Experimental Validation of Friction Models for Rotor-Rubbing

2019 ◽  
Author(s):  
Juan Jauregui ◽  
Oscar De Santiago Duran
Keyword(s):  
Friction Force ◽  
Cross Correlation ◽  
Tangential Force ◽  
Nonlinear Behavior ◽  
Experimental Results ◽  
Friction Forces ◽  
Rotating Speed ◽  
Friction Models ◽  
The Cross ◽  
Set Up

Abstract The work presented here is a continuation of a set of experiments that were designed for predicting friction forces during rotor rubbing. The experimental set up consisted of a rotor rubbing a fixed surface. The surface had two force sensors, one aligned with the tangential force, and the other aligned in the radial direction. This set up allowed us to measure the friction component and the normal force. The measurements were complemented with a couple of accelerometers mounted on the bearings, and the accelerations and the friction force were measured simultaneously. All the data were analyzed using the Continuous Wavelet Transform (CWT) and the cross-correlation function. The CWT produces a spectrogram that is useful for identifying the nonlinear behavior of the phenomenon. The cross-correlation is used to measure the similarities between the friction force and the acceleration measurements. At low friction levels, experimental results show a sub-synchronous vibration at half of the rotating speed. This pattern is always present regardless of the friction source, but it is impossible to reproduce this effect using current friction models. The experimental results were compared to numerical results, these results were computed with the Muszynska’s model that is based on the physics of the phenomenon, but their predictions differ significantly from the experimental results. One of the reasons for these discrepancies lay on the fact that rotor-rubbing models consider the friction as an external force instead of modifying the system parameters.

Experimental Study of a Variable Pressure Damper on Automotive Valve Motion

1996 ◽  
Author(s):  
Jin-Jang Liou ◽  
Grodrue Huang ◽  
Wensyang Hsu
Keyword(s):  
Experimental Study ◽  
Friction Coefficient ◽  
Friction Force ◽  
High Speed ◽  
Experimental Results ◽  
Variable Pressure ◽  
Friction Forces ◽  
Valve Spring ◽  
Valve Motion

Abstract A variable pressure damper (VPD) is used here to adjusted the friction force on the valve spring to investigate the relation between the friction force and the valve bouncing phenomenon. The friction force on the valve spring is found experimentally, and the corresponding friction coefficient is also determined. Dynamic valve displacements at different speeds with different friction forces are calibrated. Bouncing and floating of the valve are observed when the camshaft reaches high speed. From the measured valve displacement, the VPD is shown to have significant improvement in reducing valve bouncing distance and eliminating floating. However, experimental results indicate that the valve bouncing can not be eliminated completely when the camshaft speed is at 2985 rpm.

scholarly journals Experimental investigation of a single-degree-of-freedom system with Coulomb friction

2020 ◽  
Vol 99 (3) ◽  
pp. 1781-1799
Author(s):  
Luca Marino ◽  
Alice Cicirello
Keyword(s):  
Experimental Investigation ◽  
Degree Of Freedom ◽  
Experimental Results ◽  
Systematic Observation ◽  
Stick Slip ◽  
Friction Forces ◽  
Single Degree Of Freedom ◽  
Sdof System ◽  
Single Degree ◽  
Set Up

AbstractThis paper presents an experimental investigation of the dynamic behaviour of a single-degree-of-freedom (SDoF) system with a metal-to-metal contact under harmonic base or joined base-wall excitation. The experimental results are compared with those yielded by mathematical models based on a SDoF system with Coulomb damping. While previous experiments on friction-damped systems focused on the characterisation of the friction force, the proposed approach investigates the steady response of a SDoF system when different exciting frequencies and friction forces are applied. The experimental set-up consists of a single-storey building, where harmonic excitation is imposed on a base plate and a friction contact is achieved between a steel top plate and a brass disc. The experimental results are expressed in terms of displacement transmissibility, phase angle and top plate motion in the time and frequency domains. Both continuous and stick-slip motions are investigated. The main results achieved in this paper are: (1) the development of an experimental set-up capable of reproducing friction damping effects on a harmonically excited SDoF system; (2) the validation of the analytical model introduced by Marino et al. (Nonlinear Dyn, 2019. https://doi.org/10.1007/s11071-019-04983-x) and, particularly, the inversion of the transmissibility curves in the joined base-wall motion case; (3) the systematic observation of stick-slip phenomena and their validation with numerical results.

Experimental Study of Friction in a Pneumatic Actuator at Constant Velocity

1993 ◽  
Vol 115 (3) ◽  
pp. 575-577 ◽  
Author(s):  
Lee E. Schroeder ◽  
Rajendra Singh
Keyword(s):  
Experimental Study ◽  
Experimental Method ◽  
Friction Force ◽  
Constant Velocity ◽  
Sliding Friction ◽  
Pneumatic Actuator ◽  
Friction Forces ◽  
Friction Models ◽  
Semi Empirical ◽  
Force Data

This paper describes an experimental method of determining sliding friction forces in a pneumatic actuator. Several empirical and semi-empirical friction models are evaluated using measured friction force data. A repeatability study is also performed to qualitatively assess friction randomness and a change in friction regimes.

