SlidingFrictionSpecies contains the parameters used to describe sliding friction. More...

#include <SlidingFrictionSpecies.h>

Inheritance diagram for SlidingFrictionSpecies:

Public Types
typedef SlidingFrictionInteraction	InteractionType
	The correct Interaction type for this FrictionForceSpecies. More...

Public Member Functions
	SlidingFrictionSpecies ()
	The default constructor. More...

	SlidingFrictionSpecies (const SlidingFrictionSpecies &s)
	The default copy constructor. More...

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

void	read (std::istream &is)
	Reads the species properties from an input stream. More...

void	write (std::ostream &os) const
	Writes the species properties to an output stream. More...

virtual std::string	getBaseName () const
	Used in Species::getName to obtain a unique name for each Species. More...

void	setSlidingStiffness (Mdouble new_kt)
	Allows the spring constant to be changed. More...

Mdouble	getSlidingStiffness () const
	Allows the spring constant to be accessed. More...

void	setSlidingDissipation (Mdouble new_dispt)
	Allows the tangential viscosity to be changed. More...

Mdouble	getSlidingDissipation () const
	Allows the tangential viscosity to be accessed. More...

void	setSlidingFrictionCoefficient (Mdouble new_mu)
	Allows the (dynamic) Coulomb friction coefficient to be changed; also sets mu_s by default. More...

Mdouble	getSlidingFrictionCoefficient () const
	Allows the (dynamic) Coulomb friction coefficient to be accessed. More...

void	setSlidingFrictionCoefficientStatic (Mdouble new_mu)
	Allows the static Coulomb friction coefficient to be changed. More...

Mdouble	getSlidingFrictionCoefficientStatic () const
	Allows the static Coulomb friction coefficient to be accessed. More...

bool	getUseAngularDOFs () const
	Returns true if torques have to be calculated. More...

void	mix (SlidingFrictionSpecies const S, SlidingFrictionSpecies const T)
	creates default values for mixed species More...

void	setCollisionTimeAndNormalAndTangentialRestitutionCoefficient (Mdouble tc, Mdouble eps, Mdouble beta, Mdouble mass)
	Sets k, disp, kt, dispt such that it matches a given tc and eps for a collision of two particles of masses m0,m1. More...

void	setCollisionTimeAndNormalAndTangentialRestitutionCoefficientNoDispt (Mdouble tc, Mdouble eps, Mdouble beta, Mdouble mass)
	Sets k, disp, kt (with dispt=0) such that it matches a given tc and eps for a collision of two particles of mass m. More...

Public Member Functions inherited from BaseSpecies
	BaseSpecies ()
	The default constructor. More...

	BaseSpecies (const BaseSpecies &p)
	The copy constructor. More...

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

virtual BaseSpecies *	copy () const =0
	Creates a deep copy of the object from which it is called. More...

void	setHandler (SpeciesHandler *handler)
	Sets the pointer to the handler to which this species belongs. More...

SpeciesHandler *	getHandler () const
	Returns the pointer to the handler to which this species belongs. More...

Mdouble	average (Mdouble a, Mdouble b)
	defines the average of two variables by the harmonic mean. More...

virtual void	mixAll (BaseSpecies const S, BaseSpecies const T)=0
	creates default values for mixed species More...

virtual Mdouble	getInteractionDistance () const =0
	returns the largest separation distance at which adhesive short-range forces can occur. More...

virtual BaseInteraction *	getNewInteraction (BaseInteractable P, BaseInteractable I, Mdouble timeStamp)=0
	returns new Interaction object. 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 std::string	getName () const =0
	A purely virtual function. 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...

Private Attributes
Mdouble	slidingStiffness_
	tangential stiffness. More...

Mdouble	slidingDissipation_
	tangential dissipation coefficient. More...

Mdouble	slidingFrictionCoefficient_
	(dynamic) Coulomb friction coefficient More...

Mdouble	slidingFrictionCoefficientStatic_
	static Coulomb friction coefficient (by default set equal to mu) More...

Detailed Description

SlidingFrictionSpecies contains the parameters used to describe sliding friction.

See SlidingFrictionInteraction::computeForce for a description of the force law.

