Aerothermoelastic Analysis of Cylindrical Piezolaminated Shells Using Multifield Layerwise Theory

2002 ◽  
Author(s):  
Il-Kwon Oh ◽  
In Lee
Keyword(s):  
Electric Fields ◽  
Thermal Stresses ◽  
Geometrically Nonlinear ◽  
Piezoelectric Actuation ◽  
Layerwise Theory ◽  
Physical Description ◽  
Aerodynamic Pressure ◽  
Nonlinear Finite Elements ◽  
Supersonic Flutter ◽  
Flutter Boundary

For the aerothermoelastic analysis of cylindrical piezolaminated shells, geometrically nonlinear finite elements based on the multi-field layerwise theory have been developed. Present multi-field layerwise theory describes zigzag displacement, thermal and electric fields providing a more realistic multi-physical description of fully and partially piezolaminated panels. By applying a Hans Krumhaar’s supersonic piston theory, supersonic flutter analyses are performed for the cylindrical piezolaminted shells subject to thermal and piezoelectric loads. The possibility to increase flutter boundary and reduce thermoelastic deformations of piezolaminated panels is examined using piezoelectric actuation. Results show that active piezoelectric actuation can effectively increase the critical aerodynamic pressure by retarding the coalescence of flutter modes and compensating thermal stresses.

Analysis of damage formation and propagation in metallic thin films under the action of thermal stresses and electric fields

1996 ◽  
Vol 2 (3) ◽  
pp. 231-258 ◽  
Author(s):  
Dimitrios Maroudas ◽  
Matthew N. Enmark ◽  
Cora M. Leibig ◽  
Sokrates T. Pantelides
Keyword(s):  
Thin Films ◽  
Electric Fields ◽  
Thermal Stresses ◽  
Metallic Thin Films

scholarly journals A physical mechanism producing suprathermal populations and initiating substorms in the Earth's magnetotail

2008 ◽  
Vol 26 (6) ◽  
pp. 1617-1639 ◽  
Author(s):  
D. V. Sarafopoulos
Keyword(s):  
Magnetic Field ◽  
Electric Fields ◽  
Plasma Sheet ◽  
Physical Mechanism ◽  
Energetic Particles ◽  
Dimensional Structure ◽  
Magnetospheric Substorms ◽  
Physical Description ◽  
Fundamental Building Block ◽  
Field Lines

Abstract. We suggest a candidate physical mechanism, combining there dimensional structure and temporal development, which is potentially able to produce suprathermal populations and cross-tail current disruptions in the Earth's plasma sheet. At the core of the proposed process is the "akis" structure; in a thin current sheet (TCS) the stretched (tail-like) magnetic field lines locally terminate into a sharp tip around the tail midplane. At this sharp tip of the TCS, ions become non-adiabatic, while a percentage of electrons are accumulated and trapped: The strong and transient electrostatic electric fields established along the magnetic field lines produce suprathermal populations. In parallel, the tip structure is associated with field aligned and mutually attracted parallel filamentary currents which progressively become more intense and inevitably the structure collapses, and so does the local TCS. The mechanism is observationally based on elementary, almost autonomous and spatiotemporal entities that correspond each to a local thinning/dipolarization pair having duration of ~1 min. Energetic proton and electron populations do not occur simultaneously, and we infer that they are separately accelerated at local thinnings and dipolarizations, respectively. In one example energetic particles are accelerated without any dB/dt variation and before the substorm expansion phase onset. A particular effort is undertaken demonstrating that the proposed acceleration mechanism may explain the plasma sheet ratio Ti/Te≈7. All our inferences are checked by the highest resolution datasets obtained by the Geotail Energetic Particles and Ion Composition (EPIC) instrument. The energetic particles are used as the best diagnostics for the accelerating source. Near Earth (X≈10 RE) selected events support our basic concept. The proposed mechanism seems to reveal a fundamental building block of the substorm phenomenon and may be the basic process/structure, which is now missing, that might help explain the persistent, outstanding deficiencies in our physical description of magnetospheric substorms. The mechanism is tested, checked, and found consistent with substorm associated observations performed ~30 and 60 RE away from Earth.

