Статті в журналах: "Underplatform damper"

1

Gastaldi, Chiara, Teresa M. Berruti, and Muzio M. Gola. "Best practices for underplatform damper designers." Proceedings of the Institution of Mechanical Engineers, Part C: Journal of Mechanical Engineering Science 232, no. 7 (February 1, 2018): 1221–35. http://dx.doi.org/10.1177/0954406217753654.

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The purpose of this paper is to offer a practical demonstration of how essential preoptimization is in the design of underplatform dampers for turbine blades. Preoptimization can be thought of as a “prescreening” which allows excluding, since the early design stages, a high number of poorly performing damper–platform configurations. This concept, previously presented by the authors, is here extended and its generality for all blade bending modes is rigorously demonstrated. The paper addresses a test case where the introduction of curved-flat underplatform dampers is necessary to avoid a dangerous resonance crossing in the operating rotational speed range of a real turbine disk. It is shown how preoptimized dampers are the only ones that manage to satisfy all functional requirements, including those in the nonlinear operating regime. The same set of dampers may have been identified by exploring, through hundreds of computationally intensive nonlinear calculations, the performance of all possible damper configurations. The latter approach, i.e. iterative design, is unpractical and has to be repeated for each new set of blades since it is based on a test case-specific trial-and-error procedure. Preoptimization substitutes iterations with knowledge of the damper behavior and can therefore be considered as “informed design”: viable damper configurations are instantly singled out through simple but insightful considerations on the damper equilibrium of forces and moments.

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2

Berruti, Teresa, Christian M. Firrone, M. Pizzolante, and Muzio M. Gola. "Fatigue Damage Prevention on Turbine Blades: Study of Underplatform Damper Shape." Key Engineering Materials 347 (September 2007): 159–64. http://dx.doi.org/10.4028/www.scientific.net/kem.347.159.

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Forced vibrations can lead to an irreparable damage of a blade array. Devices called “underplatform damper” that dissipate the vibration energy are employed in order to reduce blade vibration amplitude. The present paper deals with the design of the underplatform damper. A numerical code to calculate the forced response of a blade array with dampers has been previously purposely developed. A method is here proposed for the estimation of the unknown contact parameters demanded by the code. The computation results are here validated by means of comparison with experimental results on a static test rig. Three dampers with different shape are tested.

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3

Sanliturk, K. Y., D. J. Ewins, and A. B. Stanbridge. "Underplatform Dampers for Turbine Blades: Theoretical Modeling, Analysis, and Comparison With Experimental Data." Journal of Engineering for Gas Turbines and Power 123, no. 4 (October 1, 1998): 919–29. http://dx.doi.org/10.1115/1.1385830.

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This paper describes a theoretical model for analyzing the dynamic characteristics of wedge-shaped underplatform dampers for turbine blades, with the objective that this model can be used to minimize the need for conducting expensive experiments for optimizing such dampers. The theoretical model presented in the paper has several distinct features to achieve this objective including: (i) it makes use of experimentally measured contact characteristics (hysteresis loops) for description of the basic contact behavior of a given material combination with representative surface finish, (ii) the damper motion between the blade platform locations is determined according to the motion of the platforms, (iii) three-dimensional damper motion is included in the model, and (iv) normal load variation across the contact surfaces during vibration is included, thereby accommodating contact opening and closing during vibration. A dedicated nonlinear vibration analysis program has been developed for this study and predictions have been verified against experimental data obtained from two test rigs. Two cantilever beams were used to simulate turbine blades with real underplatform dampers in the first experiment. The second experiment comprised real turbine blades with real underplatform damper. Correlation of the predictions and the experimental results revealed that the analysis can predict (i) the optimum damping condition, (ii) the amount of response reduction, and (iii) the natural frequency shift caused by friction dampers, all with acceptable accuracy. It has also been shown that the most commonly used underplatform dampers in practice are prone to rolling motion, an effect which reduces the damping in certain modes of vibration usually described as the lower nodal diameter bladed-disk modes.

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4

Panning, Lars, Walter Sextro, and Karl Popp. "Spatial Dynamics of Tuned and Mistuned Bladed Disks with Cylindrical and Wedge-Shaped Friction Dampers." International Journal of Rotating Machinery 9, no. 3 (2003): 219–28. http://dx.doi.org/10.1155/s1023621x03000198.

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One of the main tasks in the design of turbomachines like turbines, compressors, and fans is to increase the reliability and efficiency of the arrangement. Failures due to blade cracks are still a problem and have to be minimized with respect to costs and safety aspects. To reduce the maximum stresses, the blades can be coupled via friction damping devices such as underplatform dampers that are pressed onto the blade platforms by centrifugal forces. In this work, a method will be presented to optimize two different types of underplatform dampers in bladed disk applications with respect to a maximum damping effect.In practice, underplatform dampers with various geometric properties—cylindrical and wedge-shaped—are commonly used and lead to different contact conditions. A discretization of the contact areas between the blade platforms and the dampers is applied to be able to investigate nearly arbitrary contact geometries and spatial blade vibrations. The functionality of the two mentioned damper types has been studied in detail under different working conditions of the assembly. The advantages and disadvantages of both damper types are pointed out and strategies are presented to improve the damper design. In this context, the influence of mistuning effects is discussed in terms of statistical mistuning of the blades' natural frequencies due to manufacturing tolerances as well as systematical mistuning due to a deliberate slight variation of the blade masses or geometries.

