FrictionSpecies Class Reference

FrictionSpecies contains the parameters used to describe sliding, rolling and torsional friction. More...

#include <FrictionSpecies.h>

Inheritance diagram for FrictionSpecies:

Public Types
typedef FrictionInteraction	InteractionType
	The correct Interaction type for this FrictionForceSpecies. More...
Public Types inherited from SlidingFrictionSpecies
typedef SlidingFrictionInteraction	InteractionType
	The correct Interaction type for this FrictionForceSpecies. More...

Public Member Functions
	FrictionSpecies ()
	The default constructor. More...
	FrictionSpecies (const FrictionSpecies &s)
	The default copy constructor. More...
	~FrictionSpecies ()
	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...
std::string	getBaseName () const override
	Used in Species::getName to obtain a unique name for each Species. More...
bool	getUseAngularDOFs () const override
	Returns true if torques have to be calculated. More...
void	mix (FrictionSpecies *S, FrictionSpecies *T)
	creates default values for mixed species More...
void	setRollingStiffness (Mdouble new_kt)
	Allows the spring constant to be changed. More...
Mdouble	getRollingStiffness () const
	Allows the spring constant to be accessed. More...
void	setRollingDissipation (Mdouble new_dispt)
	Allows the tangential viscosity to be changed. More...
Mdouble	getRollingDissipation () const
	Allows the tangential viscosity to be accessed. More...
void	setRollingFrictionCoefficient (Mdouble new_mu)
	Allows the (dynamic) Coulomb friction coefficient to be changed; also sets mu_s by default. More...
Mdouble	getRollingFrictionCoefficient () const
	Allows the (dynamic) Coulomb friction coefficient to be accessed. More...
void	setRollingFrictionCoefficientStatic (Mdouble new_mu)
	Allows the static Coulomb rolling friction coefficient to be changed. More...
Mdouble	getRollingFrictionCoefficientStatic () const
	Allows the static Coulomb rolling friction coefficient to be accessed. More...
void	setTorsionStiffness (Mdouble new_kt)
	Allows the torsion stiffness to be changed. More...
Mdouble	getTorsionStiffness () const
	Allows the torsion stiffness to be accessed. More...
void	setTorsionDissipation (Mdouble new_dispt)
	Allows the torsion viscosity to be changed. More...
Mdouble	getTorsionDissipation () const
	Allows the torsion viscosity to be accessed. More...
void	setTorsionFrictionCoefficient (Mdouble new_mu)
	Allows the (dynamic) Coulomb torsion friction coefficient to be changed; also sets mu_s by default. More...
Mdouble	getTorsionFrictionCoefficient () const
	Allows the (dynamic) Coulomb torsion friction coefficient to be accessed. More...
void	setTorsionFrictionCoefficientStatic (Mdouble new_mu)
	Allows the static Coulomb torsion friction coefficient to be accessed. More...
Mdouble	getTorsionFrictionCoefficientStatic () const
	Allows the static Coulomb torsion friction coefficient to be accessed. More...
Public Member Functions inherited from SlidingFrictionSpecies
	SlidingFrictionSpecies ()
	The default constructor. More...
	SlidingFrictionSpecies (const SlidingFrictionSpecies &s)
	The default copy constructor. More...
	~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...
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 override
	Returns true if torques have to be calculated. More...
void	mix (SlidingFrictionSpecies *S, SlidingFrictionSpecies *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...
void	setIsSuperquadricSpecies (bool isSuperquadricSpecies)
bool	getIsSuperquadricSpecies () const
Public Member Functions inherited from BaseForce
BaseSpecies *	getBaseSpecies () const
void	setBaseSpecies (BaseSpecies *baseSpecies)

Private Attributes
Mdouble	rollingStiffness_
	rolling stiffness. More...
Mdouble	rollingDissipation_
	rolling dissipation coefficient. More...
Mdouble	rollingFrictionCoefficient_
	(dynamic) Coulomb rolling friction coefficient. More...
Mdouble	rollingFrictionCoefficientStatic_
	static Coulomb rolling friction coefficient (by default set equal to the dynamic one). More...
Mdouble	torsionStiffness_
	rolling stiffness. More...
Mdouble	torsionDissipation_
	rolling dissipation coefficient. More...
Mdouble	torsionFrictionCoefficient_
	(dynamic) Coulomb torsion friction coefficient. More...
Mdouble	torsionFrictionCoefficientStatic_
	static Coulomb torsion friction coefficient (by default set equal to the dynamic one). More...

Detailed Description

FrictionSpecies contains the parameters used to describe sliding, rolling and torsional friction.

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

Todo:

TW: should this class be renamed SlidingRollingTorsionFrictionSpecies?

Member Typedef Documentation

InteractionType

typedef FrictionInteraction FrictionSpecies::InteractionType

The correct Interaction type for this FrictionForceSpecies.

Constructor & Destructor Documentation

FrictionSpecies() [1/2]

FrictionSpecies::FrictionSpecies

(

)

The default constructor.