Definition at line 36 of file SlidingFrictionSpecies.h.

Member Typedef Documentation

typedef SlidingFrictionInteraction SlidingFrictionSpecies::InteractionType

The correct Interaction type for this FrictionForceSpecies.

Definition at line 40 of file SlidingFrictionSpecies.h.

Constructor & Destructor Documentation

SlidingFrictionSpecies::SlidingFrictionSpecies ( )

The default constructor.

Definition at line 35 of file SlidingFrictionSpecies.cc.

References slidingDissipation_, slidingFrictionCoefficient_, slidingFrictionCoefficientStatic_, and slidingStiffness_.

 {
     slidingStiffness_ = 0;
     slidingDissipation_ = 0;
     slidingFrictionCoefficient_ = 0;
     slidingFrictionCoefficientStatic_ = 0;
 #ifdef DEBUG_CONSTRUCTOR
     std::cout<<"SlidingFrictionSpecies::SlidingFrictionSpecies() finished"<<std::endl;
 #endif
 }

SlidingFrictionSpecies::SlidingFrictionSpecies ( const SlidingFrictionSpecies & s )

The default copy constructor.

Parameters

[in] s the species that is copied

Definition at line 49 of file SlidingFrictionSpecies.cc.

References slidingDissipation_, slidingFrictionCoefficient_, slidingFrictionCoefficientStatic_, and slidingStiffness_.

 {
     slidingStiffness_ = s.slidingStiffness_;
     slidingDissipation_ = s.slidingDissipation_;
     slidingFrictionCoefficient_ = s.slidingFrictionCoefficient_;
     slidingFrictionCoefficientStatic_ = s.slidingFrictionCoefficientStatic_;
 #ifdef DEBUG_CONSTRUCTOR
     std::cout<<"SlidingFrictionSpecies::SlidingFrictionSpecies(const SlidingFrictionSpecies &p) finished"<<std::endl;
 #endif
 }

SlidingFrictionSpecies::~SlidingFrictionSpecies ( )

virtual

The default destructor.

Definition at line 60 of file SlidingFrictionSpecies.cc.

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

Member Function Documentation

std::string SlidingFrictionSpecies::getBaseName ( ) const

virtual

Used in Species::getName to obtain a unique name for each Species.

Returns: a string containing the name of the species (minus the word "Species")

Reimplemented in FrictionSpecies.

Definition at line 95 of file SlidingFrictionSpecies.cc.

 {
     return "SlidingFriction";
 }

Mdouble SlidingFrictionSpecies::getSlidingDissipation ( ) const

Allows the tangential viscosity to be accessed.

Definition at line 132 of file SlidingFrictionSpecies.cc.

References slidingDissipation_.

Referenced by SlidingFrictionInteraction::computeFrictionForce(), and mix().

 {
     return slidingDissipation_;
 }

Mdouble SlidingFrictionSpecies::getSlidingFrictionCoefficient ( ) const

Allows the (dynamic) Coulomb friction coefficient to be accessed.

Definition at line 154 of file SlidingFrictionSpecies.cc.

References slidingFrictionCoefficient_.

Referenced by SlidingFrictionInteraction::computeFrictionForce(), and mix().

 {
     return slidingFrictionCoefficient_;
 }

Mdouble SlidingFrictionSpecies::getSlidingFrictionCoefficientStatic ( ) const

Allows the static Coulomb friction coefficient to be accessed.

Definition at line 174 of file SlidingFrictionSpecies.cc.

References slidingFrictionCoefficientStatic_.

Referenced by SlidingFrictionInteraction::computeFrictionForce(), and mix().

 {
     return slidingFrictionCoefficientStatic_;
 }

Mdouble SlidingFrictionSpecies::getSlidingStiffness ( ) const

Allows the spring constant to be accessed.

Definition at line 115 of file SlidingFrictionSpecies.cc.

References slidingStiffness_.

Referenced by SlidingFrictionInteraction::computeFrictionForce(), SlidingFrictionInteraction::getElasticEnergy(), mix(), and setCollisionTimeAndNormalAndTangentialRestitutionCoefficient().

