For most conditions, friction is not affected by surface area as the coefficient of friction (mu) is constant. That is my understanding.
However, I thought I recalled an example where this didn't hold for some materials. (I'm ignoring snow and ice for now) I'm thinking ultra high molecular weight polyethylene (UHMWPE, UHMW) on stainless steel or UHMWPE on UHMWPE.
I can find no reference to that - so I'm thinking I just misremembered.
Are there any materials or situations where decreasing surface area also decreases friction (static or dynamic)?
Hi Steve. Spoiler Alert, won't answer but share an experience. When measuring friction in plastic-plastic and plastic-metal samples we found smaller friction on smaller samples. Then we realized that our capacity of cutting perfect flat surfaces on our samples was the problem. Due to distortion, bigger surface areas weren't as flat as the small ones, so measured friction seemed bigger at the former do to an uneven contact patch.
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