Lubrication and lubricants

Lubrication and lubricants.jpg


1. semester - University of Leeds, UK


Prof. Rob Hewson

Course Points (ECTS)


Contact Information

University of Leeds, UK

Course Material

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Course Overview

Module objectives

The fundamental syllabus goal is to present the students with basic knowledge on tribological contact in mechanical systems in relative motion. The course presents the importance, role and properties of contact surfaces, materials and surroundings. Furthermore, the influence of the components of a tribological system and contact conditions on the properties of friction and tear is explained. The course covers the types and the role of lubricants, as well as their influence on the quality of lubrication, friction, and on various friction and wear mechanics. In relation to these topics, the analytical techniques available for the analysis of surface properties, lubricants, tribological behaviour and wider systems are presented.

Knowledge outcome

The students will be able to independently analyse and evaluate the basic tribological parameters, such as the suitability of materials and surface finish, selection of lubricants and contact loads. They will independently analyse the expected tribological effects and their influence on friction and wear. They will know the basic tools and techniques used to analyse the surfaces and tribological properties of mechanical systems.


Outline syllabus

  • Introduction: definition, topics, course framework, the importance of tribology in mechanical systems and the economical aspects of tribology.
  • Basic characteristics of contact surfaces: geometric surface, real contact surface, Greenwood-Williamson model of contact, plasticity index according to the GW and Whitehouse models, surface roughness (qualitative and quantitative parameters and their influence on tribological properties), topography (Sk, K and other parameters, measurement, influence on tribological properties, values), hardness (physical principle of measurement, influence of creep and friction), toughness (impact on the real contact surface, properties and influence of different materials, influence of plasticity index), influence on the tribological contacts (examples and effects on different materials and components).
  • Basics of tribological contacts: contact types (line, point, elliptical), Hertz contact stresses (derivation, distribution, size, profile stress form), contacts with and without friction (stresses on and under the surface with and without the consideration of friction, the influence of friction on the stress-strain state of the contact, impact on the tribological properties, fatigue...), contact temperature (Archard and Ashby model of contact temperatures, key influences on the tribological properties and the change of materials).
  • Lubricants: types of base oils (mineral, synthetic, biodegradable) and additives (friction modifiers, anti-wear), their role, physically-chemical properties of lubricants (viscosity, viscosity index, pressure-viscosity, temperature-viscosity, thermal properties of lubricants etc.), criteria for the selection of lubricants.
  • Quality of lubrication: Stribeck curve and the basic modes of lubrication (hydrodynamic lubrication, two-dimensional Reynolds equation, solutions for selected cases, elastohydrodinamic lubrication and pressure distribution, influence of viscosity, deformations, mixed lubrication, the influence of surfaces, boundary lubrication), characteristics and the influence on component life.
  • Friction: causes of friction in mechanical systems, rules and exceptions (Amonton, Coulomb), models and influences (contribution of Tabor and Rabinowicz), a modern view on the sources of friction, friction of lubricated contacts, influences, friction of dry contacts and characteristic solid materials for non-lubricated contacts and dry lubricants (graphite, MoS2, polymeric materials…), friction characteristics for different materials.
  • Types of wear and their basic characteristics (sliding and rolling fatigue, delamination theory, formation of wear particles, abrasion, erosion, adhesion, corrosion, oxidation, fretting, cavitation).
  • Basics of damage and surface characterisation: examples of typical surface damages (pitting, galling etc.), types and techniques for the characterisation of surfaces and damages on machine elements, quality of lubrication and lubricants, techniques.

Monitoring of student progress:

  • 1 written and/or oral examination


  • J. A. Williams, Engineering tribology, Oxford University Press, Oxford, 1994. – selected chapters
  • G.W. Stachowiak, A.W. Batchelor, Engineering tribology, Elsevier, Amsterdam, 2005. – selected chapters
  • E.R. Booser, Handbook of lubrication, CRC Press, Boca Raton, 7th ed., 1990. – selected chapters
  • B. Bhushan, Modern Tribology Handbook, CRC Press, Boca Raton, 2001. – selected chapters
  • K. Miyoshi, Y.W. Chung, Surface diagnostics in tribology, World Scientific, Singapore, 1993. – selected chapters