 {
     return slidingStiffness_;
 }

bool SlidingFrictionSpecies::getUseAngularDOFs ( ) const

virtual

Returns true if torques have to be calculated.

Returns true for any FrictionForceSpecies except EmptyFrictionSpecies, because for spherical particles, torques are only caused by tangential forces. See SpeciesHandler::useAngularDOFs for more details

Returns: true

Implements BaseSpecies.

Definition at line 185 of file SlidingFrictionSpecies.cc.

 {
     return true;
 }

void SlidingFrictionSpecies::mix	(	SlidingFrictionSpecies *const	SFrictional,
		SlidingFrictionSpecies *const	TFrictional
	)

creates default values for mixed species

For all parameters we assume that the harmonic mean of the parameters of the original two species is a sensible default.

Parameters

[in]	SFrictional	the first species whose properties are mixed to create the new species
[in]	TFrictional	the second species whose properties are mixed to create the new species

Definition at line 196 of file SlidingFrictionSpecies.cc.

References BaseSpecies::average(), getSlidingDissipation(), getSlidingFrictionCoefficient(), getSlidingFrictionCoefficientStatic(), getSlidingStiffness(), slidingDissipation_, slidingFrictionCoefficient_, slidingFrictionCoefficientStatic_, and slidingStiffness_.

 {
     slidingStiffness_ = average(SFrictional->getSlidingStiffness(), TFrictional->getSlidingStiffness());
     slidingDissipation_ = average(SFrictional->getSlidingDissipation(), TFrictional->getSlidingDissipation());
     slidingFrictionCoefficient_ = average(SFrictional->getSlidingFrictionCoefficient(), TFrictional->getSlidingFrictionCoefficient());
     slidingFrictionCoefficientStatic_ = average(SFrictional->getSlidingFrictionCoefficientStatic(), TFrictional->getSlidingFrictionCoefficientStatic());
 }

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

virtual

Reads the species properties from an input stream.

Parameters

[in] is input stream (typically the restart file)

Implements BaseObject.

Definition at line 82 of file SlidingFrictionSpecies.cc.

References slidingDissipation_, slidingFrictionCoefficient_, slidingFrictionCoefficientStatic_, and slidingStiffness_.

Referenced by FrictionSpecies::read().

 {
     //BaseSpecies::read(is);
     std::string dummy;
     is >> dummy >> slidingStiffness_;
     is >> dummy >> slidingDissipation_;
     is >> dummy >> slidingFrictionCoefficient_;
     is >> dummy >> slidingFrictionCoefficientStatic_;
 }

void SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficient	(	Mdouble	tc,
		Mdouble	eps,
		Mdouble	beta,
		Mdouble	mass
	)

Sets k, disp, kt, dispt such that it matches a given tc and eps for a collision of two particles of masses m0,m1.

Definition at line 205 of file SlidingFrictionSpecies.cc.

References LinearPlasticViscoelasticNormalSpecies::getDissipation(), LinearPlasticViscoelasticNormalSpecies::getLoadingStiffness(), getSlidingStiffness(), LinearViscoelasticNormalSpecies::getStiffness(), constants::pi, LinearViscoelasticNormalSpecies::setCollisionTimeAndRestitutionCoefficient(), LinearPlasticViscoelasticNormalSpecies::setDissipation(), LinearPlasticViscoelasticNormalSpecies::setLoadingStiffness(), setSlidingDissipation(), setSlidingStiffness(), and mathsFunc::square().

 {
     Mdouble stiffness;
     //the dynamic cast is needed to check if the normal force species is LinearViscoelasticSpecies; otherwise this function cannot be used
     LinearViscoelasticNormalSpecies* species = dynamic_cast<LinearViscoelasticNormalSpecies*>(this);
     if (species!= nullptr)
     {
         species->setCollisionTimeAndRestitutionCoefficient(tc, eps, mass);
         stiffness = species->getStiffness();
     }
     else
     {
         LinearPlasticViscoelasticNormalSpecies* species2 = dynamic_cast<LinearPlasticViscoelasticNormalSpecies*>(this);
         if (species2 != nullptr)
         {
             species2->setDissipation(-mass / tc * std::log(eps));
             species2->setLoadingStiffness(.5 * mass * (mathsFunc::square(constants::pi/tc) + mathsFunc::square(species2->getDissipation()) /mass));
             stiffness = species2->getLoadingStiffness();
         }
         else
         {
             std::cerr << "SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficient only works for LinearViscoelasticSlidingFrictionSpecies or LinearPlasticViscoelasticSlidingFrictionSpecies" << std::endl;
             exit(-1);
         }
     }
 