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5

Pesaresi, L., L. Salles, R. Elliott, A. Jones, J. S. Green, and C. W. Schwingshackl. "Numerical and Experimental Investigation of an Underplatform Damper Test Rig." Applied Mechanics and Materials 849 (August 2016): 1–12. http://dx.doi.org/10.4028/www.scientific.net/amm.849.1.

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During operation mechanical structures can experience large vibration amplitudes. One of the challenges encountered in gas-turbine blade design is avoiding high-cycle fatigue failure usually caused by large resonance stresses driven by aeroelastic excitation. A common approach to control the amplitude levels relies on increasing friction damping by incorporating underplatform dampers (UPD). An accurate prediction of the dynamics of a blade-damper system is quite challenging, due to the highly nonlinear nature of the friction interfaces and detailed validation is required to ensure that a good modelling approach is selected. To support the validation process, a newly developed experimental damper rig will be presented, based on a set of newly introduced non-dimensional parameters that ensure a similar dynamic behaviour of the test rig to a real turbine blade-damper system. An ini- tial experimental investigation highlighted the sensitivity of the measured response with regards to settling and running in of the damper, and further measurements identified a strong dependence of the nonlinear behaviour to localised damper motion. Numerical simulations of the damper rig with a simple macroslip damper model were performed during the preliminary design, and a comparison to the measured data highlighted the ability of the basic implicit model to capture the resonance frequencies of the system accuratelyю

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6

Petrov, E. P., and D. J. Ewins. "Advanced Modeling of Underplatform Friction Dampers for Analysis of Bladed Disk Vibration." Journal of Turbomachinery 129, no. 1 (February 1, 2006): 143–50. http://dx.doi.org/10.1115/1.2372775.

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Advanced structural dynamic models for both wedge and split underplatform dampers have been developed. The new damper models take into account inertia forces and the effects of normal load variation on stick-slip transitions at the contact interfaces. The damper models are formulated for the general case of multiharmonic forced response analysis. An approach for using the new damper models in the dynamic analysis of large-scale finite element models of bladed disks is proposed and realized. Numerical investigations of bladed disks are performed to demonstrate the capabilities of the new models and an analysis of the influence of the damper parameters on the forced response of bladed disks is made.

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7

Gola, M. M., and C. Gastaldi. "Latest investigations on underplatform damper inner mechanics." VESTNIK of the Samara State Aerospace University, no. 5-1(47) (June 15, 2015): 215. http://dx.doi.org/10.18287/1998-6629-2014-0-5-1(47)-215-226.

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8

Szwedowicz, Jaroslaw. "30-Year Anniversary of Friction Damper Technolgy in Turbine Blades." Mechanical Engineering 132, no. 04 (April 1, 2010): 54–55. http://dx.doi.org/10.1115/1.2010-apr-8.

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This article discusses the use of friction damper technology in turbine blades. In 1980, Jerry Griffin published an integrated approach for the underplatform friction damper design, utilizing centrifugal loading. The idea was to apply an individual metal piece, which is pressed by the centrifugal load against the platforms of vibrating turbine blades. The dissipation energy is then produced by friction sliding between the vibrating platforms and the pressed damper. Griffin’s findings have opened up friction damping technology, which is now commonly utilized by many Original Equipment Manufacturers in gas and steam turbines. Every year, new publications show the development of sophisticated interdisciplinary knowledge for predicting the nonlinear blade dynamic behavior in the most reliable manner. Friction dampers reduce resonance amplitudes several times with respect to that for sticking contact condition. But they only act efficiently in a narrow frequency range for the resonance of interest. Therefore, other technologies are continuously being developed, based for instance on piezomaterials, which can extend the allowable limits of High Cyclic Fatigue for the conventional blade alloys.

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9

Afzal, Mohammad, Leif Kari, and Ines Lopez Arteaga. "Adaptive control of normal load at the friction interface of bladed disks using giant magnetostrictive material." Journal of Intelligent Material Systems and Structures 31, no. 8 (March 13, 2020): 1111–25. http://dx.doi.org/10.1177/1045389x20910269.

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A novel application of magnetostrictive actuators in underplatform dampers of bladed disks is proposed for adaptive control of the normal load at the friction interface to achieve the desired friction damping in the structure. Friction damping in a bladed disk depends on operating parameters, such as rotational speed, engine excitation order, nodal diameter normal contact load, and contact interface parameters, such as contact stiffness and friction coefficient. The operating parameters have a fixed value, whereas the contact interface parameters vary in an unpredictable way at an operating point. However, the ability to vary some of these parameters such as the normal contact load in a controlled manner is desirable to attain an optimum damping in the bladed disk at different operating conditions. Under the influence of an external magnetic field, magnetostrictive materials develop an internal strain that can be exploited to vary the normal contact load at the friction interface, which makes them a potentially good candidate for this application. A commercially available magnetostrictive alloy, Terfenol-D is considered in this analysis that is capable of providing magnetostrain up to 2 × 10-3 under prestress and a blocked force over 1500 N. A linearized model of the magnetostrictive material, which is accurate enough for a direct current application, is employed to compute the output force of the actuator. A nonlinear finite element contact analysis is performed to compute the normal contact load between the blade platform and the underplatform damper as a result of magnetostrictive actuation. The nonlinear contact analysis is performed for different actuator mounting configurations and the obtained results are discussed. The proposed solution is potentially applicable to adaptively control vibratory stresses in bladed disks and consequently to reduce failure due to high-cycle fatigue. Finally, the practical challenges in employing magnetostrictive actuators in underplatform dampers are discussed.

