One-dimensional dynamic microslip friction model

2006 ◽  
Vol 292 (3-5) ◽  
pp. 881-898 ◽  
Author(s):  
Ender Cigeroglu ◽  
Wangming Lu ◽  
Chia-Hsiang Menq
Keyword(s):  
Friction Model ◽  
One Dimensional ◽  
Microslip Friction

A Comparison of Two Microslip Contact Models for Studying the Mechanics of Underplatform Dampers

2018 ◽  
Author(s):  
Chao Xu ◽  
Dongwu Li ◽  
Muzio M. Gola ◽  
Chiara Gastaldi
Keyword(s):  
Friction Coefficient ◽  
Friction Model ◽  
Tangential Displacement ◽  
Tangential Stiffness ◽  
Contact Loads ◽  
Contact Kinematics ◽  
Contact Models ◽  
Friction Models ◽  
Microslip Friction ◽  
Contact Parameters

In turbine blade systems, under-platform dampers are widely used to attenuate excessive resonant vibrations. Subjected to vibration excitation, the components with frictionally constrained interfaces can involve very complex contact kinematics induced by tangential and normal relative motions. To effectively calculate the dynamics of a blade-damper system, contact models which can accurately reproduce the interface normal and tangential motions are required. The large majority of works have been developed using macroslip friction models to model the friction damping at the contact interface. However, for those cases with small tangential displacement where high normal loads are applied, macroslip models are not enough to give accurate results. In this paper two recently published microslip models are compared, between them and against the simple macroslip spring-slider model. The aim is to find to which extent these models can accurately predict damper mechanics. One model is the so called GG array, where an array of macroslip elements is used. Each macroslip element of the GG array is assigned its own contact parameters and for each of them four parameters are needed: normal stiffness, tangential stiffness, normal gap and friction coefficient. The other one is a novel continuous microslip friction model. The model is based on a modification of the original classic IWAN model to couple normal and tangential contact loads. Like the GG array the model needs normal and tangential stiffness, and friction coefficient. Unlike the GG array the model is continuous and, instead of the normal gap required by the GG array, the Modified IWAN model needs a preload value. The two models are here applied to the study of the mechanics of a laboratory under-platform damper test rig. The results from the two models are compared and allow their difference, both for damper mechanics and for the complex-spring coefficients, to be assessed.

Frictional Damping of Flutter: Microslip Versus Macroslip

2016 ◽  
Vol 138 (6) ◽  
Author(s):  
Robert Hudson ◽  
Alok Sinha
Keyword(s):  
Harmonic Balance ◽  
Function Method ◽  
Friction Model ◽  
Describing Function ◽  
Friction Dampers ◽  
Method Of Harmonic Balance ◽  
Frictional Damping ◽  
Negative Damping ◽  
Describing Function Method ◽  
Microslip Friction

Friction dampers are utilized in turbomachinery to reduce blade vibrations resulting from aeroelastic interactions. In this paper, the microslip friction model is applied to a blade with blade to ground damper and subjected to negative damping. Analysis using the describing function method, also known as the method of harmonic balance, is used to identify the behavior of the system and the maximum negative damping that can be stabilized by such a damper. These results are compared to those for the macroslip friction model.

scholarly journals The Modified One-Dimensional Hydrodynamic Model Based on the Extended Chezy Formula

Water ◽  
2018 ◽  
Vol 10 (12) ◽  
pp. 1743
Author(s):  
Junwei Zhou ◽  
Weimin Bao ◽  
Yu Li ◽  
Li Cheng ◽  
Muxi Bao
Keyword(s):  
Hydrodynamic Model ◽  
Calibration Method ◽  
Friction Model ◽  
Flood Routing ◽  
Flow Depth ◽  
Parameter Calibration ◽  
Simulation Test ◽  
One Dimensional ◽  
Hydraulic Experiment ◽  
Peak Value

Although steady uniform friction formulas have been introduced to the framework of a one-dimensional (1D) hydrodynamic model for centuries, the error of friction calculation inevitably undermines the performance of flood routing. Based on successful results of unsteady channel friction research studies, a newly proposed unsteady friction model is introduced to establish a modified 1D hydrodynamic model (namely, the modified SVN model). With the help of a carefully designed parameter calibration method, the performance of the modified SVN model was compared with that of the original SVN model in a simulation test for a hydraulic experiment. This study’s results revealed that compared with the original SVN model, the modified SVN model could achieve a better simulation in both the flow depth and the sectional averaged velocity simulations. Furthermore, it could reduce the peak value error and the time-at-peak error as well, indicating that the use of an unsteady friction model can efficiently improve the performance of a 1D hydrodynamic model.

Friction Damping Modeling in High Stress Contact Areas Using Microslip Friction Model

2008 ◽  
Author(s):  
Francisco J. Marquina ◽  
Armando Coro ◽  
Alberto Gutie´rrez ◽  
Roberto Alonso ◽  
David J. Ewins ◽  
...  
Keyword(s):  
Coulomb Friction ◽  
High Stress ◽  
Friction Model ◽  
Imperial College ◽  
Rotor Blades ◽  
Contact Method ◽  
Friction Damping ◽  
Common Solution ◽  
Coulomb Friction Law ◽  
Microslip Friction

It is well known that friction is really important to reduce amplitudes of vibration of rotor blades. Underplatform dampers are a common solution for introducing friction damping, but there are also other friction damping sources on blades that are produced in places with high normal loads and small relative displacements (e.g. lockplates and blade-disc joints). Several approaches based on the classical Coulomb friction law have been used in order to model the friction damping at those interfaces, but their results are not accurate enough for those cases with small displacements where high normal loads appear. This paper presents simulations of typical cases of friction on rotor blades (underplatform dampers, lockplates and blade root) using a method based on macroslip and the method developed by ‘Industria de TurboPropulsores’ (ITP) based on microslip (InTerPart MIcroslip COntact method), and their comparison with experimental results obtained with several tests performed at Imperial College London (IC). The comparison shows that, for cases with high normal loads and small displacements, the ITPMICO method obtains further more accurate results than based-on-macroslip one.

