Computes the forces corresponding to sliding friction. More...

#include <MindlinInteraction.h>

Inheritance diagram for MindlinInteraction:

Public Types
typedef MindlinSpecies	SpeciesType
	An alias name for MindlinSpecies data type. More...

Public Member Functions
	MindlinInteraction (BaseInteractable P, BaseInteractable I, unsigned timeStamp)
	Constructor. More...

	MindlinInteraction (const MindlinInteraction &p)
	Copy constructor. More...

	MindlinInteraction ()
	Empty constructor. More...

virtual	~MindlinInteraction ()
	Destructor. More...

void	computeFrictionForce ()
	Computes the tangential force generated due to compression in the sliding spring. Does take into account if the interaction is between particle-particle or particle-wall. More...

void	read (std::istream &is) override
	Interaction read function, which accepts an std::istream as input. More...

void	write (std::ostream &os) const override
	Interaction write function, which accepts an std::ostream as input. More...

void	integrate (Mdouble timeStep) override
	Increments the amount of compression in sliding spring. More...

Mdouble	getElasticEnergy () const override
	Returns the amount of elastic energy stored in sliding spring. More...

Mdouble	getTangentialOverlap () const override
	Returns the amount of tangential overlap which is needed by BaseInteraction::writeToFstat(). More...

std::string	getBaseName () const
	Returns the type/name of interaction (sliding friction interaction) More...

const Vec3D	getTangentialForce () const override
	Returns the sliding friction force vector. More...

const Mdouble	getTangentialForceDirection () const

Mdouble	getAbsoluteNormalForcePrevious () const
	Returns the absolute value of the norm (length) of the previous Normal force vector. More...

void	setAbsoluteNormalForcePrevious (Mdouble absoluteNormalForcePrevious)
	allows the previous normal force to be (re)set from external classes More...

const MindlinSpecies *	getSpecies () const
	Returns a const pointer of type MindlinSpecies*. More...

void	reverseHistory () override
	A useful feature if one wants to return to the initial state of the spring. However, reverse history decrements the current state to the state corresponding to previous time step. Decrements the value of slidingSpring_. More...

void	rotateHistory (Matrix3D &rotationMatrix) override
	When periodic particles are used, some interactions need certain history properties rotated (e.g. tangential springs). This is the function for that. More...

void	setTangentialStiffnessZero (Mdouble newKt0)

Mdouble	getTangentialStiffnessZero ()

Mdouble	getTangentialStiffness ()

void	updateTangentialStiffnessZero (Mdouble rad, double shearMod)

void	updateTangentialStiffnessInitial (Mdouble fric)

void	updateTangentialStiffnessInitial2 (const Mdouble fric, const Vec3D direction)

void	updateTangentialStiffnessUnloading (const Mdouble fric, const Vec3D direction)

void	updateTangentialStiffnessReloading (const Mdouble fric, const Vec3D direction)

void	updateTangentialStiffnessReloadingTanUp (const Mdouble fric, const Vec3D direction)

void	updateTangentialStiffnessUnloadingTanDown (const Mdouble fric, const Vec3D direction)

void	updateK_t (const Mdouble fric, const Vec3D direction, const bool useTurningPoint, const bool isLoading)

Public Member Functions inherited from BaseInteraction
	BaseInteraction (BaseInteractable P, BaseInteractable I, Mdouble timeStamp)
	A constructor takes the BaseInteractable objects which are interacting (come into contact) and time the interaction starts. More...

	BaseInteraction (const BaseInteraction &p)
	Copy constructor. More...

	BaseInteraction ()
	Empty constructor. More...

virtual	~BaseInteraction ()
	The default destructor. More...

virtual void	actionsOnErase ()
	If an interaction needs to do something before it gets erased, add it here. E.g. Liquid bridges rupture at the end of their lifetime, and the liquid bridge volume has to be redistributed. The reason this action is not done in the destructor is that this action should not be taken when erasing ghost interactions. More...

virtual void	computeForce ()
	Virtual function that contains the force law between the two objects interacting. More...

void	writeToFStat (std::ostream &os) const
	Writes forces data to the FStat file. More...

virtual std::string	getName () const
	Virtual function which allows interactions to be named. More...

void	setDistance (Mdouble distance)
	Sets the interaction distance between the two interacting objects. More...

void	setNormal (Vec3D normal)
	Sets the normal vector between the two interacting objects. More...