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10

Firrone, Christian M., and Stefano Zucca. "Underplatform dampers for turbine blades: The effect of damper static balance on the blade dynamics." Mechanics Research Communications 36, no. 4 (June 2009): 515–22. http://dx.doi.org/10.1016/j.mechrescom.2009.01.002.

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11

Pesaresi, L., J. Armand, C. W. Schwingshackl, L. Salles, and C. Wong. "An advanced underplatform damper modelling approach based on a microslip contact model." Journal of Sound and Vibration 436 (December 2018): 327–40. http://dx.doi.org/10.1016/j.jsv.2018.08.014.

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12

Pesaresi, L., L. Salles, A. Jones, J. S. Green, and C. W. Schwingshackl. "Modelling the nonlinear behaviour of an underplatform damper test rig for turbine applications." Mechanical Systems and Signal Processing 85 (February 2017): 662–79. http://dx.doi.org/10.1016/j.ymssp.2016.09.007.

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13

Li, Dongwu, Daniele Botto, Chao Xu, Tong Liu, and Muzio Gola. "A micro-slip friction modeling approach and its application in underplatform damper kinematics." International Journal of Mechanical Sciences 161-162 (October 2019): 105029. http://dx.doi.org/10.1016/j.ijmecsci.2019.105029.

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14

Yangxiong, Luo, Jiang Xianghua, and Wang Yanrong. "Modeling of Microslip Friction and Its Application in the Analysis of Underplatform Damper." International Journal of Aeronautical and Space Sciences 19, no. 2 (June 2018): 388–98. http://dx.doi.org/10.1007/s42405-018-0039-x.

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15

Panning, Lars. "Symmetric and Asymmetric Underplatform Dampers for Turbine Blades." PAMM 6, no. 1 (December 2006): 251–52. http://dx.doi.org/10.1002/pamm.200610106.

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16

Gola, Muzio M. "A general geometrical theory of turbine blade underplatform asymmetric dampers." Mechanical Systems and Signal Processing 191 (May 2023): 110167. http://dx.doi.org/10.1016/j.ymssp.2023.110167.

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17

ZHANG, Dayi, Bin GAO, Jie HONG, Jianwei FU, and Xiangyun GE. "Experimental investigation on dynamic response of flat blades with underplatform dampers." Chinese Journal of Aeronautics 32, no. 12 (December 2019): 2667–78. http://dx.doi.org/10.1016/j.cja.2019.04.022.

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18

Gastaldi, C., Teresa M. Berruti, and Muzio M. Gola. "A novel test rig for friction parameters measurement on underplatform dampers." International Journal of Solids and Structures 185-186 (March 2020): 170–81. http://dx.doi.org/10.1016/j.ijsolstr.2019.08.030.

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19

Gastaldi, C., and Teresa M. Berruti. "Direct measurement of the damping and stiffening capabilities of cylindrical underplatform dampers." Mechanical Systems and Signal Processing 139 (May 2020): 106632. http://dx.doi.org/10.1016/j.ymssp.2020.106632.

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20

Zucca, Stefano, Christian M. Firrone, and Muzio Gola. "Modeling underplatform dampers for turbine blades: a refined approach in the frequency domain." Journal of Vibration and Control 19, no. 7 (March 30, 2012): 1087–102. http://dx.doi.org/10.1177/1077546312440809.

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21

Yuan, Ye, A. Jones, R. Setchfield, and C. W. Schwingshackl. "Robust design optimisation of underplatform dampers for turbine applications using a surrogate model." Journal of Sound and Vibration 494 (March 2021): 115528. http://dx.doi.org/10.1016/j.jsv.2020.115528.

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22

Zucca, S., D. Di Maio, and D. J. Ewins. "Measuring the performance of underplatform dampers for turbine blades by rotating laser Doppler Vibrometer." Mechanical Systems and Signal Processing 32 (October 2012): 269–81. http://dx.doi.org/10.1016/j.ymssp.2012.05.011.

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23

Yuan, Jie, Alfredo Fantetti, Enora Denimal, Shubham Bhatnagar, Luca Pesaresi, Christoph Schwingshackl, and Loic Salles. "Propagation of friction parameter uncertainties in the nonlinear dynamic response of turbine blades with underplatform dampers." Mechanical Systems and Signal Processing 156 (July 2021): 107673. http://dx.doi.org/10.1016/j.ymssp.2021.107673.

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24

Sazhenkov, Nikolai, Irina Semenova, Mikhail Nikhamkin, and Sergei Semenov. "A substructure-based numerical technique and experimental analysis of turbine blades damping with underplatform friction dampers." Procedia Engineering 199 (2017): 820–25. http://dx.doi.org/10.1016/j.proeng.2017.09.085.

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25

Firrone, Christian M. "Measurement of the kinematics of two underplatform dampers with different geometry and comparison with numerical simulation." Journal of Sound and Vibration 323, no. 1-2 (June 2009): 313–33. http://dx.doi.org/10.1016/j.jsv.2008.12.019.

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26

Popp, Karl, Lars Panning, and Walter Sextro. "Vibration Damping by Friction Forces: Theory and Applications." Journal of Vibration and Control 9, no. 3-4 (March 2003): 419–48. http://dx.doi.org/10.1177/107754603030780.

