DEM stress tensor

[akhilkmat]

Can anyone let me know where can I find the exact formula used for finding the stress/strain in DEM post processing ( image attached )? or else can you confirm its the one mentioned in this link -> https://www.cfdem.com/media/DEM/docu/fix_ave_euler.html.

Ps: It should be a per particle quantity (tensor) , an intermediate step before calculating the actual stress tensor.

Thanks,
Akhil Mathews