Investigation and modelling of rubber stationary friction on rough surfaces [Elektronische Ressource] / von André Le Gal

André Le Gal

Informations

• Publié par: gottfried_wilhelm_leibniz_universitat_hannover
• Publié le: 01 janvier 2007
• Nombre de lectures: 37
• Langue: English
• Poids de l'ouvrage: 5 Mo

Extrait

Investigation and Modelling of Rubber
Stationary Friction on Rough Surfaces








Von der Fakultät für Maschinenbau
der Gottfried Wilhelm Leibniz Universität Hannover
zur Erlangung des akademischen Grades
Doktor-Ingenieur
genehmigte




Dissertation



von
Dipl.-Ing. André Le Gal
geb. am 09. Oktober 1978 in Ploemeur (F)




2007


































Vorsitzender: Prof. Dr.-Ing. B.-A. Behrens
1. Referent: Prof. Dr.-Ing. G. Poll
2. Referent: g. J. Wallaschek
3. Referent: Prof. Dr. R. H. Schuster

Tag der Promotion: 17.08.2007

Acknowledgment


The following work has been carried out during my activity as research associate at the
Deutsches Institut für Kautschuktechnologie (D.I.K.) between 2002 and 2006 in Hannover.

I would like to express my sincere gratitude to my thesis supervisor, Prof. Dr.-Ing. G. Poll, for
his guidance throughout the course of my PhD.

I would like to thank Prof. Dr. R.H. Schuster for giving me the opportunity to carry out my
PhD at the D.I.K. and being part of the commission as well as Prof. Dr.-Ing. B.-A. Behrens
and Prof. Dr.-Ing. J. Wallaschek for their participation as commission members.

I warmly thank Dr. M. Klüppel for the fruitful collaboration during the last four years and his
encouragements to accomplish this work. Also, I am grateful to Prof. Dr. G. Heinrich and Dr.
T. Alshuth for introducing me into rubber technology and the fascinating field of elastomer
physics.

I wish to express my sincere thank to my predecessors at the D.I.K. for their guidance during
the firsts steps of this work: Dr. J. Meier, Dr. F. Abraham, A. Müller and Dr. M. Säwe. During
this work, I have collaborated with many colleagues from the D.I.K. and the University of
Hanover for whom I have great regards for their support at some stages and I wish to extend
my thanks to all those who have helped, in particular within the Material Modelling and
Concepts department.

A special thank is due to Dr. L. Guy from Rhodia for fruitful discussions on wet grip of tyres –
and rugby – as well as his decisive contribution regarding the two-scaling-regimes approach
for the modelling of hysteresis friction.

The financial support of the Deutsche Kautschuk-Gesellschaft (DKG), Deutsche Forschung-
Gesellschaft (DFG Forschergruppe: “Dynamische Kontaktprobleme mit Reibung bei
Elastomeren“) is gratefully acknowledged.

My special gratitude is due to my family for their loving support, in particular my mother for
thher 50 birthday this year.

I owe my loving thanks to my wife Eva Peregi for her constant encouragement and
understanding during the accomplishment of this work.


Abstract


This work deals with the investigation and modelling of rubber stationary sliding friction on
rough surfaces. Through a novel physically motivated approach of dynamic contact problems,
new insights in the understanding of rubber friction are achieved. This is of high interest for
materials developers and road constructors regarding the prediction of wet grip performance
of tyres on road tracks.

Improvements of contact mechanics are proposed within the frame of a generalized
Greenwood-Williamson theory for rigid/soft frictional pairings. The self-affine character of
rough surfaces leads to a multi-scale excitation of rubber during sliding process and the
resulting hysteresis friction arises from material losses integrated over a range of frequencies.
Beside a complete analytical formulation of contact parameters, the morphology of
macrotexture is considered via the introduction of a second scaling range at large length
scales, leading to a finer description of length scales that mostly contribute to hysteresis
friction. On the other side, adhesion friction is related to the real area of contact and the
interfacial shear strength which illustrates the kinetics of peeling effects distributed within the
contact area at small length scales. This confirms well-known viscoelastic features exhibited
by hysteresis and adhesion friction of elastomers on rough surfaces. The high frequency
viscoelastic properties of filled elastomers are estimated by combining relaxation
spectroscopy methods. As a result, a generalized master procedure is proposed for filled
composites based on thermally activated processes of the bound rubber at the vicinity of filler
particles above the glass transition temperature.