     //from Deen...Kuipers2006, eq. 43 and 30
     setSlidingStiffness(2.0 / 7.0 * stiffness * (mathsFunc::square(constants::pi) + mathsFunc::square(log(beta))) / (mathsFunc::square(constants::pi) + mathsFunc::square(log(eps))));
     if (beta != 0.0)
         setSlidingDissipation(-2 * log(beta) * sqrt(1.0 / 7.0 * mass * getSlidingStiffness() / (mathsFunc::square(constants::pi) + mathsFunc::square(log(beta)))));
     else
         setSlidingDissipation(2. * sqrt(1.0 / 7.0 * mass * getSlidingStiffness()));
 }

void SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficientNoDispt	(	Mdouble	tc,
		Mdouble	eps,
		Mdouble	beta,
		Mdouble	mass
	)

Sets k, disp, kt (with dispt=0) such that it matches a given tc and eps for a collision of two particles of mass m.

Sets k, disp, kt, dispt such that it matches a given tc and eps for a collision of two particles of masses m0,m1.

Definition at line 240 of file SlidingFrictionSpecies.cc.

References LinearViscoelasticNormalSpecies::getStiffness(), constants::pi, LinearViscoelasticNormalSpecies::setCollisionTimeAndRestitutionCoefficient(), setSlidingDissipation(), setSlidingStiffness(), and mathsFunc::square().

 {
     //the dynamic cast is needed to check if the normal force species is LinearViscoelasticSpecies; otherwise this function cannot be used
     LinearViscoelasticNormalSpecies* species = dynamic_cast<LinearViscoelasticNormalSpecies*>(this);
     if (species == nullptr)
     {
         std::cerr << "SlidingFrictionSpecies::setCollisionTimeAndNormalAndTangentialRestitutionCoefficient only works for LinearViscoelasticSlidingFrictionSpecies" << std::endl;
         exit(-1);
     }
     species->setCollisionTimeAndRestitutionCoefficient(tc, eps, mass);
     //from BeckerSchwagerPoeschel2008, eq. 56
     setSlidingStiffness(2.0 / 7.0 * species->getStiffness() * mathsFunc::square(acos(-beta) / constants::pi));
     setSlidingDissipation(0);
 }

void SlidingFrictionSpecies::setSlidingDissipation ( Mdouble new_dispt )

Allows the tangential viscosity to be changed.

Definition at line 121 of file SlidingFrictionSpecies.cc.

References slidingDissipation_.

Referenced by setCollisionTimeAndNormalAndTangentialRestitutionCoefficient(), and setCollisionTimeAndNormalAndTangentialRestitutionCoefficientNoDispt().

 {
     if (new_dispt >= 0)
         slidingDissipation_ = new_dispt;
     else
     {
         std::cerr << "Error in setSlidingDissipation" << std::endl;
         exit(-1);
     }
 }

void SlidingFrictionSpecies::setSlidingFrictionCoefficient ( Mdouble new_mu )

Allows the (dynamic) Coulomb friction coefficient to be changed; also sets mu_s by default.

Definition at line 139 of file SlidingFrictionSpecies.cc.

References slidingFrictionCoefficient_, and slidingFrictionCoefficientStatic_.

Referenced by ChuteBottom::makeRoughBottom().

 {
     if (new_mu >= 0)
     {
         slidingFrictionCoefficient_ = new_mu;
         slidingFrictionCoefficientStatic_ = slidingFrictionCoefficient_;
     }
     else
     {
         std::cerr << "Error in setSlidingFrictionCoefficient" << std::endl;
         exit(-1);
     }
 }

void SlidingFrictionSpecies::setSlidingFrictionCoefficientStatic ( Mdouble new_mu )

Allows the static Coulomb friction coefficient to be changed.

