Sensitivity Analysis and Design of an Open-Loop Active Normal Force for Dry Friction Dampers

2017 ◽  
Author(s):  
Yaguang Wu ◽  
Yu Fan ◽  
Lin Li ◽  
Jiuzhou Liu
Keyword(s):  
Frequency Band ◽  
Dry Friction ◽  
Normal Force ◽  
Constant Term ◽  
Open Loop ◽  
Forced Response ◽  
Time Varying ◽  
Best Constant ◽  
Friction Dampers ◽  
Resonance Frequencies

In this paper we design an open-loop active normal force for dry friction dampers, aiming to enhance the damping effect. The active normal force is composed of a constant term plus a time-varying term with zero mean value. The constant term is the best constant normal force that minimizes the forced response in the resonant frequency band. The time-varying force can be expressed by the Fourier Series and here we assume that it is composed of four harmonics with respect to the excitation frequency. Overall eight unknown parameters are therefore to be determined, namely the combination coefficients of the fours harmonics and phase differences between them. First, the global sensitivity of these parameters with respect to the forced response are analysed, in order to select the most significant parameters and to eliminate the unimportant ones. To do that the Fourier Amplitude Sensitivity Test (FAST) is performed based on the Lumped Parameter Model, where the forced response of is calculated by the Multi-Harmonic Balance Method (MHBM) combined with Alternating Frequency/Time domain (AFT). The arc-length continuation technique is used to improve the convergence. We found that the interaction between the amplitude and phase of the second harmonic significantly impacts the forced response around resonance frequencies. Then only these two parameters are considered to minimize the forced response in the frequency band, rather than considering all eight parameters. Results show that a further 25% reduction of the response peak can be achieved by the designed time-varying normal force in comparison with the best constant normal force. The proposed design process is applicable for any dry friction dampers if it is possible to impose an open-loop active normal force.

scholarly journals Test-Model Correlation of Dry-Friction Damping Phenomena in Aero-Engines

2008 ◽  
Author(s):  
P. Jean ◽  
C. Gibert ◽  
C. Dupont ◽  
J.-P. Lombard
Keyword(s):  
Dry Friction ◽  
Forced Response ◽  
Test Model ◽  
Friction Damping ◽  
Bladed Disks ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Resonance Frequencies ◽  
Non Linear ◽  
Aero Engines

In order to control the risk of high cycle fatigue of bladed disks, it is important to predict precisely the vibration levels and to design damping solutions to attenuate them. Therefore, Snecma has made some efforts in the last years in order to characterize better the damping in aero-engines. Among the various damping sources, friction damping is particularly difficult to model due to its non-linear behaviour [1]. For that purpose, two methods based on multi-harmonic balance strategy have been especially developed for Snecma, dedicated to the study of the non-linear forced response of bladed disks. The first one enables to model the bladed disk equipped with dry-friction dampers [2], and the second one takes into account intrinsic friction located in disk-blade interface [3]. To validate both models experimentally, a test campaign has been carried out in a vacuum chamber on a rotating bladed disk excited by piezoelectric actuators. The blade shanks have been softened in order to increase friction effects. Experimental results show a regular and reproducible behaviour of the non-linear forced response, over various rotation speed and excitation levels. The contributions of friction dampers and friction in blade attachment have been decoupled thanks to glue applied in the blade root. Both friction phenomena that were observed experimentally at resonance of the blade first bending mode have been reproduced numerically. After updating modeling parameters, an acceptable correlation was found on resonance frequencies, amplitudes and damping levels over the full experimental setup range, which validates these numerical tools for their use in design process.