Ply and Rubber Stresses and Contact Forces for a Loaded Radial Tire

1983 ◽  
Vol 11 (1) ◽  
pp. 20-37 ◽  
Author(s):  
M. J. Trinko
Keyword(s):  
Iteration Process ◽  
Contact Forces ◽  
Geometrically Nonlinear ◽  
Inflation Pressure ◽  
Radial Tire ◽  
Contact Patch ◽  
Nonlinear Finite Elements ◽  
Vertical Displacements ◽  
Linear Material ◽  
Extract Information

Abstract A P215/75R15, steel-belted radial tire subjected to inflation pressure and footprint loading is modeled using laminated, geometrically nonlinear finite elements. The resulting stresses in both the rubber and the plies are presented. Assumptions made include fixed boundary conditions at the bead-flange interface, linear material property representation, and symmetry with respect to the meridional and tread centerline planes. The footprint loading is simulated by enforcing vertical displacements at selected nodes of the model to yield a contact patch force distribution. In-plane patch forces are not included. Experimental results are given showing comparisons with analytical predictions. Advantages of this approach over models presented earlier are the capability to extract information from each layer and to apply displacements directly to the contact patch rather than using a Fourier approach. The model is exercised using the MSC/NASTRAN program. The straightforward restart capability along with the ability to include or exclude nodal points in the contact patch set during the iteration process make the MSC/NASTRAN program convenient to use for this class of problems.

Nonlinear Panel Flutter of Composite Sandwich Plates with Thermal Effect

2008 ◽  
Vol 24 (2) ◽  
pp. 179-188 ◽  
Author(s):  
L.-C. Shiau ◽  
S.-Y. Kuo
Keyword(s):  
Time Integration ◽  
Sandwich Plates ◽  
Transverse Displacement ◽  
Panel Flutter ◽  
Maximum Displacement ◽  
Plate Temperature ◽  
Aerodynamic Pressure ◽  
Flutter Boundary ◽  
Motion Speed ◽  
Nonlinear Panel Flutter

ABSTRACTBy considering the total transverse displacement of a sandwich plate as the sum of the displacement due to bending of the plate and that due to shear deformation of the core, a high precision higher order triangular plate element is developed for the nonlinear panel flutter analysis of thermally buckled sandwich plates. Von Karman large deformation assumptions and quasi-steady aerodynamic theory are employed for the analysis. Newmark numerical time integration method is applied to solve the nonlinear governing equations in time domain. Results show that temperature will increase both the maximum displacement and motion speed of the plate. But the maximum displacement and velocity of the plate will not vary much with the aerodynamic pressure. Buckle pattern change phenomenon occurred in some specific case will increase the flutter boundary and change the flutter motion type of the plate. Temperature gradient increases the overall stiffness of the plate, which in turn stabilizes the sandwich panel and increases the flutter boundary of the plate.

A Feedback Linearization Approach for Panel Flutter Suppression With Piezoelectric Actuation

2010 ◽  
Vol 6 (3) ◽  
Author(s):  
Oluseyi O. Onawola ◽  
S. C. Sinha
Keyword(s):  
Feedback Control ◽  
Electric Fields ◽  
Feedback Linearization ◽  
Plate Theory ◽  
Nonlinear Partial Differential Equation ◽  
Control Panel ◽  
Panel Flutter ◽  
Piezoelectric Actuation ◽  
Nonlinear Feedback ◽  
Flutter Suppression

Panel flutter suppression by exact state transformations and feedback control using piezoelectric actuation is presented. A nonlinear control system is designed for a simply supported rectangular panel with bonded piezoelectric layers based on the von Kármán large-deflection plate theory. The governing nonlinear partial differential equation for the panel is reduced to a set of ordinary differential equations using a two mode approximation. Distributed piezoelectric actuators and sensors connected to processing networks are used as modal actuators and sensors to actively control panel vibrations. The control inputs are given by the electric fields required to drive the actuators based on piezoelectric actuation. Nonlinear feedback control laws are formulated through a transformation of the discretized nonlinear system into an equivalent controllable linear system. The simulated results show that the resulting closed-loop system based on feedback linearized controllers effectively suppress panel flutter limit-cycle motions.