A microslip friction model with normal load variation induced by normal motion

2007 ◽  
Vol 50 (3) ◽  
pp. 609-626 ◽  
Author(s):  
Ender Cigeroglu ◽  
Ning An ◽  
Chia-Hsiang Menq
Keyword(s):  
Normal Load ◽  
Friction Model ◽  
Load Variation ◽  
Microslip Friction

Modelling of Mechanical Systems With Friction Interfaces Considering Variable Normal Contact Load and Tangential Micro/Macro Slip

2016 ◽  
Author(s):  
Dongwu Li ◽  
Chao Xu
Keyword(s):  
Normal Load ◽  
Friction Model ◽  
Hysteretic Model ◽  
Friction Contact ◽  
Restoring Force ◽  
Normal Contact ◽  
Load Variation ◽  
Proposed Model ◽  
Frictional Damping ◽  
Microslip Friction

Mechanical structures with frictionally constrained interfaces often involve complex contact kinematics induced by tangential and normal relative motions. The tangential motion induces stick-micro/macro slip friction and causes energy dissipation. The normal motion induces normal load variation and possible separation of the joint interfaces. For effective analysis of dynamics of jointed structures, a reduced friction contact model is needed to characterize the nonlinear, coupled normal and tangential contact behaviors precisely. However, most developed microslip friction contact models considers only constant normal load. In this paper, an improved microslip friction model with normal load variation induced by normal motion is proposed. The tangential stick-micro/macro slip friction is modeled by continuous Iwan hysteretic model. This model is characterized by a slippage uniform distribution density function and a linear stiffness at stick state. The coupling relationship between tangential nonlinear restoring force and normal load variation is built. This leads to generalization of the original Iwan hysteretic friction model to consider the effect of variable normal load. The proposed model is applied to model a 7-dofs frictional damping experimental system. The results show that normal load variation and tangential microslip motion exert an important effect on prediction of friction contact behaviors. The proposed model is capable of generating asymmetric hysteresis loops and intermittent normal separation. The numerical simulation fit well with the experimental results for the 7-dofs frictional damping system, which validates the effectiveness and accuracy of the proposed model.

scholarly journals Experimental Study on Dry Friction Damping Characteristics of the Steam Turbine Blade Material with Nonconforming Contacts

2015 ◽  
Vol 2015 ◽  
pp. 1-15 ◽  
Author(s):  
Jun Wu ◽  
Ruishan Yuan ◽  
Zhenwu He ◽  
Di Zhang ◽  
Yonghui Xie
Keyword(s):  
Relative Motion ◽  
Dynamic Characteristics ◽  
Dry Friction ◽  
Friction Model ◽  
Equivalent Stiffness ◽  
Hysteresis Model ◽  
Equivalent Damping ◽  
Steam Turbine Blade ◽  
Microslip Friction ◽  
Dry Friction Damping

An experiment system has been established to study the dry friction damping dynamic characteristics of the steam turbine blade material 1Cr13. The friction dynamic characteristics of the specimens with nonconforming contact surfaces are measured under different parameters. The experiment results are compared with that of the macroslip hysteresis model and the Mindlin microslip friction model in detail. The results show that the experimental result of the tangential contact stiffness is in good agreement with that of the theory result based on the fractal theory and the Hertz contact theory by Jiang et al., 2009. The dimensionless equivalent stiffness and equivalent damping obtained by the macroslip hysteresis model agree well with the experimental results when relative motion is relatively large. However, the results of the macroslip hysteresis model differ a lot from the experimental results when relative motion is relatively small. Compared with the macroslip hysteresis model, the Mindlin microslip friction model can predict the dimensionless equivalent stiffness and equivalent damping accurately during the whole measurement range. The linear regularities of dimensionless equivalent stiffness and equivalent damping are obtained, which decrease the difficulty of building the vibration analysis model of the blade with sufficient accuracy.

Sensitivity Analysis of a Microslip Friction Model

2004 ◽  
Vol 47 (1) ◽  
pp. 74-79
Author(s):  
Thomas Paez ◽  
Angel Urbina ◽  
Dan Gregory ◽  
Brian Resor
Keyword(s):  
Energy Dissipation ◽  
Linear Equations ◽  
Element Model ◽  
Friction Model ◽  
Model Parameters ◽  
System Behavior ◽  
Transient Time ◽  
Mechanical Joints ◽  
Linear Framework ◽  
Microslip Friction

Real physical systems subjected to dynamic environments all display nonlinear behavior, yet they are most frequently modeled in a linear framework. The main reasons are, first, that it is convenient and efficient to solve linear equations, and second, that the system behavior can often be accurately approximated using linear governing equations. Experience shows that much of the nonlinearity of system behavior arises from the dynamic action of mechanical joints in systems. When the linear framework is used, the stiffness of joints is modeled as linear, and the damping is modeled as linear and viscous. To model mechanical joints otherwise requires a nonlinear framework and mathematical finite element model that accommodates transient time domain analysis. This study investigates a particular mechanical joint energy dissipation model: the Iwan model for energy dissipation caused by microslip friction. The sensitivity of energy dissipation in a system due to variation of model parameters is studied. The results of a combined numerical/experimental example that uses a model calibrated to a sequence of experiments are presented.

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