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In this paper, we deal with the vibrational behavior of mechanical structures interconnected by contacts with friction. The focus is set on the utilization of friction forces that are generated in the contact interfaces with the objective to increase damping and to reduce vibration amplitudes in order to prevent structures from failures owing to high resonance stresses. We present a comparison and classification of different contact models that are most commonly used, including the derivation of a three-dimensional contact model under consideration of rough surfaces. We give different solution methods for problems with non-linear friction elements. The effectiveness of friction damping devices is pointed out by a single-degree-of-freedom friction oscillator, beam-like structures with frictional interfaces and different underplatform dampers in turbo-machinery applications. It can be shown that in many practical applications friction damping devices provide a remarkable decrease of vibration amplitudes.

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27

Petrov, E. P. "Method for Direct Parametric Analysis of Nonlinear Forced Response of Bladed Disks With Friction Contact Interfaces." Journal of Turbomachinery 126, no. 4 (October 1, 2004): 654–62. http://dx.doi.org/10.1115/1.1776588.

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An effective method for direct parametric analysis of periodic nonlinear forced response of bladed disks with friction contact interfaces has been developed. The method allows, forced response levels to be calculated directly as a function of contact interface parameters such as the friction coefficient, contact surface stiffness (normal and tangential coefficients), clearances, interferences, and the normal stresses at the contact interfaces. The method is based on exact expressions for sensitivities of the multiharmonic interaction forces with respect to variation of all parameters of the friction contact interfaces. These novel expressions are derived in the paper for a friction contact model, accounting for the normal load variation and the possibility of separation-contact transitions. Numerical analysis of effects of the contact parameters on forced response levels has been performed using large-scale finite element models of a practical bladed turbine disk with underplatform dampers and with shroud contacts.

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28

Petrov, E. P., and D. J. Ewins. "Method for Analysis of Nonlinear Multiharmonic Vibrations of Mistuned Bladed Disks With Scatter of Contact Interface Characteristics." Journal of Turbomachinery 127, no. 1 (January 1, 2005): 128–36. http://dx.doi.org/10.1115/1.1812781.

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An efficient method for analysis of nonlinear vibrations of mistuned bladed disk assemblies has been developed. This development has facilitated the use of large-scale finite element models for realistic bladed disks, used hitherto in analysis of linear vibration, to be extended for the analysis of nonlinear multiharmonic vibration. The new method is based on a technique for the exact condensation of nonlinear finite element models of mistuned bladed disks. The model condensation allows the size of the nonlinear equations to be reduced to the number of degrees of freedom where nonlinear interaction forces are applied. The analysis of nonlinear forced response for simplified and realistic models of mistuned bladed disks has been performed. For a practical high-pressure bladed turbine disk, several types of nonlinear forced response have been considered, including mistuning by (i) scatter of underplatform dampers, (ii) shroud gap scatter, and (iii) blade frequency scatter in the presence of nonlinear shroud interactions.

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29

Berruti, T. "A test rig for the investigation of the dynamic response of a bladed disk with underplatform dampers." Mechanics Research Communications 37, no. 6 (September 2010): 581–83. http://dx.doi.org/10.1016/j.mechrescom.2010.07.008.

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30

Gastaldi, Chiara, Emanuele Grossi, and Teresa M. Berruti. "On the choice of contact parameters for the forced response calculation of a bladed disk with underplatform dampers." Journal of the Global Power and Propulsion Society 1 (June 20, 2017): 5D19RH. http://dx.doi.org/10.22261/5d19rh.

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AbstractUnderplatform dampers (UPDs) are still in use to reduce the vibration amplitude of turbine blades and to shift the position of resonant frequencies. The dynamics of blades with UPDs is nonlinear and the analysis is challenging from both the experimental and the numerical point of view. A key point in obtaining a predictive numerical tool is the choice of the correct contact parameters (contact stiffness and friction coefficient) that are required as input to the contact model. The paper presents different approaches to choose these parameters: the contact stiffness in normal and tangential direction are both calculated and measured. The calculation is based on the analytical models in literature, the measurements are carried out on a dedicated test rig. The friction coefficient is also measured. Test results of the forced response of the same bladed disk with UPDs are available for each blade, they come from an experimental campaign under controlled excitation and centrifugal force. The forced response of the bladed disk is not used as a mean to tune the contact parameters, but rather as a validation tool: the effect of the different choices of contact parameters in the code is highlighted by the comparison of the calculated and experimental forced response of the bladed disk.

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31

Firrone, Christian M., Stefano Zucca, and Muzio M. Gola. "The effect of underplatform dampers on the forced response of bladed disks by a coupled static/dynamic harmonic balance method." International Journal of Non-Linear Mechanics 46, no. 2 (March 2011): 363–75. http://dx.doi.org/10.1016/j.ijnonlinmec.2010.10.001.

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32

Zhang, Dayi, Jianwei Fu, Qicheng Zhang, and Jie Hong. "An effective numerical method for calculating nonlinear dynamics of structures with dry friction: application to predict the vibration response of blades with underplatform dampers." Nonlinear Dynamics 88, no. 1 (December 2, 2016): 223–37. http://dx.doi.org/10.1007/s11071-016-3239-6.

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33

Denimal, E., C. Wong, L. Salles, and L. Pesaresi. "On the Efficiency of a Conical Underplatform Damper for Turbines." Journal of Engineering for Gas Turbines and Power 143, no. 2 (February 1, 2021). http://dx.doi.org/10.1115/1.4049665.

