Friction Due to Elastic-Plastic Contact of Rough Surfaces

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Half Plane ◽  
Normal Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Tangential Component ◽  
Force Term ◽  
Three Dimensional Model ◽  
Tangential Plane ◽  
Elastic Plastic

A three dimensional model based on CEB elastic-plastic contact leads to the derivation of two force components due to the shoulder-shoulder interaction of the asperities. A normal force component is resulted that upon summation of all possible interactions, in a statistical sense, obtains the normal force between the two surfaces. A second component of asperity force would be along the tangential plane (mean plane). When there is not net applied tangential force the tangential component of force on an asperity due to all its interactions would vanish. Upon impending motion, however, the tangential force can no longer cancel since the existence of a net tangential applied load would disrupt the symmetry of loading in the tangential direction. A three dimensional elastic-plastic model then furnishes a half-plane tangential elastic-plastic force term that would exist when relative movement of one surface on another occurs along an arbitrary axis in the tangential plane. This paper addresses an account of friction due to the elastic-plastic interaction of two surfaces by recognizing that the tangential half-plane elasto-plastic force term is the resisting force when two surfaces in elastic-plastic contact are made to slide.

An Extension of CEB Elastic-Plastic Contact Model

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Contact Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Asperity Contact ◽  
Force Component ◽  
Normal Contact ◽  
Elastic Plastic ◽  
Force Components ◽  
Plastic Parts

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is by developing the equations governing the shoulder-shoulder contact of asperities based on the Chang, Etsion and Bogy (CEB) model of contact in which volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Each force component comprises elastic and elastic-plastic parts. Statistical summation of normal force components leads to the derivation of the normal contact force for the elastic-plastic contact akin to the CEB model. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction.

Closed-Form Equations for Three Dimensional Elastic-Plastic Contact of Nominally Flat Rough Surfaces

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Closed Form ◽  
Contact Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Asperity Contact ◽  
Force Component ◽  
Elastic Plastic ◽  
Functional Forms

Approximate closed-form equations governing the shoulder-shoulder contact of asperities are derived based on a generalization by Chang, Etsion, and Bogy. The work entails the consideration of asperity shoulder-shoulder contact in which the volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact gives rise to a slanted contact force comprising tangential and normal components. Each force component comprises elastic and plastic terms, which upon statistical summation yields the force component for the elastic and plastic forces for the contact of two rough surfaces. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction. Two sets of equations are found. In the first set of equations the functional forms are simpler and provide approximation of contact force to within 9%. The second set is enhanced equations derived from the first set of approximate equations that achieve an accuracy of within 0.2%.

Three Dimensional Elastic-Plastic Contact of Nominally Flat Rough Surfaces: Approximate Closed-Form Equations

2007 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Closed Form ◽  
Contact Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Asperity Contact ◽  
Force Component ◽  
Elastic Plastic ◽  
Form Closure

Approximate closed-form (closure) equations governing the shoulder-shoulder contact of asperities are derived based on a generalization of Chang, Etsion and Bogy (CEB). The work entails the consideration of asperity shoulder-shoulder contact in which volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact gives rise to a slanted contact force comprising tangential and normal components. Each force component comprises elastic and elastic-plastic terms, which upon statistical summation yields the force component for the elastic and elastic-plastic force for the contact of two rough surfaces. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction. Two sets of closure equations are found. In the first set of equations the functional forms are simpler and provide approximation of contact force to within nine percent (9%). The second set of closure equations are closed form equations of more complicated form but with accuracy to within 0.2 percent (0.2%).

Combined Force and Moment in a Three Dimensional Model of Elastic Contact of Nominally Flat Rough Surfaces

2008 ◽  
Author(s):  
A. Sepehri ◽  
K. Farhang
Keyword(s):  
Half Plane ◽  
Contact Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Three Dimensional ◽  
Radius Of Curvature ◽  
Three Dimensional Model ◽  
Tangential Contact ◽  
Applied Forces ◽  
Approximate Equations

In this paper we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment and thereby contact moment is derived. Through this scheme it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force however is shown to be of a much smaller order than the contact normal force. Approximate closed form equations are found for contact force and moment as functions of separation, asperity radius of curvature sum, mean plane slope and nominal contact dimension. The approximate equations are shown to give error within seven percent.