void	setOverlap (Mdouble overlap)
	Set the overlap between the two interacting object. More...

void	setContactPoint (Vec3D contactPoint)
	Set the location of the contact point between the two interacting objects. More...

void	setTimeStamp (Mdouble timeStamp)
	Updates the time step of the interacting. Note, timesteps used to find completed interactions. More...

void	setSpecies (BaseSpecies *species)
	Set the Species of the interaction; note this can either be a Species or MixedSpecies. More...

void	setP (BaseInteractable *P)
	Sets the first object involved in the interaction (normally a particle). More...

void	setI (BaseInteractable *I)
	Sets the second object involved in the interaction (often particle or wall). More...

void	setHandler (InteractionHandler *handler)
	Sets the pointer to the interaction hander which is storing this interaction. More...

InteractionHandler *	getHandler () const
	Gets a point to the interaction handlers to which this interaction belongs. More...

const Vec3D &	getForce () const
	Gets the current force (vector) between the two interacting objects. More...

const Vec3D &	getTorque () const
	Gets the current torque (vector) between the two interacting objects. More...

const Vec3D &	getNormal () const
	Gets the normal vector between the two interacting objects. More...

const Vec3D &	getContactPoint () const
	Gets constant reference to contact point (vector). More...

Mdouble	getOverlap () const
	Returns a Mdouble with the current overlap between the two interacting objects. More...

Mdouble	getContactRadius () const
	Returns a Mdouble with the current contact between the two interacting objects. More...

void	removeFromHandler ()
	Removes this interaction from its interaction hander. More...

void	copySwitchPointer (const BaseInteractable original, BaseInteractable ghost) const
	This copies the interactions of the original particle and replaces the original with the ghost copy. More...

void	gatherContactStatistics ()

BaseInteractable *	getP ()
	Returns a pointer to first object involved in the interaction (normally a particle). More...

BaseInteractable *	getI ()

const BaseInteractable *	getP () const

const BaseInteractable *	getI () const
	Returns a constant pointer to the second object involved in the interaction. More...

Mdouble	getTimeStamp () const
	Returns an Mdouble which is the time stamp of the interaction. More...

Mdouble	getDistance () const
	Returns an Mdouble which is the norm (length) of distance vector. More...

const Vec3D &	getRelativeVelocity () const
	Returns a constant reference to a vector of relative velocity. More...

Mdouble	getNormalRelativeVelocity () const
	Returns a double which is the norm (length) of the relative velocity vector. More...

Mdouble	getAbsoluteNormalForce () const
	Returns the absolute value of the norm (length) of the Normal force vector. More...

virtual BaseInteraction *	copy () const =0
	Makes a copy of the interaction and returns a pointer to the copy. More...

unsigned int	getMultiContactIdentifier () const

void	setMultiContactIdentifier (unsigned int multiContactIdentifier_)

virtual void	actionsAfterTimeStep ()

virtual unsigned	getNumberOfFieldsVTK () const

virtual std::string	getTypeVTK (unsigned i) const

virtual std::string	getNameVTK (unsigned i) const

virtual std::vector< Mdouble >	getFieldVTK (unsigned i) const

void	setForce (Vec3D force)
	set total force (this is used by the normal force, tangential forces are added use addForce) More...

Public Member Functions inherited from BaseObject
	BaseObject ()
	Default constructor. More...

	BaseObject (const BaseObject &p)
	Copy constructor, copies all the objects BaseObject contains. More...

virtual	~BaseObject ()
	virtual destructor More...

virtual void	moveInHandler (const unsigned int index)
	Except that it is virtual, it does the same thing as setIndex() does. More...

void	setIndex (const unsigned int index)
	Allows one to assign an index to an object in the handler/container. More...

void	setId (const unsigned int id)
	Assigns a unique identifier to each object in the handler (container) which remains constant even after the object is deleted from the container/handler. More...

unsigned int	getIndex () const
	Returns the index of the object in the handler. More...

unsigned int	getId () const
	Returns the unique identifier of any particular object. More...

Protected Attributes
Vec3D	slidingSpring_
	Stores the amount of sliding spring ( $\delta$ ) compression from the expression $f_t=-k\delta-\nurelVel$ . Set in the member function integrate(), used in computeFrictionForce(). More...

Vec3D	slidingSpringPrevious_

Vec3D	slidingSpringVelocity_
	Stores the rate at which the sliding spring compressed or relaxed. Set in the member function computeFrictionForce() and used in integrate(). More...