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Abstract Underplatform dampers (UPDs) are commonly used in aircraft engines to limit the risk of high-cycle fatigue of turbine blades. The latter is located in a groove between two consecutive blades. The dry friction contact interface between the damper and the blades dissipates energy and so reduces the vibration amplitudes. Two common geometries of dampers are used nowadays, namely wedge and cylindrical dampers, but their efficiency is limited when the blades have an in-phase motion (or a motion close to it), since the damper tends to have a pure rolling motion. The objective of this study is to analyze a new damper geometry, based on a conical shape, which prevents from this pure rolling motion of the damper and ensures a high kinematic slip. The objective of this study is to demonstrate the damping efficiency of this geometry. Hence, in a first part, the kinematic slip is approximated with analytical considerations. Then, a nonlinear dynamic analysis is performed, and the damping efficiency of this new geometry is compared to the wedge and the cylindrical geometries. The results demonstrate that the conical damper has a high damping capacity and is more efficient and more robust than the two others.

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34

Gastaldi, Chiara, and Muzio M. Gola. "Pre-optimization of Asymmetrical Underplatform Dampers." Journal of Engineering for Gas Turbines and Power 139, no. 1 (August 16, 2016). http://dx.doi.org/10.1115/1.4034191.

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The numerical coupled optimization of an underplatform damper is the exploration of its dynamics through a finite element model which includes both the damper and the blades. This is an effective approach if the initial damper mass and geometry have been previously selected (i.e., pre-optimized) in such a way that those parameter combinations leading to undesirable damper behavior are ruled out a priori: —ensure that damper jamming is avoided by ruling out the undesirable combinations of platform and friction angles; —ensure that damper lift-off is avoided through an appropriate choice of the shape and position of the damper-platform flat contact surface and the position of the damper mass center; —set upper and lower to the value of damper-platform contact forces (as a multiple of the damper centrifugal force), the first being related to friction and wear problems, and the second to the very existence of bilateral contacts. The above is strongly dependent on the effective values of friction coefficients, which can vary by a factor of over two with temperature, frequency and contact pressure. The paper illustrates the pre-optimization procedure using, as an example, a rigid bar damper with a curved-flat cross section. In order to validate the method against experimental data and to determine the necessary real contact parameters, the paper capitalizes on already developed tools presented in the previous ASME papers: the test rig developed at the AERMEC lab, the numerical model representing the damper dynamics, and the automatic random sampling tuning procedure.

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35

Quaegebeur, Samuel, Benjamin Chouvion, and Fabrice Thouverez. "Impact of Mistuned Underplatform Dampers On the Nonlinear Vibration of Bladed Disks." Journal of Engineering for Gas Turbines and Power, July 22, 2021. http://dx.doi.org/10.1115/1.4051868.

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Анотація:

Abstract Before the final experimental validation and certification of a turboengine, designers perform a numerical simulation of its vibratory properties, among other things, in order to estimate its lifespan and adjust the design in an optimization process. One possible practical solution to decrease the vibratory response is to add underplatform dampers to the system. These components dissipate energy by friction and are widely employed in turbomachinery. However, a specific underplatform damper is usually efficient only for a specific mode. The purpose of this work is to investigate the possibility of adding different kinds of underplatform dampers to the cyclic structure in order to decrease the vibratory energy over a larger panel of modes. Different methods exist to determine the vibrations of nonlinear cyclic symmetric systems, but creating a robust methodology to account for the additional effect of mistuning remains a big challenge in the community. In this paper, the structure is mistuned through the friction coefficient of the dampers and not by altering its geometry, as is usually done in the literature. First, assuming a cyclic symmetric structure, the performance of the dampers is assessed for specific modes. Then, employing a method recently developed, the efficiency of an intentional mistuning pattern of underplatform dampers is studied and an optimal pattern proposed.

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36

Petrov, E. P. "Explicit Finite Element Models of Friction Dampers in Forced Response Analysis of Bladed Disks." Journal of Engineering for Gas Turbines and Power 130, no. 2 (February 25, 2008). http://dx.doi.org/10.1115/1.2772633.

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Анотація:

A generic method for analysis of nonlinear forced response for bladed disks with friction dampers of different designs has been developed. The method uses explicit finite element modeling of dampers, which allows accurate description of flexibility and, for the first time, dynamic properties of dampers of different designs in multiharmonic analysis of bladed disks. Large-scale finite element damper and bladed disk models containing 104−106 degrees of freedom can be used. These models, together with detailed description of contact interactions over contact interface areas, allow for any level of refinement required for modeling of elastic damper bodies and for modeling of friction contact interactions. Numerical studies of realistic bladed disks have been performed with three different types of underplatform dampers: (i) a “cottage-roof” (also called “wedge”) damper, (ii) seal wire damper, and (iii) a strip damper. Effects of contact interface parameters and excitation levels on damping properties of the dampers and forced response are extensively explored.

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37

Gastaldi, Chiara, Teresa M. Berruti, and Muzio M. Gola. "The Effect of Surface Finish on the Proper Functioning of Underplatform Dampers." Journal of Vibration and Acoustics 142, no. 5 (May 15, 2020). http://dx.doi.org/10.1115/1.4046954.

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Abstract Underplatform dampers are used to limit the resonant vibration of turbine blades. In recent years, various strategies have been implemented to maximize their damping capability. Curved-flat dampers are preferred to ensure a predictable bilateral contact, while a pre-optimization procedure was developed to exclude all those cross-sectional shapes that will bring the damper to roll and thus limit the amount of dissipated energy. The pre-optimization bases its predictions on the assumption that the effective width of the flat contact interface corresponds to the nominal one. It is shown here that this hypothesis cannot be relied upon: the energy dissipated by two nominally identical dampers, machined according to the usual industrial standards, may differ by a factor up to three due to the morphology of the flat-to-flat contact interface. Five dampers have been tested on two dedicated test rigs, available in the AERMEC laboratory, specially designed to reveal the details of the damper behavior during operation. Their contact interfaces are scanned by means of a profilometer. In each case, the mechanics, the kinematics, and the effectiveness of the dampers in terms of cycle shape and dissipated energy are correlated to the morphology of the specific contact surface. To complete the picture, a state-of-the-art numerical simulation tool is used to show how this tribo-mechanic phenomenon, in turn, influences the damper effect on the dynamic response of the turbine.

