Dry Cohesion for Elastic Contact Forces

Dry cohesion for elastic contact forces (linear reversible cohesive force) in MercuryDPM referred to as ReversibleAdhesive (ReversibleAdhesiveSpecies, ReversibleAdhesiveInteraction).

Dry cohesion models the attractive forces due to van-der-Walls interactions between particles in contact or close proximity. They decrease rapidly with distance, so they are very short-ranged. For elastic contact forces, the dry cohesion is elastic as well. For simplicity, the elastic adhesive (i.e. acting opposite to the normal direction) force can be implemented as a linear force, as in Figure (add)

\( f_{ij}^{nc} = \begin{cases} -f_{max}^{nc} & \quad \text{if} \quad \delta{ij}^{n} > 0 \\ -f_{max}^{nc} - k_c \delta_{ij}^{n} & \quad \text{if} \quad -f_{ij}^{nc, max}/k_c\leq \delta_{ij}^{n} < 0 \\ 0 & \quad \text{else} \end{cases} \)

Header:

#include "Species/AdhesiveForceSpecies/ReversibleAdhesiveSpecies.h" 

Interaction force:

void ReversibleAdhesiveInteraction::computeAdhesionForce() 

The model parameters are set using ReversibleAdhesiveSpecies member functions.

Unit test: AdhesiveForceUnitTest.cpp