bool Law2_ScGeom_MindlinPhys_HertzWithLinearShear::go(shared_ptr<IGeom>& ig, shared_ptr<IPhys>& ip, Interaction* contact){
Body::id_t id1(contact->getId1()), id2(contact->getId2());
ScGeom* geom = static_cast<ScGeom*>(ig.get());
MindlinPhys* phys=static_cast<MindlinPhys*>(ip.get());
const Real uN=geom->penetrationDepth;
if (uN<0) {
if (neverErase) {phys->shearForce = phys->normalForce = Vector3r::Zero(); phys->kn=phys->ks=0; return true;}
else return false;
}
// normal force
Real Fn=phys->kno*pow(uN,3/2.);
phys->normalForce=Fn*geom->normal;
//phys->kn=3./2.*phys->kno*std::pow(uN,0.5); // update stiffness, not needed
// shear force
Vector3r& Fs=geom->rotate(phys->shearForce);
Real ks= nonLin>0 ? phys->kso*std::pow(uN,0.5) : phys->kso;
Vector3r shearIncrement;
if(nonLin>1){
State *de1=Body::byId(id1,scene)->state.get(), *de2=Body::byId(id2,scene)->state.get();
Vector3r shiftVel=scene->isPeriodic ? Vector3r(scene->cell->velGrad*scene->cell->hSize*contact->cellDist.cast<Real>()) : Vector3r::Zero();
Vector3r shift2 = scene->isPeriodic ? Vector3r(scene->cell->hSize*contact->cellDist.cast<Real>()): Vector3r::Zero();
Vector3r incidentV = geom->getIncidentVel(de1, de2, scene->dt, shift2, shiftVel, /*preventGranularRatcheting*/ nonLin>2 );
Vector3r incidentVn = geom->normal.dot(incidentV)*geom->normal; // contact normal velocity
Vector3r incidentVs = incidentV-incidentVn; // contact shear velocity
shearIncrement=incidentVs*scene->dt;
} else { shearIncrement=geom->shearIncrement(); }
Fs-=ks*shearIncrement;
// Mohr-Coulomb slip
Real maxFs2=pow(Fn,2)*pow(phys->tangensOfFrictionAngle,2);
if(Fs.squaredNorm()>maxFs2) Fs*=sqrt(maxFs2)/Fs.norm();
// apply forces
Vector3r f=-phys->normalForce-phys->shearForce; /* should be a reference returned by geom->rotate */ assert(phys->shearForce==Fs);
scene->forces.addForce(id1,f);
scene->forces.addForce(id2,-f);
scene->forces.addTorque(id1,(geom->radius1-.5*geom->penetrationDepth)*geom->normal.cross(f));
scene->forces.addTorque(id2,(geom->radius2-.5*geom->penetrationDepth)*geom->normal.cross(f));
return true;
}
bool Law2_ScGeom_MindlinPhys_MindlinDeresiewitz::go(shared_ptr<IGeom>& ig, shared_ptr<IPhys>& ip, Interaction* contact){
Body::id_t id1(contact->getId1()), id2(contact->getId2());
ScGeom* geom = static_cast<ScGeom*>(ig.get());
MindlinPhys* phys=static_cast<MindlinPhys*>(ip.get());
const Real uN=geom->penetrationDepth;
if (uN<0) {
if (neverErase) {phys->shearForce = phys->normalForce = Vector3r::Zero(); phys->kn=phys->ks=0; return true;}
else {return false;}
}
// normal force
Real Fn=phys->kno*pow(uN,3/2.);
phys->normalForce=Fn*geom->normal;
// exactly zero would not work with the shear formulation, and would give zero shear force anyway
if(Fn==0) return true;
//phys->kn=3./2.*phys->kno*std::pow(uN,0.5); // update stiffness, not needed
// contact radius
Real R=geom->radius1*geom->radius2/(geom->radius1+geom->radius2);
phys->radius=pow(Fn*pow(R,3/2.)/phys->kno,1/3.);
// shear force: transform, but keep the old value for now
geom->rotate(phys->usTotal);
//Vector3r usOld=phys->usTotal; //The variable set but not used
Vector3r dUs=geom->shearIncrement();
phys->usTotal-=dUs;
#if 0
Vector3r shearIncrement;
shearIncrement=geom->shearIncrement();
Fs-=ks*shearIncrement;
// Mohr-Coulomb slip
Real maxFs2=pow(Fn,2)*pow(phys->tangensOfFrictionAngle,2);
if(Fs.squaredNorm()>maxFs2) Fs*=sqrt(maxFs2)/Fs.norm();
#endif
// apply forces
Vector3r f=-phys->normalForce-phys->shearForce;
scene->forces.addForce(id1,f);
scene->forces.addForce(id2,-f);
scene->forces.addTorque(id1,(geom->radius1-.5*geom->penetrationDepth)*geom->normal.cross(f));
scene->forces.addTorque(id2,(geom->radius2-.5*geom->penetrationDepth)*geom->normal.cross(f));
return true;
}
bool Law2_ScGeom_MindlinPhys_Mindlin::go(shared_ptr<IGeom>& ig, shared_ptr<IPhys>& ip, Interaction* contact){
const Real& dt = scene->dt; // get time step
Body::id_t id1 = contact->getId1(); // get id body 1
Body::id_t id2 = contact->getId2(); // get id body 2
State* de1 = Body::byId(id1,scene)->state.get();
State* de2 = Body::byId(id2,scene)->state.get();
ScGeom* scg = static_cast<ScGeom*>(ig.get());
MindlinPhys* phys = static_cast<MindlinPhys*>(ip.get());
const shared_ptr<Body>& b1=Body::byId(id1,scene);
const shared_ptr<Body>& b2=Body::byId(id2,scene);
bool useDamping=(phys->betan!=0. || phys->betas!=0. || phys->alpha!=0.);
bool LinDamp=true;
if (phys->alpha!=0.) {LinDamp=false;} // use non linear damping
// tangential and normal stiffness coefficients, recomputed from betan,betas at every step
Real cn=0, cs=0;
/****************/
/* NORMAL FORCE */
/****************/
Real uN = scg->penetrationDepth; // get overlapping
if (uN<0) {
if (neverErase) {phys->shearForce = phys->normalForce = Vector3r::Zero(); phys->kn=phys->ks=0; return true;}
else return false;
}
