SAE ARP6255A

Employing “ball-on-ring” philosophy, a nonrotating steel ball is held in a vertically mounted chuck and, using an applied load, is forced against an axially mounted steel rotating ring. The test ring is rotated at a fixed speed while being partially immersed in a lubricant reservoir. This maintains the ring in a wet condition and continuously transports a lubricating film of test fluid to the ball and ring interface. The diameter of the wear scar generated on the test ball is used as a measure of the fluid’s lubricating properties. The apparatus can be used by adjusting the operating conditions to reproduce two different wear mechanisms. Therefore, the ALTE can assess a lubricant’s performance in that regard. These mechanisms are described below. The Aviation Lubricant Tribology Evaluator (ALTE) is a device designed to assess the relative lubricating performance of aviation turbine oils in the following scenarios: (1) A mixed lubrication situation combining hydrodynamic/EHD mechanisms and boundary layer mechanisms - "Mild wear"; (2) A lubrication situation wherein boundary layer films have broken down, and metal-to-metal contact has been initiated - "Severe wear". The aim of the ALTE is to produce test conditions which allow lubricants to be evaluated on a laboratory scale, in a timely manner without deviating greatly from representative wear mechanisms. The ARP was updated throughout to Rev. A, most notably to clarify the severe wear testing procedure and the report section, and to make various editorial corrections.