Measured and Predicted Static Friction for Real Rough Surfaces in Point Contact

2012 ◽  
Vol 134 (3) ◽  
Author(s):  
Jose M. García ◽  
Ashlie Martini
Keyword(s):  
Numerical Model ◽  
Yield Strength ◽  
Rough Surface ◽  
Rough Surfaces ◽  
Point Contact ◽  
Surface Profile ◽  
Static Friction ◽  
Cold Hardening ◽  
Quantitative Prediction ◽  
Statistical Parameters

A numerical model to predict static friction for metallic point contacts was developed and validated by comparison to experimental measurements using a specially designed test rig. Key aspects of the numerical model were the incorporation of a digitized real rough surface profile, application of discrete convolution fast Fourier transform (DC-FFT) to predict local asperity interference, and modification of the yield strength to capture the effect of cold hardening. It was found that these model features are critically important to quantitative prediction of static friction. The model significantly underestimated the static friction coefficient if randomly generated surfaces having statistical parameters the same as the measured rough surface were used; digitized real rough surfaces enabled accurate predictions. Further, the model was able to describe the static friction of worn surfaces after cold hardening was introduced through modification of material yield strength. This work illustrates the importance of incorporating the surface features and the change of those features with wear to accurately and reliably predict static friction.

Development of Theoretical Contact Width Formulas and a Numerical Model for Curved Rough Surfaces

2004 ◽  
Author(s):  
Shao Wang
Keyword(s):  
Numerical Model ◽  
Rough Surfaces ◽  
Contact Region ◽  
Roughness Parameter ◽  
Surface Profile ◽  
Root Mean Square Roughness ◽  
Load Parameter ◽  
Contact Parameter ◽  
Equivalent Radius ◽  
Contact Width

The apparent contact area of curved rough surfaces can be larger than that predicted by the Hertz theory due to asperity interaction outside the Hertzian region. In the present study, simple theoretical formulas for the contact semi-width and radius were derived, and a numerical contact model was developed based on an iterative scheme for the elastic deformation of the macroscopic surface profile and the asperity deformation. Both the theoretical formulas and the numerical model are based on a general power-law relationship between the local apparent pressure and real-to-apparent contact ratio. Numerical results of the contact semi-width agree well with the prediction of the formula. The apparent contact region becomes increasingly larger than the Hertzian region as the dimensionless roughness parameter increases, or as the dimensionless load parameter decreases, while the effect of the load exponent is relatively small. The ratio of the contact semi-width to the Hertzian semi-width is mainly determined by a dimensionless contact parameter involving the root-mean-square roughness, the equivalent radius and the Hertzian semi-width or radius. When applied to fractal regular surfaces, the present theory indicates that the influence of the fractal dimension on the contact behavior is due to its effects on both the area-load coefficient and the load exponent.

Periodic Numerical Rough Surface Filtered Generation

2020 ◽  
Vol 143 (8) ◽  
Author(s):  
Runqing Liu ◽  
Tao Tao ◽  
Xuesong Mei
Keyword(s):  
Rough Surface ◽  
Rough Surfaces ◽  
Target Surface ◽  
Statistical Parameters ◽  
Random Surface ◽  
Periodic Surface ◽  
Actual Surface ◽  
Maximum Period ◽  
Good Improvement ◽  
Random Part

Abstract Numerical surface filtered generation is one of the main methods for generating numerical rough surfaces, but when faced with rough surfaces with waviness or large periodicity, traditional filtering methods cannot be implemented well. Because of this, the paper adopts the method of decomposing and synthesizing the maximum period and random part of the periodic rough surface. By decomposing the statistical parameters of the target surface, the statistical parameters of the ideal periodic surface and the random surface are generated, respectively, and then according to the surface parameters generate the surfaces and synthesize them. By comparing the statistical parameters and morphology of the synthesized surface with its actual surface, it can be found that this method can well achieve the generation of periodic rough surfaces, which is a good improvement to the original filter generation method.

Point Contact EHL Based on Optically Measured Three-Dimensional Rough Surfaces

1997 ◽  
Vol 119 (3) ◽  
pp. 375-384 ◽  
Author(s):  
Dong Zhu ◽  
Xiaolan Ai
Keyword(s):  
Rough Surface ◽  
Rough Surfaces ◽  
Three Dimensional ◽  
Point Contact ◽  
Elastohydrodynamic Lubrication ◽  
Peak Height ◽  
Machining Process ◽  
Maximum Pressure ◽  
Pressure Peak ◽  
Surface Profiles

This paper presents a numerical solution for the elastohydrodynamic lubrication in point contacts, using optically measured three-dimensional rough surface profiles as input data. The multi-grid computer program originally developed by Ai and Cheng (1993, 1994) is modified, so that both contacting surfaces can be three-dimensional measured rough surfaces moving at different velocities. Many different engineering surfaces are measured and analyzed in the present study, demonstrating that the numerical analysis is practical for real surfaces of bearings, cams, gears and other components, as long as a significant EHL film still exists. In addition, discussions are given in this paper for the effects of three-dimensional rough surface topography, which is related to machining process. It appears that, for the circular contact cases analyzed, surface roughness texture and orientation do not have a significant effect on the average film thickness, but they do affect the maximum pressure peak height and asperity deformation in the contact zone considerably.

