A Dynamic Friction Model for Unlubricated Rough Planar Surfaces

2003 ◽  
Vol 125 (4) ◽  
pp. 788-796 ◽  
Author(s):  
Xi Shi ◽  
Andreas A. Polycarpou
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Harmonic Excitation ◽  
Published Data ◽  
Dynamic Friction ◽  
Time Varying ◽  
Friction Forces ◽  
Dynamic Friction Coefficient ◽  
Normal Separation ◽  
The Mean

Modeling dynamic or kinetic friction for realistic engineering surfaces continues to be a challenge, partly due to the coupling between system dynamics and interfacial forces. In this paper, a dynamic friction coefficient model for realistic rough surfaces under external normal vibrations is developed. From the system dynamic model, the instantaneous time varying normal separation at the interface is obtained under normal harmonic excitation. Subsequently, the instantaneous dynamic contact and tangential (friction) forces are calculated as a function of the instantaneous normal separation. The dynamic friction coefficient defined as the ratio of the time varying friction to the interfacial normal forces that explicitly includes interfacial damping, is also calculated. The results show that a mean increase in the instantaneous normal separation may or may not lead to a decrease of the mean friction force and the mean friction coefficient, which is supported by published data. For unlubricated elastic sliding contact conditions considered in this paper, the effect of damping on the dynamic friction coefficient is found to be negligible, whereas loss of contact causes significant apparent dynamic friction force and dynamic friction coefficient reductions. Several different interpretations of the time varying dynamic friction coefficient are presented and the implications of using a simple constant value to represent the time varying dynamic friction coefficient are discussed.

Adhesive Effects on Dynamic Friction for Unlubricated Rough Planar Surfaces

2004 ◽  
Author(s):  
Xi Shi ◽  
Andreas A. Polycarpou
Keyword(s):  
Friction Coefficient ◽  
Mean Value ◽  
Friction Model ◽  
Major Influence ◽  
Dynamic Friction ◽  
Friction Behavior ◽  
Friction Forces ◽  
Normal Contact ◽  
Continuous Contact ◽  
Dynamic Friction Coefficient

As the size of contacting and sliding tribosystems decrease, intermolecular or adhesive forces become significant partly due to nanometer size surface roughness. The presence of adhesion has a major influence on the interfacial contact and friction forces as well as the microtribosystem dynamics and thus influences the overall dynamic friction behavior. In this paper, a dynamic friction model that explicitly includes adhesion, interfacial damping and the system dynamics for realistic rough surfaces was developed. The results show that the amplitude and mean value of the time varying normal contact and friction forces increase in the presence of adhesion under continuous contact conditions. Also, due to the attractive nature of adhesion, its presence delays or eliminates the occurrence of loss of contact. Furthermore, in the presence of significant adhesion, dynamic friction behavior is significantly more complicated compared to the no adhesion case, and the dynamic friction coefficient predictions may be misleading. Thus, it is more appropriate to discuss dynamic friction force instead of dynamic friction coefficient under dynamic conditions.

Adhesive Effects on Dynamic Friction for Unlubricated Rough Planar Surfaces

2006 ◽  
Vol 128 (4) ◽  
pp. 841-850 ◽  
Author(s):  
Xi Shi ◽  
Andreas A. Polycarpou
Keyword(s):  
Friction Coefficient ◽  
Mean Value ◽  
Friction Model ◽  
Major Influence ◽  
Dynamic Friction ◽  
Friction Behavior ◽  
Friction Forces ◽  
Normal Contact ◽  
Continuous Contact ◽  
Dynamic Friction Coefficient

As the size of contacting and sliding tribosystems decrease, intermolecular or adhesive forces become significant partly due to nanometer size surface roughness. The presence of adhesion has a major influence on the interfacial contact and friction forces as well as the microtribosystem dynamics (microtribodynamics) and thus influences the overall dynamic friction behavior. In this paper, a dynamic friction model that explicitly includes adhesion, interfacial damping, and the system dynamics for realistic rough surfaces was developed. The results show that the amplitude and mean value of the time varying normal contact and friction forces increase in the presence of adhesion under continuous contact conditions. Also, due to the attractive nature of adhesion, its presence delays or eliminates the occurrence of loss of contact. Furthermore, in the presence of significant adhesion, dynamic friction behavior is significantly more complicated compared to the no adhesion case, and the dynamic friction coefficient predictions may be misleading. Thus, it is more appropriate to discuss dynamic friction force instead of dynamic friction coefficient under dynamic conditions.

