Tribometer

A simple tribometer is described by a hanging mass and a mass resting on a horizontal surface, connected to each other via a string and pulley. The coefficient of friction, µ, when the system is stationary, is determined by increasing the hanging mass until the moment that the resting mass begins to slide. Then using the general equation for friction force:

${\displaystyle F=\mu \mathbb {N} }$

Where N, the normal force, is equal to the weight (mass x gravity) of the sitting mass (m_T) and F, the loading force, is equal to the weight (mass x gravity) of the hanging mass (m_H).

To determine the kinetic coefficient of friction the hanging mass is increased or decreased until the mass system moves at a constant speed.

In both cases, the coefficient of friction is simplified to the ratio of the two masses:

${\displaystyle \mu \ =m_{H}/m_{T}}$

In most test applications using tribometers, wear is measured by comparing the mass or surfaces of test specimens before and after testing. Equipment and methods used to examine the worn surfaces include optical microscopes, scanning electron microscopes, optical interferometry and mechanical roughness testers.

Tribometers are often referred to by the specific contact arrangement they simulate or by the original equipment developer. Several arrangements are:

• Four ball [3]
• Pin on disc
• Ball on disc
• Ring on ring
• Ball on three plates
• Reciprocating pin (usually referred to as SRV or HFRR) [4]
• Block on ring
• Bouncing ball [5]
• Fretting test machine
• Twin disc

• Abrasion
• Twist compression tester
• Tribology