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.

Response Prediction of Frictionally Constraint Blade Systems Based on a Variable Normal Load Microslip Model

2010 ◽  
Author(s):  
Yalin Liu ◽  
Zili Xu ◽  
Shangguan Bo ◽  
Linzhong Li
Keyword(s):  
Time Domain ◽  
Degrees Of Freedom ◽  
Normal Load ◽  
Response Prediction ◽  
Friction Model ◽  
Time Dependent ◽  
Friction Contact ◽  
Contact Kinematics ◽  
Multiple Variables ◽  
Microslip Friction

A discrete microslip friction contact model, which can consider time-dependent/space-related normal load, has been established to investigate the contact kinematics in the contact interfaces between adjacent blade shrouds. The model extends the capability of Csaba’s model in dealing with the situation of variant normal load. A Fast Anti-alias Fourier transform (FAFT) is introduced to the alternating frequency/time domain method (AFT) to improve the accuracy of spectrum analysis and extend analysis spectrum range. The developed friction model and the modified AFT are applied to calculate nonlinear vibration for a simplified shrouded blade, and the effect of parameters on resonant frequency and amplitude of shrouded blade are investigated and discussed. Comparing with existing variable normal load macroslip model, the model proposed here has the mathematically tractable characteristic and can be easily used. Combining with the AFT method, it is suitable for the analysis of complex system with multiple variables and degrees of freedom, and it can meet the engineering need.

Experimental Investigations of the Rubber-Asphalt Sliding Pair Dynamics

2002 ◽  
Author(s):  
Ante Bozˇic´ ◽  
Ivan Petrovic´ ◽  
Nedjeljko Peric´ ◽  
Jadranko Matusˇko
Keyword(s):  
Friction Coefficient ◽  
Dynamic Behavior ◽  
Friction Force ◽  
Contact Surface ◽  
Friction Model ◽  
Laboratory Model ◽  
Experimental Investigations ◽  
Dynamic Friction ◽  
The Road ◽  
Friction Models

A laboratory model for experimental investigations of the rubber-asphalt sliding pair has been designed with the purpose of better understanding of dynamic behavior of the friction force in the contact patch between the car tire and the road. Its design is described and some experimental results are given. These results confirm that it is essential to use a dynamic friction model in order to describe friction force in contact between the car tire and the road. Moreover, they indicate that the existing dynamic friction models night be physically incorrect regarding the change of friction coefficient for an asperity bristle passing through the contact surface.

scholarly journals A study on the vibration dissipation mechanism of the rotating blade with dovetail joint

2021 ◽  
pp. 146134842098533
Author(s):  
Chaofeng Li ◽  
Zengchuang Shen ◽  
Zilin Chen ◽  
Houxin She
Keyword(s):  
Dry Friction ◽  
Vibration Reduction ◽  
Friction Model ◽  
Rotating Speed ◽  
System Parameters ◽  
Tangential Stiffness ◽  
Damping Characteristics ◽  
Rotating Blade ◽  
Spatial Beam ◽  
Dissipation Mechanism

The vibration dissipation mechanism of the rotating blade with a dovetail joint is studied in this paper. Dry friction damping plays an indispensable role in the direction of vibration reduction. The vibration level is reduced by consuming the total energy of the turbine blade with the dry friction device on the blade-root in the paper. The mechanism of the vibration reduction is revealed by the variation of the friction force and the energy dissipation ratio of dry friction. In this paper, the flexible blade with a dovetail interface feature is discretized by using the spatial beam element based on the finite element theory. Then the classical Coulomb-spring friction model is introduced to obtain the dry friction model on the contact interfaces of the tenon-mortise structure. What is more, the effects of the system parameters (such as the rotating speed, the friction coefficient, the installation angle of the tenon) and the excitation level on blade damping characteristics are discussed, respectively. The results show that the variation of the system parameters leads to a significant change of damping characteristics of the blade. The variation of the tangential stiffness and the position of the external excitation will affect the nonlinear characteristics and vibration damping characteristics.

An improved nonlinear model considering relative velocity for the friction behavior between untwisted glass-fiber tow and roller

2021 ◽  
pp. 004051752110308
Author(s):  
Yang Liu ◽  
Zhong Xiang ◽  
Xiangqin Zhou ◽  
Zhenyu Wu ◽  
Xudong Hu
Keyword(s):  
Friction Coefficient ◽  
Glass Fiber ◽  
Relative Velocity ◽  
Friction Model ◽  
Woven Fabric ◽  
Test Results ◽  
Application Process ◽  
Friction Behavior ◽  
Improved Model

Friction between the tow and tool surface normally happens during the tow production, fabric weaving, and application process and has an important influence on the quality of the woven fabric. Based on this fact, this paper studied the influence of tension and relative velocity on the three kinds of untwisted-glass-fiber tow-on-roller friction with a Capstan-based test setup. Furthermore, an improved nonlinear friction model taking both tension and velocity into account was proposed. According to statistical test results, firstly, the friction coefficient was found to be positively correlated with tension and relative velocity. Secondly, tension and velocity were complementary on the tow-on-roller friction behavior, with neither being superior to the other. Thirdly, an improved model was found to present well the nonlinear characteristics between friction coefficient and tension and velocity, and predicational results of the model were found to agree well with the observations from Capstan tests.