Forced Response of Interlocked Vane Segments: Numerical Predictions and Experimental Results

2006 ◽  
Author(s):  
Stefano Zucca ◽  
Sergio Filippi ◽  
Fabio Droetti ◽  
Muzio M. Gola
Keyword(s):  
Tangential Force ◽  
Harmonic Balance Method ◽  
Outer Radius ◽  
Forced Response ◽  
Experimental Results ◽  
Numerical Code ◽  
Friction Forces ◽  
Normal Contact ◽  
Numerical Predictions ◽  
Local Compliance

Resonant vibrations affect fatigue life of vane segments. Friction damping is employed to reduce vibration amplitude. When vane segments are assembled, they are twisted so that lower platforms are in contact. The sum of displacements of the two ends of the lower platform after twisting is defined ‘interlocking’. Different ‘interlocking’ values correspond to different values of normal contact force. When interlocked vanes vibrate under external force excitation, energy is dissipated by friction forces at lower platform contacts providing damping to the system. The aim of this paper is the experimental validation of a numerical code for forced response calculation of interlocked vane segments. Since friction forces depend on relative displacements of bodies in contact, the system is nonlinear. System force response is computed by means of Harmonic Balance Method (HBM). Contact model implemented in the code is characterised by tangential and normal stiffness to take into account local compliance of the contact area. Gross slip occurs when the instantaneous ratio of tangential force to normal force is equal to the friction coefficient. Also effect of microslip is taken in account. The experimental set-up used to validate the code is made of a vane segment fixed at the outer radius to an aluminium frame and in contact with two supports at the inner radius. Comparison between the numerical predictions and experimental results is performed for different values of interlocking (i.e. force normal to the contact).

Validation of Friction Model Parameters Identified Using the Inverse Harmonic Balance Method

2015 ◽  
Author(s):  
Abdallah Hadji ◽  
Njuki Mureithi
Keyword(s):  
Friction Force ◽  
Harmonic Balance ◽  
Contact Point ◽  
Harmonic Balance Method ◽  
Friction Model ◽  
Balance Method ◽  
Model Parameters ◽  
Intermediate Step ◽  
Friction Forces ◽  
Friction Models

A hybrid friction model was recently developed by Azizian and Mureithi [1] to simulate the friction behavior of tube-support interaction. However, identification of the model parameters remains unresolved. In previous work, the friction model parameters were identified using reverse the 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 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 closer 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.

Nonlinear Behavior of Pedestal Looseness Fault Rotor-Bearing System with Slowly Varying Mass

2010 ◽  
Vol 29-32 ◽  
pp. 2096-2101
Author(s):  
Yue Gang Luo ◽  
Song He Zhang ◽  
Bin Wu ◽  
Bang Chun Wen
Keyword(s):  
Fault Diagnosis ◽  
Dynamic Model ◽  
Chaotic Motion ◽  
Nonlinear Behavior ◽  
Speed Increase ◽  
Rotating Speed ◽  
Rotor Bearing ◽  
Set Up ◽  
Varying Mass ◽  
Bearing System

The dynamic model of the pedestal looseness fault rotor-bearing system with slowly varying mass was set up. The complex characteristics of the rotor-bearing system were numerically studied. Along with the increase of the looseness mass, the chaotic motion area and amplitude range increase in the region of critical rotating speed; and P-3 motion area disappears in the region of twice-critical rotating speed, chaos is the main motion form. Along with the increase of the coefficient of mass slowly varying amplitude, the instable rotating speed increase, and the chaotic motion area decreases, P-n motion area increases in the region of critical rotating speed and twice-critical rotating speed. The conclusions may provide basis reference for fault diagnosis.

Effects of rotational speed on the leakage behavior, temperature increase, and swirl development of labyrinth seal in a compressor stator well

2016 ◽  
Vol 231 (13) ◽  
pp. 2362-2374 ◽  
Author(s):  
Gaowen Liu ◽  
Xiaozhi Kong ◽  
Yuxin Liu ◽  
Qing Feng
Keyword(s):  
Flow Characteristics ◽  
Internal Flow ◽  
Labyrinth Seal ◽  
Swirl Flow ◽  
Tip Clearance ◽  
Experimental Results ◽  
Test Rig ◽  
Experimental Conditions ◽  
Rotating Speed ◽  
Set Up

