This document provides an introduction to the basics of tribology, which is the study of friction, lubrication, and wear between surfaces in contact. It discusses how tribology encompasses many fields of engineering and industry. Surfaces in contact are not flat and have roughness at multiple scales, from nanometers to centimeters. Both the physical roughness and chemical properties of surfaces need to be considered in tribology as they influence contact area, stresses, lubrication, and compatibility. A variety of methods can characterize surface properties. Understanding surfaces is fundamental to tribology as the interaction between surface asperities dictates tribological forces.

1. Introduction to the Basics of
Tribology
Lec. 1
Dr. Ameer Ali Kamel

2. Outline
•
•
•
Origin/Definition of “Tribology”
Encompassing Fields
Fundamentals of Tribology:
(T
erm and Field)
•
•
•
•
Surfaces in Contact
Friction
Lubrication
Wear
•
•
Concluding Words
Upcoming Topics in Series

3. What is Tribology ?
• Tribology comes from the Greek word, “tribos”,
meaning “rubbing” or “to rub”
• And from the suffix, “ology” means “the study of”
• Therefore, Tribology is the study of rubbing,
or… “the study of things that rub”.
• This includes the fields of:
•
•
•
Friction,
Lubrication, and
Wear.

4. “Tribology” is a new word…
• Coined by Dr. H. Peter
1966
Jost in England in
• “The Jost Report”, provided to the British Parliament –
Ministry for Education and Science, indicated… “Potential
savings of over £515 million per
industry by better application of
practices.”
year ($800 million) for
tribological principles and
But…
Tribology is not a new field!

5. The First Recorded Tribologist – 2400 B.C.
Figure taken from
“History of Tribology”,
by Duncan Dowson.
Transporting the statue of Ti – from a tomb at Saqqara, Egypt

6. The First Recorded Tribologist – 2400 B.C.
Transporting the statue of Ti – from a tomb at Saqqara, Egypt

7. The First Recorded Tribologist – 2400 B.C.
The first recorded tribologist – pouring lubricant (water?)
in front of the sledge in the transport of the statue of Ti.

8. A more famous Tribologist – 500 years ago
Leonardo Da Vinci
Ball Bearing
4-Ball T
est Geometry
Sled Friction T
est
Geometry

9. A more famous Tribologist – 500 years ago
ASTM D1894 – Static
and Kinetic COFs of
Plastic Film & Sheeting
Leonardo Da Vinci
ASTM D5183 - COF
ASTM D2266, D2596 – EP
ASTM D4172, D2783 - Wear
Ball Bearing
4-Ball T
est Geometry
Sled Friction T
est
Geometry

10. A more famous Tribologist – 500 years ago
ASTM D1894 – Static
and Kinetic COFs of
Plastic Film & Sheeting
Leonardo Da Vinci
Two Observations:
1. The areas in contact have no effect on
friction.
If the load of an object is doubled, its
friction will also be doubled.
2. ASTM D5183 - COF
ASTM D2266, D2596 – EP
ASTM D4172, D2783 - Wear
Ball Bearing
4-Ball T
est Geometry
Sled Friction T
est
Geometry

11. Tribology 101 - Basics
Applications and Fields which
Encompass Modern Tribology

12. Tribology is All Around Us,
In Applications from Simple to Complex
and Scales from Small to Large
• Individual Components
• Assemblies or Products
• Manufacturing Processes
• Construction/Exploration
• Natural Phenomena

13. Individual Components
Gears
Brake & Clutch Pads
Bearings

14. Assemblies or Products
Rock Climbing
Shoes
Pocket Watch
Engines
Curling Stones

15. Manufacturing Processes
Turning
Rolling
Stamping Grinding/Polishing

16. Construction/Exploration
Mine Slurry Pumps
Oil Drilling Rig
Excavator
Chunnel Digging Drill Space Shuttle

17. Natural Phenomena
Wear
Erosion
Friction
Wind Erosion
Water
Super-
hydrophobicity:
On/Off Stiction:
Gecko Feet
Lotus Leaf
Plate T
ectonics

18. Tribology 101 - Basics
In Parallel to these different Scales,
There are Many Areas of
Engineering and Industry which
have a Need to Use/Understand Tribology

