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[Bruno Chareyre <bruno.chareyre@xxxxxxxxxxx>]

kan a écrit :
> Hi, dear all,
>  
> When I develop my code to calculate the shear force I meet some problem.
> From the literature, we know that
> Deta_Shear Force = ks*deta_shear_displacement
> while the deta_shear_displacement is the deta displacement at the 
> shear direction at each contact.
> my problem now is that, how to calculate this displacement ?
>  
> I know for normal displacement at each contact, at each time step, 
> when we get the resultant displacement during this time step, then we 
> get the new position for each particle, so we can get the distance 
> between the center of the particles, which is the normal distance. so 
> we can get the normal displacement and use the 
> NormalForce=kn*normal_displacement.
Its a matter of vocabulary.
I think you make a confusion between "displacement" and "position". In 
the normal direction, you get at each time-step the "POSITION" (i.e. 
interpenetration), not the displacement.
So that NormalForce=kn*interpenetration.

>  
> but how can I calculate the deta shear displacement? it seems that I 
> need to store the old position of each particles, which means a 
> doubled storage of the memory and lower speed.
shear_displacement = (velocity1 - velocity2 + r1*rotational_velocity1 - 
r2*rotational_velocity2)*dt

This IS a displacement.

So that shear_force = shear_force + shear_displacement*ks

No need to store initial orientations.

Check ElasticContactLaw.

Bruno

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Chareyre Bruno
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