Feasibility Research on Coupled Friction/Piezoelectric Dampers

2018 ◽  
Author(s):  
Lin Li ◽  
Yaguang Wu ◽  
Yu Fan
Keyword(s):  
Dry Friction ◽  
Harmonic Balance ◽  
Vibrational Mode ◽  
Piezoelectric Materials ◽  
Harmonic Balance Method ◽  
Forced Response ◽  
Friction Dampers ◽  
Feasibility Research ◽  
Aero Engines ◽  
Better Than

A new passive damper coupling the energy dissipative mechanisms of dry friction and piezoelectric shunting circuit is proposed. The idea is to embed the shunted piezoelectric materials to the dry friction dampers at appropriate positions, so that the elastic deformation of the dry friction dampers can be utilized to generate additional damping. Moreover, this provides a more practical way to install the piezoelectric dampers into realistic mechanical systems such as aero-engines. A five Degree-of-freedom (DOFs) lumped system model is introduced to demonstrate the feasibility of such an idea. The damping performance is revealed using the forced response results obtained by the Multi Harmonic Balance Method (MHBM). We show that the coupled damper significantly outperforms the standalone piezoelectric or dry friction dampers. The coupled damper is better than, at least equivalent to, the case where both piezoelectric and dry friction dampers are applied but in uncoupled manner. Eventually, the mechanism of the proposed damper is further explained from the perspective of vibrational mode and energy conversion.

Blades Forced Response Analysis With Friction Dampers

1998 ◽  
Vol 120 (2) ◽  
pp. 468-474 ◽  
Author(s):  
M. Berthillier ◽  
C. Dupont ◽  
R. Mondal ◽  
J. J. Barrau
Keyword(s):  
Time Domain ◽  
Dry Friction ◽  
Time Domain Analysis ◽  
Domain Analysis ◽  
Frequency Domain Analysis ◽  
Forced Response ◽  
Response Analysis ◽  
Friction Damper ◽  
Friction Dampers ◽  
Fan Blade

A multiharmonic frequency domain analysis combined with a Craig-Bampton component mode synthesis is presented to compute the dry friction damped forced response of blades. The accuracy of the analysis is established, for a cantilever beam with a dry friction damper attached, by comparison with experimental results and time domain analysis. The method has then been applied to a model fan blade damped by a blade to ground damper.

scholarly journals Improved Reliability of Bladed Disks due to Friction Dampers

1997 ◽  
Author(s):  
Walter Sextro ◽  
Karl Popp ◽  
Ivo Wolter
Keyword(s):  
Dry Friction ◽  
Three Dimensional ◽  
Line Contact ◽  
Two Dimensional ◽  
Centrifugal Forces ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Bladed Disk Assembly

Friction dampers are installed underneath the blade platforms to improve the reliability. Because of centrifugal forces the dampers are pressed onto the platforms. Due to dry friction and the relative motion between blades and dampers, energy is dissipated, which results in a reduction of blade vibration amplitudes. The geometry of the contact is in many cases like a Hertzian line contact. A three-dimensional motion of the blades results in a two-dimensional motion of one contact line of the friction dampers in the contact plane. An experiment with one friction damper between two blades is used to verify the two-dimensional contact model including microslip. By optimizing the friction dampers masses, the best damping effects are obtained. Finally, different methods are shown to calculate the envelope of a three-dimensional response of a detuned bladed disk assembly (V84.3-4th-stage turbine blade) with friction dampers.

A Study of Effect of Various Normal Force Loading Forms on Frictional Stick-Slip Vibration

2021 ◽  
Author(s):  
Xiaocui Wang ◽  
◽  
Runlan Wang ◽  
Bo Huang ◽  
Jiliang Mo ◽  
...  
Keyword(s):  
Dynamic Behaviour ◽  
Normal Force ◽  
Time Varying ◽  
Stick Slip ◽  
Vibration Signals ◽  
Theoretical Methods ◽  
Normal Forces ◽  
Frequency Domains ◽  
Amplitude Vibration ◽  
Fourier Spectra

In this work, a comparative study is performed to investigate the influence of time-varying normal forces on the friction properties and friction-induced stick-slip vibration by experimental and theoretical methods. In the experiments, constant and harmonic-varying normal forces are applied, respectively. The measured vibration signals under two loading forms are compared in both time and frequency domains. In addition, mathematical tools such as phase space reconstruction and Fourier spectra are used to reveal the science behind the complicated dynamic behaviour. It can be found that the friction system shows steady stick-slip vibration, and the main frequency does not vary with the magnitude of the constant normal force, but the size of limit cycle increases with the magnitude of the constant normal force. In contrast, the friction system harmonic normal force shows complicated behaviour, for example, higher-frequency larger-amplitude vibration occurs as the frequency of the normal force increases. The interesting findings offer a new way for controlling friction-induced stick-slip vibration in engineering applications.