Vec3D	tangentialForce_
	Computes the tangential force such that $\|f_t\|=\mu*\|f_n\|$ . Set and computed in computeFrictionForce(). More...

Vec3D	tangentialForcePrevious_

Mdouble	tangentialForceDirection_

Vec3D	tangentialForceTurningPointLU_

Vec3D	tangentialForceTurningPointUL_

Vec3D	tangentialForceTurningPointLUTemp_

Vec3D	tangentialForceTurningPointULTemp_

Vec3D	tangentialDisplacementTurningPointUL_

Vec3D	tangentialDisplacementTurningPointLU_

Mdouble	tangentialStiffnessZero_

Mdouble	tangentialStiffnessZeroPrevious_

Mdouble	tangentialStiffness_

bool	priorLoadingFlag_

Vec3D	tangentialForceTemp_

Vec3D	tangentialDisplacementTemp_

Vec3D	tangentialForceTemp2_

Vec3D	tangentialDisplacementTemp2_

Mdouble	tangentialDisplacementSL_

Vec3D	initialTangentialVelocity_

Mdouble	absoluteNormalForcePrevious_

Additional Inherited Members
Protected Member Functions inherited from BaseInteraction
Mdouble	getEffectiveRadius () const
	Returns a Mdouble to the effective radius of the interaction. (Not corrected for the overlap) More...

Mdouble	getEffectiveMass () const
	Returns a Mdouble to the effective radius of the interaction. (Not corrected for the overlap) More...

Mdouble	getEffectiveCorrectedRadius ()
	Returns a Mdouble to the effective radius corrected for the overlaps of the particles. More...

void	addForce (Vec3D force)
	add an force increment to the total force. More...

void	addTorque (Vec3D torque)

void	setTorque (Vec3D torque)
	set the total force (this is used by the normal force, tangential torques are added use addTorque) More...

void	setRelativeVelocity (Vec3D relativeVelocity)
	set the relative velocity of the current of the interactions. More...

void	setNormalRelativeVelocity (Mdouble normalRelativeVelocit)
	set the normal component of the relative velocity. More...

void	setAbsoluteNormalForce (Mdouble absoluteNormalForce)
	the absolute values of the norm (length) of the normal force More...

const BaseSpecies *	getBaseSpecies () const
	Return a constant point to BaseSpecies of the interaction. More...

virtual Mdouble	getElasticEnergyAtEquilibrium (Mdouble adhesiveForce) const

Detailed Description

Computes the forces corresponding to sliding friction.

Definition at line 39 of file MindlinInteraction.h.

Member Typedef Documentation

typedef MindlinSpecies MindlinInteraction::SpeciesType

An alias name for MindlinSpecies data type.

Definition at line 45 of file MindlinInteraction.h.

Constructor & Destructor Documentation

MindlinInteraction::MindlinInteraction	(	BaseInteractable *	P,
		BaseInteractable *	I,
		unsigned	timeStamp
	)

Constructor.

Parameters

[in]	P
[in]	I
[in]	timeStamp

Definition at line 39 of file MindlinInteraction.cc.

References absoluteNormalForcePrevious_, initialTangentialVelocity_, priorLoadingFlag_, Vec3D::setZero(), slidingSpring_, slidingSpringPrevious_, tangentialDisplacementSL_, tangentialDisplacementTemp2_, tangentialDisplacementTemp_, tangentialDisplacementTurningPointLU_, tangentialDisplacementTurningPointUL_, tangentialForceDirection_, tangentialForceTemp2_, tangentialForceTemp_, tangentialForceTurningPointLU_, tangentialForceTurningPointLUTemp_, tangentialForceTurningPointUL_, tangentialForceTurningPointULTemp_, tangentialStiffness_, tangentialStiffnessZero_, and tangentialStiffnessZeroPrevious_.

