Question about the source code of base_mechanics.py

[fsenoner]

Dear Pybamm team,

may I ask one question about the source code of the base_mechanics.py file in the particle_mechanics folder:

# stress evaluated at the surface of the particles
# Ai2019 eq [7] with r=R
stress_r_surf = pybamm.Scalar(0)

Why is the mechanical stress in radial direction set to 0?

Thank you

[brosaplanella]

I am not familiar with this model, but it seems to be a consequence of the equations (see equation [7] of the paper: https://iopscience.iop.org/article/10.1149/2.0122001JES/pdf). If I understand it is a direct consequence of the boundary condition in Table II.