New question #172345 on Yade:
https://answers.launchpad.net/yade/+question/172345

Hi yade-developers/users,

To calculate macro stress tensor from micro quantities, we usually the formula 
sigma_ij = 1/V sum(L_i x F_j), where L is the branch vector and F is the 
contact force and the summation is over all contacts. The branch vector is the 
connection between two contacting particles. My question is how about the 
boundary contact when rigid boundaries are used. I think these contacts should 
be considered (please correct me if I'm wrong). So these boundary branch 
vectors should be connections between particle center and the contacting 
points, right?
Then regarding to the calculation of fabric tensor, phi_ij = 1/N_c sum(n_i x 
n_j), where N_c is the total contact number, n is the unit normal of the 
contact plane. So with rigid boundary, each inter-particle contact should be 
counted twice while the boundary contact should only be considered once. Is my 
understanding correct? Or all the contacts should be treated in the same manner?
Also in the calculation of branch vector tensor, do we have to treat the 
inter-particle branch vector and the boundary branch vector differently?

I'm quite confused about these calculations. Hope anyone can help.

Best regards!
Ning

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