         : BaseInteraction(P, I, timeStamp)
 {
     slidingSpring_.setZero();
     //k_edit
     //setting the "previousSlidingSpring_" initially to zero, as before a contact
     //this parameter should (obviously) not carry a value.
     slidingSpringPrevious_.setZero();
     //similarly, setting the turning point tangential forces to zero, as a "new"
     //interaction will clearly have no such history
     tangentialForceTurningPointLU_.setZero();
     tangentialForceTurningPointUL_.setZero();
     //k_edit
     //setting the K_t0 parameter by default to zero...
     tangentialStiffnessZero_ = 0;
     //...and its previous value...
     tangentialStiffnessZeroPrevious_ = 0;
 
     absoluteNormalForcePrevious_ = 0;
     //k_edit
     //...and, similarly, the "normal" tangential stiffness, K_t
     tangentialStiffness_ = 0;
     //k_edit
     //setting the tangential force direction by default to -1 (i.e. acting against the motion!)
     tangentialForceDirection_ = -1;
     //k_edit
     //setting to zero the temporary 'holders' which store intermediate values of tangential force
     //and displacement during multiple-step force calculations
     tangentialForceTemp_.setZero();
     tangentialForceTemp2_.setZero();
     tangentialDisplacementTemp_.setZero();
     tangentialDisplacementTemp2_.setZero();
     //Similarly for temporary turning point force values...
     tangentialForceTurningPointLUTemp_.setZero();
     tangentialForceTurningPointULTemp_.setZero();
     //...and the turning point displacement values
     tangentialDisplacementTurningPointUL_.setZero();
     tangentialDisplacementTurningPointLU_.setZero();
     //k_edit
     //setting the variable which stores the minimum displacement for simple loading to zero
     tangentialDisplacementSL_ = 0;
     //k_edit
     //setting the priorLoadingFlag to zero as, when an interaction is created for the first time,
     //there will, by definition, have been no prior loading
     priorLoadingFlag_ = 0;
     //ensuring that the initial tangential velocity of a new interaction is zero until updated
     initialTangentialVelocity_.setZero();
 
 #ifdef DEBUG_CONSTRUCTOR
     std::cout<<"MindlinInteraction::MindlinInteraction() finished"<<std::endl;
 #endif
 }

MindlinInteraction::MindlinInteraction ( const MindlinInteraction & p )

Copy constructor.

Parameters

[in] p

Definition at line 94 of file MindlinInteraction.cc.

References absoluteNormalForcePrevious_, initialTangentialVelocity_, priorLoadingFlag_, slidingSpring_, tangentialDisplacementSL_, tangentialDisplacementTemp2_, tangentialDisplacementTemp_, tangentialDisplacementTurningPointLU_, tangentialDisplacementTurningPointUL_, tangentialForceDirection_, tangentialForceTemp2_, tangentialForceTemp_, tangentialForceTurningPointLU_, tangentialForceTurningPointLUTemp_, tangentialForceTurningPointUL_, tangentialForceTurningPointULTemp_, tangentialStiffness_, tangentialStiffnessZero_, and tangentialStiffnessZeroPrevious_.

         : BaseInteraction(p)
 {
     slidingSpring_=p.slidingSpring_;
     //k_edit
     //setting the K_t0 parameter to that possessed by the interaction
     //to be copied....
     tangentialStiffnessZero_ = p.tangentialStiffnessZero_;
     //...and its previous value...
     tangentialStiffnessZeroPrevious_ = p.tangentialStiffnessZeroPrevious_;
     //...and the same for the "normal" tangential stiffness parameter
     tangentialStiffness_ = p.tangentialStiffness_;
     //k_edit
     //allowing turning point forces to be copied when an interaction is copied
     tangentialForceTurningPointLU_ = p.tangentialForceTurningPointLU_;
     tangentialForceTurningPointUL_ = p.tangentialForceTurningPointUL_;
     //k_edit
     //allowing the direction of the tangential force to be "remembered" also
     //by the copied interaction
     tangentialForceDirection_ = p.tangentialForceDirection_;
     //k_edit
     //copying the temporary 'holders' which store intermediate values of tangential force
     //and displacement during multiple-step force calculations
     tangentialForceTemp_ = p.tangentialForceTemp_;
     tangentialForceTemp2_ = p.tangentialForceTemp2_;
     tangentialDisplacementTemp_ = p.tangentialDisplacementTemp_;
     tangentialDisplacementTemp2_ = p.tangentialDisplacementTemp2_;
     //and similarly for the temporary turning point variables
     tangentialForceTurningPointLUTemp_ = p.tangentialForceTurningPointLUTemp_;
     tangentialForceTurningPointULTemp_ = p.tangentialForceTurningPointULTemp_;
     //...and the displacement equivalents
     tangentialDisplacementTurningPointUL_ = p.tangentialDisplacementTurningPointUL_;
     tangentialDisplacementTurningPointLU_ = p.tangentialDisplacementTurningPointLU_;
     //k_edit
     //copying the variable which stores the minimum displacement for simple loading
     tangentialDisplacementSL_ = p.tangentialDisplacementSL_;
     //k_edit
     priorLoadingFlag_ = p.priorLoadingFlag_;
     //copying the initial tangential velocity
     initialTangentialVelocity_ = p.initialTangentialVelocity_;
 
     absoluteNormalForcePrevious_ = p.absoluteNormalForcePrevious_;
 #ifdef DEBUG_CONSTRUCTOR
     std::cout<<"MindlinInteraction::MindlinInteraction(const MindlinInteraction& p) finished"<<std::endl;
 #endif
 }