Loading and Unloading Processes in Elastic-Plastic Contact of a Rough Surface With a Flat

2008 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Contact Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Tangential Direction ◽  
Asperity Contact ◽  
Force Component ◽  
Normal Contact ◽  
Elastic Plastic ◽  
Force Components ◽  
Plastic Parts

Three dimensional elastic-plastic contact of two nominally flat rough surfaces is considered. Equations governing the shoulder-shoulder contact of asperities are derived based on the Chang, Etsion and Bogy (CEB) model of contact in which volume conservation is assumed in the plastic flow regime. Shoulder-shoulder asperity contact yields a slanted contact force consisting of both tangential (parallel to mean plane) and normal components. Each force component comprises elastic and elastic-plastic parts. Statistical summation of normal force components leads to the derivation of the normal contact force for the elastic-plastic contact akin to the CEB model. Half-plane tangential force due to elastic-plastic contact is derived through the statistical summation of tangential force component along an arbitrary tangential direction.

An Analytical Solution for Three-Dimensional Elliptical Elastic-Plastic Rolling Contact

2014 ◽  
Vol 658 ◽  
pp. 207-212
Author(s):  
Gabriel Popescu
Keyword(s):  
Residual Stresses ◽  
Yield Criterion ◽  
Tangential Force ◽  
Rolling Direction ◽  
Three Dimensional ◽  
Rolling Contact ◽  
Material Behavior ◽  
Hertzian Contact ◽  
Plastic Behavior ◽  
Elastic Plastic

An analytical three-dimensional elastic-plastic over-rolling solution is used to evaluate the plastic strains and residual stresses. Central to this plastic contact formulation is the incremental approach to deal with non-linear material behavior. The Prandtl-Reuss constitutive equations in conjunction with Huber-Mises-Hencky yield criterion and Ramberg-Osgood strain-hardening relationships are applied to describe the plastic behavior of common hardened bearing steel. The model was extended to include the tangential force in the rolling direction, assumed to be proportional to the hertzian contact pressure. Comparisons of three-dimensional pure rolling and rolling/sliding contact results were provided to elucidate the differences in residual stresses and residual profiles in case of kinematic and work-hardening materials.

Influence of Lined Pipe Fabrication on Liner Wrinkling

2019 ◽  
Author(s):  
Ilias Gavriilidis ◽  
Spyros A. Karamanos
Keyword(s):  
Plastic Material ◽  
Numerical Models ◽  
Three Dimensional ◽  
Local Buckling ◽  
Short Wave ◽  
Dimensional Model ◽  
Three Dimensional Model ◽  
Imperfection Sensitivity ◽  
Elastic Plastic ◽  
Outer Pipe

Abstract An economical method to protect offshore pipelines against corrosive ingredients of hydrocarbons is a double-walled (also called “lined” or “bi-metallic”) pipe, in which a thick-walled low-alloy carbon steel (“outer pipe”) is lined internally with a thin layer (“liner pipe”) from a corrosion resistant alloy material. During the deep-water installation, a lined pipe is subjected to severe plastic loading, which may result in detachment of the liner pipe from the outer pipe forming short-wave wrinkles, followed by local buckling. In the current study, alternative lined pipe manufacturing processes are investigated, including elastic, plastic hydraulic and thermo-hydraulic expansion of the outer pipe, for different initial gaps between the two pipes. The problem is solved numerically, accounting for geometric non-linearities, local buckling phenomena and elastic-plastic material behaviour for both the liner and outer pipe. Two types of numerical models are developed, a quasi-two-dimensional model, examining the mechanical bonding between the pipes, and a three-dimensional model, repeating the manufacturing process and investigating its effect on the mechanical behaviour of a lined pipe subjected to monotonic bending. In addition, the influence of initial geometric imperfections on liner pipe buckling is investigated, showing the imperfection sensitivity of the lined pipe bending behaviour, for each fabrication process.

