LinearPlasticViscoelasticInteraction.cc

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#include "LinearPlasticViscoelasticInteraction.h"
#include "InteractionHandler.h"
#include "Particles/BaseParticle.h"
#include <iomanip>
#include <fstream>
#include <Species/NormalForceSpecies/LinearPlasticViscoelasticNormalSpecies.h>
#include <cmath>    // std::max
LinearPlasticViscoelasticInteraction::LinearPlasticViscoelasticInteraction(BaseInteractable* P, BaseInteractable* I, Mdouble timeStamp)
        : BaseInteraction(P, I, timeStamp)
{
    maxOverlap_=0;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"LinearPlasticViscoelasticInteraction::LinearPlasticViscoelasticInteraction() finished"<<std::endl;
#endif
}
LinearPlasticViscoelasticInteraction::LinearPlasticViscoelasticInteraction(const LinearPlasticViscoelasticInteraction &p)
        : BaseInteraction(p)
{
    maxOverlap_=p.maxOverlap_;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"LinearPlasticViscoelasticInteraction::LinearPlasticViscoelasticInteraction(const LinearPlasticViscoelasticInteraction &p finished"<<std::endl;
#endif
}
LinearPlasticViscoelasticInteraction::~LinearPlasticViscoelasticInteraction()
{
#ifdef DEBUG_DESTRUCTOR
    std::cout<<"LinearPlasticViscoelasticInteraction::~LinearPlasticViscoelasticInteraction() finished"<<std::endl;
#endif
}

void LinearPlasticViscoelasticInteraction::write(std::ostream& os) const
{
    BaseInteraction::write(os);
    os << " maxOverlap " << maxOverlap_;
}
void LinearPlasticViscoelasticInteraction::read(std::istream& is)
{
    BaseInteraction::read(is);
    helpers::readOptionalVariable<Mdouble>(is,"maxOverlap",maxOverlap_);
}
std::string LinearPlasticViscoelasticInteraction::getBaseName() const
{
    return "LinearPlasticViscoelastic";
}
void LinearPlasticViscoelasticInteraction::computeLinearPlasticViscoelasticForce()
{
    // Compute the relative velocity vector of particle P w.r.t. I
    setRelativeVelocity(getP()->getVelocityAtContact(getContactPoint()) - getI()->getVelocityAtContact(getContactPoint()));
    // Compute the projection of vrel onto the normal (can be negative)
    setNormalRelativeVelocity(Vec3D::dot(getRelativeVelocity(), getNormal()));

    if (getOverlap() > 0) //if contact forces
    {
        const LinearPlasticViscoelasticNormalSpecies* species = getSpecies();

        //calculate the overlap above which the max. unloading stiffness becomes active (the 'fluid branch')
        Mdouble effectiveDiameter = 2.0 * getEffectiveRadius();
        Mdouble deltaStar = (species->getUnloadingStiffnessMax() 
            / (species->getUnloadingStiffnessMax() - species->getLoadingStiffness())) 
            * species->getPenetrationDepthMax() * effectiveDiameter;
    
        //increase max overlap if necessary
        if (getOverlap()>getMaxOverlap())
            setMaxOverlap(std::min(deltaStar, getOverlap()));
            
        //calculate the unloading stiffness
        Mdouble unloadingStiffness = species->getLoadingStiffness() 
            + (species->getUnloadingStiffnessMax() - species->getLoadingStiffness()) * (getMaxOverlap() / deltaStar);

        //calculate the overlap where the force is zero
        Mdouble equilibriumOverlap = (unloadingStiffness - species->getLoadingStiffness()) / unloadingStiffness * maxOverlap_;

        //compute elastic force
        Mdouble normalForce = unloadingStiffness * (getOverlap() - equilibriumOverlap);

        //decrease max overlap if necessary
        Mdouble cohesiveForce = -species->getCohesionStiffness() * getOverlap();
        if (normalForce < cohesiveForce) {
            setMaxOverlap((unloadingStiffness + species->getCohesionStiffness()) 
                / (unloadingStiffness - species->getLoadingStiffness()) * getOverlap());
            //only necessary because the timeStep is finite:
            normalForce = cohesiveForce;
        }

        //add dissipative force
        normalForce -= species->getDissipation() * getNormalRelativeVelocity();
        
        setAbsoluteNormalForce(std::abs(normalForce)); //used for further corce calculations;
        setForce(getNormal() * normalForce);
        setTorque(Vec3D(0.0, 0.0, 0.0));
    }
    else
    {
        setAbsoluteNormalForce(0.0);
        setForce(Vec3D(0.0, 0.0, 0.0));
        setTorque(Vec3D(0.0, 0.0, 0.0));
    }
}
void LinearPlasticViscoelasticInteraction::computeNormalForce()
{
    computeLinearPlasticViscoelasticForce();
}
Mdouble LinearPlasticViscoelasticInteraction::getElasticEnergy() const
{
   if (getOverlap() > 0)
        return 0.5 * (getSpecies()->getLoadingStiffness() * mathsFunc::square(getOverlap()));
    else
        return 0.0;
}
const LinearPlasticViscoelasticNormalSpecies* LinearPlasticViscoelasticInteraction::getSpecies() const
{
    return dynamic_cast<const LinearPlasticViscoelasticNormalSpecies*>(getBaseSpecies());
}
Mdouble LinearPlasticViscoelasticInteraction::getMaxOverlap() const
{
    return maxOverlap_;
}
void LinearPlasticViscoelasticInteraction::setMaxOverlap(const Mdouble maxOverlap)
{
    maxOverlap_ = maxOverlap;
}
Mdouble LinearPlasticViscoelasticInteraction::getUnloadingStiffness() const
{
    const LinearPlasticViscoelasticNormalSpecies* species = getSpecies();
    Mdouble effectiveDiameter = 2.0*getEffectiveRadius();
    Mdouble deltaMaxFluid = species->getPenetrationDepthMax() * effectiveDiameter / (1.0-species->getLoadingStiffness()/species->getUnloadingStiffnessMax());
    if (getOverlap() > deltaMaxFluid)
        return species->getUnloadingStiffnessMax();
    else
        return species->getLoadingStiffness() + (species->getUnloadingStiffnessMax() - species->getLoadingStiffness()) * getMaxOverlap()/deltaMaxFluid;
}