MindlinInteraction::MindlinInteraction ( )

Empty constructor.

Definition at line 143 of file MindlinInteraction.cc.

References FATAL, and logger.

 {
 #ifdef MERCURY_USE_MPI
     logger(FATAL,"MindlinInteractions are currently not implemented in parallel MercuryDPM");
 #endif
 }

MindlinInteraction::~MindlinInteraction ( )

virtual

Destructor.

Definition at line 152 of file MindlinInteraction.cc.

 {
 #ifdef DEBUG_DESTRUCTOR
     std::cout<<"MindlinInteraction::~MindlinInteraction() finished"<<std::endl;
 #endif
 }

Member Function Documentation

void MindlinInteraction::computeFrictionForce ( )

Computes the tangential force generated due to compression in the sliding spring. Does take into account if the interaction is between particle-particle or particle-wall.

Definition at line 262 of file MindlinInteraction.cc.

Referenced by MindlinRollingTorsionInteraction::computeFrictionForce().

                                               {
     //If tangential forces are absent
     if (getAbsoluteNormalForce() == 0.0) return;
 
     const MindlinSpecies *species = getSpecies();//dynamic_cast
 
     //Checking if the relevant particle species has a non-zero friction coefficient
     if (species->getSlidingFrictionCoefficient() != 0.0) {
         //Compute the tangential component of relativeVelocity_
         Vec3D tangentialRelativeVelocity = getRelativeVelocity() - getNormal() * getNormalRelativeVelocity();
         {
             // *************************************************************************************************************************
             // **********************************************GENERAL CALCULATIONS*******************************************************
             // *************************************************************************************************************************
             //used to Integrate the spring
             //if particle-wall
             if (dynamic_cast<BaseParticle *>(getI()) == 0) {
                 slidingSpringVelocity_ = tangentialRelativeVelocity;
             }
                 //if particle-particle
             else {
                 slidingSpringVelocity_ = (tangentialRelativeVelocity -
                                           Vec3D::dot(slidingSpring_, getP()->getVelocity() - getI()->getVelocity()) *
                                           getNormal() / getDistance());
             }
             //integrate(getHandler()->timeStep_);
             slidingSpring_ += slidingSpringVelocity_ * getHandler()->getDPMBase()->getTimeStep();
 
             //1) Calculating the current value of K_t0
             //This is identical for both unloading and loading (under constant normal force) and hence can
             //potentially later be moved for neatness/efficiency
             Mdouble r1 = 1.0 * getEffectiveRadius();
             updateTangentialStiffnessZero(r1, species->getShearModulus());
 
             //2) Calculating the relevant tangential dissipation constant based on the current stiffness (and other relevant parameters)
             Mdouble slidingDissipationCoefficient =  species->getSlidingDissipation()*sqrt(8.0*getEffectiveMass()*tangentialStiffnessZero_);
 
             //3) Using the parameters determined above, calculating the tangential force as per Di Maio and Di Renzo eqn. (37)
             tangentialForce_ = - tangentialStiffnessZero_ * slidingSpring_ - slidingDissipationCoefficient * tangentialRelativeVelocity;
 
             //applying the Coulomb criterion (Di Maio and Di Renzo eqn. (36)) to ensure falsely large tangential forces are avoided
             //if all is OK, i.e. if tangential force is smaller than mu*f_n, we simply add the tangential force calculated.
             if (tangentialForce_.getLength() < (species->getSlidingFrictionCoefficient() * getAbsoluteNormalForce()) ) {
                 addForce(tangentialForce_);
             }
                 //otherwise, we take the force as mu*f_n and recalculate the spring length accordingly
             else {
 
                 tangentialForce_ *= species->getSlidingFrictionCoefficient() * getAbsoluteNormalForce() / tangentialForce_.getLength();
                 //adding the force as mu*f_n
                 addForce(tangentialForce_);
                 //updating the spring length accordingly
                 slidingSpring_ = -(tangentialForce_ + slidingDissipationCoefficient * tangentialRelativeVelocity) / tangentialStiffnessZero_;
             }
         }
     }
     slidingSpringPrevious_ = slidingSpring_;
 }

Mdouble MindlinInteraction::getAbsoluteNormalForcePrevious ( ) const

Returns the absolute value of the norm (length) of the previous Normal force vector.

