Reduced-Order Nonlinear Damping Model: Formulation and Application to Postflutter Aeroelastic Behavior

AIAA Journal ◽  
2021 ◽  
pp. 1-11
Author(s):  
X. Q. Wang ◽  
Pengchao Song ◽  
Marc P. Mignolet ◽  
P. C. Chen
Keyword(s):  
Nonlinear Damping ◽  
Model Formulation ◽  
Reduced Order ◽  
Damping Model

scholarly journals Passive Vibration Reduction Analysis of the Mistuned Blisk Deposited Hard Coating Using Modified Reduced-Order Model

Coatings ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 812
Author(s):  
Feng Gao ◽  
Bingqiang Li ◽  
Xiuting Liu
Keyword(s):  
Vibration Reduction ◽  
Synthesis Method ◽  
Reduced Order Model ◽  
Hard Coating ◽  
Order Model ◽  
Reduced Order ◽  
Damping Characteristics ◽  
Vibration Responses ◽  
Novel Strategy ◽  
Damping Model

To improve the reliability and safety of the mistuned blisk (integrally bladed disk), a novel strategy for passive vibration reduction by the hard coating was developed, and the vibration and damping characteristics of the HCM (hard-coating mistuned) blisk were investigated in this work. Firstly, by the proposed criterion called FDSD (frequency difference and its standard deviation), a classical reduced-order model established by the component mode synthesis method was modified to carry out modal analysis for high computational efficiency. Then, forced vibration responses of the HCM blisk were achieved by the Rayleigh damping model. Next, a specific benchmark of a mistuned blisk deposited NiCoCrAlY + YSZ hard coating was chosen to conduct numerical calculations, and the results were compared with those obtained from the FOM (full-order model) and experimental test, respectively. Finally, the influence of the hard coating and coating thickness on the mistuned blisk were investigated, in particular.

Nonlinear System Identification of Frictional Connections in a Bolted Beam Assembly

2012 ◽  
Author(s):  
Melih Eriten ◽  
Mehmet Kurt ◽  
Guanyang Luo ◽  
Donald M. McFarland ◽  
Lawrence A. Bergman ◽  
...  
Keyword(s):  
System Identification ◽  
Nonlinear System ◽  
Energy Levels ◽  
Nonlinear System Identification ◽  
Flow Analysis ◽  
Nonlinear Damping ◽  
Experimental Measurements ◽  
Slow Flow ◽  
Reduced Order Models ◽  
Reduced Order

In modern structures, mechanical joints are ubiquitous, significantly influencing a structure’s dynamics. Frictional connections contained in a joint provide coupling of forces and moments between assembled components as well as localized nonlinear energy dissipation. Certain aspects of the mechanics of these friction connections are yet to be fully understood and characterized in a dynamical systems framework. This work applies a nonlinear system identification (NSI) technique to characterize the influence of frictional connections on the dynamics of a bolted beam assembly. The methodology utilized in this work combines experimental measurements with slow-flow dynamic analysis and empirical mode decomposition, and reconstructs the dynamics through reduced-order models. These are in the form of single-degree-of-freedom linear oscillators (termed intrinsic modal oscillators — IMOs) with forcing terms derived directly from the experimental measurements through slow-flow analysis. The derived reduced order models are capable of reproducing the measured dynamics, whereas the forcing terms provide important information about nonlinear damping effects. The NSI methodology is applied to model nonlinear friction effects in a bolted beam assembly. A ‘monolithic’ beam with identical geometric and material properties is also tested for comparison. Three different forcing (energy) levels are considered in the tests in order to study the energy-dependencies of the damping nonlinearities induced in the beam from the bolted joint. In all cases, the NSI technique employed is successful in identifying the damping nonlinearities, their spatial distributions and their effects on the vibration modes of the structural component.

Nonlinear Reduced-Order Models for Aerodynamic Lift of Oscillating Airfoils

2016 ◽  
Author(s):  
Muhammad Saif Ullah Khalid ◽  
Imran Akhtar
Keyword(s):  
Numerical Simulations ◽  
Strouhal Number ◽  
Lift Force ◽  
Multiple Scales ◽  
Primary Resonance ◽  
Nonlinear Damping ◽  
Van Der Pol Oscillator ◽  
Reduced Order ◽  
Naca 0012 ◽  
Unsteady Lift

For the present study, setting Strouhal Number as the control parameter, we perform numerical simulations for the flow over oscillating NACA-0012 airfoil at Reynolds Number 103. Temporal profiles of the unsteady lift, and their respective spectra clearly indicate the solution to be a period-1 attractor for low Strouhal numbers. This study reveals that aerodynamic forces produced by the oscillating airfoils are independent of the initial kinematic conditions that proves existence of the limit cycle. Frequencies present in the oscillating lift force are composed of the fundamental harmonics, and its odd harmonics. Using these numerical simulations, we observe the shedding frequencies nearly equal to the excitation frequencies in all the cases. Hence, considering it as a primary resonance case, we model the unsteady lift force through a modified van der Pol oscillator. Using the method of multiple scales and spectral analysis of the steady-state CFD solutions, we estimate the frequencies and the damping terms in the reduced-order model. We prove the applicability of this model to all the planar motions of airfoil; heaving, pitching and flapping. With the increasing Strouhal number, the nonlinear damping terms for all types of motion approach similar magnitudes. Another important aspect in one of the currently-proposed model is capturing the time-averaged value of the aero-dynamic lift force.

