A new interesting theory by Persson on wear commented

A very interesting wear theory by Persson and coworkers has been recently proposed (in fact, it is still under review!). 

I make some comments and simplifications here to show general trends

https://www.researchgate.net/publication/387143610_Some_comments_on_a_r…

Wear is a complex problem, and I don't think this theory will give easily quantatitative predictions, but it certainly deserves attention. 

My abstract follows

Persson and coauthors (Persson, et al 2024, Xu and Persson 2024) have recently proposed an interesting theory of wear which is based on particle formation due to fatigue crack growth at different scales of roughness. The theory perhaps is the first one to take into account of a full characterization of the roughness, but in the original form many details of actual roughness features and the material properties do not permit to elucidate general simple trends. We attempt to make general comments having in mind the case of metals wear to show the main effects of the various macroscopic parameters in the theory. It is found that wear rate in the elastic theory very strongly depends on friction coefficient and hugely on rms roughness, showing even a regime of wearless behaviour below friction coefficient of about 0.2. It is shown that an elasto-plastic theory probably mitigates these effects, as it depends only quadratically on friction coefficient, and has no dependence at all on any feature of roughness. However, the present oversimplistic perfectly plastic model truncating the elastic prediction, and the use of a crack propagation theory which is irrespective of large plastic flow can make the theory more hardly quantitative in general.

Thanks, MC