materi_plasti_phimob

The mobilized friction angle $\phi_{mob}$ is added to the node_dof records. It is defined as the angle, in radians, for which the yield function

$$f = 0.5 ( \sigma_2 - \sigma_0 ) + 0.5 ( \sigma_2 + \sigma_0 ) * sin( \phi_{mob} ) - c cos( \phi_{mob} )$$

becomes zero. This is available for mohr-coulomb and matsuoka-nakai plasticity only. Please realise that in regions with substantial cohesion the mobilized friction angle $\phi_{mob}$ can exceed the friction angle $\phi$ from the plasticity law. In case of zero cohesion, or cohesion small relative to the stresses, yield is reached if the $\phi_{mob}$ reaches the friction angle $\phi$. The definition above can give either negative or positive values for $\phi_{mob}$; negative values simply indicate that the stress state is far away from yielding.