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[Vaclav Smilauer <eudoxos@xxxxxxxx>]

> Thank you for your comments. I can understand it. You know, from the
> mechanical concept, the shear modulus (G) can be represented by E/2*(1
> +v) for homogeneous isotropic materials, here E is young modulus, v is
> poisson ratio. So, can we decide G_over_E is equal to 1/2*(1+v)
> directly? Can we use 1/2*(1+v) to calculate kt/kn?
> Thank you so much.

No, I don't think that would work; the notation in the code (G_over_E)
is a little misleading again, G=kt/A and E=kn/A on the interaction level
are different from Young and shear modulus for continuum (in the sense
of how a RVE of particles would behave globally), depending on packing
configuration etc.

Eq (3.39), pg 51 of my thesis gives some a relationship between kt/kn
and Poisson's ratio based on the microplane theory analogy (see the
article referenced for details), but there is a number of suppositions,
such as fixed particle radius (otherwise the dimensional analysis would
have to take in account more parameters). (pg 52 shows that it matches
in a sense)

HTH, Vaclav