Advanced Measuring Equipment for Studying the Lubrication State in Tribocontacts

A tribocontact, i.e. the contact between two bodies in relative motion, is difficult to access with most sensors. In such contacts, lubrication is essential to ensure smooth running behaviour and long service life. It is often not possible to investigate tribocontacts in machinery without modifying the machine itself. In this work, the lubrication state was intentionally varied in a laboratory test rig, and the effect of lubrication loss on running behaviour was investigated.

The study was conducted using a pin-on-disc tribometer. To provide a defined lubrication condition, a pump was used to supply lubricant continuously; towards the end of the test, the pump was switched off in order to study lubrication loss. Using an ultrasonic sensor, the Triboacoustic Pin, the film thickness in the contact was measured during the test run, providing detailed information on the amount of lubricant present in the contact. A high-speed thermal camera was used to measure the temperature of the disc after it had passed through the contact. A high-speed camera was used to study the contact dynamics, in particular loss of contact under unfavourable vibration conditions. A 3D laser Doppler vibrometer was used to scan the dynamics of the test rig at several rotational speeds, enabling contactless operational vibration analysis of the test rig.

It was found that all the sensors used can provide information on the lubrication state in the contact without influencing the contact situation, as they are either contactless sensors or sensors that can be applied to existing machine components. The individual sensors can provide detailed information, for example on film thickness, temperature distribution or loss of contact. This knowledge can be used, for example, to optimise the type of lubricant or the amount of lubrication for machinery.