Friction Dampers: Measurement, Modelling and Application to Blade Vibration Control

1995 ◽  
Author(s):  
Kenan Y. Sanliturk ◽  
Anthony B. Stanbridge ◽  
David J. Ewins
Keyword(s):  
Harmonic Balance Method ◽  
Theoretical Modelling ◽  
Dynamic Force ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Response Characteristics ◽  
Joint Characteristics ◽  
Contact Behaviour ◽  
Better Than

Abstract This paper describes a procedure that combines the measurement of dry-friction contact behaviour, its theoretical modelling and the analysis of structures with friction joints. The experimental part describes a friction damper test rig which is specifically designed for measuring the dynamic force-response characteristics of a joint. A hybrid mathematical model, which is a combination of the traditional macro- and micro-slip models, is proposed to represent the joint characteristics and it is shown that such a model represents the measured behaviour better than any of the traditional ones. The final part of the paper demonstrates the procedure applied to a blade-damper test structure and which includes testing, analysis and correlation of both sets of results. The non-linear response levels are predicted using a dedicated program based on the Harmonic Balance Method and it is found that the proposed analysis procedure can predict the amount of response reduction, the optimum friction damper load and the locked natural frequency quite accurately.

scholarly journals Friction Damper Optimisation: Simulation of Rainbow Tests

1999 ◽  
Author(s):  
Kenan Y. Sanliturk ◽  
David J. Ewins ◽  
Robert Elliott ◽  
Jeff S. Green
Keyword(s):  
Harmonic Balance Method ◽  
Lumped Parameter Model ◽  
Friction Damper ◽  
Blade Vibration ◽  
Friction Dampers ◽  
Lumped Parameter ◽  
Engine Order ◽  
Resonance Response ◽  
Theoretical Predictions ◽  
Different Characteristics

Friction dampers have been used to reduce turbine blade vibration levels for a considerable period of time. However, optimal design of these dampers has been quite difficult due both to a lack of adequate theoretical predictions and to difficulties in conducting reliable experiments. One of the difficulties of damper weight optimisation via the experimental route has been the inevitable effects of mistuning. Also, conducting separate experiments for different damper weights involves excessive cost. Therefore, current practice in the turbomachinery industry has been to conduct so-called ‘rainbow tests’ where friction dampers with different weights are placed between blades with a predefined configuration. However, it has been observed that some rainbow test results have been difficult to interpret and have been inconclusive for determining the optimum damper weight for a given bladed-disc assembly. A new method of analysis — a combination of Harmonic Balance Method and structural modification approaches — is presented in this paper for the analysis of structures with friction interfaces and the method is applied to search for qualitative answers about the so-called ‘rainbow tests’ in turbomachinery applications. A simple lumped-parameter model of a bladed-disc model was used and different damper weights were modelled using friction elements with different characteristics. Resonance response levels were obtained for bladed discs with various numbers of blades under various engine-order excitations. It was found that rainbow tests, where friction dampers with different weights are used on the same bladed-disc assembly, can be used to find the optimum damper weight if the mode of vibration concerned has weak blade-to-blade coupling (the case where the disc is almost rigid and blades vibrate almost independently from each other). Otherwise, it is very difficult to draw any reliable conclusion from such expensive experiments.

Friction Damper Optimization: Simulation of Rainbow Tests

1999 ◽  
Vol 123 (4) ◽  
pp. 930-939 ◽  
Author(s):  
K. Y. Sanliturk ◽  
D. J. Ewins ◽  
R. Elliott ◽  
J. S. Green
Keyword(s):  
Harmonic Balance Method ◽  
Lumped Parameter Model ◽  
Friction Damper ◽  
Blade Vibration ◽  
Disk Model ◽  
Friction Dampers ◽  
Bladed Disk ◽  
Theoretical Predictions ◽  
Optimization Simulation ◽  
Bladed Disk Assembly

Friction dampers have been used to reduce turbine blade vibration levels for a considerable period of time. However, optimal design of these dampers has been quite difficult due both to a lack of adequate theoretical predictions and to difficulties in conducting reliable experiments. One of the difficulties of damper weight optimization via the experimental route has been the inevitable effects of mistuning. Also, conducting separate experiments for different damper weights involves excessive cost. Therefore, current practice in the turbomachinery industry has been to conduct so-called “rainbow tests” where friction dampers with different weights are placed between blades with a predefined configuration. However, it has been observed that some rainbow test results have been difficult to interpret and have been inconclusive for determining the optimum damper weight for a given bladed-disk assembly. A new method of analysis—a combination of the harmonic balance method and structural modification approaches—is presented in this paper for the analysis of structures with friction interfaces and the method is applied to search for qualitative answers about the so-called “rainbow tests” in turbomachinery applications. A simple lumped-parameter model of a bladed-disk model was used and different damper weights were modeled using friction elements with different characteristics. Resonance response levels were obtained for bladed disks with various numbers of blades under various engine-order excitations. It was found that rainbow tests, where friction dampers with different weights are used on the same bladed-disk assembly, can be used to find the optimum damper weight if the mode of vibration concerned has weak blade-to-blade coupling (the case where the disk is almost rigid and blades vibrate almost independently from each other). Otherwise, it is very difficult to draw any reliable conclusion from such expensive experiments.

