TRIBOLOGY

TRIBOLOGY

I ask our five year old grandson if he could give me the meaning of the word “tribology”.  He thought for a moment then said the following:

“OK Bob, (he calls me Bob) we’ve been studying Indians in school this year and triology (his word) is how a bunch of Indians live in teepees, around a campfire to cook and stay warm in the winter.  That’s trilogy!  What do you think?”

Not too shabby for pre-“K”.  Actually, tribology is defined as, “a study that deals with the design, friction, wear and lubrication of interacting surfaces in relative motion (as in bearings or gears).”  

As stated by the definition, tribology involves the study of three subject areas:  1.) Friction, 2.) Wear and 3.) Lubrication.  The study is interdisciplinary and involves very complex mechanical mechanisms including the weight of the rolling or sliding members, surface roughness of the members, profile of the surfaces, any dirt, grit, etc. that may interfere with movement and several others.  It has been estimated that six percent (6%) of our GNP is wasted and this waste results from friction and unnecessary wear of interacting parts.  I know this is very difficult to believe but my sources are current and reputable.   Even with this being the case, the average four year curriculum for mechanical engineering students involves only two (2) hours devoted to study and understanding friction and wear.  To make bad matters worse, most references on the subject are greatly outdated and provide sketchy information at best.  This is certainly true for more recent polymers and material composites.  The work just has not been done.

Let us very quickly look at the three components relative to tribology.  In this fashion, we will obtain a better understanding of the entire field of study.

Friction is a force that resists the sliding or rolling of one solid object over another.  Sometimes friction is very desirable; i.e. walking, driving a car on city streets, etc.  The negative effects become obvious when we consider we lose approximately twenty percent (20%) of an automobile engine’s power due to friction.  A great number of machinery failures result solely from friction and wear.

Wear is the removal of material from a solid surface as a result of mechanical action exerted by one solid on another.  There are four basic types of wear: 1.) Adhesive, 2.) Abrasive, 3.) Corrosive and 4.) Surface-fatigue.  Wear physically removes material from the surfaces of the interacting member with the harder material wearing the softer material.

Lubrication is the introduction of a lubricant between interacting solid surfaces to mitigate wear and friction.  The need for this dates back at least four thousand years.  The ancient Egyptians understood friction and wear and used animal fats as a lubricant.  There are three classifications for lubricants: 1.) Fluid film, 2.) Boundary and 3.) Solid.  It is fascinating to me that our body produces lubrication in a continuous fashion.  Our joints would not survive without this liquid lubrication and without this lubrication we would have a painful time in trying to bend, stretch, etc.  You get the picture.

As you can see, this is a fascinating field of study but a very complex subject to be studied.  If you are interested, I would recommend you taking a look at “The Journal of Tribology”.  It is found in the ASME digital library and will provide the latest information and data relative to university research and corporate activity.   I am in the process of completing a “white paper” for PDHonline that will provide much more information and basic grounding for the three areas of study we have just mentioned.  If interested, please log on and take a look.