The stator well in a compressor is the space between the rotor and stator inside the mainstream annulus flow. Labyrinth seals are normally used to control the internal flow in the stator well. The upstream and downstream rotating cavities of the labyrinth seal can lead to substantial temperature rise and swirl development in this region. Additionally, due to the centrifugal expansion and thermal expansion, the tip clearance of labyrinth seal changes dramatically at different rotational speeds and temperatures in the stator well. A test rig capable to establish different rotational speeds and pressure ratios was designed according to the simplified model of the labyrinth seal in a compressor stator well (one stage). The leakage flow rate and change in total temperature across the stator well were measured. This paper also contains the experimental results of swirl ratios in the outlet rotating cavity to reveal the swirl development. Special emphasis in this work lies on acquiring the working tip clearance precisely. The set up tip clearance was measured with plug gauges, while the radial displacements of labyrinth ring and stator casing were measured separately with two high precision laser distance sensors. Two-dimensional, axisymmetric swirl flow numerical simulations were performed to get a further understanding about the basic flow characteristics and to evaluate their ability to predict the experimental results. The computational results of discharge coefficient, windage heating, and swirl ratio were compared to those obtained from test rig measurements. Particularly, when calculating, the tip clearance, the inlet parameters, and the outlet parameters of numerical model at a specific rotating speed were set to be the same with the experimental conditions.

Static Friction and the Law of Rubber Friction

1963 ◽  
Vol 36 (2) ◽  
pp. 365-376 ◽  
Author(s):  
V. V. Lavrentev
Keyword(s):  
Friction Force ◽  
Contact Time ◽  
Sliding Friction ◽  
Tangential Force ◽  
Static Friction ◽  
Experimental Results ◽  
The Other ◽  
Chemical Bonds ◽  
Vulcanized Rubber ◽  
Rubber Friction

Abstract a) The true static friction of vulcanized rubber is in practice immeasurably small (equal to zero, according to theory). b) The static friction as usually determined is an initial friction force. c) The initial friction force is equal to the sliding friction force in accelerated movement. It depends on the contact time, the rate of growth of the tangential force and the other conditions of experiment. d) With long contact times, particularly at higher temperatures, strong chemical bonds are formed between the vulcanized rubber and the track, leading to true static friction. e) The theoretical law of friction agrees well with the experimental results over the whole range of normal pressures. f) Good approximations are given in the range of low normal pressures by Coulomb's law (5) and in the rubber of high normal pressures by that of Thirion (7).

Set-Up of a Test Bench for the Investigation of Single Parameter Effects in Abrasive Processes by Force Measurements

2014 ◽  
Vol 1052 ◽  
pp. 441-446 ◽  
Author(s):  
Dirk Bähre ◽  
Shi Qi Fang ◽  
Jacqueline Gliche ◽  
Kirsten Trapp
Keyword(s):  
Test Bench ◽  
Tangential Force ◽  
Cutting Speed ◽  
Feed Speed ◽  
Machining Parameters ◽  
Force Coefficient ◽  
Friction Forces ◽  
Abrasive Tools ◽  
Influencing Parameters ◽  
Set Up

Abrasive processes are influenced by many different parameters. For a systematic investigation of these influencing parameters, a test bench for abrasive tools has been developed and set up on a 3-axis milling machine. The test bench is capable to control the machining parameters, such as the cutting speed and the feed speed, regulate the lubrication conditions, such as the temperature or the flow rate, and measure the cutting force during the process. Impacts of the single force components are investigated by means of the abrasive tools in contact with the rotating workpieces and the calculation of the tangential force coefficient. In this paper, the set-up of the test bench is explained and the systematic proceeding in investigating the impacts is exemplified by cooling lubricants because the surface of the workpiece, the wear of the tool, the temperature and the friction forces are often influenced by the type of cooling lubricant and its composition. The aim of the test bench for tools is to understand the correlations of the single influencing parameters in abrasive processes. The first results of comparative investigations with cooling lubricants of different viscosities are presented and discussed.

Analysis of the Positioning Process of Objects by the System of Oblique Friction Force Fields on the Example of the MSC Adams Model

2020 ◽  
Author(s):  
Tomasz Piatkowski ◽  
Miroslaw Wolski
Keyword(s):  
Numerical Simulations ◽  
Friction Force ◽  
Force Fields ◽  
Positioning Precision ◽  
Friction Models ◽  
The Cross ◽  
Sorting System ◽  
Theoretical Analyses

Abstract The paper concerns modelling of the rotational positioning process of cuboid objects with the system of oblique friction force fields produced by two conveyors. These conveyors are used when introducing streams of objects onto trays of the cross-belt sorting system. The purpose of positioning is to place the objects parallel to the edges of the trays with the greatest possible precision. The positioning precision depends on the choice of the conveyors’ motion velocities and conveyors’ position to each other, which can be determined on the basis of numerical simulations. During theoretical analyses, contact and friction models available in the MSC Adams environment were taken into account.

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