Static Friction Coefficient Model for Metallic Rough Surfaces

1988 ◽  
Vol 110 (1) ◽  
pp. 57-63 ◽  
Author(s):  
W. R. Chang ◽  
I. Etsion ◽  
D. B. Bogy
Keyword(s):  
Friction Coefficient ◽  
Surface Topography ◽  
Material Properties ◽  
Adhesion Force ◽  
Rough Surfaces ◽  
Static Friction ◽  
External Loading ◽  
Height Distribution ◽  
Static Friction Coefficient ◽  
Shear Interface

The friction force required to shear interface bonds of contacting metallic rough surfaces is calculated, taking into account the prestress condition of contacting asperities. The surfaces are modeled by a collection of spherical asperities with Gaussian height distribution. Previous analyses for adhesion force and contact load of such surfaces are used to obtain the static friction coefficient. It is shown that this coefficient is affected by material properties and surface topography, and that it actually depends on the external loading contrary to the classical law of friction.

A Model for Contact and Static Friction of Nominally Flat Rough Surfaces Under Full Stick Contact Condition

2008 ◽  
Vol 130 (3) ◽  
Author(s):  
D. Cohen ◽  
Y. Kligerman ◽  
I. Etsion
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Friction Force ◽  
Contact Area ◽  
Rough Surfaces ◽  
Normal Load ◽  
Static Friction ◽  
Contact Condition ◽  
Maximum Friction ◽  
Static Friction Coefficient

A model for elastic-plastic nominally flat contacting rough surfaces under combined normal and tangential loading with full stick contact condition is presented. The model incorporates an accurate finite element analysis for contact and sliding inception of a single elastic-plastic asperity in a statistical representation of surface roughness. It includes the effect of junction growth and treats the sliding inception as a failure mechanism, which is characterized by loss of tangential stiffness. A comparison between the present model and a previously published friction model shows that the latter severely underestimates the maximum friction force by up to three orders of magnitude. Strong effects of the normal load, nominal contact area, mechanical properties, and surface roughness on the static friction coefficient are found, in breach of the classical laws of friction. Empirical equations for the maximum friction force, static friction coefficient, real contact area due to the normal load alone and at sliding inception as functions of the normal load, material properties, and surface roughness are presented and compared with some limited available experimental results.

A Static Friction Model for Elastic-Plastic Contacting Rough Surfaces

2004 ◽  
Vol 126 (1) ◽  
pp. 34-40 ◽  
Author(s):  
Lior Kogut ◽  
Izhak Etsion
Keyword(s):  
Friction Coefficient ◽  
Rough Surfaces ◽  
Static Friction ◽  
Friction Model ◽  
Plasticity Index ◽  
High Plasticity ◽  
Elastic Plastic ◽  
Static Friction Coefficient ◽  
Contact Adhesion ◽  
Limiting Case

A model that predicts the static friction for elastic-plastic contact of rough surfaces is presented. The model incorporates the results of accurate finite element analyses for the elastic-plastic contact, adhesion and sliding inception of a single asperity in a statistical representation of surface roughness. The model shows strong effect of the external force and nominal contact area on the static friction coefficient in contrast to the classical laws of friction. It also shows that the main dimensionless parameters affecting the static friction coefficient are the plasticity index and adhesion parameter. The effect of adhesion on the static friction is discussed and found to be negligible at plasticity index values larger than 2. It is shown that the classical laws of friction are a limiting case of the present more general solution and are adequate only for high plasticity index and negligible adhesion. Some potential limitations of the present model are also discussed pointing to possible improvements. A comparison of the present results with those obtained from an approximate CEB friction model shows substantial differences, with the latter severely underestimating the static friction coefficient.

