Hi Kashif,

The friction can increase if you reduce the force such that you operate in a different lambda ratio and thus a different lubrication regime. This can be further explained by an understanding of your friction coefficient with the Strickberg Diagram (please see attached reference to Lubricants and lubrication by Mang and Dressel 2007).

Hope this helps,

Oscar

This can be explained by different reasons. To find the best explanation, you should take SEM images from wear surfaces of samples under various normal loads. By doing so, you can evaluate the wear mechanism of the specimens under different normal loads. One of the possibilities is that, under normal load of 1 N, a tribolayer can be formed, reducing the shear strength of the interface, and thereby reducing the COF.

Best regards,

Amir

Oscar O'Dwyer Lancaster-Jones the friction need not always be with the lubricating surfaces right. It will be between the two bodies in sliding as in pin on disc case or ball on disc. In that case it may be wear asperities may get introduced between two surfaces as an abrasive this may also induce the higher friction right?

What do you think about it?

Thanks for this nice question Kashif Usman

Hemanth Gurumurthy Yes, good point. The friction can increase due to the asperities being removed and these third body particles creating higher friction. Hence why the other comment is useful, to check what is happening to your sample and determine if particles are embedded/restricting motion, from wearing or the environment. If you are operating in boundary lubrication then your asperities (two surfaces) will be in contact, but that generally is higher friction. However, if the load is decreased, the general result is less wear, and if you cant see visually much change in the sample I don't think it may be third bodies, but it doesn't rule it out entirely.

Thank you for your discussion point, certainly interesting.

Oscar