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38

Petrov, Evgeny, Luca Di Mare, Holger Hennings, and Robert Elliott. "Forced Response of Mistuned Bladed Disks in Gas Flow: A Comparative Study of Predictions and Full-Scale Experimental Results." Journal of Engineering for Gas Turbines and Power 132, no. 5 (March 5, 2010). http://dx.doi.org/10.1115/1.3205031.

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An integrated experimental-numerical study of forced response for a mistuned bladed disk has been performed. A full chain for the predictive forced response analysis has been developed including data exchange between the computational fluid dynamics code and a code for the prediction of the nonlinear forced response for a bladed disk. The experimental measurements are performed at a full-scale single stage test rig with excitation by aerodynamic forces from gas flow. The numerical modeling approaches and the test rig setup are discussed. Comparison of experimentally measured and predicted values of blade resonance frequencies and response levels for a mistuned bladed disk without dampers is performed. A good correspondence between frequencies at which individual blades have maximum response levels is achieved. The effects of structural damping and underplatform damper parameters on amplitudes and resonance frequencies of the bladed disk are explored. It is shown that the underplatform damper significantly reduces scatters in values of the individual blade frequencies and maximum forced response levels.

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39

Armand, J., L. Pesaresi, L. Salles, and C. W. Schwingshackl. "A Multiscale Approach for Nonlinear Dynamic Response Predictions With Fretting Wear." Journal of Engineering for Gas Turbines and Power 139, no. 2 (September 13, 2016). http://dx.doi.org/10.1115/1.4034344.

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Accurate prediction of the vibration response of aircraft engine assemblies is of great importance when estimating both the performance and the lifetime of their individual components. In the case of underplatform dampers, for example, the motion at the frictional interfaces can lead to a highly nonlinear dynamic response and cause fretting wear at the contact. The latter will change the contact conditions of the interface and consequently impact the nonlinear dynamic response of the entire assembly. Accurate prediction of the nonlinear dynamic response over the lifetime of the assembly must include the impact of fretting wear. A multiscale approach that incorporates wear into the nonlinear dynamic analysis is proposed, and its viability is demonstrated for an underplatform damper system. The nonlinear dynamic response is calculated with a multiharmonic balance approach, and a newly developed semi-analytical contact solver is used to obtain the contact conditions at the blade–damper interface with high accuracy and low computational cost. The calculated contact conditions are used in combination with the energy wear approach to compute the fretting wear at the contact interface. The nonlinear dynamic model of the blade–damper system is then updated with the worn profile and its dynamic response is recomputed. A significant impact of fretting wear on the nonlinear dynamic behavior of the blade–damper system was observed, highlighting the sensitivity of the nonlinear dynamic response to changes at the contact interface. The computational speed and robustness of the adopted multiscale approach are demonstrated.

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40

Gastaldi, Chiara, Johann Gross, Maren Scheel, Teresa M. Berruti, and Malte Krack. "Modeling Complex Contact Conditions and Their Effect on Blade Dynamics." Journal of Engineering for Gas Turbines and Power 143, no. 1 (December 24, 2020). http://dx.doi.org/10.1115/1.4049186.

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Abstract Dry friction devices such as underplatform dampers are commonly included in turbine bladed disks designs to mitigate structural vibrations and avoid high cycle fatigue failures. The design of frictionally damped bladed disks requires adequate models to represent the friction contact. A widely used approach connects contact node pairs with normal and tangential springs and a Coulomb friction law. This simple model architecture is effective in capturing the softening behavior typically observed on frictionally damped structures subjected to increasing forcing levels. An unexpected hardening behavior was observed on the frequency response functions (FRFs) of a two-blades-plus-damper system tested by the authors in a controlled laboratory environment. The reason behind this unexpected behavior will be carefully analyzed and linked to the damper kinematics and to the dependence of contact elasticity on the contact pressure. The inadequacy of contact models with constant spring values will be discussed and alternatives will be proposed. The importance of being able to represent complex contact conditions in order to effectively predict the system dynamics is shown here using a laboratory demonstrator; however, its implications are relevant to any other case where large contact pressure variations are to be expected. The nonlinear steady-state simulations of the blades-plus-damper system will be carried out using an in-house code exploiting the multiharmonic balance method in combination with the alternating frequency time method.

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41

Schwingshackl, C. W., E. P. Petrov, and D. J. Ewins. "Effects of Contact Interface Parameters on Vibration of Turbine Bladed Disks With Underplatform Dampers." Journal of Engineering for Gas Turbines and Power 134, no. 3 (January 9, 2012). http://dx.doi.org/10.1115/1.4004721.

