In lubricants, the addition of ZDDP to an oil formulation is known to increase friction while reducing wear. I am trying to help students understand that low wear rates does not necessarily mean low friction and visa versa. What is a practical example of reducing wear while increasing friction?
For example, not automatic car clutches. It is known that when the clutch is engaged and disengaged slowly, the clutch wears out more quickly: longer friction under light loads causes greater wear than shorter friction under heavy loads.
Another example is the mechanical machining (drilling, milling, turning and grinding) of metals. For each material and tool there are recommendations for the load and speed of the cutting, which bring minimal wear of the tool with maximum efficiency of the machining. There are materials that "like" high speeds at low loads (low friction), but there are also materials that can only be processed in reverse at very high loads and low speeds (high friction). These materials include alloys with low thermal conductivity: stainless steels, titanium and nickel based alloys.
In early hip joint replacements, the lower friction PFTE material was used initially due to the lower friction in comparison to other materials, but it had much greater wear and then removed from clinical practice. Look up John Charnley PTFE low friction hip joint replacement.
Hope this helps,
Oscar
In case of new assembly of piston and cylinder, particles wear rate is more and due to less contact area, friction is also less, but lubrication film is unstable as irregular surface at mating points. With the passage of time, wear rate will come down and friction will increase. Ofcourse, lubricating film will take care of this
Hi,
I realize that the scenario you use could be useful to impulse the studients thinking. But I think too, that they need realize that friction coefficient and wear rate, see as similar but they are different concepts, and follow differents mechanisms.The following paper by Peter Blau, could find useful too:
Article The Significance and Use of the Friction Coefficient
Regards, Mario.
As in case of FSW of MMCs generally wear rate or loss were reduced with the grain refinement as well the uniform distribution of RPs in the processed zone
Another interesting example is the coating of brake discs. Coating with e.g. tungsten carbide reduces the wear of the disc - thus the total wear of a friction brake is primarily represented by the friction linings. This solution was developed by Buderus/Bosch and is already in series production in some Porsche models (Porsche Surface Coated Brake/PSCB). This disc coating offers the additional advantage of a lower susceptibility to rust. In tests, we were able to observe a reduction in total wear by up to 85 % compared to a conventional grey cast iron disc.
Kind regards,
David
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