Investigating the effect of linear velocity in reciprocating contacts

Abstract

In Tribology, the well-known Stribeck curve is often used to relate friction behaviour to the properties of a system. Richard Stribeck, (Jacobson, 2003), (Stribeck, 1902) developed these curves while researching various bearings and found that the Stribeck curve can be generated for all tribological contacts of the Hertzian type. These curves give a relation between the coefficient of friction and the Sommerfeld number for a lubricant and given surfaces. All his test work was done on contacts that move in a single direction, unidirectional motion. This leaves the question, could Stribeck curves be applied to reciprocating contacts and how does linear velocity affect wear in these contacts? This research project is aimed to further the knowledge on how linear velocity affects reciprocating contacts with a focus on Stribeck curves and lubricity. Tests were conducted on two reciprocating instruments using ball and disk configurations. Two parameters were varied to change the linear velocity, namely oscillating frequency, and stroke length. To shift focus away from viscosity, n-Hexadecane was used as the base fluid due to its lack of lubrication properties. To improve the base fluid lubricity 3 carboxylic acids with 3 different chain lengths were used as additives.