A New Method to Find the Forced Response of Nonlinear Systems with Dry Friction

2021 ◽  
Author(s):  
Gregory L. Altamirano ◽  
Meng-Hsuan Tien ◽  
Kiran D'Souza
Keyword(s):  
Dry Friction ◽  
Coulomb Friction ◽  
Nonlinear Response ◽  
Piecewise Linear ◽  
Time Integration ◽  
Nonlinear Behavior ◽  
Forced Response ◽  
New Method ◽  
Analysis Tools ◽  
Compatibility Constraint

Abstract Coulomb friction has an influence on the behavior of numerous mechanical systems. Coulomb friction systems or dry friction systems are nonlinear in nature. This nonlinear behavior requires complex and time demanding analysis tools to capture the dynamics of these systems. Recently, efforts have been made to develop efficient analysis tools able to approximate the forced response of systems with dry friction. The objective of this paper is to introduce a methodology that assists in these efforts. In this method, the piecewise-linear nonlinear response is separated into individual linear responses that are coupled together through compatibility constraint equations. The new method is demonstrated on a number of systems of varying complexity. The results obtained by the new method are validated through the comparison with results obtained by time integration. The computational savings of the new method is also discussed.

The Modelling of the Opening and Closure of a Crack

1995 ◽  
Vol 117 (3A) ◽  
pp. 370-377 ◽  
Author(s):  
O. N. L. Abraham ◽  
J. A. Brandon
Keyword(s):  
Fourier Series ◽  
Cantilever Beam ◽  
Time Domain ◽  
Dry Friction ◽  
Transverse Crack ◽  
Normal Modes ◽  
Time Varying ◽  
Interaction Forces ◽  
Vibration Properties ◽  
Connection Matrices

The paper presents a method which utilizes substructure normal modes to predict the vibration properties of a cantilever beam with a breathing transverse crack. The two segments of the cantilever beam, separated by the crack, are related to one another by time varying connection matrices representing the interaction forces. The connection matrices are expanded in a Fourier series leading to a classical eigenvalue problem. Subsequently, the initial formulation is extended to avoid interference of the crack interfaces with a time domain formulation. The Lagrange multipliers, used to enforce the exact continuity constraints when the crack is closed, produce the interfaces forces needed for the modelling of interface dry friction.

Decentralized MRAC for Large-Scale Interconnected Systems With State and Input Delays by Integrators Inclusion

2017 ◽  
Vol 139 (9) ◽  
Author(s):  
Seyed Hamid Hashemipour ◽  
Nastaran Vasegh ◽  
Ali Khaki Sedigh
Keyword(s):  
Large Scale ◽  
Practical Method ◽  
Open Loop ◽  
Loop System ◽  
Input Delay ◽  
Time Varying ◽  
Delay Compensation ◽  
State And Input Delays ◽  
Input Delays ◽  
Model Reference Adaptive

This paper investigates the problem of decentralized model reference adaptive control (MRAC) for a class of large-scale systems with time-varying delays in the interconnected terms and state and input delays. The upper bounds of interconnection terms with time-varying delays and external disturbances are assumed to be completely unknown. By integrators inclusion, a dynamic input delay compensator is established for input delay compensation and it is used as a practical method for state calculation x(t + R). Also, a method is presented for a class of decentralized feedback controllers, which can evolve the closed-loop system error uniformly bounded stable. As a numerical example, the proposed technique is applied to an unstable open-loop system to show the feasibility and effectiveness of the method.

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