/* Hertz-Mindlin's formulation (PFC)
Note that the normal stiffness here is a secant value (so as it is cannot be used in the GSTS)
In the first place we get the normal force and then we store kn to be passed to the GSTS */
Real Fn = phys->kno*std::pow(uN,1.5); // normal Force (scalar)
if (includeAdhesion) {
Fn -= phys->adhesionForce; // include adhesion force to account for the effect of Van der Waals interactions
phys->isAdhesive = (Fn<0); // set true the bool to count the number of adhesive contacts
}
phys->normalForce = Fn*scg->normal; // normal Force (vector)
if (calcEnergy){
Real R=scg->radius1*scg->radius2/(scg->radius1+scg->radius2);
phys->radius=pow((Fn+(includeAdhesion?phys->adhesionForce:0.))*pow(R,3/2.)/phys->kno,1/3.); // attribute not used anywhere, we do not need it
}
/*******************************/
/* TANGENTIAL NORMAL STIFFNESS */
/*******************************/
phys->kn = 3./2.*phys->kno*std::pow(uN,0.5); // here we store the value of kn to compute the time step
/******************************/
/* TANGENTIAL SHEAR STIFFNESS */
/******************************/
phys->ks = phys->kso*std::pow(uN,0.5); // get tangential stiffness (this is a tangent value, so we can pass it to the GSTS)
/************************/
/* DAMPING COEFFICIENTS */
/************************/
// Inclusion of local damping if requested
// viscous damping is defined for both linear and non-linear elastic case
if (useDamping && LinDamp){
Real mbar = (!b1->isDynamic() && b2->isDynamic()) ? de2->mass : ((!b2->isDynamic() && b1->isDynamic()) ? de1->mass : (de1->mass*de2->mass / (de1->mass + de2->mass))); // get equivalent mass if both bodies are dynamic, if not set it equal to the one of the dynamic body
//Real mbar = de1->mass*de2->mass / (de1->mass + de2->mass); // equivalent mass
Real Cn_crit = 2.*sqrt(mbar*phys->kn); // Critical damping coefficient (normal direction)
Real Cs_crit = 2.*sqrt(mbar*phys->ks); // Critical damping coefficient (shear direction)
// Note: to compare with the analytical solution you provide cn and cs directly (since here we used a different method to define c_crit)
cn = Cn_crit*phys->betan; // Damping normal coefficient
cs = Cs_crit*phys->betas; // Damping tangential coefficient
if(phys->kn<0 || phys->ks<0){ cerr<<"Negative stiffness kn="<<phys->kn<<" ks="<<phys->ks<<" for ##"<<b1->getId()<<"+"<<b2->getId()<<", step "<<scene->iter<<endl; }
}
else if (useDamping){ // (see Tsuji, 1992)
Real mbar = (!b1->isDynamic() && b2->isDynamic()) ? de2->mass : ((!b2->isDynamic() && b1->isDynamic()) ? de1->mass : (de1->mass*de2->mass / (de1->mass + de2->mass))); // get equivalent mass if both bodies are dynamic, if not set it equal to the one of the dynamic body
cn = phys->alpha*sqrt(mbar)*pow(uN,0.25); // normal viscous coefficient, see also [Antypov2011] eq. 10
cs = cn; // same value for shear viscous coefficient
}
/***************/
/* SHEAR FORCE */
/***************/
Vector3r& shearElastic = phys->shearElastic; // reference for shearElastic force
// Define shifts to handle periodicity
const Vector3r shift2 = scene->isPeriodic ? scene->cell->intrShiftPos(contact->cellDist): Vector3r::Zero();
const Vector3r shiftVel = scene->isPeriodic ? scene->cell->intrShiftVel(contact->cellDist): Vector3r::Zero();
// 1. Rotate shear force
shearElastic = scg->rotate(shearElastic);
Vector3r prev_FsElastic = shearElastic; // save shear force at previous time step
// 2. Get incident velocity, get shear and normal components
Vector3r incidentV = scg->getIncidentVel(de1, de2, dt, shift2, shiftVel, preventGranularRatcheting);
Vector3r incidentVn = scg->normal.dot(incidentV)*scg->normal; // contact normal velocity
Vector3r incidentVs = incidentV - incidentVn; // contact shear velocity
// 3. Get shear force (incrementally)
shearElastic = shearElastic - phys->ks*(incidentVs*dt);
/**************************************/
/* VISCOUS DAMPING (Normal direction) */
/**************************************/
// normal force must be updated here before we apply the Mohr-Coulomb criterion
if (useDamping){ // get normal viscous component
phys->normalViscous = cn*incidentVn;
Vector3r normTemp = phys->normalForce - phys->normalViscous; // temporary normal force
// viscous force should not exceed the value of current normal force, i.e. no attraction force should be permitted if particles are non-adhesive
// if particles are adhesive, then fixed the viscous force at maximum equal to the adhesion force
// *** enforce normal force to zero if no adhesion is permitted ***
if (phys->adhesionForce==0.0 || !includeAdhesion){
if (normTemp.dot(scg->normal)<0.0){
phys->normalForce = Vector3r::Zero();
phys->normalViscous = phys->normalViscous + normTemp; // normal viscous force is such that the total applied force is null - it is necessary to compute energy correctly!
