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[ceguo <question172345@xxxxxxxxxxxxxxxxxxxxx>]

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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