When two materials collide or rub against each other

[kenny1999]

When two materials of the same type or different type collide or rub against each other (either slightly or vigorously) that happens around us every day everywhere
At the molecular level, do they lose any particles/atoms because of the collision?

 

[jrmichler]

Yes. Sometimes there is welding at the molecular level. The subject is too large to cover in a post, so start by searching tribology. Another search term is theory (or theories) of friction.

One mechanism of wear is welding at asperities, followed by tearing off microscopic pieces, which show up as wear particles.

 

[kenny1999]

Yes. Sometimes there is welding at the molecular level. The subject is too large to cover in a post, so start by searching tribology. Another search term is theory (or theories) of friction.

One mechanism of wear is welding at asperities, followed by tearing off microscopic pieces, which show up as wear particles.

Hi. It's easy to imagine that any wear or breakage will cause loss of atoms / particles that we can easily observe and understand with naked eyes. I hope to know about ANY other collision of lesser extent that does not cause wear or breakage

 

[chemisttree]

And if the material is crystalline, defects such as crystal dislocations can be introduced at the surface and increase the chemical activity in a process known as mechanochemical activation.