Modeling underplatform dampers for turbine blades: a refined approach in the frequency domain

Friction damping is one of the most exploited systems of passive control of the vibration of mechanical systems. In order to mitigate vibration of turbine blades, friction dampers are commonly included in the bladed disk design. A common type of blade-to-blade friction dampers are the so-called underplatform dampers (UPDs); these are metal devices placed under the blade platforms and held in contact with them by the centrifugal force acting during rotation. The effectiveness of UPDs to dissipate energy by friction and reduce vibration amplitude depends mostly on the damper geometry and material and on the static loads pressing the damper against the blade platforms. The common procedure used to estimate the static loads acting on UPDs consists in decoupling the static and the dynamic balance of the damper. A preliminary static analysis of the contact is performed in order to compute the static pressure distribution over the damper/blade interfaces, assuming that it does not change when vibration occurs. In this paper a coupled approach is proposed. The static and the dynamic displacements of blade and UPD are coupled together during the forced response calculation. Both the primary structure (the bladed disk) and the secondary structure (the damper) are modeled by finite elements and linked together by contact elements, allowing for stick, slip and lift off states, placed between each pair of contact nodes, by using a refined version of the state-of-the-art friction contact model. In order to model accurately the blade/damper contact with a large number of contact nodes without increasing proportionally the size of the set of nonlinear equations to be solved, damper and blade dynamics are modeled by linear superposition of a truncated series of normal modes. The proposed method is applied to a bladed disk under cyclic symmetric boundary conditions in order to show the capabilities of the method compared to the classical decoupled approaches.

[1]  Ning An,et al.  Forced Response Prediction of Constrained and Unconstrained Structures Coupled Through Frictional Contacts , 2009 .

[2]  Chia-Hsiang Menq,et al.  Characterization of Contact Kinematics and Application to the Design of Wedge Dampers in Turbomachinery Blading: Part 2—Prediction of Forced Response and Experimental Verification , 1998 .

[3]  Walter Sextro,et al.  Asymmetrical Underplatform Dampers in Gas Turbine Bladings: Theory and Application , 2004 .

[4]  M. Allara,et al.  A model for the characterization of friction contacts in turbine blades , 2009 .

[5]  David J. Ewins,et al.  Underplatform Dampers for Turbine Blades: Theoretical Modelling, Analysis and Comparison With Experimental Data , 1999 .

[6]  E. P. Petrov.  Explicit Finite Element Models of Friction Dampers in Forced Response Analysis of Bladed Discs , 2007 .

[7]  Evgeny Petrov,et al.  Explicit Finite Element Models of Friction Dampers in Forced Response Analysis of Bladed Disks , 2008 .

[8]  D. J. Ewins,et al.  Advanced Modeling of Underplatform Friction Dampers for Analysis of Bladed Disk Vibration , 2007 .

[9]  Stefano Zucca,et al.  Range of variability in the dynamics of semi-cylindrical friction dampers for turbine blades. , 2008 .

[10]  E. Petrov,et al.  A Method for Use of Cyclic Symmetry Properties in Analysis of Nonlinear Multiharmonic Vibrations of Bladed Disks (2003-GT-38480) , 2004 .

[11]  G. B. Sinclair,et al.  Contact Stresses in Dovetail Attachments: Physical Modeling , 2002 .

[12]  C. Menq,et al.  Characterization of 3D contact kinematics and prediction of resonant response of structures having 3D frictional constraint , 1998 .

[13]  Stefano Zucca,et al.  Effect of Static/Dynamic Coupling on the Forced Response of Turbine Bladed Disks With Underplatform Dampers , 2009 .

[14]  Alberto Cardona,et al.  Fast Fourier nonlinear vibration analysis , 1998 .

[15]  D. J. Ewins,et al.  Analytical Formulation of Friction Interface Elements for Analysis of Nonlinear Multi-Harmonic Vibrations of Bladed Disks , 2003 .

[16]  C. Menq,et al.  STICK–SLIP–SEPARATION ANALYSIS AND NON-LINEAR STIFFNESS AND DAMPING CHARACTERIZATION OF FRICTION CONTACTS HAVING VARIABLE NORMAL LOAD , 1998 .

[17]  J. Szwedowicz,et al.  Numerical and Experimental Damping Assessment of a Thin-Walled Friction Damper in the Rotating Setup With High Pressure Turbine Blades , 2006 .

[18]  Muzio Gola,et al.  Measurement of Tangential Contact Hysteresis During Microslip , 2004 .

[19]  Walter Sextro,et al.  Spatial Dynamics of Tuned and Mistuned Bladed Disks with Cylindrical and Wedge-Shaped Friction Dampers , 2003 .

[20]  Jörg Wallaschek,et al.  Multiharmonic Forced Response Analysis of a Turbine Blading Coupled by Nonlinear Contact Forces , 2010 .

[21]  Chia-Hsiang Menq,et al.  NON-LINEAR SPRING RESISTANCE AND FRICTION DAMPING OF FRICTIONAL CONSTRAINT HAVING TWO-DIMENSIONAL MOTION , 1998 .

[22]  Jerry H. Griffin,et al.  FRICTION DAMPING OF CIRCULAR MOTION AND ITS IMPLICATIONS TO VIBRATION CONTROL , 1991 .

[23]  Christian Maria Firrone,et al.  Modeling a friction damper: analysis of the experimental data and comparison with numerical results , 2006 .

[24]  Tony F. Chan,et al.  Arc-Length Continuation and Multigrid Techniques for Nonlinear Elliptic Eigenvalue Problems , 1982 .

[25]  Chia-Hsiang Menq,et al.  Characterization of Contact Kinematics and Application to the Design of Wedge Dampers in Turbomachinery Blading: Part 1—Stick-Slip Contact Kinematics , 1998 .

[26]  David J. Ewins,et al.  Underplatform Dampers for Turbine Blades: Theoretical Modeling, Analysis, and Comparison With Experimental Data , 2001 .

[27]  David J. Ewins,et al.  MODELLING TWO-DIMENSIONAL FRICTION CONTACT AND ITS APPLICATION USING HARMONIC BALANCE METHOD , 1996 .

[28]  Ning An,et al.  A microslip friction model with normal load variation induced by normal motion , 2007 .

[29]  J. Griffin.  Friction Damping of Resonant Stresses in Gas Turbine Engine Airfoils , 1980 .