Tribology in space environment

We are able to offer on one hand standardised friction and wear testing using a Pin-on-Disc-type Ultra High Vacuum tribometer, but also offer very specialised and unique equipment which enables to simulate cyclic closed contact, like e.g. in relais, or at end stops, and to measure forces necessry to re-open the contact, i.e. the adhesion forces. This effect is herein referred to as "Cold Welding", but other terms may be e.g. stiction. Two facilities cover the most dangerous types of contacts: Impact and Fretting. The latter may also be adopted to fretting wear tests.

Finally, the test chamber enables testing of tribo-components under vacuum. This includes tests with specimen size and modes of movements defined by customers or performance tests of components and/or mechanisms under vacuum.

Plain Bearing Vacuum Tribometer

Plain bearings are used for articulations or linear guidance systems dedicated to single shot or low life time requirement. These include for example solar array panel articulations, radiator panel articulations, HDRM fold back articulations, exploration rovers articulations and linear guidances, landing pointing system articulations. The plain bearing tribometer allows the measurments of friction and wear parameters of a complete bearing for alternate rotations <180°C and small loads <150N. The working environment will be the same as for the vacuum tribometer: it works under vacuum between -100 to +300°C

Plain Bearing Vacuum Tribometer Characteristics

Ultra High Vacuum Tribometer

This facility enables the investigation of materials and coatings with respect to friction and wear properties. It enables on-line measurement of friction force during unidirectional sliding according to standardised pin-on-disc or ball-on-disc geometries. Environments vary from vacuum, non aggressive gases or to air with controlled humidity. Measurement of wear is done by profilometry, SEM or microbalance, investigation of surface structure or material transfer by SEM/EDX. Reproducibility and Repeatability of test results proven by European Round Robin Test.

Image of the Ultra High Vacuum Tribometer: Internal View showing the Tribo-System with ball holder and disc

The device is fully PC-controlled. To the control parameters, e.g. sliding distance, trip level, can be selected to end tests under specific conditions. On-line-data acquisition offers to post-process data, e.g. for automatic calculation of friction coefficients in running-in- or steady state, as well as endurance of solid lubricant coatings.

Measurement of

• Friction force / coefficient
• Wear (geometric or mass loss)
• Environmental Data
• Optional (e.g. residual gas, user defined)

Ultra High Vacuum Tribometer Characteristics

Pin-On-Ring Tribometer

This facility enables to investigate friction and wear properties of materials in pure sliding friction according to standardised pin-on-ring or ball-on-ring geometries or in combined rolling/sliding between ring/ring. The pin is riding on the circumference of the ring (i.e. coatings has to be applied on round surfaces.) In Pin-On-Ring geometry a induction heating system can be attached, which enables to test up to 700°C. The facility enables also investigation of abrasive wear, by use of abrasive wheels instead of standard rollers. Using an oil reservoir, also lubricated testing up to +200°C can be done. Digital data processing via PC is available for test parameters like temperature and humidity, and friction force and linear wear. Load up to 750 N can be applied, but with max. friction force of 200N.

Pin-On-Ring Tribometer Characteristics

Surface Profiling and Topographie

In parallel to the tribology test, a high resolution profilometer has been set up in order to assess the wearing surface. The apparatus from the firma "Veeco" is able to reach a subnanometer resolution for a surface of some square millimeters. It provides accurate, non-contact surface metrology with applications in R&D; process development, failure and wear analysis and process control. It provides surface details for applications in thick films, optics, ceramics, advanced materials, precision surfaces, micro-electronics and many more. It utilizes white light interferometry for the high resolution 3D surface height measurements, from sub-nanometer roughness to millimeter-high steps.Tools and software for quantifying and visualizing surface data are also included.

It provides 3D-topography together with macros to calculate wear volumes on flat but also on spherical and cylindrical bodies. Scanning areas range from 0,3x0,2mm to 5,0x3,8mm. Highest resolutions are 0,5x0,5 µm in lateral and in vertical <0,1nm. The vertical scanning range may reach up to 1mm.

Wear volumes

can be measured via this optical profiler: An example of a ball after a friction test can be seen on the image below. The original spherical surface of the ball was subtracted. The remaining peak refers to the volume of material which is sticking on the ball. This net volume on the ball can be calculated.