}
else{phys->normalForce -= phys->normalViscous;}
}
else if (includeAdhesion && phys->adhesionForce!=0.0){
// *** limit viscous component to the max adhesive force ***
if (normTemp.dot(scg->normal)<0.0 && (phys->normalViscous.norm() > phys->adhesionForce) ){
Real normVisc = phys->normalViscous.norm(); Vector3r normViscVector = phys->normalViscous/normVisc;
phys->normalViscous = phys->adhesionForce*normViscVector;
phys->normalForce -= phys->normalViscous;
}
// *** apply viscous component - in the presence of adhesion ***
else {phys->normalForce -= phys->normalViscous;}
}
if (calcEnergy) {normDampDissip += phys->normalViscous.dot(incidentVn*dt);} // calc dissipation of energy due to normal damping
}
/*************************************/
/* SHEAR DISPLACEMENT (elastic only) */
/*************************************/
Vector3r& us_elastic = phys->usElastic;
us_elastic = scg->rotate(us_elastic); // rotate vector
Vector3r prevUs_el = us_elastic; // store previous elastic shear displacement (already rotated)
us_elastic -= incidentVs*dt; // add shear increment
/****************************************/
/* SHEAR DISPLACEMENT (elastic+plastic) */
/****************************************/
Vector3r& us_total = phys->usTotal;
us_total = scg->rotate(us_total); // rotate vector
Vector3r prevUs_tot = us_total; // store previous total shear displacement (already rotated)
us_total -= incidentVs*dt; // add shear increment NOTE: this vector is not passed into the failure criterion, hence it holds also the plastic part of the shear displacement
bool noShearDamp = false; // bool to decide whether we need to account for shear damping dissipation or not
/********************/
/* MOHR-COULOMB law */
/********************/
phys->isSliding=false;
phys->shearViscous=Vector3r::Zero(); // reset so that during sliding, the previous values is not there
Fn = phys->normalForce.norm();
if (!includeAdhesion) {
Real maxFs = Fn*phys->tangensOfFrictionAngle;
if (shearElastic.squaredNorm() > maxFs*maxFs){
phys->isSliding=true;
noShearDamp = true; // no damping is added in the shear direction, hence no need to account for shear damping dissipation
Real ratio = maxFs/shearElastic.norm();
shearElastic *= ratio; phys->shearForce = shearElastic; /*store only elastic shear displacement*/ us_elastic*= ratio;
if (calcEnergy) {frictionDissipation += (us_total-prevUs_tot).dot(shearElastic);} // calculate energy dissipation due to sliding behavior
}
else if (useDamping){ // add current contact damping if we do not slide and if damping is requested
phys->shearViscous = cs*incidentVs; // get shear viscous component
phys->shearForce = shearElastic - phys->shearViscous;}
else if (!useDamping) {phys->shearForce = shearElastic;} // update the shear force at the elastic value if no damping is present and if we passed MC
}
else { // Mohr-Coulomb formulation adpated due to the presence of adhesion (see Thornton, 1991).
Real maxFs = phys->tangensOfFrictionAngle*(phys->adhesionForce+Fn); // adhesionForce already included in normalForce (above)
if (shearElastic.squaredNorm() > maxFs*maxFs){
phys->isSliding=true;
noShearDamp = true; // no damping is added in the shear direction, hence no need to account for shear damping dissipation
Real ratio = maxFs/shearElastic.norm(); shearElastic *= ratio; phys->shearForce = shearElastic; /*store only elastic shear displacement*/ us_elastic *= ratio;
if (calcEnergy) {frictionDissipation += (us_total-prevUs_tot).dot(shearElastic);} // calculate energy dissipation due to sliding behavior
}
else if (useDamping){ // add current contact damping if we do not slide and if damping is requested
phys->shearViscous = cs*incidentVs; // get shear viscous component
phys->shearForce = shearElastic - phys->shearViscous;}
else if (!useDamping) {phys->shearForce = shearElastic;} // update the shear force at the elastic value if no damping is present and if we passed MC
}
/************************/
/* SHEAR ELASTIC ENERGY */
/************************/
// NOTE: shear elastic energy calculation must come after the MC criterion, otherwise displacements and forces are not updated
if (calcEnergy) {
shearEnergy += (us_elastic-prevUs_el).dot((shearElastic+prev_FsElastic)/2.); // NOTE: no additional energy if we perform sliding since us_elastic and prevUs_el will hold the same value (in fact us_elastic is only keeping the elastic part). We work out the area of the trapezium.
