Re: The whole truth about hard material scratching softer material

Dear John

Thank you for your interesting question. Although I'm not an expert in 
the field of material science (sorry!) I'd like to try to give an answer:

When we study science we have the idea that nature follows simple 
laws, "functions" you call them. For very simple situations - a stone 
falls from a bridge - we can describe nature with simple formulas. But 
when we take a closer look we have to admit that we always make MODELS 
from nature. The stone feels the air resistance and a real stone falls 
slower than the simple Galilei formula predicts. 

I'm afraid that in the case of friction or wear there's no "whole truth" 
in the sense that a simple formula describes the wear between two 
materials perfectly. Of course, material scientists and engineers do have 
models and approximate formulas (which I don’t know) but they don’t 
have “THE function” or “the WHOLE truth”.