A New Signal Processing Technique to Estimate Velocity Dependent Dynamic Friction Coefficient

2006 ◽  
Vol 321-323 ◽  
pp. 1241-1244
Author(s):  
Ki Hong Shin
Keyword(s):  
Friction Coefficient ◽  
Surface Condition ◽  
Rotating Disk ◽  
Processing Technique ◽  
Mapping Method ◽  
Dynamic Friction ◽  
State Variables ◽  
Signal Processing Technique ◽  
Friction Forces ◽  
Dynamic Friction Coefficient

In general, dynamic friction coefficient in a dry surface condition is dependent on the relative velocity between two sliding bodies. A conventional method of estimating the velocity dependent dynamic friction coefficient is time consuming and requires a special jig to measure the friction forces. In this paper, a new technique called the state space mapping method is proposed based on the nonlinear dynamics of a 1-DOF friction oscillator. One body is constructed as a single degree of freedom system and another body is formed as a moving base that may be built as a rotating disk or a horizontally oscillating plate. The resulting friction induced vibration system is used to estimate the dynamic friction coefficient. The measured vibration signals are utilized to construct a three dimensional plot of acceleration versus state variables. Then, the velocity dependent dynamic friction coefficient can be estimated from the plot. The natural frequency can also be estimated from the plot, which can be used to verify the quality of the results.

scholarly journals A Simple Mechanistic Model for Friction of Rough Partially Lubricated Surfaces

2021 ◽  
Vol 69 (3) ◽  
Author(s):  
Gianluca Costagliola ◽  
Tobias Brink ◽  
Julie Richard ◽  
Christian Leppin ◽  
Aude Despois ◽  
...  
Keyword(s):  
Aluminum Alloy ◽  
Friction Coefficient ◽  
Mechanistic Model ◽  
Applied Pressure ◽  
Real Contact Area ◽  
Experimental Measurements ◽  
Dynamic Friction ◽  
Real Contact ◽  
Dynamic Friction Coefficient ◽  
Direct Measurements

AbstractWe report experimental measurements of friction between an aluminum alloy sliding over steel with various lubricant densities. Using the topography scans of the surfaces as input, we calculate the real contact area using the boundary element method and the dynamic friction coefficient by means of a simple mechanistic model. Partial lubrication of the surfaces is accounted for by a random deposition model of oil droplets. Our approach reproduces the qualitative trends of a decrease of the macroscopic friction coefficient with applied pressure, due to a larger fraction of the micro-contacts being lubricated for larger loads. This approach relates direct measurements of surface topography to realistic distributions of lubricant, suggesting possible model extensions towards quantitative predictions.

scholarly journals Experimental Study on the Transition between Static and Kinetic Frictions of Steel/Shale Pairs

2021 ◽  
Vol 2021 ◽  
pp. 1-12
Author(s):  
Qin Lian ◽  
Chunxu Yang ◽  
Jifei Cao
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Critical Distance ◽  
Dynamic Friction ◽  
Stick Slip ◽  
Dynamic Friction Coefficient ◽  
The Coefficient Of Friction ◽  
The Difference ◽  
Stick Slip Motion ◽  
Insight Into

The transition between static and kinetic frictions of steel/shale pairs has been studied. It was found that the coefficient of friction decreased exponentially from static to dynamic friction coefficient with increasing sliding displacement. The difference between static and dynamic friction coefficients and the critical distance Dc under the dry friction condition is much larger than that under the lubricated condition. The transition from static to dynamic friction coefficient is greatly affected by the normal load, quiescent time, and sliding velocity, especially the lubricating condition. Maintaining continuous lubrication of the contact area by the lubricant is crucial to reduce or eliminate the stick-slip motion. The results provide an insight into the transition from static to dynamic friction of steel/shale pairs.

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.