}
/**************************************************/
/* VISCOUS DAMPING (energy term, shear direction) */
/**************************************************/
if (useDamping){ // get normal viscous component (the shear one is calculated inside Mohr-Coulomb criterion, see above)
if (calcEnergy) {if (!noShearDamp) {shearDampDissip += phys->shearViscous.dot(incidentVs*dt);}} // calc energy dissipation due to viscous linear damping
}
/****************/
/* APPLY FORCES */
/****************/
if (!scene->isPeriodic)
applyForceAtContactPoint(-phys->normalForce - phys->shearForce, scg->contactPoint , id1, de1->se3.position, id2, de2->se3.position);
else { // in scg we do not wrap particles positions, hence "applyForceAtContactPoint" cannot be used
Vector3r force = -phys->normalForce - phys->shearForce;
scene->forces.addForce(id1,force);
scene->forces.addForce(id2,-force);
scene->forces.addTorque(id1,(scg->radius1-0.5*scg->penetrationDepth)* scg->normal.cross(force));
scene->forces.addTorque(id2,(scg->radius2-0.5*scg->penetrationDepth)* scg->normal.cross(force));
}
/********************************************/
/* MOMENT CONTACT LAW */
/********************************************/
if (includeMoment){
// *** Bending ***//
// new code to compute relative particle rotation (similar to the way the shear is computed)
// use scg function to compute relAngVel
Vector3r relAngVel = scg->getRelAngVel(de1,de2,dt);
//Vector3r relAngVel = (b2->state->angVel-b1->state->angVel);
Vector3r relAngVelBend = relAngVel - scg->normal.dot(relAngVel)*scg->normal; // keep only the bending part
Vector3r relRot = relAngVelBend*dt; // relative rotation due to rolling behaviour
// incremental formulation for the bending moment (as for the shear part)
Vector3r& momentBend = phys->momentBend;
momentBend = scg->rotate(momentBend); // rotate moment vector (updated)
momentBend = momentBend-phys->kr*relRot; // add incremental rolling to the rolling vector
// ----------------------------------------------------------------------------------------
// *** Torsion ***//
Vector3r relAngVelTwist = scg->normal.dot(relAngVel)*scg->normal;
Vector3r relRotTwist = relAngVelTwist*dt; // component of relative rotation along n
// incremental formulation for the torsional moment
Vector3r& momentTwist = phys->momentTwist;
momentTwist = scg->rotate(momentTwist); // rotate moment vector (updated)
momentTwist = momentTwist-phys->ktw*relRotTwist;
#if 0
// code to compute the relative particle rotation
if (includeMoment){
Real rMean = (scg->radius1+scg->radius2)/2.;
// sliding motion
Vector3r duS1 = scg->radius1*(phys->prevNormal-scg->normal);
Vector3r duS2 = scg->radius2*(scg->normal-phys->prevNormal);
// rolling motion
Vector3r duR1 = scg->radius1*dt*b1->state->angVel.cross(scg->normal);
Vector3r duR2 = -scg->radius2*dt*b2->state->angVel.cross(scg->normal);
// relative position of the old contact point with respect to the new one
Vector3r relPosC1 = duS1+duR1;
Vector3r relPosC2 = duS2+duR2;
Vector3r duR = (relPosC1+relPosC2)/2.; // incremental displacement vector (same radius is temporarily assumed)
// check wheter rolling will be present, if not do nothing
Vector3r x=scg->normal.cross(duR);
Vector3r normdThetaR(Vector3r::Zero()); // initialize
if(x.squaredNorm()==0) { /* no rolling */ }
else {
Vector3r normdThetaR = x/x.norm(); // moment unit vector
phys->dThetaR = duR.norm()/rMean*normdThetaR;} // incremental rolling
// incremental formulation for the bending moment (as for the shear part)
Vector3r& momentBend = phys->momentBend;
momentBend = scg->rotate(momentBend); // rotate moment vector
momentBend = momentBend+phys->kr*phys->dThetaR; // add incremental rolling to the rolling vector FIXME: is the sign correct?
#endif
// check plasticity condition (only bending part for the moment)
Real MomentMax = phys->maxBendPl*phys->normalForce.norm();
Real scalarMoment = phys->momentBend.norm();
if (MomentMax>0){
if(scalarMoment > MomentMax)
{
Real ratio = MomentMax/scalarMoment; // to fix the moment to its yielding value
phys->momentBend *= ratio;
}
}
// apply moments
Vector3r moment = phys->momentTwist+phys->momentBend;
scene->forces.addTorque(id1,-moment);
scene->forces.addTorque(id2,moment);
}
return true;
// update variables
//phys->prevNormal = scg->normal;
}
// The following code was moved from Ip2_FrictMat_FrictMat_MindlinCapillaryPhys.cpp
void Ip2_FrictMat_FrictMat_MindlinCapillaryPhys::go( const shared_ptr<Material>& b1 //FrictMat
, const shared_ptr<Material>& b2 // FrictMat
, const shared_ptr<Interaction>& interaction)
{
if(interaction->phys) return; // no updates of an already existing contact necessary
shared_ptr<MindlinCapillaryPhys> contactPhysics(new MindlinCapillaryPhys());
interaction->phys = contactPhysics;
FrictMat* mat1 = YADE_CAST<FrictMat*>(b1.get());
FrictMat* mat2 = YADE_CAST<FrictMat*>(b2.get());
/* from interaction physics */
Real Ea = mat1->young;
Real Eb = mat2->young;
Real Va = mat1->poisson;
Real Vb = mat2->poisson;
Real fa = mat1->frictionAngle;
Real fb = mat2->frictionAngle;
/* from interaction geometry */
GenericSpheresContact* scg = YADE_CAST<GenericSpheresContact*>(interaction->geom.get());
Real Da = scg->refR1>0 ? scg->refR1 : scg->refR2;
Real Db = scg->refR2;
//Vector3r normal=scg->normal; //The variable set but not used
/* calculate stiffness coefficients */
Real Ga = Ea/(2*(1+Va));
Real Gb = Eb/(2*(1+Vb));
Real G = (Ga+Gb)/2; // average of shear modulus
Real V = (Va+Vb)/2; // average of poisson's ratio
Real E = Ea*Eb/((1.-std::pow(Va,2))*Eb+(1.-std::pow(Vb,2))*Ea); // Young modulus
Real R = Da*Db/(Da+Db); // equivalent radius
Real Rmean = (Da+Db)/2.; // mean radius
Real Kno = 4./3.*E*sqrt(R); // coefficient for normal stiffness
Real Kso = 2*sqrt(4*R)*G/(2-V); // coefficient for shear stiffness
Real frictionAngle = std::min(fa,fb);
Real Adhesion = 4.*Mathr::PI*R*gamma; // calculate adhesion force as predicted by DMT theory
/* pass values calculated from above to MindlinCapillaryPhys */
contactPhysics->tangensOfFrictionAngle = std::tan(frictionAngle);
//mindlinPhys->prevNormal = scg->normal; // used to compute relative rotation
contactPhysics->kno = Kno; // this is just a coeff
contactPhysics->kso = Kso; // this is just a coeff
contactPhysics->adhesionForce = Adhesion;
contactPhysics->kr = krot;
contactPhysics->ktw = ktwist;
contactPhysics->maxBendPl = eta*Rmean; // does this make sense? why do we take Rmean?
