Pin on Disk Test
Pin on disk apparatus
Pin on disk wear test: important factors and test conditions
- Pin shape. Typically, the pin can be of any shape. Ball on disk test uses a ball pin or a lens. Flat pin or chip shaped pins can also be used.
- Pin alignment. If the pin is flat ended, the alignment should be ensured, since otherwise non-uniform loading occurs resulting in non-uniform wear and possibly overloaded conditions. The edges of the flat specimens should not be sharp, otherwise the chipping may occur.
- Pin material. The choice of the pin material is very important. It should be noted, that typically, the tribological behavior for the same pair of materials is different depending on which material is used for the pin and which material is used for the disc. This is specifically true for the case of the contact between ‘soft’ and ‘hard’ materials. This difference comes from the fact that the wear occurs mainly on the softer material. If the ball on disc case is considered, if the ball is softer it will be worn faster and form a flat on flat contact with pressure profile significantly different for the initial one. If the disk is softer, than the groove will form on the disk and plouging wear will occur.
- Pin location. It is possible to place a pin on the top of the disk. However, in many cases the pin is pressed against the disk from the bottom. It is typically done to avoid getting the wear particles back into contact once they are formed or to collect the wear particles for further analysis. Due to gravity, the wear particles will be falling down.
Further information can be found here.
Wear scar/wear rate/wear volume analysis
In the modern tribometers, the wear scars can be analyzed using inline imaging systems, such as optical profilometers, Atomic Force Microscopes, etc. This analysis can also be performed several times during the test, thus giving the opportunity to measure the wear rate, wear volume and surface roughness evolution in time. This information can be used to develop accurate wear models and move towards predictive tribology.
An example of a worn ball surface topography measurement is shown below:
Why Testing using Pin-on-Disk?
Currently, there is a trend to reduce the size of machine elements, increase power, reduce maintenance and improve reliability. These requirements push the design limits and require innovative solutions. Testing these solutions on a scale of a full machine would be too expensive, but also time consuming. Therefore the universal experimental set-ups are often used to perform tribological research on a prototyping phase, prior to full scale tests.
Pin on disk, pin on ring, pin on flat, ball on flat tests are all similar to each other with the differences in the geometry of a specific tribometer and the pin.
Pin on Disk Testing Standards
In research of materials, coatings and lubricants standardized tests are used to improve the reproducibility and for simplicity. The data collected using standard tests can also be used to compare the results obtained by various laboratories. The standards in tribology were developed by ASTM, DIN as shown below.
ASTM G 99 – Standard Test method for wear testing on a pin-on-disk test apparatus.
DIN 50324 – Testing of friction and wear.
DIN ISO 7148-1 – Testing the tribological behavior of material for sliding bearings Part 1: Testing of bearing materials, test procedure A, pin on disk.
DIN ISO 7148-2 – Testing the tribological behavior of plastic materials for sliding bearings, test procedure A, pin on disk.
A full list of tribology related testing standards can be found here.
. Mechano-chemical decomposition of organic friction modifiers with multiple reactive centres induces superlubricity of ta-C, Takuya Kuwahara, Pedro A. Romero, Stefan Makowski, Volker Weihnacht, Gianpietro Moras & Michael Moseler, Nature Communications, volume 10, Article number: 151 (2019), https://doi.org/10.1038/s41467-018-08042-8.
. Open System Tribology and Influence of Weather Condition,Yezhe Lyu, Ellen Bergseth & Ulf Olofsson, Scientific Reports volume 6, Article number: 32455 (2016), https://doi.org/10.1038/srep32455.
. Tests according to several testing standards (ASTM G99, ASTM G133, ASTM F732): https://www.element.com/more-sectors/medical-device/pin-on-disk-wear-testing.