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 Resonance Tracking Algorithm for the Prediction of Turbine Forced Response With Friction Dampers

2000 ◽  
Author(s):  
C. Bréard ◽  
J. S. Green ◽  
M. Vahdati ◽  
M. Imregun
Keyword(s):  
Rotor Blade ◽  
Turbine Blades ◽  
Turbine Rotor ◽  
Forced Response ◽  
Rotor Blades ◽  
Test Case ◽  
Friction Damper ◽  
Blade Vibration ◽  
Frequency Shifts ◽  
Friction Dampers

This paper presents an iterative method for determining the resonant speed shift when non-linear friction dampers are included in turbine blade roots. Such a need arises when conducting response calculations for turbine blades where the unsteady aerodynamic excitation must be computed at the exact resonant speed of interest. The inclusion of friction dampers is known to raise the resonant frequencies by up to 20% from the standard assembly frequencies. The iterative procedure uses a viscous, time-accurate flow representation for determining the aerodynamic forcing, a look-up table for evaluating the aerodynamic boundary conditions at any speed, and a time-domain friction damping module for resonance tracking. The methodology was applied to an HP turbine rotor test case where the resonances of interest were due to the 1T and 2F blade modes under 40 engine-order excitation. The forced response computations were conducted using a multi-stage approach in order to avoid errors associated with “linking” single stage computations since the spacing between the two bladerows was relatively small. Three friction damper elements were used for each rotor blade. To improve the computational efficiency, the number of rotor blades was decreased by 2 to 90 in order to obtain a stator/rotor blade ratio of 4/9. However, the blade geometry was skewed in order to match the capacity (mass flow rate) of the components and the condition being analysed. Frequency shifts of 3.2% and 20.0% were predicted for the 1T/40EO and 2F/40EO resonances in about 3 iterations. The predicted frequency shifts and the dynamic behaviour of the friction dampers were found to be within the expected range. Furthermore, the measured and predicted blade vibration amplitudes showed a good agreement, indicating that the methodology can be applied to industrial problems.

Harmonic Balance Vibration Analysis of Turbine Blades With Friction Dampers

1997 ◽  
Vol 119 (1) ◽  
pp. 96-103 ◽  
Author(s):  
K. Y. Sanliturk ◽  
M. Imregun ◽  
D. J. Ewins
Keyword(s):  
Harmonic Balance ◽  
Turbine Blades ◽  
Numerical Test ◽  
Harmonic Balance Method ◽  
Nonlinear Behavior ◽  
Friction Damper ◽  
Friction Dampers ◽  
Equivalent Time ◽  
Time Marching ◽  
Detailed Assessment

Although considerable effort has been devoted to the formulation of predictive models of friction damper behavior in turbomachinery applications, especially for turbine blades, the problem is far from being solved due to the complex nonlinear behavior of the contact surfaces. This paper primarily focuses on analytical and numerical aspects of the problem and addresses the problem in the frequency domain while exploring the viability of equivalent time-domain alternatives. The distinct features of this work are: (i) the modelling of nonlinear friction damper behavior as an equivalent amplitude-dependent complex stiffness via a first-order harmonic balance method (HBM), (ii) the use of sine sweep excitation in time-marching analysis, (iii) the application of the methodology to numerical test cases, including an idealised 3D turbine blade model with several friction dampers, (iv) the verification of the numerical findings using experimental data, and (v) a detailed assessment of the suitability of HBM for the analysis of structures with friction dampers.

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.

Vibration Control of Offshore Platform Structure with Friction Dampers

2014 ◽  
Vol 638-640 ◽  
pp. 318-321
Author(s):  
Da Hai Zhao ◽  
Jing Lin Zhang
Keyword(s):  
Energy Dissipation ◽  
Vibration Control ◽  
Equation Of Motion ◽  
Offshore Platform ◽  
Wave Loads ◽  
Friction Damper ◽  
Friction Dampers ◽  
Offshore Platform Structure ◽  
Better Than

The performance of friction dampers to mitigate waves and earthquakes in tower-type offshore platform is investigated in this paper. Taking the offshore platform of TOWER-1 as an example, the equation of motion of offshore platform structure under earthquake and wave loads was established. The response reductions of offshore platform structure by different peak earthquakes were analyzed. The results show that the responses of the tower-type offshore platform structure under wave and earthquake could be effectively reduced by friction damper, and the energy dissipation ability of the friction damper differs in the different floors. The friction dampers give good response reductions in different peak earthquakes, and the response reductions of displacement are better than those of acceleration.

scholarly journals Dynamic Characteristics of a Segmented Supercritical Driveline with Flexible Couplings and Dry Friction Dampers

