Pin on disc dry sliding wear testing machine provides the data for wear (height loss). We can measure the mass loss. From both we can find out wear rate of a sample with known density. Which one is preferable, & why? With increase in rpm will wear rate decrease? Why/why not?
I worked mostly in boundary lubrication. I found out that wear rate is related to heat; thus when wear rate slow down at higher rpm heat will increase and a solid tribofilm will form on the substrate which is resistant to wear depending on the additives.
Hello Sandeep,
As per my knowledge, it depends upon hardness of specimen (pin) and counter object (disc). By the way most of the times wear rate and also coefficient of friction decreases with increase in sliding velocity because of increase in strain hardening effect of the material and also the surface temperature.
This is related to the less time for the asperities contact which leads to less time for asperities deformation and thermal activation of the rubbing surfaces causing oxidation and forms an oxide tribofilm on the interface. Also, the real contact area will be decreased causing a decline in the boundary friction coefficient and wear rate with rising of the sliding speed.
Article Improving the Tribological Characteristics of Piston Ring As...
Absolutely hardness of specimen play an important roles. But temperature and wear debris at the onset will provide a reaction with the additives that establish a solid tribofilm that protect the surface. We call it a tribo healing film. Please review some of my articles in the boundary lubrication regim
Please get in touch with Dr. P. Dinesh Babu, Senior Assistant Professor, SASTRA University. He can provide more details.
Again, I tried so many procedures. What ever they say you should establish solid tribofilm which depend greatly on the additives and temperature to decrease your wear rate. I analy this experimentally and theoretically. Temperature is crucial especially in the boundary regime. If you have the wrong additives temperature will not help. Thus I studied all these variables and optimize the best possible conditions using Design of Experiment softwares (DOE) by Statess. You can access my publications in tribology transactions and Wear if you like to verify. Take care
Dear Sandeep.
You clould contact I. A. Buyanovskii.
In my opinion if the appliyed load doesn’t had any variations and the rpm are incremented the friction coefficient should decrease, so wear rate should decrease.
I totally disagree that if you increment friction wear rate will decrease. Wear rate does not depend on friction totally. There are other factors such as temp and surface finish and chemistry of lubricant
I din't' mentioned or write anything as "increment friction" ..What I writed was .."if the rpm-2pi/60 are incremented"...the friction coefficient decrease. Only in the follow up of the question: "With increase in rpm will wear rate decrease? Why/why not?...From there I don't know what exactly are the boundry conditions of the experiment.
As I said from previous experience, all depend on the temperature and surface treatment with the additives. Sometimes asperities debris with reaction temperature will play a positive role in decreasing the wear rate for long duration tests due to the formation of solid tribofilm with high modulus. You can use DOE software to optimize your variables and find out about running variable speeds. Look at tribology transactions and WEAR journals
When you mentioned temperature. A what temperature you are making reference?; Oil temperature,? Surface temperature?, contac zone temperature?T..he temperature depend of friction and pressure.
What kind of additive had been used?...If had has been use Addtives called non-temperature dependent, over-based sulfonate, operates by a different mechanism as temperarture addtive. Non-temperaure additive contains a colloidal carbonate salt dispersed within the sulfonate. During the interaction with iron, the colloidal carbonate will form a film that can act as a barrier between metal surfaces much like the temperature dependent; however, it does not need the elevated temperatures to start the reaction. In the other hand is had has been use EP additive temperature depended as boron, chlorine, phosphorus, and sulfur they are activated by reacting with the metal surface when the temperatures are elevated due to the extreme pressure. The chemical reaction between the additive and metal surface is driven by the heat produced from friction. Is necesary to know what are the boundry conditions so from there we can think an a acurate answers.
Thank you all for your paricipation. From this discussion can I conclude that wear rate of pin decreases with increasing sliding velocity in dry sliding (Al-Si-TiB2 pin and EN56 disc)due to
1- less contact time between the asperities,
2- oxide film acts as barrier for wear
3- at higher rpm coefficient of friction decreases thus wear rate decreases.
In my work I have gone for 10, 20 & 30N. Beyond these loads, there may be any transition of wear. And change in wear mechanisms. Plz provide some suggestions to help me in my work.
yes,
This is related to the less time for the asperities contact which leads to less time for asperities deformation and thermal activation of the rubbing surfaces causing oxidation and forms an oxide tribofilm on the interface. Also, the real contact area will be decreased causing a decline in the boundary friction coefficient and wear rate with rising of the sliding speed.
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When asperity is reduced the wear debris will react with the additives depending on the temperature and sometimes it will benefit from forming a solid tribofilm that will help in reducing wear rate
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