Modeling of Piezo-Actuated Stick-Slip Micro-Drives: An Overview

2012 ◽  
Vol 81 ◽  
pp. 39-48 ◽  
Author(s):  
Ha Xuan Nguyen ◽  
Christoph Edeler ◽  
Sergej Fatikow
Keyword(s):  
Mechanical Model ◽  
Integrated Model ◽  
Friction Model ◽  
Fundamental Importance ◽  
Future Research ◽  
Stick Slip ◽  
Research Activities ◽  
Model Combining ◽  
Friction Models

This paper gives an overview about problems of modeling of piezo-actuated stick-slip micro-drives. It has been found that existing prototypes of such devices have been investigated empirically. There is only few research dealing with the theory behind this kind of drives. By analyzing the current research activities in this field, it is believed that the model of the drive depends strongly on the friction models, but in most cases neglecting any influences of the guilding system.These analyses are of fundamental importance for an integrated model combining friction model and mechanical model offering promising possibilities for future research.

Viscous Friction Effect During the Process of Tightening and Loosening of Bolted Joints

2021 ◽  
Author(s):  
Qingyuan Lin ◽  
Yong Zhao ◽  
Qingchao Sun ◽  
Kunyong Chen
Keyword(s):  
Friction Coefficient ◽  
Viscous Friction ◽  
Normal Pressure ◽  
Friction Model ◽  
Bolted Joints ◽  
Critical Parameters ◽  
Bolted Joint ◽  
Sliding Velocity ◽  
Friction Effect ◽  
Bearing Friction

Abstract Bolted connection is one of the most widely used mechanical connections because of its easiness of installation and disassembly. Research of bolted joints mainly focuses on two aspects: high precision tightening and improvement of anti-loosening performance. The under-head bearing friction coefficient and the thread friction coefficient are the two most important parameters that affect the tightening result of the bolted joint. They are also the most critical parameters that affect the anti-loosening performance of the bolted joint. Coulomb friction model is a commonly used model to describe under-head bearing friction and thread friction, which considers the friction coefficient as a constant independent of normal pressure and relative sliding velocity. In this paper, the viscous effect of the under-head bearing friction and thread friction is observed by measuring the friction coefficient of bolted joints. The value of the friction coefficient increases with the increase of the relative sliding velocity and the decrease of the normal pressure. It is found that the Coulomb viscous friction model can better describe the friction coefficient of bolted joints. Taking into account the dense friction effect, the loosening prediction model of bolted joints is modified. The experimental results show that the Coulomb viscous friction model can better describe the under-head bearing friction coefficient and thread friction coefficient. The model considering the dense effect can more accurately predict the loosening characteristics of bolted joints.

Numerical Investigation of Size Effect on Dry Friction Behavior in Micro Upsetting Process

2014 ◽  
Vol 997 ◽  
pp. 321-324
Author(s):  
Wei Zheng ◽  
Guang Chun Wang ◽  
Bing Tao Tang ◽  
Xiao Juan Lin ◽  
Yan Zhi Sun
Keyword(s):  
Friction Coefficient ◽  
Size Effect ◽  
Dry Friction ◽  
Normal Pressure ◽  
Friction Model ◽  
Strain Hardening Exponent ◽  
Forming Process ◽  
Friction Behavior ◽  
Initial Yield Stress ◽  
Coulomb’S Friction

After modifying the Wahime/Bay friction model, a new friction model suitable for micro-forming process without lubrication is established. In this model, it is shows that the friction coefficient is a function of strain hardening exponent, the normal pressure and the initial yield stress of material. Based on the experimental data, the micro-upsetting process is simulated using the proposed friction model. The simulation results are used to investigate the size effect on the dry friction behavior. It is found that the Coulomb’s friction coefficient is dropping with miniaturization of specimens when the amount of reduction is not too large.