Symmetry ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 281
Author(s):  
Zhonghe Huang ◽  
Jianping Tan ◽  
Chuliang Liu ◽  
Xiong Lu
Keyword(s):  
Dry Friction ◽  
Vibration Suppression ◽  
Parameter Analysis ◽  
Friction Damper ◽  
Dynamic Effects ◽  
Angular Misalignment ◽  
Friction Dampers ◽  
Response Characteristics ◽  
Flexible Diaphragm ◽  
Simulation And Experiment

Helicopter tail rotors adopt a segmented driveline connected by flexible couplings, and dry friction dampers to suppress resonance. Modeling for this system can provide a basic foundation for parameter analysis. In this work, the lateral-torsional vibration equation of the shaft with continuous internal damping is established. The static and dynamic effects caused by flexible diaphragm couplings subject to parallel and angular misalignment is derived. A novel dual rub-impact model between the shaft and dry friction damper with multiple stages is proposed. Finally, a model of a helicopter tail rotor driveline incorporating all the above elements is formulated. Numerical simulations are carried out by an improved Adams–Bashforth method following the design flowchart. The dynamics of multiple vibration suppression, and the static and dynamic misalignment are analyzed to illustrate the accuracy and characteristics of the model. The coeffect of the rub impact and the misalignment on shafts and dampers are presented through the results of simulation and experiment. It provides an accurate and comprehensive mathematical model for the helicopter driveline. Response characteristics of multiple damping stages, static and dynamic misalignment, and their interaction are revealed.

Seismic performance evaluation of multi-story CBFs equipped with SMA-friction damping braces

2021 ◽  
pp. 1045389X2098700 ◽  
Author(s):  
Canxing Qiu ◽  
Jiawang Liu ◽  
Jun Teng ◽  
Zuohua Li ◽  
Xiuli Du
Keyword(s):  
Strain Hardening ◽  
Ground Motions ◽  
Residual Deformation ◽  
Martensite Phase ◽  
Friction Damper ◽  
Concentrically Braced Frames ◽  
Friction Damping ◽  
Friction Mechanism ◽  
Building Collapse ◽  
Response Characteristics

Shape memory alloys (SMAs) gained increasing attentions from the perspective of seismic protection, primarily because of their excellent superelasticity, satisfactory damping and high fatigue life. However, the superelastic strain of SMAs has an upper limit, beyond which the material completes the austenite to martensite phase transformation and is followed by noticeable strain hardening. The strain hardening behavior would not only induce high force demand to the protected structures, but also cause unrecoverable deformation. More importantly, the SMAs may fracture if the deformation demand exceeds their capacity under severe earthquakes. In the case of installing SMA braces (SMABs) in the multi-story concentrically braced frames (CBFs), the material failure would lead to the malfunction of SMABs and this further causes building collapse. The friction mechanism could behave as a “fuse” through capping the strength demand at a constant level. Therefore, this paper suggests connecting the SMAB with a friction damper to achieve a novel brace, i.e. the SMA-friction damping brace (SMAFDB). A proof-of-concept test was carried out on a homemade specimen and the test results validated the novel brace behaves in a desirable manner. In addition, to explore the seismic response characteristics of the SMAFDB within structures, a six-story CBF equipped with SMAFDBs was designed and compared against those incorporated with SMABs or friction damping braces (FDBs) at the frequently occurred earthquake (FOE), design basis earthquake (DBE) and maximum considered earthquake (MCE). The comparative results show the SMAFDB is superior to the counterparts. Under the FOE and DBE ground motions, the SMAFDBs successfully eliminated residual deformations as the SMABs do, and achieved identical maximum interstory drift as the FDBs. Under the MCE ground motions, the SMAFDBs not only well addressed the brace failure problem that was possibly encountered in the SMABs, but also better controlled residual deformation than the FDBs.

Development of a dual-stage and visual-servo filming robot

2021 ◽  
pp. 095965182199136
Author(s):  
Liang-Chien Liu ◽  
Ping-Han Yang ◽  
Shih-Chi Liao ◽  
Bing-Peng Li ◽  
Fu-Cheng Wang ◽  
...  
Keyword(s):  
Fast Response ◽  
Tracking Performance ◽  
Visual Servo ◽  
Response Characteristics ◽  
Lower Stage ◽  
Upper Stage ◽  
Dual Stage ◽  
Switching Controller ◽  
Similar Evaluation ◽  
Better Than

This article presents the development of a visual-servo filming robot for dolly & truck style camera movement in filming applications. The robot was implemented with a fast-response slider as the upper stage on top of the slow-response tracked robot body as the lower stage, to improve target tracking performance. A new switching controller was developed, which controlled the stages’ motions by balancing and adjusting the weights of vision error and slider’s noncentering error of the upper stage, thus achieving tracking performance better than the traditional master–slave control strategy. The simulations were carried out to evaluate the tracking performance of the model, particularly focusing on evaluating how the dual stage improves the overall response of the model. The similar evaluation was executed experimentally as well. Both results confirm that the fast-response characteristics of the upper stage can compensate the slow dynamics of lower stage, the tracked robot which is inevitably heavy due to its composition.

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