/* compute viscous coefficients */
if(en && betan) throw std::invalid_argument("Ip2_FrictMat_FrictMat_MindlinCapillaryPhys: only one of en, betan can be specified.");
if(es && betas) throw std::invalid_argument("Ip2_FrictMat_FrictMat_MindlinCapillaryPhys: only one of es, betas can be specified.");
// en or es specified, just compute alpha, otherwise alpha remains 0
if(en || es){
Real logE = log((*en)(mat1->id,mat2->id));
contactPhysics->alpha = -sqrt(5/6.)*2*logE/sqrt(pow(logE,2)+pow(Mathr::PI,2))*sqrt(2*E*sqrt(R)); // (see Tsuji, 1992)
}
// betan specified, use that value directly; otherwise give zero
else{
contactPhysics->betan=betan ? (*betan)(mat1->id,mat2->id) : 0;
contactPhysics->betas=betas ? (*betas)(mat1->id,mat2->id) : contactPhysics->betan;
}
};
void Law2_ScGeom_CFpmPhys_CohesiveFrictionalPM::go(shared_ptr<IGeom>& ig, shared_ptr<IPhys>& ip, Interaction* contact){
ScGeom* geom = static_cast<ScGeom*>(ig.get());
CFpmPhys* phys = static_cast<CFpmPhys*>(ip.get());
const int &id1 = contact->getId1();
const int &id2 = contact->getId2();
Body* b1 = Body::byId(id1,scene).get();
Body* b2 = Body::byId(id2,scene).get();
Real displN = geom->penetrationDepth; // NOTE: the sign for penetrationdepth is different from ScGeom and Dem3DofGeom: geom->penetrationDepth>0 when spheres interpenetrate
Real Dtensile=phys->FnMax/phys->kn;
Real Dsoftening = phys->strengthSoftening*Dtensile;
/*to set the equilibrium distance between all cohesive elements when they first meet -> allows one to work with initial stress-free assembly*/
if ( contact->isFresh(scene) ) { phys->initD = displN; phys->normalForce = Vector3r::Zero(); phys->shearForce = Vector3r::Zero();}
Real D = displN - phys->initD; // interparticular distance is computed depending on the equilibrium distance
/* Determination of interaction */
if (D < 0){ //spheres do not touch
if (!phys->isCohesive){ scene->interactions->requestErase(contact); return; } // destroy the interaction before calculation
if ((phys->isCohesive) && (abs(D) > (Dtensile + Dsoftening))) { // spheres are bonded and the interacting distance is greater than the one allowed ny the defined cohesion
phys->isCohesive=false;
// update body state with the number of broken bonds
CFpmState* st1=dynamic_cast<CFpmState*>(b1->state.get());
CFpmState* st2=dynamic_cast<CFpmState*>(b2->state.get());
st1->numBrokenCohesive+=1;
st2->numBrokenCohesive+=1;
//// the same thing but from ConcretePM
//const shared_ptr<Body>& body1=Body::byId(contact->getId1(),scene), body2=Body::byId(contact->getId2(),scene); assert(body1); assert(body2);
//const shared_ptr<CFpmState>& st1=YADE_PTR_CAST<CFpmState>(body1->state), st2=YADE_PTR_CAST<CFpmState>(body2->state);
//{ boost::mutex::scoped_lock lock(st1->updateMutex); st1->numBrokenCohesive+=1; }
//{ boost::mutex::scoped_lock lock(st2->updateMutex); st2->numBrokenCohesive+=1; }
// end of update
scene->interactions->requestErase(contact); return;
}
}
/*NormalForce*/
Real Fn=0, Dsoft=0;
if ((D < 0) && (abs(D) > Dtensile)) { //to take into account strength softening
Dsoft = D+Dtensile; // Dsoft<0 for a negative value of Fn (attractive force)
Fn = -(phys->FnMax+(phys->kn/phys->strengthSoftening)*Dsoft); // computes FnMax - FnSoftening
}
else {
Fn = phys->kn*D;
}
phys->normalForce = Fn*geom->normal; // NOTE normal is position2-position1 - It is directed from particle1 to particle2
/*ShearForce*/
Vector3r& shearForce = phys->shearForce;
// using scGeom function rotateAndGetShear
State* st1 = Body::byId(id1,scene)->state.get();
State* st2 = Body::byId(id2,scene)->state.get();
geom->rotate(phys->shearForce);
const Vector3r& dus = geom->shearIncrement();
//Linear elasticity giving "trial" shear force
shearForce -= phys->ks*dus;
// needed for the next timestep
phys->prevNormal = geom->normal;
/* Morh-Coulomb criterion */
Real maxFs = phys->FsMax + Fn*phys->tanFrictionAngle;
if (shearForce.squaredNorm() > maxFs*maxFs){
shearForce*=maxFs/shearForce.norm(); // to fix the shear force to its yielding value
}
/* Apply forces */
Vector3r f = phys->normalForce + shearForce;
// these lines to adapt to periodic boundary conditions (NOTE applyForceAtContactPoint computes torque induced by normal and shear force too)
if (!scene->isPeriodic)
applyForceAtContactPoint(f , geom->contactPoint , id2, st2->se3.position, id1, st1->se3.position);
else { // in scg we do not wrap particles positions, hence "applyForceAtContactPoint" cannot be used when scene is periodic
scene->forces.addForce(id1,-f);
scene->forces.addForce(id2,f);
scene->forces.addTorque(id1,(geom->radius1-0.5*geom->penetrationDepth)* geom->normal.cross(-f));
scene->forces.addTorque(id2,(geom->radius2-0.5*geom->penetrationDepth)* geom->normal.cross(-f));
}
/* Moment Rotation Law */
// NOTE this part could probably be computed in ScGeom to avoid copy/paste multiplication !!!
