Sliding interaction

Sliding contact forces in MercuryDPM implemented as SlidingSpecies, SlidingInteraction

Header:

#include <Species/FrictionForceSpecies/SlidingFrictionSpecies.h> 

Interaction function:

#include "Interactions/FrictionForceInteractions/SlidingFrictionInteraction.h" 

The user can use one of the following species into the main program:

include <Species/LinearViscoelasticSlidingFrictionSpecies.h>

include <Species/LinearPlasticViscoelasticSlidingFrictionSpecies.h>

include <Species/HertzianViscoelasticSlidingFrictionSpecies.h>

include <Species/HertzianSinterSlidingFrictionSpecies.h>

Unite Test: TangentialSpringUnitTest.cpp