What is Tribology?

And what does it have to do with piston rings?
By Lake Speed Jr. and Keith Jones

Tribology, this strange word is the study of friction, wear and lubrication. You also might be wondering what tribology has to do with piston rings? Beside the fact that piston rings operate on a thin film of oil, there’s quite a bit of tribology related to piston rings. Let me explain.

The highest source of friction in an engine comes from the contact between the cylinder wall and the piston ring. Research from both Ford Motor Company and the US Department of Energy concluded that roughly 45% of all engine friction comes from the piston ring to cylinder wall interface.

Because a piston has to change direction with each stroke of the engine, the piston rings accelerate and decelerate 250 times each second at 7,500 RPM. The constant changes in speed and load (due to the changes in cylinder pressure with each of the 4 engine cycles) create a unique and interesting phenomenon – a piston ring experiences all three forms of lubrication during each engine cycle.