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The design of high cycle fatigue resistant bladed disks requires the ability to predict the expected damping of the structure in order to evaluate the dynamic behavior and ensure structural integrity. Highly sophisticated software codes are available today for this nonlinear analysis, but their correct use requires a good understanding of the correct model generation and the input parameters involved to ensure a reliable prediction of the blade behavior. The aim of the work described in this paper is to determine the suitability of current modeling approaches and to enhance the quality of the nonlinear modeling of turbine blades with underplatform dampers. This includes an investigation of a choice of the required input parameters, an evaluation of their best use in nonlinear friction analysis, and an assessment of the sensitivity of the response to variations in these parameters. Part of the problem is that the input parameters come with varying degrees of uncertainty because some are experimentally determined, others are derived from analysis, and a final set are often based on estimates from previous experience. In this investigation the model of a commercial turbine bladed disk with an underplatform damper is studied, and its first flap, first torsion, and first edgewise modes are considered for 6 EO and 36 EO excitation. The influence of different contact interface meshes on the results is investigated, together with several distributions of the static normal contact loads, to enhance the model setup and, hence, increase accuracy in the response predictions of the blade with an underplatform damper. A parametric analysis is carried out on the friction contact parameters and the correct setup of the nonlinear contact model to determine their influence on the dynamic response and to define the required accuracy of the input parameters.

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42

Gastaldi, Chiara, Teresa M. Berruti, and Muzio M. Gola. "The Relevance of Damper Pre-Optimization and Its Effectiveness on the Forced Response of Blades." Journal of Engineering for Gas Turbines and Power 140, no. 6 (April 5, 2018). http://dx.doi.org/10.1115/1.4038773.

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The purpose of this paper is to propose an effective strategy for the design of turbine blades with underplatform dampers (UPDs). The strategy involves damper “pre-optimization,” already proposed by the authors, to exclude, before the blades-coupled nonlinear calculation, all those damper configurations leading to low damping performance. This paper continues this effort by applying pre-optimization to determine a damper configuration which will not jam, roll, or detach under any in-plane platform kinematics (i.e., blade bending modes). Once the candidate damper configuration has been found, the damper equilibrium equations are solved by using both the multiharmonic balance method (MHBM) and the direct-time integration (DTI) for the purpose of finding the correct number of Fourier terms to represent displacements and contact forces. It is shown that contrarily to non-preoptimized dampers, which may display an erratic behavior, one harmonic term together with the static term ensures accurate results. These findings are confirmed by a state-of-the-art code for the calculation of the nonlinear forced response of a damper coupled to two blades. Experimental forced response functions (FRF) of the test case with a nominal damper are available for comparison. The comparison of different damper configurations offers a “high-level” validation of the pre-optimization procedure and highlights the strong influence of the blades mode of vibration on the damper effectiveness. It is shown that the pre-optimized damper is not only the most effective but also the one that leads to a faster and more flexible calculation.

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43

Denimal, E., F. El Haddad, C. Wong, and L. Salles. "Topological Optimization of Under-Platform Dampers With Moving Morphable Components and Global Optimization Algorithm for Nonlinear Frequency Response." Journal of Engineering for Gas Turbines and Power 143, no. 2 (February 1, 2021). http://dx.doi.org/10.1115/1.4049666.

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Abstract To limit the risk of high cycle fatigue, underplatform dampers (UDPs) are traditionally used in aircraft engines to control the level of vibration. Many studies demonstrate the impact of the geometry of the damper on its efficiency, thus the consideration of topological optimization (TO) to find the best layout of the damper seems natural. Because of the nonlinear behavior of the structure due to the friction contact interface, classical methods of TO are not usable. This study proposes to optimize the layout of an UDP to reduce the level of nonlinear vibrations computed with the multiharmonic balance method (MHBM). The approach of TO employed is based on the moving morphable components (MMC) framework together with the Kriging and the efficient global optimization algorithm to solve the optimization problem. The results show that the level of vibration of the structure can be reduced to 30% and allow for the identification of different efficient geometries.

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44

Gastaldi, Chiara, and Muzio M. Gola. "Platform Centered Reduction: a Process Capturing the Essentials for Blade-Damper Coupled Optimization." Journal of Engineering for Gas Turbines and Power, November 21, 2020. http://dx.doi.org/10.1115/1.4049187.

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Abstract The purpose of this paper is to develop an attractive tool for designers in the initial design phase of the damping of turbomachinery blades through dry friction underplatform dampers. The paper shows how, to this purpose, certain reasonable simplifications are introduced in the procedure and in the model, leaving the customary full high fidelity computations to the final design verification analysis. The key simplifications here considered are: the blade neck is modelled with Euler beam finite elements (FE) to speed up the updating of its dimensions during the optimisation process; the contact forces exerted by the dampers on the blade platform are represented by the resultant forces and moments applied to a reference point on the platform, associated to its displacements and rotations; the airfoil, which, due to its complex shape, is considered fixed during the coupled optimization of the damper, is obtained from a full 3D FE model after a component mode synthesis reduction. It is shown that the process captures the essentials of the nonlinear dynamics of the blade-damper problem without sacrificing in any way the accuracy of the results. This hybrid model is then employed in the process where the domains of optimal matching between the damper and the blade is searched for by exploring the influence of blade neck thickness (flexibility) and damper mass. Such a purposely simplified process allows a clear identification of relationships between relevant blade features and response with a focus on fatigue life.

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45

Hoffmann, Thomas, Lars Panning-von Scheidt, and Jörg Wallaschek. "Measured and Simulated Forced Response of a Rotating Turbine Disk With Asymmetric and Cylindrical Underplatform Dampers." Journal of Engineering for Gas Turbines and Power 142, no. 5 (February 14, 2020). http://dx.doi.org/10.1115/1.4045337.