Reconstruction of Real Rough Surface Based on Fractal and the Study on Bolt Assemble Technique

2012 ◽  
Vol 248 ◽  
pp. 426-432 ◽  
Author(s):  
Wei Wang ◽  
Qiang Tang ◽  
Xiao Dong Xu ◽  
Shui Qing Gong ◽  
Xiao Peng Liu
Keyword(s):  
Finite Element ◽  
Rough Surface ◽  
Rough Surfaces ◽  
Surface Profile ◽  
Element Analysis ◽  
Fractal Characteristic ◽  
Fractal Models ◽  
Relationship Model ◽  
Bolt Connection ◽  
2D And 3D

Aiming at the importance of the microcosmic topography of connecting surface and bolt assembling technique to the bolt connection performance, the fractal characteristic of bolt joint rough surface is studied based on the power spectrum of its micro surface profile. Fractal models of 2D and 3D rough surfaces are presented by W-M function and the 2D and 3D bolt joint rough surfaces are reconstructed. Imageware and Pro/e are used to build the bolt connecting model based on the real rough surface presented by W-M function. The preload is imitated by the PREST179 element. The finite element transient analysis is used to imitate the speed and force size of the bolt tightening. The relationship model between tighten speed, preload size and connecting performance whose target is contact stress is presented based on the finite element analysis results. According the model, the single bolt precise assembling technique is obtained.

A Numerical Model for the Contact of Layered Elastic Bodies With Real Rough Surfaces

1992 ◽  
Vol 114 (2) ◽  
pp. 334-340 ◽  
Author(s):  
S. J. Cole ◽  
R. S. Sayles
Keyword(s):  
Numerical Model ◽  
Rough Surfaces ◽  
Surface Profile ◽  
Test Case ◽  
Measuring Instrument ◽  
Profile Data ◽  
Frictionless Contact ◽  
Varying Thickness ◽  
Pressure Distributions ◽  
Elastic Bodies

A numerical model for the two-dimensional dry, frictionless contact of two elastic bodies with real rough surfaces, where one body has a rigidly bonded surface layer, is presented. The model uses surface profile data directly recorded with a stylus measuring instrument and is suitable for use on a microcomputer. Verification of the accuracy of the model by reproduction of test case results is presented. Contact pressure distributions for layers of varying thickness and elastic modulus are presented.

Rubber–Road Contact: Comparison of Physics-Based Theory and Indoor Experiments

2016 ◽  
Vol 44 (3) ◽  
pp. 150-173 ◽  
Author(s):  
Mehran Motamedi ◽  
Saied Taheri ◽  
Corina Sandu
Keyword(s):  
Rough Surface ◽  
Practical Importance ◽  
Surface Profile ◽  
Surface Characteristics ◽  
Mechanical Analysis ◽  
Friction Model ◽  
Rubber Friction ◽  
Optical Profilometer ◽  
Viscoelastic Modulus ◽  
Longitudinal Slip

ABSTRACT For tire designers, rubber friction is a topic of pronounced practical importance. Thus, development of a rubber–road contact model is of great interest. In this research, to predict the effectiveness of the tread compound in a tire as it interacts with the pavement, the physics-based multiscale rubber-friction theories developed by B. Persson and M. Klüppel were studied. The strengths of each method were identified and incorporated into a consolidated model that is more comprehensive and proficient than any single, existing, physics-based approach. In the present work, the friction coefficient was estimated for a summer tire tread compound sliding on sandpaper. The inputs to the model were the fractal properties of the rough surface and the dynamic viscoelastic modulus of rubber. The sandpaper-surface profile was measured accurately using an optical profilometer. Two-dimensional parameterization was performed using one-dimensional profile measurements. The tire tread compound was characterized via dynamic mechanical analysis. To validate the friction model, a laboratory-based, rubber-friction test that could measure the friction between a rubber sample and any arbitrary rough surface was designed and built. The apparatus consisted of a turntable, which can have the surface characteristics of choice, and a rubber wheel in contact with the turntable. The wheel speed, as well as the turntable speed, could be controlled precisely to generate the arbitrary values of longitudinal slip at which the dynamic coefficient of friction was measured. The correlation between the simulation and the experimental results was investigated.