19. Tribology is
Engineering
also
and
in Virtually every Area of
Industry
•
•
•
Aerospace
Agriculture
Automotive
•
•
•
•
Fabric/Clothing
Flooring
Food Processing
Highway/Transportation
Depts.
Lubricant Manufacturers
Medical Diagnostics
Medical Implants
Military
Pharmaceutical
Shoe Manufacturers
Sports Equipment Companies
Universities/Educators
• Engine: Piston ring/cylinder,
Bearings, valve seats, injectors
Brakes/clutch
Tooling/Machining/Sheet metal
forming
•
• •
•
•
•
•
•
•
•
• Coatings Providers
•
•
Low Friction
Wear Resistant
• Thin Films or Hardfacings
•
•
•
Cosmetics/Personal
Dental Implants
Energy
Care
•
•
•
•
Nuclear
Wind
Fossil
Solar
•
•
•
•
Mechanical Engineering
Materials Science Engineering
Physics
Chemistry

20. Commonality in Tribology
What do All These Diverse Fields
and Applications have in Common?
What do we need to think about as
engineers and scientists when we
design products or friction/wear
experiments?

21. Commonality…
Every Application has:
Surfaces in Contact, and
in Relative Motion
(e.g. sliding, rolling, impacting)

22. Tribology Basics - Surfaces in Contact
So let’s begin by looking
closely at a surface…

23. The Surface is not Simple…
Lubricant
Adsorbed
Contaminants
Oxide
Surface Properties
“Disturbed Material”
Bulk Material
Properties –
“Handbook
values”

24. The Surface is not Simple…
Lubricant
Adsorbed
Contaminants
Oxide
nms - µms
Surface Properties
“Disturbed Material”
≈
Bulk Material
Properties –
“Handbook
values”
mms - cms

25. Nor is it Flat!
Lubricant
Adsorbed
Contaminants
Oxide
Surface Properties
Disturbed Material
Bulk Material
Properties
All engineering surfaces have a roughness, and this
roughness plays an important role in tribology.

26. Nor is it Flat!
Lubricant
Adsorbed
Contaminants
Oxide
Surface Properties
Disturbed Material
Bulk Material
Properties
All engineering surfaces have a roughness, and this
roughness plays an important role in tribology.
Surface Roughness comes from all prior history of the
part: Manufacturing, handling and prior use in application.

27. We need to think about…
2 Aspects of a Surface:
Physical - Surface Roughness
•
•
•
•
Dictates Contact Area
Dictates Contact Stresses
Lubricant Paths or Reservoirs
• Chemical - Intervening Layers
•
•
•
Chemical Compatibility
Shear Strength
Lubricant Properties, e.g. Viscosity

28. We need to think about…
2 Aspects of a Surface:
Physical - Surface Roughness
•
•
•
•
Dictates Contact Area
Dictates Contact Stresses
Paths or Reservoirs for
Lubricants/debris
• Chemical - Intervening Layers
•
•
•
Chemical Compatibility
Shear Strength
Lubricant Properties, e.g. Viscosity
Bead Blasted
Ground

29. We need to think about…
2 Aspects of a Surface:
• Physical - Surface Roughness
•
•
•
Dictates Contact Area
Dictates Contact Stresses
Lubricant Paths or Reservoirs
• Chemical - Intervening Layers
•
•
•
Chemical Compatibility
Shear Strength
Lubricant Properties, e.g. Viscosity,
EP or boundary-forming

30. Surface Characterization
Variety of Methods available, if needed
• Physical Characterization
• Roughness
• Macro – Waviness and Form (CMM)
• Micro – Surface Roughness
–
–
–
Stylus Profilometers (contact)
Optical Profilometers (non-contact)
AFM (sub-micron)
• Hardness
• Indent, Scratch
• Chemical Characterization
•
•
Infrared, XPS, Raman, Auger
Lubricant Shear properties→Viscometry

31. Tribology Basics
Summary of Surfaces in Contact
• Tribo-Forces are Dictated by Interaction
Asperities
of
• Asperities have Mechanical and Chemical
Properties
Methods Exist to Characterize these
Properties
•
• Asperity Geometry and Distribution result
from Manufacturing Method, Handling and
Prior Rubbing History

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