Return the absolve normal force. This is the magnitude of the normal force.

Todo:

Ant: Check this comment.

Returns: Mdouble that contains the absolute norm (length) of the normal force.

Definition at line 406 of file MindlinInteraction.cc.

References absoluteNormalForcePrevious_.

 {
     return absoluteNormalForcePrevious_;
 }

std::string MindlinInteraction::getBaseName ( ) const

Returns the type/name of interaction (sliding friction interaction)

Returns: std::string

Definition at line 377 of file MindlinInteraction.cc.

 {
     return "Mindlin";
 }

Mdouble MindlinInteraction::getElasticEnergy ( ) const

overridevirtual

Returns the amount of elastic energy stored in sliding spring.

Returns: Mdouble

Reimplemented from BaseInteraction.

Reimplemented in MindlinRollingTorsionInteraction.

Definition at line 331 of file MindlinInteraction.cc.

References Vec3D::getLengthSquared(), slidingSpring_, and tangentialStiffness_.

Referenced by MindlinRollingTorsionInteraction::getElasticEnergy().

 {
 
     //new_edit replacing outdated 'getSlidingStiffness()'
     //return 0.5 * getSpecies()->getSlidingStiffness() * slidingSpring_.getLengthSquared();
     return 0.5 * tangentialStiffness_ * slidingSpring_.getLengthSquared();
 }

const MindlinSpecies * MindlinInteraction::getSpecies ( ) const

Returns a const pointer of type MindlinSpecies*.

Returns: const MindlinSpecies*

Definition at line 370 of file MindlinInteraction.cc.

References BaseInteraction::getBaseSpecies().

Referenced by computeFrictionForce().

 {
     return dynamic_cast<const MindlinSpecies*>(getBaseSpecies());
 }

const Vec3D MindlinInteraction::getTangentialForce ( ) const

overridevirtual

Returns the sliding friction force vector.

Returns: const Vec3D

Reimplemented from BaseInteraction.

Definition at line 353 of file MindlinInteraction.cc.

References tangentialForce_.

 {
     return tangentialForce_;
 }

const Mdouble MindlinInteraction::getTangentialForceDirection ( ) const

Definition at line 363 of file MindlinInteraction.cc.

References tangentialForceDirection_.

 {
     return tangentialForceDirection_;
 }

Mdouble MindlinInteraction::getTangentialOverlap ( ) const

overridevirtual

Returns the amount of tangential overlap which is needed by BaseInteraction::writeToFstat().

Returns: Mdouble

Todo:: TWnow this should be positive

Reimplemented from BaseInteraction.

Definition at line 341 of file MindlinInteraction.cc.

References Vec3D::dot(), Vec3D::getLength(), Vec3D::getUnitVector(), and slidingSpring_.

 {
     //k_edit Indeed it should - todo done :)
     //k_edit
     //Updating sliding spring to give positive / negative values dependent on the direction of the extension
     return slidingSpring_.getLength() * slidingSpring_.dot(slidingSpring_.getUnitVector(slidingSpring_),Vec3D(1.0,1.0,1.0));
 }

Mdouble MindlinInteraction::getTangentialStiffness ( )

Definition at line 193 of file MindlinInteraction.cc.

References tangentialStiffness_.

                                                    {
     return tangentialStiffness_;
 }

Mdouble MindlinInteraction::getTangentialStiffnessZero ( )

Definition at line 187 of file MindlinInteraction.cc.

References tangentialStiffnessZero_.

                                                        {
     return tangentialStiffnessZero_;
 }

void MindlinInteraction::integrate ( Mdouble timeStep )

overridevirtual

Increments the amount of compression in sliding spring.

Parameters

[in] timeStep the dt

Reimplemented from BaseInteraction.

Reimplemented in MindlinRollingTorsionInteraction.

Definition at line 324 of file MindlinInteraction.cc.

References slidingSpring_, and slidingSpringVelocity_.

