We have tested two samples of oils. One is pure while the other contains carbonaseous nano particles. To our surprise the following is observed :
In case of the nano particles based oil the coefficient of friction reduced as load increased. The experiment has been done with different rpm but in all the cases we found that CoF was lesser at higher loads.
while in pure oil the CoF is higher at higher loads...
Dear Shubrajit Bhaumik, I think this paradox is explained by different load capacity of lubricate layer in contact . The lubricants which "reinforced" nanoparticles are better carrying the increasing normal load while pure lubricant can't perform this function in full measure.
At the second, the changing of friction mechanism from sliding to rolling due to arrangement of nanaparticles as a microballs on smooth contact surface is possible when gap between contacting bodies is diminished under load increasing. In this case (boundary friction) the sizes of particles and gap became comparable.
All the best, Serge
Dear Shubrajit Bhaumik, I think this paradox is explained by different load capacity of lubricate layer in contact . The lubricants which "reinforced" nanoparticles are better carrying the increasing normal load while pure lubricant can't perform this function in full measure.
At the second, the changing of friction mechanism from sliding to rolling due to arrangement of nanaparticles as a microballs on smooth contact surface is possible when gap between contacting bodies is diminished under load increasing. In this case (boundary friction) the sizes of particles and gap became comparable.
All the best, Serge
I hope, the paper attached (with list of references) will be helpful for you.
Hi Shubrajit
I think that all depends on the lubrication regime. For instance, if the surfaces are in the boundary/mixed lubrication regime is possible by the action of rolling decrease the friction coefficient, only in the case if the surfaces are very smooth. In this case, asperities are being covered by the nanoparticles, then enhancing the rolling action. On the other hand, by using oil with no nanoparticles in the boundary/mixed lubrication regime, friction will increase with normal load, as asperities will be in more intimate contact then increasing surface adhesion. I attached a paper that you can read and support the discussion. I hope it helps
co fefficienct of friction of oil with nanoparticles, the nanoparticles are act as a point contat between the surfaceses instead of line contact. therefore the coefficient of friction is less compared with oil as a lubricant.
Dear Shubrajit
Looking into my files I found this very interesting article of the TLT magazine where you can find a nice explanation of the effect of the nanoparticles. I hope it helps
There cases where vthe lubricant reacts chemically with the vsurface and generate a low friction region .Well that is what happens in lubrication of geas and chain tooth. the low shear layer formed wears away , leading to aera of chain sprocket and gear teeths.
- Badges
- Science topic
- Similar topics
- Engineering
- Thermal Engineering
- Thermofluid
- Fluid Mechanics