yade-dev team mailing list archive

[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

Hi Vincent,

This is quite epistemologic. Let's see if we can converge somewhere on this ground.

> A parameter (physical or not) like mu (friction coefficient) has nothing to do within the bodies. This is an "inter-bodies" parameter
> and the bodies are rigid.

I'd say : if a parameter is inter-body, then it involves body 1 and body 2. You can't say
it is not linked to bodies if it is linked to both of them. Additionaly, an interaction is
nothing. It is just a word that we use, but it doesn't exist and so it can't carry
information. Only solid particles exist in our world.

For bodies being rigid, this is a Montpellier view of things. For me they are deformable,
even if we display them on screen with constant shapes. This is the base of e.g.
Hertz-Mindlin law.

> 1 - mu_A and mu_B have lost their physical meaning (if they had)

Did you hear about scratch hardness (or Mohs hardness, fr : dureté, see
http://en.wikipedia.org/wiki/Mohs_scale)
SH is defined for individual minerals, even though it can only be defined by measuring the
result of interactions between them.
Now, lets say I define scratch hardness of a contact (measuring for instance the force
needed to indent).
I'm quite sure the hardness of diamond-talc and quartz-talc will be exactly the same : it
will be the hardness of talc.
What is so different with friction? Why couldn't we say that some grains are more
frictional than others?

Also, it is well known in foundations engineering that a soil-concrete contact will have
the shear strength of the soil (or even less in some cases), not any sort of average
soil-concrete strength : the weakest fails first.

> 2 - I will have problem if someday (after bzr update) the mean rule if changed for a max rule by someone well-intentioned

Don't worry, it would be reverted quite fast... I'll take care of that for you. :-)

Cheers.

Bruno