Friction Characteristics and Adhesion Force Under Low Normal Load

1995 ◽  
Vol 117 (4) ◽  
pp. 569-574 ◽  
Author(s):  
Yasuhisa Ando ◽  
Yuichi Ishikawa ◽  
Tokio Kitahara
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Adhesion Force ◽  
Normal Load ◽  
Adhesion Forces ◽  
Test Pieces ◽  
Before And After ◽  
Constant Normal Load ◽  
The Mean ◽  
Steel Balls

The friction coefficient and adhesion force between steel balls and flat test pieces were measured during friction under low normal load in order to examine the tribological characteristics. First, the friction coefficients were measured under a constant normal load of 0.8 to 2350 μN, and the adhesion forces were measured before and after each friction. The result showed that the friction coefficient was highest at low normal loads, while the friction force divided by the sum of the normal load and the mean adhesion force was almost constant over the whole range of loads. Second, when the normal load was reduced gradually during friction, friction still acted when the normal load became negative and a pulling off force was applied to the surface. Thus an adhesion force acts during friction and this adhesion force affects the friction force in the same way as the normal load.

Experimental investigation and prediction method of fretting wear in rack-plane spline couplings

2020 ◽  
pp. 135065012093983
Author(s):  
Xiangzhen Xue ◽  
Jipeng Jia ◽  
Qixin Huo ◽  
Junhong Jia
Keyword(s):  
Friction Coefficient ◽  
Wear Mechanism ◽  
Static Friction ◽  
Experimental Results ◽  
Fretting Wear ◽  
Accurate Estimation ◽  
Dynamic Friction ◽  
Static Friction Coefficient ◽  
Dynamic Friction Coefficient ◽  
Involute Spline

To investigate the fretting wear of involute spline couplings in aerospace, rack-plane spline couplings rather than the conventional involute spline couplings in aerospace were used to conduct tribological experiments, and it was assumed that the rack-plane spline couplings exhibit consistent contact stress with the real involute spline couplings in aerospace. The relationships among the static friction coefficient, dynamic friction coefficient, and fretting friction coefficient were established via tribological experiments, as well as the fretting-wear mechanism of the rack-plane spline couplings was examined. A fretting-wear estimation model based on the fretting-wear mechanism was developed. By applying the modified Archard equation and Arbitrary Lagrangian–Eulerian adaptive, mesh smoothing algorithm of Abacus was used. According to our experimental results, the fretting wear of the rack-plane spline couplings consisted primarily of abrasive wear, oxidative wear, and adhesive wear. For both, lubrication and non-lubrication settings, the fretting friction coefficient of 18CrNi4A steel (0.27) fluctuated between 0.12 (dynamic friction coefficient) and 0.35 (static friction coefficient). The fretting-wear results estimated via numerical prediction were consistent with the experimental results. When sm (vibration amplitude) was 20, 35, and 50 µm, the most difference in the fretting wear between the experimental results and numerical estimation was 0.001, 0.0007, and 0.001 mm, respectively. Therefore, the proposed model provides a method for accurate estimation of the fretting-wear. Additionally, the model contributes to the precise design of involute spline couplings in aerospace.

Nonlinear dynamic response analysis on gear-rotor-bearing transmission system

2016 ◽  
Vol 24 (9) ◽  
pp. 1632-1651 ◽  
Author(s):  
Shihua Zhou ◽  
Guiqiu Song ◽  
Mengnan Sun ◽  
Zhaohui Ren
Keyword(s):  
Friction Coefficient ◽  
Friction Force ◽  
Nonlinear Dynamic ◽  
Nonlinear Differential Equations ◽  
Transmission System ◽  
Dynamic Responses ◽  
Response Analysis ◽  
Light Load ◽  
Rotor Bearing ◽  
The Mean

A coupled lateral-torsional nonlinear dynamic model with 16-degree-of-freedom (16-DOF) of gear-rotor-bearing transmission system (GRBTS) is developed after comprehensive considering the nonlinear features associated with time-varying meshing stiffness, backlash, transmission error, friction force, input/output load, gravity and gear eccentricity. Based on the nonlinear differential equations, the coupled multi-body dynamic responses of the GRBTS are demonstrated using the Runge-Kutta numerical method, and the effects of friction coefficient and mean load on the dynamic characteristics are investigated. The results show that the friction force could enlarge the vibration amplitude and affect the low frequency components seriously. The mean load excitation has a complicated influence on the coupled GRBTS, and the torsional vibration is the dominate response. Whereas the mean load excitation has a certain extent vibration suppression, and light load and heavy load could no longer effectively control the nonlinear vibration of the GRBTS. With the increasing of rotational speed, the friction coefficient and mean load ranges of the chaotic behavior widen and the chaotic characteristics strengthens. It is shown that small parameter random perturbation might be propagated in the vibration system and lead to relatively large vibration of the system. The contribution to provide a reference for the design and study of gear system.

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