Vibrational Smoothing in Systems with Dynamic Friction

AbstractDynamic friction occurs not only between two contact objects sliding against each other, but also between two relative sliding surfaces several nanometres apart. Many emerging micro- and nano-mechanical systems that promise new applications in sensors or information technology may suffer or benefit from noncontact friction. Herein we demonstrate the distance-dependent friction energy dissipation between the tip and the heterogeneous polymers by the bimodal atomic force microscopy (AFM) method driving the second order flexural and the first order torsional vibration simultaneously. The pull-in problem caused by the attractive force is avoided, and the friction dissipation can be imaged near the surface. The friction dissipation coefficient concept is proposed and three different contact states are determined from phase and energy dissipation curves. Image contrast is enhanced in the intermediate setpoint region. The work offers an effective method for directly detecting the friction dissipation and high resolution images, which overcomes the disadvantages of existing methods such as contact mode AFM or other contact friction and wear measuring instruments.

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A Simple Mechanistic Model for Friction of Rough Partially Lubricated Surfaces

Tribology Letters ◽

10.1007/s11249-021-01467-1 ◽

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.

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Sensitivity analysis of the influence of particle dynamic friction, rolling resistance and volume/shear work ratio on wear loss and friction force using DEM model of dry sand rubber wheel test

Tribology International ◽

10.1016/j.triboint.2021.106853 ◽

2021 ◽

pp. 106853

Author(s):

Egidijus Katinas ◽

Rostislav Chotěborský ◽

Miloslav Linda ◽

Jiři Kuře

Keyword(s):

Sensitivity Analysis ◽

Friction Force ◽

Rolling Resistance ◽

Wear Loss ◽

Particle Dynamic ◽

Dynamic Friction ◽

Dry Sand ◽

Dem Model

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Study on Friction in Automotive Shock Absorbers Part 1: Friction Simulation Using a Dynamic Friction Model in the Contact Zone of an FEM Model

Vehicles ◽

10.3390/vehicles3020014 ◽

2021 ◽

Vol 3 (2) ◽

pp. 212-232

Author(s):

Ludwig Herzog ◽

Klaus Augsburg

Keyword(s):

Ride Comfort ◽

Viscous Friction ◽

Simulation Method ◽

Friction Model ◽

Model Parameters ◽

Dynamic Friction ◽

Friction Modeling ◽

Shock Absorbers ◽

Operation Conditions ◽

Wide Range

The important change in the transition from partial to high automation is that a vehicle can drive autonomously, without active human involvement. This fact increases the current requirements regarding ride comfort and dictates new challenges for automotive shock absorbers. There exist two common types of automotive shock absorber with two friction types: The intended viscous friction dissipates the chassis vibrations, while the unwanted solid body friction is generated by the rubbing of the damper’s seals and guides during actuation. The latter so-called static friction impairs ride comfort and demands appropriate friction modeling for the control of adaptive or active suspension systems. In this article, a simulation approach is introduced to model damper friction based on the most friction-relevant parameters. Since damper friction is highly dependent on geometry, which can vary widely, three-dimensional (3D) structural FEM is used to determine the deformations of the damper parts resulting from mounting and varying operation conditions. In the respective contact zones, a dynamic friction model is applied and parameterized based on the single friction point measurements. Subsequent to the parameterization of the overall friction model with geometry data, operation conditions, material properties and friction model parameters, single friction point simulations are performed, analyzed and validated against single friction point measurements. It is shown that this simulation method allows for friction prediction with high accuracy. Consequently, its application enables a wide range of parameters relevant to damper friction to be investigated with significantly increased development efficiency.

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Boundary and Mixed Friction in the Presence of Dynamic Normal Loads: Part I—System Model

Journal of Tribology ◽

10.1115/1.2831239 ◽

1995 ◽

Vol 117 (2) ◽

pp. 255-260 ◽

Cited By ~ 21

Author(s):

Andreas A. Polycarpou ◽

Andres Soom

Keyword(s):

Important Variable ◽

Friction Model ◽

System Model ◽

Dynamic Friction ◽

Discrete Elements ◽

Friction Forces ◽

Contact Compliance ◽

Stiffness Characteristics ◽

Nonlinear Normal ◽

Linearized Model

The instantaneous normal motion between bodies in a sliding contact is an important variable in determining dynamic friction under unsteady sliding conditions. In order to model friction under dynamic conditions, it is therefore necessary to combine a dynamic model of the sliding system with an accurate model of the friction process. In the present work, the nonlinear normal dynamics of a friction test apparatus are described by a linearized model at a particular steady loading and sliding condition in a mixed or boundary-lubricated regime. The geometry is a line contact. The Hertzian bulk contact compliance and film and asperity damping and stiffness characteristics are included as discrete elements. In Part I of the paper, a fifth-order model is developed for the normal dynamics of the system, using both the Eigensystem Realization Algorithm (ERA) and classical experimental modal analysis techniques. In Part II, this system model is combined with a friction model, developed independently, to describe dynamic friction forces under both harmonic and impulsive applied normal loads.

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PREDICATION FOR RELATIVE MOTION OF THE COLONOSCOPE IN COLONOSCOPY

Journal of Mechanics in Medicine and Biology ◽

10.1142/s0219519413500231 ◽

2013 ◽

Vol 13 (03) ◽

pp. 1350023 ◽

Cited By ~ 1

Author(s):

WU BIN CHENG ◽

MICHAEL A. J. MOSER ◽

SIVARUBAN KANAGARATNAM ◽

WEN JUN ZHANG

Keyword(s):

Frictional Force ◽

Frictional Contact ◽

Linear Complementarity ◽

Intestinal Wall ◽

Deformable Objects ◽

Dynamic Friction ◽

Unilateral Constraints ◽

Common Procedure ◽

Mechanical Compliance ◽

Signorini's Problem

Colonoscopy is common procedure frequently carried out. It is not without its problems, which include looping formation. Looping formation prevents the tip of the colonoscope itself from advancing, thus further probing induces a risk of perforation, significant patient discomfort, and failure of colonoscopy. During colonoscopy, the manipulated colonoscope for intubation in the colon goes through the friction between the colonoscope and the colon. Due to major frictional force, the sigmoidal colon forms looping with the scope during intubation. The interactive frictional force between the colon and the colonoscope is highly complex because of frictional contact between two deformable objects. In this paper, contact force computation was formulated into a linear complementarity problem (LCP) by linearizing Signorini's problem, which was adapted into non-interpenetration with unilateral constraints. Frictional force was computed by the mechanical compliance of finite element method (FEM) models with the consideration of dynamic friction between the colonoscope and the intestinal wall. Furthermore, we presented a mathematical model of the elongation of the colon that predicts the motion of scope relative to the intestinal wall in colonoscopy.

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