Quaternionr delta( b1->state->ori * phys->initialOrientation1.conjugate() *phys->initialOrientation2 * b2->state->ori.conjugate()); delta.normalize(); //relative orientation
AngleAxisr aa(delta); // axis of rotation - this is the Moment direction UNIT vector; angle represents the power of resistant ELASTIC moment
if(aa.angle() > Mathr::PI) aa.angle() -= Mathr::TWO_PI; // angle is between 0 and 2*pi, but should be between -pi and pi
phys->cumulativeRotation = aa.angle();
//Find angle*axis. That's all. But first find angle about contact normal. Result is scalar. Axis is contact normal.
Real angle_twist(aa.angle() * aa.axis().dot(geom->normal) ); //rotation about normal
Vector3r axis_twist(angle_twist * geom->normal);
Vector3r moment_twist(axis_twist * phys->kr);
Vector3r axis_bending(aa.angle()*aa.axis() - axis_twist); //total rotation minus rotation about normal
Vector3r moment_bending(axis_bending * phys->kr);
Vector3r moment = moment_twist + moment_bending;
Real MomentMax = phys->maxBend*std::fabs(phys->normalForce.norm());
Real scalarMoment = moment.norm();
/*Plastic moment */
if(scalarMoment > MomentMax)
{
Real ratio = 0;
ratio *= MomentMax/scalarMoment; // to fix the moment to its yielding value
moment *= ratio;
moment_twist *= ratio;
moment_bending *= ratio;
}
phys->moment_twist = moment_twist;
phys->moment_bending = moment_bending;
scene->forces.addTorque(id1,-moment);
scene->forces.addTorque(id2, moment);
}
bool Law2_ScGeom_JCFpmPhys_JointedCohesiveFrictionalPM::go(shared_ptr<IGeom>& ig, shared_ptr<IPhys>& ip, Interaction* contact){
const int &id1 = contact->getId1();
const int &id2 = contact->getId2();
ScGeom* geom = static_cast<ScGeom*>(ig.get());
JCFpmPhys* phys = static_cast<JCFpmPhys*>(ip.get());
Body* b1 = Body::byId(id1,scene).get();
Body* b2 = Body::byId(id2,scene).get();
Real Dtensile=phys->FnMax/phys->kn;
string fileCracks = "cracks_"+Key+".txt";
string fileMoments = "moments_"+Key+".txt";
/// Defines the interparticular distance used for computation
Real D = 0;
/*this is for setting the equilibrium distance between all cohesive elements at the first contact detection*/
if ( contact->isFresh(scene) ) {
phys->normalForce = Vector3r::Zero();
phys->shearForce = Vector3r::Zero();
if ((smoothJoint) && (phys->isOnJoint)) {
phys->jointNormal = geom->normal.dot(phys->jointNormal)*phys->jointNormal; //to set the joint normal colinear with the interaction normal
phys->jointNormal.normalize();
phys->initD = std::abs((b1->state->pos - b2->state->pos).dot(phys->jointNormal)); // to set the initial gap as the equilibrium gap
} else {
phys->initD = geom->penetrationDepth;
}
}
if ( smoothJoint && phys->isOnJoint ) {
if ( phys->more || ( phys-> jointCumulativeSliding > (2*min(geom->radius1,geom->radius2)) ) ) {
if (!neverErase) return false;
else {
phys->shearForce = Vector3r::Zero();
phys->normalForce = Vector3r::Zero();
phys->isCohesive =0;
phys->FnMax = 0;
phys->FsMax = 0;
return true;
}
} else {
D = phys->initD - std::abs((b1->state->pos - b2->state->pos).dot(phys->jointNormal));
}
} else {
D = geom->penetrationDepth - phys->initD;
}
phys->crackJointAperture = D<0? -D : 0.; // for DFNFlow
if (!phys->momentBroken && useStrainEnergy) phys->strainEnergy = 0.5*((pow(phys->normalForce.norm(),2)/phys->kn) + (pow(phys->shearForce.norm(),2)/phys->ks));
else if (!phys->momentBroken && !useStrainEnergy) computeKineticEnergy(phys, b1, b2);
//Compute clustered acoustic emission events:
if (recordMoments && !neverErase){
cerr << "Acoustic emissions algorithm requires neverErase=True, changing value from False to True" << endl;
neverErase=true;
}
if (phys->momentBroken && recordMoments && !phys->momentCalculated){
if (phys->originalClusterEvent && !phys->computedCentroid) computeCentroid(phys);
if (phys->originalClusterEvent) computeClusteredMoment(phys);
if (phys->momentCalculated && phys->momentMagnitude!=0){
std::ofstream file (fileMoments.c_str(), !momentsFileExist ? std::ios::trunc : std::ios::app);
if(file.tellp()==0){ file <<"i p0 p1 p2 moment numInts eventNum time beginTime"<<endl; }
file << boost::lexical_cast<string> ( scene->iter )<<" "<< boost::lexical_cast<string> ( phys->momentCentroid[0] ) <<" "<< boost::lexical_cast<string> ( phys->momentCentroid[1] ) <<" "<< boost::lexical_cast<string> ( phys->momentCentroid[2] ) <<" "<< boost::lexical_cast<string> ( phys->momentMagnitude ) << " " << boost::lexical_cast<string> ( phys->clusterInts.size() ) << " " << boost::lexical_cast<string> ( phys->eventNumber ) << " " << boost::lexical_cast<string> (scene->time) << " " << boost::lexical_cast<string> (phys->eventBeginTime) << endl;
momentsFileExist=true;
}
}
/* Determination of interaction */
if (D < 0) { //tensile configuration
if ( !phys->isCohesive) {
if (!neverErase) return false;
else {
phys->shearForce = Vector3r::Zero();
phys->normalForce = Vector3r::Zero();
phys->isCohesive =0;
phys->FnMax = 0;
phys->FsMax = 0;
return true;
}
}
if ( phys->isCohesive && (phys->FnMax>0) && (std::abs(D)>Dtensile) ) {
nbTensCracks++;
phys->isCohesive = 0;
phys->FnMax = 0;
phys->FsMax = 0;
/// Do we need both the following lines?
