a existing program and the optimized and non-optimized results were compared.
Keywords: Optimization, simplex, lag parameters, flutter, rational functions, unsteady aerodynamics / Otimização, simplex, parâmetros de atraso, flutter, funções racionais, aerodinâmica não-estacionária
COB673 RIGID BODY ROTATION EVOLUTION DUE TO DISTURBING TORQUE WHICH IS KNOWN IN A BODY FRAME
M.L.Pivovarov1 & R.V.F.Lopes2
1 Space Research Institute, 117810, Profsoyuznaya 84/32, Moscow, Russia, E-mail: mpivovar@vm1.iki.rssi.ru
2 National Institute for Space Research - INPE, 12.227-010 - S.J. dos Campos - SP - Brazil, E-mail: rvfl@dem.inpe.br
This paper deals with the problem of rigid body rotation evolution under the action of a torque which depends on the projection of rigid body angular velocity on the body frame only. This is, so called, the rigid body with self-excitation. If the magnitude of the torque is arbitrary, the solution to the problem is known in the simplest cases only. The problem with small self-excitation is considered in the paper. This problem is of great importance from the standpoint of a number of applications in spacecraft and rigid body dynamics. In the case of small torque is it possible to use perturbation methods to obtain complete analytical and geometrical description of the rotation. In this paper the common approach to investigate the problem of rigid body rotation under the action of small torque, which is known in the body frame is described. Using this approach two problems are solved: the problem of maintaining the angular velocity of a gyroscope using the control torque which is quadratic on angular velocity, and the problem of nonsymmetric spacecraft rotation with Electric Propulsion thruster.
Keywords: Rigid body, torque, perturbation methods.