Parametric Excitation of a Microbeam-String With Asymmetric Electrodes: Multimode Dynamics and the Effect of Nonlinear Damping

2017 ◽  
Vol 139 (4) ◽  
Author(s):  
Karin Mora ◽  
Oded Gottlieb
Keyword(s):  
Evolution Equations ◽  
Multiple Scales ◽  
Orbital Stability ◽  
Nonlinear Damping ◽  
Nonlinear Beam ◽  
Reduced Order ◽  
Nonlinear Viscoelastic ◽  
Current Voltage ◽  
Spatio Temporal ◽  
Asymmetric Electrodes

The dynamic motion of a parametrically excited microbeam-string affected by nonlinear damping is considered asymptotically and numerically. It is assumed that the geometrically nonlinear beam-string, subject to only modulated alternating current voltage, is closer to one of the electrodes, thus resulting in an asymmetric dual gap configuration. A consequence of these novel assumptions is a combined parametric and hard excitation in the derived continuum-based model that incorporates both linear viscous and nonlinear viscoelastic damping terms. To understand how these assumptions influence the beam's performance, the conditions that lead to both principal parametric resonance and a three-to-one internal resonance are investigated. Such conditions are derived analytically from a reduced-order nonlinear model for the first three modes of the microbeam-string using the asymptotic multiple-scales method which requires reconstitution of the slow-scale evolution equations to deduce an approximate spatio-temporal solution. The response is investigated analytically and numerically and reveals a bifurcation structure that includes coexisting in-phase and out-of-phase solutions, Hopf bifurcations, and conditions for the loss of orbital stability culminating with nonstationary quasi-periodic solutions and chaotic strange attractors.

Life Calculation of First Stage Compressor Blade of a Trainer Aircraft

2012 ◽  
Author(s):  
J. S. Rao ◽  
Narayan Rangarajan ◽  
Rejin Ratnakar ◽  
R. Rzadkowski ◽  
M. Soliński ◽  
...  
Keyword(s):  
Air Force ◽  
Critical Speed ◽  
Iterative Solution ◽  
Nonlinear Damping ◽  
Equivalent Viscous Damping ◽  
Campbell Diagram ◽  
Compressor Rotor ◽  
Institute Of Technology ◽  
The Given ◽  
Damping Model

This paper is concerned with life estimation of a compressor rotor blade of an engine at the Air Force Institute of Technology in Warsaw used in a trainer aircraft. A bird strike is simulated by two or three blade passage blocks in the incoming flow and the pressure field is obtained from a CFD code. For the blade the Campbell diagram is prepared and the critical speeds are identified. The alternating pressures corresponding to the critical speed are obtained from an FFT. A nonlinear damping model is estimated using Lazan’s hysteresis law; the equivalent viscous damping model is determined as a function of reference strain amplitude in the given mode of vibration at the rotational speed. An iterative solution is developed with the nonlinear damping model and the resonant stress and location is determined. The life at this critical speed is determined using a cumulative damage criterion.

A Practical Mathematical Model for Nonlinear Hysteresis of Metal Rubber Isolator

2011 ◽  
Vol 105-107 ◽  
pp. 20-23 ◽  
Author(s):  
Yan Guo Zhou ◽  
Wen Zhong Qu ◽  
Li Xiao
Keyword(s):  
Practical Method ◽  
Nonlinear Damping ◽  
Mathematical Form ◽  
Nonlinear Hysteresis ◽  
Damping Behavior ◽  
Satisfactory Precision ◽  
Practical Engineering ◽  
Metal Rubber ◽  
Damping Model ◽  
Rubber Isolator

The hysteresis dynamic behavior of metal rubber mathematically modeled with a practical method is studied, and the method of parameter separated identification is presented with details. Parameters of the model are identified with the test data of metal rubber, from which the theoretical loops are reconstructed, and the mechanism of the nonlinear damping behavior of the metal rubber is investigated. The theoretical loops and the experimental one are close to each other with satisfactory accuracy. The result shows that with the simple mathematical form and the satisfactory precision, the mixed damping model can be used effectively in practical engineering. This study provides a practical and effective method in modeling and the parameter identification of the metal rubber isolator.

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