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General directions in contact modelling development

Maciolka Pawel, Jedrzejewski Jerzy

Journal of Machine Engineering

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2019

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Vol. 19, No. 4

91--109

EN

This paper presents a survey of works, selected from the period of the last twenty years, on deformations in the contact between rough surfaces. All the selected works use FEM. They deal with the modelling of individual contact asperities or the use of experiment to verify contact models. First, research directions connected with the modelling of single asperities, whose shape is usually approximated with that of a hemisphere or a half cylinder, are presented. Section 3 discusses research directions concerning models which include the layer under asperities, and models for small contact surfaces (about 1 mm2). Section 4 reviews directions in contact modelling which takes into account neighbouring asperities and laterally loaded asperities. Section 5 discusses directions in the development of models and experiments used or suitable for verifying models. Finally, conclusions concerning accurate contact deformation modelling are presented.

2

Analysis of worn surfaces by a slicing method

Czifra A., Varadi K., Palasti Kovacs B.

International Journal of Applied Mechanics and Engineering

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2004

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Vol. 9, no spec.

193-198

EN

An algorithm has been developed to characterize the surface microtopography by the analysis of the asperities. The slicing method developed defines as asperities any continuous sets of points located above the slicing plane. Distribution functions were used for characterizing the surface and the asperities and the orientation of the asperities together with their peak angle, peak radius, as well as the ratio of major and minor axes. Our tests were intended to analyze wear processes at the surface by characterizing surface microtopography. In the course of the work, we performed tests of two surfaces generated in the course of dry sliding friction. The method developed properly characterizes worn surfaces and conclusions can be drawn to the contact and wear behavior of the surface by the analysis of microtopography.

3

An asperity based model for friction in mixed lubrication

Robbe-Valloire F., Paffoni B., Progri R., Gras R.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 3

973-992

EN

We propose a model for mixed lubrication between parallel surfaces. We first analyze the microgeometry. We determine a statistical distribution for asperity height and radius. Drawing upon these geometric parameters we identify the main mechanism available on a given asperity where from we deduce the individual normal and friction forces. The five possible mechanisms are iso- or piezo-viscous hydrodynamic, elastohydrodynamic, elastoplastic and full plastic. By association of the results obtained for each asperity, we derive the mechanical behaviour for the entire contact. Several numerical applications are proposed. Theoretical results show the influence of the main contact parameters. They strongly agree with experimental results and theoretically confirm the master curve obtained by plotting the evolution of the friction coefficient versus the _ parameter with respect to a given pair of materials and their microgeometry.