Simulation of wear in roll-slip contacts

WHY

The steering system of cars is based on a rack and pinion system. Over time, the metal on these gears wears out, resulting in a loose fitting. Some other applications also make use of a rack and pinion system to translate a rotary drive motion into a linear displacement.  The wear and tear of such systems occurs through a roll-slip mechanism. Therefore a tribological method needs to be developed to simulate such roll-slip contacts and their failure mechanisms.

HOW

A modification on the Falex Multispecimen machine allows for a 2-rollers on disk geometry. During each turn these rollers rotate and slide simultaneously, simulating a roll-slip contact. The speed and load can be adjusted to achieve similar contact conditions as in the actual application. The contact can be either dry or lubricating, whereas the rollers and/or disks can be bare or coated materials. In this application series we investigated the use of coatings to decrease the friction and wear of the tribo-system, whereas the contamination of lubricant with hard particles (e.g. sand) was also taken into consideration.   

 

 

RESULT

• A roll-slip contact can be simulated by a Falex Multispecimen tester.
• Coatings can improve the wear resistance and frictional performance of roll-slip contacts.
• The presence of hard particles is a major risk for degrading the performance of a lubricant in roll-slip contacts.