Comparison of Four Friction Models: Feature Prediction

2015 ◽  
Vol 11 (3) ◽  
Author(s):  
Yun-Hsiang Sun ◽  
Tao Chen ◽  
Christine Qiong Wu ◽  
Cyrus Shafai
Keyword(s):  
Numerical Model ◽  
Viscous Friction ◽  
Friction Model ◽  
Dynamic Features ◽  
Numerical Predictions ◽  
Wide Range ◽  
Model Predictions ◽  
Friction Models ◽  
Parameter Identifications ◽  
Model Structures

In this paper, we provide not only key knowledge for friction model selection among candidate models but also experimental friction features compared with numerical predictions reproduced by the candidate models. A motor-driven one-dimensional sliding block has been designed and fabricated in our lab to carry out a wide range of control tasks for the friction feature demonstrations and the parameter identifications of the candidate models. Besides the well-known static features such as break-away force and viscous friction, our setup experimentally demonstrates subtle dynamic features that characterize the physical behavior. The candidate models coupled with correct parameters experimentally obtained from our setup are taken to simulate the features of interest. The first part of this work briefly introduces the candidate friction models, the friction features of interest, and our experimental approach. The second part of this work is dedicated to the comparisons between the experimental features and the numerical model predictions. The discrepancies between the experimental features and the numerical model predictions help researchers to judge the accuracy of the models. The relation between the candidate model structures and their numerical friction feature predictions is investigated and discussed. A table that summarizes how to select the most optimal friction model among a variety of engineering applications is presented at the end of this paper. Such comprehensive comparisons have not been reported in previous literature.

scholarly journals Validation of Friction Model Parameters Identified Using the IHB Method Using Finite Element Method

2019 ◽  
Vol 2019 ◽  
pp. 1-19
Author(s):  
Abdallah Hadji ◽  
Njuki Mureithi
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Friction Force ◽  
Harmonic Balance ◽  
Harmonic Balance Method ◽  
Friction Model ◽  
Balance Method ◽  
Model Parameters ◽  
Friction Models ◽  
Element Method

A hybrid friction model was recently developed by Azizian and Mureithi (2013) to simulate the friction behavior of tube-support interaction. However, identification and validation of the model parameters remains unresolved. In previous work, the friction model parameters were identified using the reverse harmonic method, where the following quantities were indirectly obtained by measuring the vibration response of a beam: friction force, sliding speed of the force of impact, and local displacement at the contact point. In the present work, the numerical simulation by the finite element method (FEM) of a beam clamped at one end and simply supported with the consideration of friction effect at the other is conducted. This beam is used to validate the inverse harmonic balance method and the parameters of the friction models identified previously. Two static friction models (the Coulomb model and Stribeck model) are tested. The two models produce friction forces of the correct order of magnitude compared to the friction force calculated using the inverse harmonic balance method. However, the models cannot accurately reproduce the beam response; the Stribeck friction model is shown to give the response closest to experiments. The results demonstrate some of the challenges associated with accurate friction model parameter identification using the inverse harmonic balance method. The present work is an intermediate step toward identification of the hybrid friction model parameters and, longer-term, improved analysis of tube-support dynamic behavior under the influence of friction.

A New Method for Elastic-Plastic Contact Analysis of a Deformable Sphere and a Rigid Flat

2005 ◽  
Vol 128 (2) ◽  
pp. 221-229 ◽  
Author(s):  
Li Po Lin ◽  
Jen Fin Lin
Keyword(s):  
New Method ◽  
Contact Load ◽  
Rigid Sphere ◽  
The Finite Element Method ◽  
Numerical Errors ◽  
Elastic Regime ◽  
Contact Loads ◽  
Indentation Tests ◽  
Metal Materials ◽  
Contact Parameters

A new method is developed in the present study to determine the elastoplastic regime of a spherical asperity in terms of the interference of two contact surfaces. This method provides an efficient way to solve the problem of discontinuities often present in the reported solutions for the contact load and area or the gradients of these parameters obtained at either the inception or the end of the elastoplastic regime. The well-established solutions for the elastic regime and experimental data of metal materials using indentation tests are provided as the references to determine the errors of these contact parameters due to the use of the finite-element method. These numerical errors provide the basis to adjust the contact area and contact load of a rigid sphere in contact with a flat such that the dimensionless mean contact pressure Pave∕Y (Y: the yielding strength) and the dimensionless contact load Fpc∕Fec (Fec, Fpc: the contact loads corresponding to the inceptions of the elastoplastic and fully plastic regimes, respectively) reaches the criteria arising at the inception of the fully plastic regime, which are available from the reports of the indentation tests for metal materials. These two criteria are however not suitable for the present case of a rigid flat in contact with a deformable sphere. In the case of a rigid flat in contact with a deformable sphere, the proportions in the adjustments of these contact parameters are given individually the same as those arising in the indentation case. The elastoplastic regime for each of these two contact mechanisms can thus be determined independently. By assuming that the proportion of adjustment in the elastoplastic regime is a linear function, the discontinuities appearing in these contact parameters are absent from the two ends of the elastoplastic regime in the present study. These results are presented and compared with the published results.

Sign in / Sign up

Export Citation Format

Share Document