Referenced by MindlinRollingTorsionInteraction::integrate().

 {
     slidingSpring_ += slidingSpringVelocity_ * timeStep;
 }

void MindlinInteraction::read ( std::istream & is )

overridevirtual

Interaction read function, which accepts an std::istream as input.

Parameters

[in,out] is

Reimplemented from BaseInteraction.

Reimplemented in MindlinRollingTorsionInteraction.

Definition at line 169 of file MindlinInteraction.cc.

References slidingSpring_.

Referenced by MindlinRollingTorsionInteraction::read().

 {
     //BaseInteraction::read(is);
     std::string dummy;
     is >> dummy >> slidingSpring_;
 }

void MindlinInteraction::reverseHistory ( )

overridevirtual

A useful feature if one wants to return to the initial state of the spring. However, reverse history decrements the current state to the state corresponding to previous time step. Decrements the value of slidingSpring_.

Reimplemented from BaseInteraction.

Reimplemented in MindlinRollingTorsionInteraction.

Definition at line 384 of file MindlinInteraction.cc.

References slidingSpring_, slidingSpringVelocity_, and tangentialForce_.

Referenced by MindlinRollingTorsionInteraction::reverseHistory().

 {
     slidingSpring_=-slidingSpring_;
     slidingSpringVelocity_=-slidingSpringVelocity_;
     tangentialForce_=-tangentialForce_;
 }

void MindlinInteraction::rotateHistory ( Matrix3D & rotationMatrix )

overridevirtual

When periodic particles are used, some interactions need certain history properties rotated (e.g. tangential springs). This is the function for that.

Todo:: some of these might be unneccesary

Reimplemented from BaseInteraction.

Reimplemented in MindlinRollingTorsionInteraction.

Definition at line 391 of file MindlinInteraction.cc.

References slidingSpring_, slidingSpringVelocity_, and tangentialForce_.

Referenced by MindlinRollingTorsionInteraction::rotateHistory().

 {
     slidingSpring_=rotationMatrix*slidingSpring_;
     slidingSpringVelocity_=rotationMatrix*slidingSpringVelocity_;
     tangentialForce_=rotationMatrix*tangentialForce_;
 }

void MindlinInteraction::setAbsoluteNormalForcePrevious ( Mdouble absoluteNormalForcePrevious )

allows the previous normal force to be (re)set from external classes

set absolute normal force.

Parameters

[in] absoluteNormalForce Mdouble contain the value of the absolute normal force.

Definition at line 417 of file MindlinInteraction.cc.

References absoluteNormalForcePrevious_.

 {
     absoluteNormalForcePrevious_ = absoluteNormalForcePrevious;
 }

void MindlinInteraction::setTangentialStiffnessZero ( Mdouble newKt0 )

Definition at line 181 of file MindlinInteraction.cc.

References tangentialStiffnessZero_.

                                                                   {
     tangentialStiffnessZero_ = newKt0;
 }

void MindlinInteraction::updateK_t	(	const Mdouble	fric,
		const Vec3D	direction,
		const bool	useTurningPoint,
		const bool	isLoading
	)

Definition at line 215 of file MindlinInteraction.cc.

References Vec3D::dot(), BaseInteraction::getAbsoluteNormalForce(), Vec3D::getLength(), Vec3D::getUnitVector(), tangentialForceTemp_, tangentialForceTurningPointLU_, tangentialForceTurningPointUL_, tangentialStiffness_, and tangentialStiffnessZero_.

