HertzianSinterInteraction.cc

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//Copyright (c) 2013-2014, The MercuryDPM Developers Team. All rights reserved.
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#include "HertzianSinterInteraction.h"
#include "InteractionHandler.h"
#include "Particles/BaseParticle.h"
#include "DPMBase.h"
#include "Species/NormalForceSpecies/HertzianSinterNormalSpecies.h"
#include "Math/ExtendedMath.h"
#include <iomanip>
#include <fstream>
#include <cmath>    // std::max
HertzianSinterInteraction::HertzianSinterInteraction(BaseInteractable* P, BaseInteractable* I, Mdouble timeStamp)
        : BaseInteraction(P, I, timeStamp)
{
    maxOverlap_=0;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"HertzianSinterInteraction::HertzianSinterInteraction() finished"<<std::endl;
#endif
}
HertzianSinterInteraction::HertzianSinterInteraction(const HertzianSinterInteraction &p)
        : BaseInteraction(p)
{
    maxOverlap_=p.maxOverlap_;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"HertzianSinterInteraction::HertzianSinterInteraction(const HertzianSinterInteraction &p finished"<<std::endl;
#endif
}
HertzianSinterInteraction::~HertzianSinterInteraction()
{
#ifdef DEBUG_DESTRUCTOR
    std::cout<<"HertzianSinterInteraction::~HertzianSinterInteraction() finished"<<std::endl;
#endif
}

void HertzianSinterInteraction::write(std::ostream& os) const
{
    BaseInteraction::write(os);
    os << " maxOverlap " << maxOverlap_;
}
void HertzianSinterInteraction::read(std::istream& is)
{
    BaseInteraction::read(is);
    std::string dummy;
    is >> dummy >> maxOverlap_;
}
std::string HertzianSinterInteraction::getBaseName() const
{
    return "HertzianSinter";
}
void HertzianSinterInteraction::computeSinterForce()
{
    // 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 HertzianSinterNormalSpecies* species = getSpecies();
        Mdouble effectiveDiameter = 2.0*getEffectiveRadius();

        //calculate the overlap above which the max. unloading stiffness becomes active (the 'fluid branch')
        static Mdouble maxFactor = 1
            -mathsFunc::square(cbrt((species->getLoadingModulus()+species->getCohesionModulus())/species->getUnloadingModulusMax()));
        Mdouble deltaStar = species->getPenetrationDepthMax() * effectiveDiameter/maxFactor;
    
        //increase max overlap if necessary
        if (getOverlap()>getMaxOverlap()) {
            setMaxOverlap(getOverlap());
            std::cout << "," << getHandler()->getDPMBase()->getTime();
        }
        //limit max overlap if necessary
        if (getMaxOverlap()>deltaStar)
            setMaxOverlap(deltaStar);
            
        //calculate the unloading modulus
        Mdouble loadingCohesionModulus = species->getLoadingModulus()+species->getCohesionModulus();
        Mdouble unloadingModulus = loadingCohesionModulus
            + (species->getUnloadingModulusMax() - loadingCohesionModulus) * (getMaxOverlap() / deltaStar);
            
        //calculate the overlap where the force is minimal
        Mdouble factor = 1-mathsFunc::square(cbrt(loadingCohesionModulus/unloadingModulus));
        Mdouble minOverlap = factor*maxOverlap_;

        //add dissipative force
        Mdouble normalForce = -species->getDissipation() * getNormalRelativeVelocity();

        //compute elastic force
        if (getOverlap() < minOverlap) {
            //decrease max overlap if in cohesive range
            std::cout << "." << getHandler()->getDPMBase()->getTime();
            setMaxOverlap(getOverlap()/factor);
        } else {
            Mdouble contactRadius = sqrt(2.0*effectiveDiameter * (getOverlap()-minOverlap));
            normalForce += 4./3.*unloadingModulus * contactRadius *(getOverlap()-minOverlap);
        }
                   
        setAbsoluteNormalForce(std::abs(normalForce)); //used for the friction force calculations;
        
        Mdouble contactRadius = sqrt(2.0*effectiveDiameter * getOverlap());
        normalForce -= 4./3.*species->getCohesionModulus() * contactRadius *getOverlap();
            
        setForce(getNormal() * normalForce);
        setTorque(Vec3D(0.0, 0.0, 0.0));
        
        //now add the sintering model 'modified Frenkel' of the Pokula paper
        //plasticOverlap_+=species->getSinterRate()*(deltaStar-plasticOverlap_)*getHandler()->getDPMBase()->getTimeStep();
        //x/a=sqrt(2*a*del)/a
        Mdouble x = 1e-10+sqrt(2.0*maxOverlap_/effectiveDiameter);
        //Mdouble x2 = x*x;
        Mdouble dx = 0.5/x;//+ x*(-0.5 + x2* (0.15625 + x2*(-0.0208333 +x2*(-0.00325521  +x2*(0.000189887 +x2*0.0000542535)))));
        Mdouble doverlap = x*dx*effectiveDiameter;
        //doverlap = 0.5/(factor*factor*plasticOverlap_);
        maxOverlap_ += species->getSinterRate()*doverlap*getHandler()->getDPMBase()->getTimeStep();
    }
    else
    {
        setAbsoluteNormalForce(0.0);
        setForce(Vec3D(0.0, 0.0, 0.0));
        setTorque(Vec3D(0.0, 0.0, 0.0));
    } 
}
void HertzianSinterInteraction::computeNormalForce()
{
    computeSinterForce();
}
Mdouble HertzianSinterInteraction::getElasticEnergy() const
{
   if (getOverlap() > 0)
        return 0.5 * (getSpecies()->getLoadingModulus() * mathsFunc::square(getOverlap()));
    else
        return 0.0;
}
const HertzianSinterNormalSpecies* HertzianSinterInteraction::getSpecies() const
{
    return dynamic_cast<const HertzianSinterNormalSpecies*>(getBaseSpecies());
}
Mdouble HertzianSinterInteraction::getMaxOverlap() const
{
    return maxOverlap_;
}
void HertzianSinterInteraction::setMaxOverlap(const Mdouble maxOverlap)
{
    maxOverlap_ = maxOverlap;
}
Mdouble HertzianSinterInteraction::getUnloadingModulus() const
{
    const HertzianSinterNormalSpecies* species = getSpecies();
    Mdouble effectiveDiameter = 2.0*getEffectiveRadius();
    Mdouble deltaMaxFluid = species->getPenetrationDepthMax() * effectiveDiameter / (1.0-species->getLoadingModulus()/species->getUnloadingModulusMax());
    if (getOverlap() > deltaMaxFluid)
        return species->getUnloadingModulusMax();
    else
        return species->getLoadingModulus() + (species->getUnloadingModulusMax() - species->getLoadingModulus()) * getMaxOverlap()/deltaMaxFluid;
}