phys->breakOccurred = true; // flag to trigger remesh for DFNFlowEngine
phys->isBroken = true; // flag for DFNFlowEngine
// update body state with the number of broken bonds -> do we really need that?
JCFpmState* st1=dynamic_cast<JCFpmState*>(b1->state.get());
JCFpmState* st2=dynamic_cast<JCFpmState*>(b2->state.get());
st1->nbBrokenBonds++;
st2->nbBrokenBonds++;
st1->damageIndex+=1.0/st1->nbInitBonds;
st2->damageIndex+=1.0/st2->nbInitBonds;
phys->momentBroken = true;
Real scalarNF=phys->normalForce.norm();
Real scalarSF=phys->shearForce.norm();
totalTensCracksE+=0.5*( ((scalarNF*scalarNF)/phys->kn) + ((scalarSF*scalarSF)/phys->ks) );
totalCracksSurface += phys->crossSection;
if (recordCracks){
std::ofstream file (fileCracks.c_str(), !cracksFileExist ? std::ios::trunc : std::ios::app);
if(file.tellp()==0){ file <<"iter time p0 p1 p2 type size norm0 norm1 norm2 nrg onJnt"<<endl; }
Vector3r crackNormal=Vector3r::Zero();
if ((smoothJoint) && (phys->isOnJoint)) { crackNormal=phys->jointNormal; } else {crackNormal=geom->normal;}
file << boost::lexical_cast<string> ( scene->iter ) << " " << boost::lexical_cast<string> ( scene->time ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[0] ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[1] ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[2] ) <<" "<< 1 <<" "<< boost::lexical_cast<string> ( 0.5*(geom->radius1+geom->radius2) ) <<" "<< boost::lexical_cast<string> ( crackNormal[0] ) <<" "<< boost::lexical_cast<string> ( crackNormal[1] ) <<" "<< boost::lexical_cast<string> ( crackNormal[2] ) <<" "<< boost::lexical_cast<string> ( 0.5*( ((scalarNF*scalarNF)/phys->kn) + ((scalarSF*scalarSF)/phys->ks) ) ) <<" "<< boost::lexical_cast<string> ( phys->isOnJoint ) << endl;
}
if (recordMoments && !phys->momentCalculated){
checkForCluster(phys, geom, b1, b2, contact);
clusterInteractions(phys, contact);
computeTemporalWindow(phys, b1, b2);
}
cracksFileExist=true;
if (!neverErase) return false;
else {
phys->shearForce = Vector3r::Zero();
phys->normalForce = Vector3r::Zero();
return true;
}
}
}
/* NormalForce */
Real Fn = 0;
Fn = phys->kn*D;
/* ShearForce */
Vector3r& shearForce = phys->shearForce;
Real jointSliding=0;
if ((smoothJoint) && (phys->isOnJoint)) {
/// incremental formulation (OK?)
Vector3r relativeVelocity = (b2->state->vel - b1->state->vel); // angVel are not taken into account as particles on joint don't rotate ????
Vector3r slidingVelocity = relativeVelocity - phys->jointNormal.dot(relativeVelocity)*phys->jointNormal;
Vector3r incrementalSliding = slidingVelocity*scene->dt;
shearForce -= phys->ks*incrementalSliding;
jointSliding = incrementalSliding.norm();
phys->jointCumulativeSliding += jointSliding;
} else {
shearForce = geom->rotate(phys->shearForce);
const Vector3r& incrementalShear = geom->shearIncrement();
shearForce -= phys->ks*incrementalShear;
}
/* Mohr-Coulomb criterion */
Real maxFs = phys->FsMax + Fn*phys->tanFrictionAngle;
Real scalarShearForce = shearForce.norm();
if (scalarShearForce > maxFs) {
if (scalarShearForce != 0)
shearForce*=maxFs/scalarShearForce;
else
shearForce=Vector3r::Zero();
if ((smoothJoint) && (phys->isOnJoint)) {phys->dilation=phys->jointCumulativeSliding*phys->tanDilationAngle-D; phys->initD+=(jointSliding*phys->tanDilationAngle);}
// if (!phys->isCohesive) {
// nbSlips++;
// totalSlipE+=((1./phys->ks)*(trialForce-shearForce))/*plastic disp*/.dot(shearForce)/*active force*/;
//
// if ( (recordSlips) && (maxFs!=0) ) {
// std::ofstream file (fileCracks.c_str(), !cracksFileExist ? std::ios::trunc : std::ios::app);
// if(file.tellp()==0){ file <<"iter time p0 p1 p2 type size norm0 norm1 norm2 nrg"<<endl; }
// Vector3r crackNormal=Vector3r::Zero();
// if ((smoothJoint) && (phys->isOnJoint)) { crackNormal=phys->jointNormal; } else {crackNormal=geom->normal;}
// file << boost::lexical_cast<string> ( scene->iter ) <<" " << boost::lexical_cast<string> ( scene->time ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[0] ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[1] ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[2] ) <<" "<< 0 <<" "<< boost::lexical_cast<string> ( 0.5*(geom->radius1+geom->radius2) ) <<" "<< boost::lexical_cast<string> ( crackNormal[0] ) <<" "<< boost::lexical_cast<string> ( crackNormal[1] ) <<" "<< boost::lexical_cast<string> ( crackNormal[2] ) <<" "<< boost::lexical_cast<string> ( ((1./phys->ks)*(trialForce-shearForce)).dot(shearForce) ) << endl;
// }
// cracksFileExist=true;
// }
if ( phys->isCohesive ) {
nbShearCracks++;
phys->isCohesive = 0;
phys->FnMax = 0;
phys->FsMax = 0;
/// Do we need both the following lines?