Subjective scaling of smooth surface friction

1996 ◽  
Vol 75 (5) ◽  
pp. 1957-1962 ◽  
Author(s):  
A. M. Smith ◽  
S. H. Scott
Keyword(s):  
Smooth Surface ◽  
Normal Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Correlation Coefficients ◽  
Surface Friction ◽  
Flat Surfaces ◽  
Coated Glass ◽  
The Mean ◽  
Relative Differences

1. Six men and four women, 30-51 yr of age, were asked to use the tip of the washed and dried index finger to stroke six different featureless, flat surfaces mounted on a three-dimensional force platform. The six surfaces were rosin-coated glass, glass, satin-finished aluminum, poly-vinyl chloride (PVC) plastic, Teflon, and nyloprint (polyamide plastic). The subjects were requested to indicate where the sensation produced by each surface should be placed on an unidimensional scale represented by an 18cm line labeled at one end by the words "most slippery" and at the other end by the words "most sticky." The coefficients of friction for each surface and for each subject were subsequently assessed by asking each subject to stroke the surfaces as if they were assessing its slipperiness for 5 s. 2. The finger forces normal and tangential to the stroked surfaces were digitized at 250 Hz and stored on a laboratory computer. The ratio of the mean tangential force to the mean perpendicular force during stroking was used to calculate the mean coefficient of kinetic friction. The mean friction for all subjects ranged from 0.43 for the nyloprint surface to 2.79 for the rosin-coated glass. Correlation coefficients calculated between the subjective estimates of friction and the measured coefficients of friction for each subject individually resulted in a mean correlation of 0.85 (n = 10, P < 0.001). 3. These data indicate that subjects can accurately scale relative differences in the friction of macroscopically smooth, flat surfaces, by modulating the tangential force applied to the finger while keeping the normal force relatively constant. The fact that subjects maintained a relatively constant normal force and instead varied the tangential force across different surfaces suggests that receptors sensitive to these tangential forces are important in the perception of smooth surface friction.

scholarly journals Numerical Investigation the Effect of the Different Tip Vanes on the Loading of an H-VAWT

2018 ◽  
Vol 53 ◽  
pp. 03041 ◽  
Author(s):  
Li Shoutu ◽  
Wang Yin ◽  
Yang Congxin ◽  
Li Ye
Keyword(s):  
Normal Force ◽  
Tangential Force ◽  
Three Dimensional ◽  
Fatigue Loading ◽  
Simulation Method ◽  
Power Coefficient ◽  
Speed Ratio ◽  
Force Coefficient ◽  
Average Value ◽  
Unsteady Numerical Simulation

In this paper, the effect of the three typical tip vanes on the loading of an H-VAWT is investigated by employing the three-dimensional unsteady numerical simulation method. The results show that the both transient tangential force coefficient (CT) and normal force coefficient (Cn) have obvious change when the winglet and the V type vane is used at the blade's tip, respectively. However, in three tip vanes, the CT average value is the lowest and the CT fluctuation characteristic is the highest when the winglet is used. Although the winglet and V type vane contribute to change the transient CT and Cn, the normal force is increased too, it results in increasing fatigue loading and decreasing lifetime for H-VAWT. By comparison, the effect of the plate vane on the loading is weaker. Additionally, the winglet is advantage to improve power coefficient in the low tip speed ratio.

scholarly journals Closed-Form Equations for Contact Force and Moment in Elastic Contact of Rough Surfaces

2011 ◽  
Vol 2011 ◽  
pp. 1-14 ◽  
Author(s):  
Ali Sepehri ◽  
Kambiz Farhang
Keyword(s):  
Closed Form ◽  
Half Plane ◽  
Contact Force ◽  
Normal Force ◽  
Rough Surfaces ◽  
Tangential Force ◽  
Compressive Load ◽  
Angular Misalignment ◽  
Tangential Contact ◽  
Applied Forces

It is reasonable to expect that, when two nominally flat rough surfaces are brought into contact by an applied resultant force, they must support, in addition to the compressive load, an induced moment. The existence of a net applied moment would imply noneven distribution of contact force so that there are more asperities in contact over one region of the nominal area. In this paper, we consider the contact between two rectangular rough surfaces that provide normal and tangential contact force as well as contact moment to counteract the net moment imposed by the applied forces. The surfaces are permitted to develop slight angular misalignment, and thereby contact moment is derived. Through this scheme, it is possible to also define elastic contribution to friction since the half-plane tangential contact force on one side of an asperity is no longer balanced by the half-plane tangential force component on the opposite side. The elastic friction force, however, is shown to be of a much smaller order than the contact normal force. Approximate closed-form equations are found for contact force and moment for the contact of rough surfaces.

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