Nonlinear Flutter of Laminated Composite Plates Resting on Nonlinear Elastic Foundations Using Homotopy Perturbation Method

2015 ◽  
Vol 15 (05) ◽  
pp. 1450072 ◽  
Author(s):  
Ali A. Yazdi
Keyword(s):  
Perturbation Method ◽  
Homotopy Perturbation Method ◽  
Nonlinear Partial Differential Equations ◽  
Composite Plates ◽  
Laminated Plates ◽  
Geometrically Nonlinear ◽  
Aerodynamic Pressure ◽  
Nonlinear Flutter ◽  
Homotopy Perturbation ◽  
Nonlinear Elastic

In this paper, the applicability of the homotopy perturbation method (HPM) in analyzing the flutter of geometrically nonlinear cross-ply rectangular laminated plates resting on nonlinear elastic foundation is investigated. The piston theory is employed to evaluate the aerodynamic pressure acting on the plate. The von Karman geometric nonlinear theory is used to construct the governing equations of the system. The Galerkin's method is used to reduce the nonlinear partial differential equations to a nonlinear second-order ordinary differential equation, and the HPM is employed to study the effect of initial deflection, aspect ratio and stacking sequence on the flutter pressure of cross-ply laminated plates. The results show that the first approximation of the HPM leads to highly accurate solutions for the geometrically nonlinear flutter of cross-ply rectangular laminated plates subjected to the aerodynamic pressure.

scholarly journals Smolyak-Grid-Based Flutter Analysis with the Stochastic Aerodynamic Uncertainty

2014 ◽  
Vol 2014 ◽  
pp. 1-8 ◽  
Author(s):  
Yuting Dai ◽  
Chao Yang
Keyword(s):  
Uncertainty Analysis ◽  
Parametric Uncertainty ◽  
Sparse Grids ◽  
Lattice Method ◽  
Integration Algorithm ◽  
Pressure Coefficients ◽  
Aerodynamic Pressure ◽  
Unsteady Aerodynamic ◽  
Wing Model ◽  
Flutter Boundary

How to estimate the stochastic aerodynamic parametric uncertainty on aeroelastic stability is studied in this current work. The aerodynamic uncertainty is more complicated than the structural one, and it takes more significant effect on the flutter boundary. First, the nominal unsteady aerodynamic influence coefficients were calculated with the doublet lattice method. Based on this nominal model, the stochastic uncertainty model for unsteady aerodynamic pressure coefficients was constructed with physical meaning. Afterwards, the methodology for flutter uncertainty quantification due to aerodynamic perturbation was developed, based on the nonintrusive polynomial chaos expansion theory. In order to enhance the computational efficiency, the integration algorithm, namely, Smolyak sparse grids, was employed to calculate the coefficients of the stochastic polynomial basis. Finally, the flutter uncertainty analysis methodology was applied to an aircraft's wing model. The influence of uncertainty with uniform distribution for aerodynamic pressure coefficients on flutter boundary was quantified. The numerical results indicate that, the influence of unsteady aerodynamic pressure due to the motion of coupling modes takes significant effect on flutter boundary. It is validated that the flutter uncertainty analysis based on Smolyak sparse grids integration is efficient and accurate for quantifying input uncertainty with high dimensions.

scholarly journals Swarms in Periodically Time Dependent Electric Fields

1995 ◽  
Vol 48 (3) ◽  
pp. 365 ◽  
Author(s):  
Kailash Kumar
Keyword(s):  
Integral Equation ◽  
Exact Solution ◽  
Electric Fields ◽  
Transport Theory ◽  
Time Development ◽  
Time Dependent ◽  
Bgk Model ◽  
Physical Description ◽  
Dependent Field ◽  
The Ideal

The transport theory of swarms in a time dependent electric field is formulated in terms of the Boltzmann equation expressed as an integral equation in time. It allows for a convenient physical description of the time development of the swarm for the case of a periodically time dependent field. The exact solution of the ideal charge transfer or BGK model, obtained earlier by Robson and Makabe, is expressed in a closed form.

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