phys->breakOccurred = true; // flag to trigger remesh for DFNFlowEngine
phys->isBroken = true; // flag for DFNFlowEngine
phys->momentBroken = true;
// update body state with the number of broken bonds -> do we really need that?
JCFpmState* st1=dynamic_cast<JCFpmState*>(b1->state.get());
JCFpmState* st2=dynamic_cast<JCFpmState*>(b2->state.get());
st1->nbBrokenBonds++;
st2->nbBrokenBonds++;
st1->damageIndex+=1.0/st1->nbInitBonds;
st2->damageIndex+=1.0/st2->nbInitBonds;
Real scalarNF=phys->normalForce.norm();
Real scalarSF=phys->shearForce.norm();
totalShearCracksE+=0.5*( ((scalarNF*scalarNF)/phys->kn) + ((scalarSF*scalarSF)/phys->ks) );
totalCracksSurface += phys->crossSection;
if (recordCracks){
std::ofstream file (fileCracks.c_str(), !cracksFileExist ? std::ios::trunc : std::ios::app);
if(file.tellp()==0){ file <<"iter time p0 p1 p2 type size norm0 norm1 norm2 nrg onJnt"<<endl; }
Vector3r crackNormal=Vector3r::Zero();
if ((smoothJoint) && (phys->isOnJoint)) { crackNormal=phys->jointNormal; } else {crackNormal=geom->normal;}
file << boost::lexical_cast<string> ( scene->iter ) << " " << boost::lexical_cast<string> ( scene->time ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[0] ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[1] ) <<" "<< boost::lexical_cast<string> ( geom->contactPoint[2] ) <<" "<< 2 <<" "<< boost::lexical_cast<string> ( 0.5*(geom->radius1+geom->radius2) ) <<" "<< boost::lexical_cast<string> ( crackNormal[0] ) <<" "<< boost::lexical_cast<string> ( crackNormal[1] ) <<" "<< boost::lexical_cast<string> ( crackNormal[2] ) <<" "<< boost::lexical_cast<string> ( 0.5*( ((scalarNF*scalarNF)/phys->kn) + ((scalarSF*scalarSF)/phys->ks) ) ) <<" "<< boost::lexical_cast<string> ( phys->isOnJoint ) << endl;
}
cracksFileExist=true;
// // option 1: delete contact whatsoever (if in compression, it will be detected as a new contact at the next timestep -> actually, not necesarily because of the near neighbour interaction: there could be a gap between the bonded particles and thus a broken contact may not be frictional at the next timestep if the detection is done for strictly contacting particles...) -> to TEST
// if (!neverErase) return false;
// else {
// phys->shearForce = Vector3r::Zero();
// phys->normalForce = Vector3r::Zero();
// return true;
// }
if (recordMoments && !phys->momentCalculated){
checkForCluster(phys, geom, b1, b2, contact);
clusterInteractions(phys, contact);
computeTemporalWindow(phys, b1, b2);
}
// option 2: delete contact if in tension
// shearForce *= Fn*phys->tanFrictionAngle/scalarShearForce; // now or at the next timestep? should not be very different -> to TEST
if ( D < 0 ) { // spheres do not touch
if (!neverErase) return false;
else {
phys->shearForce = Vector3r::Zero();
phys->normalForce = Vector3r::Zero();
return true;
}
}
}
}
/* Apply forces */
if ((smoothJoint) && (phys->isOnJoint)) { phys->normalForce = Fn*phys->jointNormal; } else { phys->normalForce = Fn*geom->normal; }
Vector3r f = phys->normalForce + shearForce;
/// applyForceAtContactPoint computes torque also and, for now, we don't want rotation for particles on joint (some errors in calculation due to specific geometry)
//applyForceAtContactPoint(f, geom->contactPoint, I->getId2(), b2->state->pos, I->getId1(), b1->state->pos, scene);
scene->forces.addForce (id1,-f);
scene->forces.addForce (id2, f);
// simple solution to avoid torque computation for particles interacting on a smooth joint
if ( (phys->isOnJoint)&&(smoothJoint) ) return true;
/// those lines are needed if rootBody->forces.addForce and rootBody->forces.addMoment are used instead of applyForceAtContactPoint -> NOTE need to check for accuracy!!!
scene->forces.addTorque(id1,(geom->radius1-0.5*geom->penetrationDepth)* geom->normal.cross(-f));
scene->forces.addTorque(id2,(geom->radius2-0.5*geom->penetrationDepth)* geom->normal.cross(-f));
return true;
}