Allows the static Coulomb friction coefficient to be changed; also sets mu_s by default.

Definition at line 160 of file SlidingFrictionSpecies.cc.

References slidingFrictionCoefficientStatic_.

 {
     if (new_mu >= 0)
     {
         slidingFrictionCoefficientStatic_ = new_mu;
     }
     else
     {
         std::cerr << "Error in setSlidingFrictionCoefficientStatic" << std::endl;
         exit(-1);
     }
 }

void SlidingFrictionSpecies::setSlidingStiffness ( Mdouble new_kt )

Allows the spring constant to be changed.

Definition at line 101 of file SlidingFrictionSpecies.cc.

References slidingStiffness_.

Referenced by setCollisionTimeAndNormalAndTangentialRestitutionCoefficient(), and setCollisionTimeAndNormalAndTangentialRestitutionCoefficientNoDispt().

 {
     if (new_kt >= 0)
     {
         slidingStiffness_ = new_kt;
     }
     else
     {
         std::cerr << "Error in setSlidingStiffness" << std::endl;
         exit(-1);
     }
 }

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

virtual

Writes the species properties to an output stream.

Parameters

[out] os output stream (typically the restart file)

Implements BaseObject.

Definition at line 70 of file SlidingFrictionSpecies.cc.

References slidingDissipation_, slidingFrictionCoefficient_, slidingFrictionCoefficientStatic_, and slidingStiffness_.

Referenced by FrictionSpecies::write().

         {
     //BaseSpecies::write(os);
     os << " slidingStiffness " << slidingStiffness_;
     os << " slidingDissipation " << slidingDissipation_;
     os << " slidingFrictionCoefficient " << slidingFrictionCoefficient_;
     os << " slidingFrictionCoefficientStatic " << slidingFrictionCoefficientStatic_;
 }

Member Data Documentation

Mdouble SlidingFrictionSpecies::slidingDissipation_

private

tangential dissipation coefficient.

Typically set to 2/7 of the normal force dissipation, as both the tangential and the normal spring have the same restitution coefficients (if the tangential and normal stiffnesses also have a ratio of 2/7). should always satisfy \(4*dispt*dt<mass, dispt \approx disp\), otherwise the restitution is zero and the particles stick.

Definition at line 117 of file SlidingFrictionSpecies.h.

Referenced by getSlidingDissipation(), mix(), read(), setSlidingDissipation(), SlidingFrictionSpecies(), and write().

Mdouble SlidingFrictionSpecies::slidingFrictionCoefficient_

private

(dynamic) Coulomb friction coefficient

Definition at line 120 of file SlidingFrictionSpecies.h.

Referenced by getSlidingFrictionCoefficient(), mix(), read(), setSlidingFrictionCoefficient(), SlidingFrictionSpecies(), and write().

Mdouble SlidingFrictionSpecies::slidingFrictionCoefficientStatic_

private

static Coulomb friction coefficient (by default set equal to mu)

Definition at line 123 of file SlidingFrictionSpecies.h.

Referenced by getSlidingFrictionCoefficientStatic(), mix(), read(), setSlidingFrictionCoefficient(), setSlidingFrictionCoefficientStatic(), SlidingFrictionSpecies(), and write().

Mdouble SlidingFrictionSpecies::slidingStiffness_

private

tangential stiffness.

Typically set to 2/7 of the stiffness of the normal force, as both the tangential and the normal spring have the same oscillation frequency (and thus require the same timeStep)in this case.

Definition at line 107 of file SlidingFrictionSpecies.h.

Referenced by getSlidingStiffness(), mix(), read(), setSlidingStiffness(), SlidingFrictionSpecies(), and write().

The documentation for this class was generated from the following files:

Species/FrictionForceSpecies/SlidingFrictionSpecies.h
Species/FrictionForceSpecies/SlidingFrictionSpecies.cc

Public Types

Public Member Functions

Private Attributes

Detailed Description

Member Typedef Documentation

Constructor & Destructor Documentation

Member Function Documentation

Member Data Documentation