POSTBUCKLING ANALYSIS OF VARIABLE STIFFNESS COMPOSITE PLATES USING A FINITE ELEMENT-BASED PERTURBATION METHOD

2011 ◽  
Vol 11 (04) ◽  
pp. 735-753 ◽  
Author(s):  
T. RAHMAN ◽  
S. T. IJSSELMUIDEN ◽  
M. M. ABDALLA ◽  
E. L. JANSEN
Keyword(s):  
Finite Element ◽  
Perturbation Method ◽  
Composite Plates ◽  
Variable Stiffness ◽  
Reduced Order Model ◽  
Perturbation Approach ◽  
Postbuckling Behavior ◽  
Order Model ◽  
Fast Analysis ◽  
Reduced Order

Modern fiber placement machines allow laminates with spatially varying stiffness properties to be manufactured. In earlier research, the authors optimized variable stiffness plates for maximum buckling load, demonstrating significant improvements in load-carrying capacity. In aerospace applications, panel structures are often permitted to enter the postbuckling regime during service. It is, therefore, not only important to understand their postbuckling behavior, but also to develop fast analysis methods that can subsequently be used in a design optimization framework. The aim of the present research is to study the postbuckling behavior of the optimized plates using a perturbation method that has been developed earlier within a general-purpose finite element environment. The perturbation approach is used to compute postbuckling coefficients, which are used to make a quick estimate of the postbuckling stiffness of the panel and to establish a reduced-order model. In the present work, the postbuckling analysis of variable stiffness plates is carried out using the reduced-order model, and the potential of the approach for incorporation within the optimization process is demonstrated.

Postbuckling Analysis of Variable Stiffness Composite Panels Using a Finite Element Based Perturbation Method

2009 ◽  
Author(s):  
T. Rahman ◽  
S. T. IJsselmuiden ◽  
M. M. Abdalla ◽  
E. L. Jansen
Keyword(s):  
Finite Element ◽  
Perturbation Method ◽  
Variable Stiffness ◽  
General Purpose ◽  
Reduced Order Model ◽  
Finite Element Code ◽  
Order Model ◽  
Reduced Order ◽  
Quick Estimate ◽  
Optimization Loop

In earlier research the authors optimized variable stiffness panels for maximum buckling load, using lamination parameters. The aim of the present research is to analyze those optimized panels in the postbuckling regime so that further improvement can be achieved in the future with respect to its postbuckling performance. Because the incremental-iterative nonlinear analysis in the postbuckling regime is not feasible within an optimization loop a finite element based perturbation method (Koiter type) is used to compute postbuckling coefficients, which are in turn used to make a quick estimate of the postbuckling stiffness of the panel and to establish a reduced order model. The proposed perturbation method has been implemented in a general purpose finite element code. In the present work the postbuckling analysis of variable stiffness panels carried out using the reduced order model is presented and the potential of the approach for incorporation within the optimization process is demonstrated.

Intentional Mistuning With Predominant Aerodynamic Effects

2018 ◽  
Author(s):  
Carlos Martel ◽  
José J. Sánchez
Keyword(s):  
Finite Element ◽  
Traveling Waves ◽  
Element Model ◽  
Simple Expression ◽  
Reduced Order Model ◽  
Action Mechanism ◽  
Aerodynamic Forces ◽  
Order Model ◽  
Reduced Order ◽  
Random Mistuning

Intentional mistuning is a well known procedure to decrease the uncontrolled vibration amplification effects of the inherent random mistuning and to reduce the sensitivity to it. The idea is to introduce an intentional mistuning pattern that is small but much larger that the existing random mistuning. The frequency of adjacent blades is moved apart by the intentional mistuning, reducing the effect of the blade-to-blade coupling and thus the effect of the random mistuning. The situation considered in this work is more complicated because the main source for the blade damping is the effect of the aerodynamic forces (as it happens in a blisk for a family of blade dominated modes with very similar frequencies). In this case the damping is clearly defined for the tuned traveling waves but not for each blade. The problem is analyzed using the Asymptotic Mistuning Model methodology. A reduced order model is derived that allows us to understand the action mechanism of the intentional mistuning, and gives a simple expression for the estimation of its beneficial effect. The results from the reduced model are compared with those from a finite element model of a more realistic rotor under different forcing conditions.

scholarly journals Modeling the Electrostatic Deflection of a MEMS Multilayers Based Actuator

2013 ◽  
Vol 2013 ◽  
pp. 1-6 ◽  
Author(s):  
Hassen M. Ouakad ◽  
Muhammad A. Hawwa ◽  
Hussain M. Al-Qahtani
Keyword(s):  
Finite Element ◽  
Boundary Conditions ◽  
Integrodifferential Equations ◽  
Reduced Order Model ◽  
Rigid Substrate ◽  
Order Model ◽  
Commercial Software ◽  
Reduced Order ◽  
Electrostatic Deflection

An actuator comprised of a rigid substrate and two parallel clamped-clamped microbeams is modeled under the influence of electrostatic loading. The problem is considered under the context of nonlinear Euler's mechanics, where the actuating system is described by coupled integrodifferential equations with relevant boundary conditions. Galerkin-based discretization is utilized to obtain a reduced-order model, which is solved numerically. Actuators with different gap sizes between electrode and beams are investigated. The obtained results are compared to simulations gotten by the finite-element commercial software ANSYS.

A Reduced-Order Model for Evaluating the Effect of Rotational Speed on the Natural Frequencies and Mode Shapes of Blades

2003 ◽  
Vol 125 (3) ◽  
pp. 772-776 ◽  
Author(s):  
P. Marugabandhu ◽  
J. H. Griffin
Keyword(s):  
Finite Element ◽  
Natural Frequencies ◽  
Reduced Order Model ◽  
Mode Shapes ◽  
Finite Element Analyses ◽  
Order Model ◽  
Reduced Order ◽  
Low Aspect Ratio ◽  
Centrifugal Stiffening ◽  
Fan Blade

A reduced-order model has been developed that can be used to accurately and quickly calculate the changes in the natural frequencies and mode shapes of a blade that are caused by centrifugal stiffening. It has been corroborated by comparisons with finite element analyses of a cantilevered tapered plate and with frequencies from a low aspect ratio fan blade.

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