                                                                                                                              {
     //creating a simple positive or negative integer 'multiplier', m, whose values are either +1 or -1
     //that can be used to alter the relevant equations depending on if we are loading or unloading
     Mdouble m;
     //A parameter to temporarily hold the relevant turning point so that this function can work both for
     //loading and loading.
     Vec3D turningPoint;
     //Changing the directions and turning points used in calculation depending on if we are loading or unloading
     if (isLoading) {
         m = 1;
         turningPoint = tangentialForceTurningPointUL_;
     }
     else {
         m = -1;
         turningPoint = tangentialForceTurningPointLU_;
     }
     //if the current part of the interaction can be treated as a virgin loading
     //(i.e. the turning point can be ignored), we simply update K_t in the 'standard' manner
     if (!useTurningPoint) {
         //determining the direction of the current tangential force relative to the
         //current direction of motion
         Mdouble forceDirection = Vec3D::dot(Vec3D::getUnitVector(tangentialForceTemp_),direction);
         //finding the scalar ratio f_t1 / (mu f_n1)
         //(note for a first loading f_t1 is simply equal to f_t, and similarly f_n1 f_n = const
         Mdouble forceRatio = tangentialForceTemp_.getLength() / (fric * getAbsoluteNormalForce());
         //changing the direction of the force ratio, if necessary, based on its relative orientation
         //with respect to the current tangential motion.
         if (forceDirection<0)
             forceRatio = -forceRatio;
         //using the scalar ratio to update tangential stiffness
         tangentialStiffness_ = tangentialStiffnessZero_* cbrt(1 - forceRatio);
     }
         //alternatively, if we are reloading and within the limits where the turning point force must be considered
     else {
         Vec3D resultantForce = m*(tangentialForceTemp_ - turningPoint);
         //QUESTION: Does it make sense to use the total force here? Or should I just use the tangentialForceTemp?
         Mdouble forceDirection = Vec3D::dot(Vec3D::getUnitVector(resultantForce),direction);
         Mdouble forceRatio = resultantForce.getLength() / (2 * fric * getAbsoluteNormalForce());
         //changing the direction of the force ratio, if necessary, based on its relative orientation
         //with respect to the current tangential motion.
         if (forceDirection<0)
             forceRatio = -forceRatio;
         //using the scalar ratio to update tangential stiffness
         tangentialStiffness_ = tangentialStiffnessZero_* cbrt(1 - m*forceRatio);
     }
 }

void MindlinInteraction::updateTangentialStiffnessInitial ( Mdouble fric )

void MindlinInteraction::updateTangentialStiffnessInitial2	(	const Mdouble	fric,
		const Vec3D	direction
	)

void MindlinInteraction::updateTangentialStiffnessReloading	(	const Mdouble	fric,
		const Vec3D	direction
	)

void MindlinInteraction::updateTangentialStiffnessReloadingTanUp	(	const Mdouble	fric,
		const Vec3D	direction
	)

void MindlinInteraction::updateTangentialStiffnessUnloading	(	const Mdouble	fric,
		const Vec3D	direction
	)

void MindlinInteraction::updateTangentialStiffnessUnloadingTanDown	(	const Mdouble	fric,
		const Vec3D	direction
	)

void MindlinInteraction::updateTangentialStiffnessZero	(	Mdouble	rad,
		double	shearMod
	)

Definition at line 202 of file MindlinInteraction.cc.

References BaseInteraction::getOverlap(), and tangentialStiffnessZero_.

Referenced by computeFrictionForce().

                                                                                     {
     //K_t0 = 8G_eq * sqrt(R_eq * delta_n) (Di Renzo and Di Maio)
     tangentialStiffnessZero_ = 8 * shearMod * sqrt(rad * getOverlap());
 }

void MindlinInteraction::write ( std::ostream & os ) const

overridevirtual

Interaction write function, which accepts an std::ostream as input.

Parameters

[in,out] os

Reimplemented from BaseInteraction.

Reimplemented in MindlinRollingTorsionInteraction.

Definition at line 161 of file MindlinInteraction.cc.

References slidingSpring_.

Referenced by MindlinRollingTorsionInteraction::write().

 {
     //BaseInteraction::write(os);
     os << " slidingSpring " << slidingSpring_;
 }

Member Data Documentation

Mdouble MindlinInteraction::absoluteNormalForcePrevious_

protected

Definition at line 240 of file MindlinInteraction.h.

Referenced by getAbsoluteNormalForcePrevious(), MindlinInteraction(), and setAbsoluteNormalForcePrevious().

Vec3D MindlinInteraction::initialTangentialVelocity_

protected

Definition at line 236 of file MindlinInteraction.h.

Referenced by MindlinInteraction().

bool MindlinInteraction::priorLoadingFlag_

protected

Definition at line 215 of file MindlinInteraction.h.

Referenced by MindlinInteraction().

Vec3D MindlinInteraction::slidingSpring_

protected

Stores the amount of sliding spring ( $\delta$ ) compression from the expression $f_t=-k*\delta-\nu*relVel$ . Set in the member function integrate(), used in computeFrictionForce().

Definition at line 170 of file MindlinInteraction.h.

Referenced by computeFrictionForce(), getElasticEnergy(), getTangentialOverlap(), integrate(), MindlinInteraction(), read(), reverseHistory(), rotateHistory(), and write().