Particle Wall Stress Calculations - Clarification on Methods in LIGGGHTS

Hi,

I was wondering if someone can clarify for me how the stress between a particle and the wall is calculated? I am outputting the normal stress after setting the mesh to track the stress, and I ultimately want to use the stress to calculate the total force on the mesh. I specify the mesh as follows:

fix m1 all mesh/surface/stress file meshes/filename type 1 stress on

And then I dump the resulting force using this command:

dump dumpstress1 all mesh/gran/VTK 100 post/filename*.vtk output face area stress m1

I have looked through the forums and documentation, and as far as I can tell, this command forces LIGGGHTS to output the magnitude of the normal stress and the area of each face in the mesh. After looking at the source code, I choose the flag "face" as this should dump all the stresses interpolated over the face of each component of the mesh (see comment on line 492, https://github.com/CFDEMproject/LIGGGHTS-PUBLIC/blob/master/src/dump_mes...). This should allow me to calculate the force by multiplying the stress on each face by the area of the face.

My confusion comes in with how this normal stress is calculated between a particle and a mesh. The above model uses the gran model which calculates the forces between the particle and the wall, assuming the wall is an infinite mass. I assume calculation of the stress relies on the calculation of the area of intersection between the particle and the wall? If so, how does this calculation behave with deformable particle systems?

Thanks,
-Doug