Measurements of the Static Friction Coefficient Between Tin Surfaces and Comparison to a Theoretical Model

2011 ◽  
Vol 133 (3) ◽  
Author(s):  
Rebecca D. Ibrahim Dickey ◽  
Robert L. Jackson ◽  
George T. Flowers
Keyword(s):  
Theoretical Model ◽  
Friction Coefficient ◽  
Human Error ◽  
Surface Profile ◽  
Static Friction ◽  
Quantitative Agreement ◽  
High Plasticity ◽  
Static Friction Coefficient ◽  
Experimental Apparatus ◽  
Rough Surface Contact

A new experimental apparatus is used to measure the static friction between tin surfaces under various loads. After the data is collected it is then compared to an existing theoretical model. The experiment uses the classical physics technique of increasing the incline of a plane and block until the block slides. The angle at the initiation of sliding is used to find the static friction coefficient. The experiment utilizes an automated apparatus to minimize human error. The finite element based statistical rough surface contact model for static friction under full stick by Li, Etsion, and Talke (2010, “Contact Area and Static Friction of Rough Surfaces with High Plasticity Index,” ASME Journal of Tribology, 132(3), p. 031401) is used to make predictions of the friction coefficient using surface profile data from the experiment. Comparison of the computational and experimental methods shows similar qualitative trends, and even some quantitative agreement. After adjusting the results for the possible effect of the native tin oxide film, the theoretical and experimental results can be brought into reasonable qualitative and quantitative agreement.

scholarly journals A Static Friction Model for Unlubricated Contact of Random Rough Surfaces at Micro/Nano Scale

Micromachines ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 368
Author(s):  
Shengguang Zhu ◽  
Liyong Ni
Keyword(s):  
Rough Surfaces ◽  
Static Friction ◽  
Friction Model ◽  
Elastic Contact ◽  
Nano Scale ◽  
Random Rough Surfaces ◽  
Proposed Model ◽  
Dissipation Mechanism ◽  
Rigid Plane ◽  
Contact Situation

A novel static friction model for the unlubricated contact of random rough surfaces at micro/nano scale is presented. This model is based on the energy dissipation mechanism that states that changes in the potential of the surfaces in contact lead to friction. Furthermore, it employs the statistical theory of two nominally flat rough surfaces in contact, which assumes that the contact between the equivalent rough peaks and the rigid flat plane satisfies the condition of interfacial friction. Additionally, it proposes a statistical coefficient of positional correlation that represents the contact situation between the equivalent rough surface and the rigid plane. Finally, this model is compared with the static friction model established by Kogut and Etsion (KE model). The results of the proposed model agree well with those of the KE model in the fully elastic contact zone. For the calculation of dry static friction of rough surfaces in contact, previous models have mainly been based on classical contact mechanics; however, this model introduces the potential barrier theory and statistics to address this and provides a new way to calculate unlubricated friction for rough surfaces in contact.

A Numerical Model for Simulating Liquid Particles Deposition on Surface

2018 ◽  
Author(s):  
Zhenxia Liu ◽  
Fei Zhang ◽  
Zhengang Liu
Keyword(s):  
Particle Size ◽  
Numerical Model ◽  
Particle Deposition ◽  
Surface Profile ◽  
Leading Edge ◽  
Solid Particles ◽  
Liquid Particle ◽  
Aircraft Icing ◽  
Turbine Vane ◽  
Deposition Thickness

The deposition of liquid particles, which may be converted from solid particles due to high temperature gas heating, makes much more harm on turbine vane blades compared to solid particles, since it may block film-cooling holes, worsen the cooling efficiency and aerodynamic performance of the turbine vane blades. Due to the similarity between the deposition of liquid particles on a surface and the icing on a surface, a numerical model for simulating particles deposition was developed based on the Myers icing model, an extension of the Messinger model, which has been applied in predicting aircraft icing or aero-engine icing. Compared to the conventional liquid particle deposition model, the numerical model in this paper considers the heat transfer and the flow of liquid particles during the particles phase transition from liquid state to solid state. In this model, the change of the surface profile due to the particles deposition was also considered, which was implemented with dynamic mesh technique. To test this model, deposition distribution and thickness obtained from the numerical simulations were compared to the experimental results. Additionally, a numerical simulation was conducted for liquid particle deposition on a flat plate. The result showed that the deposition thickness at the leading edge was much larger than that on the upper surface where the deposition appeared mainly at the middle and rear of the plate. The deposition mass and thickness increased with the increasing in the particle size. The effect of the particle size on the deposition thickness was more notable on the upper surface compared to that at the leading edge.

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