When two materials collide or rub against each other

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Discussion Overview

The discussion revolves around the interactions between materials when they collide or rub against each other, focusing on the molecular consequences of such interactions. It explores concepts related to wear, particle loss, and the mechanisms involved at the molecular level, including tribology and friction theories.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants propose that collisions between materials can lead to the loss of particles or atoms, particularly through mechanisms such as welding at the molecular level.
  • One participant mentions that wear can occur through welding at asperities, which results in the tearing off of microscopic pieces that manifest as wear particles.
  • Another participant expresses curiosity about collisions that do not result in observable wear or breakage, seeking examples of less severe interactions.
  • A later reply introduces the concept of crystal dislocations in crystalline materials, suggesting that such defects can increase chemical activity through a process known as mechanochemical activation.

Areas of Agreement / Disagreement

Participants present multiple perspectives on the effects of material collisions, with some agreeing on the occurrence of molecular welding and wear, while others question the extent of particle loss and seek clarification on non-destructive interactions. The discussion remains unresolved regarding the specifics of these interactions.

Contextual Notes

Limitations include the lack of detailed definitions of terms like "tribology" and "mechanochemical activation," as well as the need for further exploration of the conditions under which wear occurs or does not occur.

kenny1999
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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?
 
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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.
 
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jrmichler said:
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
 
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.
 

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