Friction investigations carried out under defined conditions show the relevance of hysteresis
and adhesion concepts on rough surfaces. In particular, the use of a tenside as lubricant
allows a quantitative measurement of both components. The model leads to satisfying
correlations with friction results within the range of low sliding velocities with a significant
improvement through the introduction of a second scaling range. In particular, the influence of
polymer and filler type can be fairly well understood. Finally, the dynamic indentation
behaviour of elastomers appears to be a promising route for further improvements in the
modelling of rubber sliding friction.


Keywords: Rubber friction, self-affine surfaces, contact mechanics
Kurzfassung


Im Rahmen dieser Arbeit werden die Reibeigenschaften von Elastomeren auf rauen
Oberflächen auf Basis einer physikalisch motivierten Modellierung der Hysterese- und
Adhäsionsanteile untersucht. Dabei wurde die Bedeutung der mikro- und makroskopischen
Rauigkeiten der Reibflächen für den Reibkontakt und damit zusammenhängende Adhäsions-
und Reibungsphänomene auf makroskopischer Längenskala aufgeklärt. Dies soll die
Entwicklung neuer Materialien mit optimierten Reibeigenschaften unterstützen.

Experimentell wurden die Reibwerte bei unterschiedlichen Kontaktbedingungen im Bereich
kleiner Geschwindigkeiten charakterisiert. Die Untersuchungen an den Modellsystemen
haben gezeigt, dass die entwickelten Modelle zur Hysterese- und Adhäsionsreibung von
Elastomeren auf rauen, selbst-affinen Oberflächen eine gute Beschreibung der
experimentellen Reibdaten erlauben. Die Hysteresereibung spiegelt die Reibexperimente mit
Seifenwasser als Lubrikant gut wider, da hier die Adhäsion durch einen tensid-stabilisierten
Wasserfilm eliminiert wird. Die Trockenreibung lässt sich gut als Summe von Hysterese- und
Adhäsionsreibung beschreiben, wobei der Adhäsionsanteil aus der wahren Kontaktfläche
kombiniert mit der Grenzflächenspannung resultiert. Dadurch können typische Polymer- und
Füllstoffeffekte auf die Reibeigenschaften vorhergesagt und physikalisch verstanden werden.
Für weitere Entwicklungen des Modells stellt das dynamische Indentationsverhalten von
Elastomeren einen interessanten Weg dar.


Stichworte: Gummireibung, selbst-affine Oberfläche, Kontaktmechanik


Table of content

1. Introduction and motivation.....................................................................................1
2. Background of rubber friction..................................................................................5
2.1 General properties of elastomers ...........................................................................5
2.1.1 Introduction.............................................................................................................5
2.1.2 Linear Viscoelascity................................................................................................8
2.1.3 Influence of filler....................................................................................................10
2.1.4 Time temperature superposition principle.............................................................11
2.2 Friction properties of elastomers ..........................................................................15
2.2.1 Physical mechanisms contributing to rubber friction.............................................15
2.2.2 Rubber friction on smooth surfaces......................................................................17
2.2.3 Rubber friction on rough surfaces.........................................................................20
2.2.4 Effects of lubricants ..............................................................................................22
2.3 Relation to tyre performance ................................................................................24
3. Modelling of rubber friction on rough surfaces......................................................28
3.1 Modelling of non-sliding contact ...........................................................................28
3.1.1 Theory of Hertz.....................................................................................................28
3.1.2 Consideration of interfacial effects..............................