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Abstract The dynamics of turbine blades with underplatform dampers (UPDs) is often experimentally explored by using small test rigs like two-blade models for cost and complexity reasons. In this paper, the dynamics of a large-scale academic turbine disk is measured on a special rotation test rig. Such measurements have rarely been published so far. The test rig supports speeds up to 3600 rpm and turbine disks up to a diameter of 1.2 m. The turbine disk is tested linearly as well as with asymmetric and cylindrical UPDs. The excitation forces and the excitation order are varied. The results prove the damper effectiveness by lowering resonance amplitudes. Additionally, the mistuning influence on the result depiction is discussed. The measurements are compared to simulations of the nonlinear frequency response functions (FRFs), showing good agreement.

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46

Li, Chaofeng, Zilin Chen, Zengchuang Shen, and Houxin She. "Analysis on vibration reduction of a rotating dovetailed blade with underplatform damper and installation preload." Mechanics Based Design of Structures and Machines, February 27, 2020, 1–20. http://dx.doi.org/10.1080/15397734.2020.1732222.

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47

Mehrdad Pourkiaee, S., Teresa Berruti, Stefano Zucca, and Geoffrey Neuville. "Experimental and Numerical Assessment of Mistuning Effects on Vibratory Response of a Bladed Disk With Underplatform Dampers." Journal of Engineering for Gas Turbines and Power 143, no. 3 (February 8, 2021). http://dx.doi.org/10.1115/1.4049772.

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Abstract This paper presents experimental and numerical investigation of mistuned forced responses of an integrally bladed disk with full set of underplatform dampers (UPDs). This research aims at providing: 1. An experimental benchmark for nonlinear dynamics of a mistuned bladed disks with UPDs. 2. A numerical model that can account for features of a mistuned forced response level. Accordingly, a detailed experimental campaign is conducted on a static test rig called Octopus. This rig is specifically designed to investigate the dynamics of a full-scale integrally bladed disk (blisk) with UPDs in a noncontact manner so that the dynamic response of the system is not modified. The effect of mistuning on experimental forced response levels is assessed and a linearized model is proposed to predict the modulation of frequency response functions (FRFs) due to the frequency splitting. In the development of the model, the mistuning pattern identified from the linear blisk without UPDs is used and it is assumed that adding the dampers does not change the structural mistuning of the blisk. In this study, the fundamental mistuning model identification (FMM ID) was employed to identify the mistuning pattern of the blisk. It is shown that the proposed model successfully predicts the modulation of linear mistuned FRFs. The linearized model is also able to predict the modulation of nonlinear mistuned FRFs in stick condition (when nonlinear friction damping is negligible) with a good accuracy validating this assumption that adding the dampers does not change the mistuning pattern.

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48

Petrov, E. P. "A High-Accuracy Model Reduction for Analysis of Nonlinear Vibrations in Structures With Contact Interfaces." Journal of Engineering for Gas Turbines and Power 133, no. 10 (May 6, 2011). http://dx.doi.org/10.1115/1.4002810.

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A highly accurate and computationally efficient method is proposed for reduced modeling of jointed structures in the frequency domain analysis of nonlinear steady-state forced response. The method has significant advantages comparing with the popular variety of mode synthesis methods or forced response matrix methods and can be easily implemented in the nonlinear forced response analysis using standard finite element codes. The superior qualities of the new method are demonstrated on a set of major problems of nonlinear forced response analysis of bladed disks with contact interfaces: (i) at blade roots, (ii) between interlock shrouds, and (iii) at underplatform dampers. The numerical properties of the method are thoroughly studied on a number of special test cases.

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49

Sever, Ibrahim A., Evgeny P. Petrov, and David J. Ewins. "Experimental and Numerical Investigation of Rotating Bladed Disk Forced Response Using Underplatform Friction Dampers." Journal of Engineering for Gas Turbines and Power 130, no. 4 (April 29, 2008). http://dx.doi.org/10.1115/1.2903845.

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In this paper, we present a methodology and results from an experimental investigation of forced vibration response for a bladed disk with fitted underplatform “cottage-roof” friction dampers, together with the corresponding numerical predictions. A carefully designed and constructed rotating test rig is used to make precise measurements, which involve only the phenomena of interest. For this purpose, the measurement rig is operated under vacuum to eliminate aerodynamic effects on the rotating blisk and noncontact excitation and measurement techniques are employed so as not to modify the bladed disk dynamics. The experimental data measured are used for validation of multiharmonic balance-based prediction tools developed at the Imperial College. Predictions are carried out both with and without taking inherent mechanical mistuning into account, which is identified from measured data. Measured and predicted response curves are compared with each other and the degree of correlation is discussed.

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50

Petrov, E. P. "Method for Sensitivity Analysis of Resonance Forced Response of Bladed Disks With Nonlinear Contact Interfaces." Journal of Engineering for Gas Turbines and Power 131, no. 2 (December 30, 2008). http://dx.doi.org/10.1115/1.2969094.

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An effective method has been developed to calculate the sensitivity of the resonance peak frequency and forced response level to variation of parameters of nonlinear friction contact interfaces and excitation. The method allows determination of the sensitivity characteristics simultaneously with the resonance peak frequency and response level calculated as a function of any parameter of interest and without significant computational expense. Capabilities of the method are demonstrated on examples of analysis of large-scale finite element models of realistic bladed disks with major types of the nonlinear contact interfaces: (i) a blisk with underplatform dampers, (ii) a bladed disk with friction damping at blade fir-tree roots, and (iii) a high-pressure bladed disk with shroud contacts. The numerical investigations show high efficiency of the method proposed.

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