National Physical Laboratory

Sliding and Reciprocating Wear and Friction

Sliding and reciprocating wear and frictionWear track formed in pin on disc test with  alumina
ball on TiN  coated steel disc showing generation of 
oxide debris at edge of wear track 

The performance of many products and engineering components depends critically on tribological properties of surfaces such as wear and friction. Indeed, wear problems cause major losses to UK industry which was estimated to amount to be £650 million in a recent study. In many wear and friction applications contacts between two relatively smooth surfaces sliding over one another takes place with material loss often occurring by adhesive wear.

Adhesive wear is the surface damage and material removal which can occur when two smooth surfaces rub against each other.  Such surfaces are never perfectly smooth and have high spots where the rubbing occurs. These local areas experience concentrated contact loads and interactions, and tend to adhere to each other and drag material away along the surface. This type of wear can occur in plain bearings and other interacting machine components, particularly if they are inadequately lubricated. The wear of brakes and clutches occurs by the same mechanism, and is kept under control by the use of dissimilar materials. Surfaces subject to adhesive wear can end up polished, with the generation of fine flakes of wear debris, or can show severe surface damage associated with surface dragging or even seizure.

NPL's activities are focussed on developing methods that will help UK industry to evaluate and solve their friction and wear problems and to enable them to develop a robust testing strategy.


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Last Updated: 25 Mar 2010
Created: 3 Aug 2007