Application of Elastic-Plastic Static Friction Model to Rough Surface With Asymmetric Asperity Distribution

2008 ◽  
Author(s):  
Chul-Hee Lee ◽  
Andreas A. Polycarpou
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Static Friction ◽  
Friction Model ◽  
Experimental Measurements ◽  
Height Distribution ◽  
Elastic Plastic ◽  
Static Friction Coefficient ◽  
Non Gaussian ◽  
Asperity Distribution

The asymmetric height distribution in surface roughness is usually indispensable in engineering surfaces prepared by specific manufacturing process. Moreover, the running-in process develops severe asymmetric roughness distribution in the surface interfaces. In this paper, the effect of asymmetric asperity distribution on static friction coefficient is investigated theoretically and by comparing it with experimental results. In order to generate a probability density function of non-Gaussian surface roughness, the Pearson system of frequency curves was used. Subsequently, the Kogut and Etsion (KE) model of elastic-plastic static friction was modified to calculate the contacting interfacial forces. For the experiments, actual roller and housing surfaces from a CV (Constant Velocity) joint were prepared to measure the static friction coefficient as it clearly shows the asymmetry of roughness distribution due to the manufacturing and also running-in process. The experimental measurements were subsequently compared with the modified KE static friction model with Gaussian as well as Pearson distributions of asperity heights. It was found that the model with Pearson distribution captures the experimental measurements well in terms of the surface conditions.

Static Friction Modeling in the Presence of Soft Thin Metallic Films

2001 ◽  
Vol 124 (1) ◽  
pp. 27-35 ◽  
Author(s):  
Zhiqiang Liu ◽  
Anne Neville ◽  
R. L. Reuben
Keyword(s):  
Thin Film ◽  
Surface Roughness ◽  
Friction Coefficient ◽  
Film Thickness ◽  
Rough Surfaces ◽  
Contact Stiffness ◽  
Surface Film ◽  
Static Friction ◽  
Static Friction Coefficient ◽  
Light Load

A numerical model is presented for computing the static friction coefficient of rough surfaces with a soft thin film. In the calculation, an improved model, based on that due to Derjaguin et al., is used in conjunction with an elastic-plastic contact model for contact with a soft coating. The effects of the film thickness and surface roughness on the static friction coefficient and contact are investigated. The numerical results reflect published experimental observations and show the static friction coefficient depends strongly on surface film thickness, external force and surface roughness. The static friction coefficient (μ) increases with the surface film thickness when the plasticity index ψ⩾0.5 whilst μ increases with decreasing film thickness in the very thin film regime when ψ=0.25 and F/AnE<10−4. For real rough surfaces, contact and friction behavior is probably heavily influenced by the existence of such soft, thin surface films, which increase the contact area due to plastic deformation of the film and the contact stiffness of the surface in the case of thin film and light load.

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 Brittle Fracture Theory Describes the Onset of Frictional Motion

2019 ◽  
Vol 10 (1) ◽  
pp. 253-273 ◽  
Author(s):  
Ilya Svetlizky ◽  
Elsa Bayart ◽  
Jay Fineberg
Keyword(s):  
Friction Coefficient ◽  
Brittle Fracture ◽  
Static Friction ◽  
Quantitative Agreement ◽  
Interface Fracture ◽  
Earthquake Dynamics ◽  
Rupture Dynamics ◽  
Static Friction Coefficient ◽  
Fracture Theory ◽  
Macroscopic Motion

Contacting bodies subjected to sufficiently large applied shear will undergo frictional sliding. The onset of this motion is mediated by dynamically propagating fronts, akin to earthquakes, that rupture the discrete contacts that form the interface separating the bodies. Macroscopic motion commences only after these ruptures have traversed the entire interface. Comparison of measured rupture dynamics with the detailed predictions of fracture mechanics reveals that the propagation dynamics, dissipative properties, radiation, and arrest of these “laboratory earthquakes” are in excellent quantitative agreement with the predictions of the theory of brittle fracture. Thus, interface fracture replaces the idea of a characteristic static friction coefficient as a description of the onset of friction. This fracture-based description of friction additionally provides a fundamental description of earthquake dynamics and arrest.

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