        : SlidingFrictionSpecies()
{
    rollingStiffness_ = 0.0;
    rollingDissipation_ = 0.0;
    rollingFrictionCoefficient_ = 0.0;
    rollingFrictionCoefficientStatic_ = 0.0;
    torsionStiffness_ = 0.0;
    torsionDissipation_ = 0.0;
    torsionFrictionCoefficient_ = 0.0;
    torsionFrictionCoefficientStatic_ = 0.0;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"FrictionSpecies::FrictionSpecies() finished"<<std::endl;
#endif
}

References rollingDissipation_, rollingFrictionCoefficient_, rollingFrictionCoefficientStatic_, rollingStiffness_, torsionDissipation_, torsionFrictionCoefficient_, torsionFrictionCoefficientStatic_, and torsionStiffness_.

FrictionSpecies() [2/2]

FrictionSpecies::FrictionSpecies

(

const FrictionSpecies &

s

)

The default copy constructor.

Parameters

[in]

s

the species that is copied

        : SlidingFrictionSpecies(s)
{
    rollingStiffness_ = s.rollingStiffness_;
    rollingDissipation_ = s.rollingDissipation_;
    rollingFrictionCoefficient_ = s.rollingFrictionCoefficient_;
    rollingFrictionCoefficientStatic_ = s.rollingFrictionCoefficientStatic_;
    torsionStiffness_ = s.torsionStiffness_;
    torsionDissipation_ = s.torsionDissipation_;
    torsionFrictionCoefficient_ = s.torsionFrictionCoefficient_;
    torsionFrictionCoefficientStatic_ = s.torsionFrictionCoefficientStatic_;
#ifdef DEBUG_CONSTRUCTOR
    std::cout<<"FrictionSpecies::FrictionSpecies(const FrictionSpecies &p) finished"<<std::endl;
#endif
}

References rollingDissipation_, rollingFrictionCoefficient_, rollingFrictionCoefficientStatic_, rollingStiffness_, torsionDissipation_, torsionFrictionCoefficient_, torsionFrictionCoefficientStatic_, and torsionStiffness_.

~FrictionSpecies()

FrictionSpecies::~FrictionSpecies

(

)

The default destructor.

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

Member Function Documentation

getBaseName()

std::string FrictionSpecies::getBaseName ( ) const

overridevirtual

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 from SlidingFrictionSpecies.

{
    return "Friction";
}

getRollingDissipation()

Mdouble FrictionSpecies::getRollingDissipation

(

)

const

Allows the tangential viscosity to be accessed.

{
    return rollingDissipation_;
}

References rollingDissipation_.

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

getRollingFrictionCoefficient()

Mdouble FrictionSpecies::getRollingFrictionCoefficient

(

)

const

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

{
    return rollingFrictionCoefficient_;
}

References rollingFrictionCoefficient_.

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

getRollingFrictionCoefficientStatic()

Mdouble FrictionSpecies::getRollingFrictionCoefficientStatic

(

)

const

Allows the static Coulomb rolling friction coefficient to be accessed.

Allows the static Coulomb friction coefficient to be accessed.

{
    return rollingFrictionCoefficientStatic_;
}

References rollingFrictionCoefficientStatic_.

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

getRollingStiffness()

Mdouble FrictionSpecies::getRollingStiffness

(

)

const

Allows the spring constant to be accessed.

{
    return rollingStiffness_;
}

References rollingStiffness_.

Referenced by FrictionInteraction::computeFrictionForce(), FrictionInteraction::getElasticEnergy(), and mix().

getTorsionDissipation()

Mdouble FrictionSpecies::getTorsionDissipation

(

)

const

Allows the torsion viscosity to be accessed.

Allows the tangential viscosity to be accessed.

{
    return torsionDissipation_;
}

References torsionDissipation_.

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

getTorsionFrictionCoefficient()

Mdouble FrictionSpecies::getTorsionFrictionCoefficient

(

)

const

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

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

{
    return torsionFrictionCoefficient_;
}

References torsionFrictionCoefficient_.

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

getTorsionFrictionCoefficientStatic()

Mdouble FrictionSpecies::getTorsionFrictionCoefficientStatic

(

)

const

Allows the static Coulomb torsion friction coefficient to be accessed.

Allows the static Coulomb friction coefficient to be accessed.

{
    return torsionFrictionCoefficientStatic_;
}

References torsionFrictionCoefficientStatic_.

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

getTorsionStiffness()

Mdouble FrictionSpecies::getTorsionStiffness

(

)

const

Allows the torsion stiffness to be accessed.

Allows the spring constant to be accessed.

{
    return torsionStiffness_;
}

References torsionStiffness_.

Referenced by FrictionInteraction::computeFrictionForce(), FrictionInteraction::getElasticEnergy(), and mix().

getUseAngularDOFs()

bool FrictionSpecies::getUseAngularDOFs ( ) const

overridevirtual

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 BaseFrictionForce.

{
    return true;
}

mix()

void FrictionSpecies::mix	(	FrictionSpecies *	S,
		FrictionSpecies *	T
	)

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]

S,T

the two species whose properties are mixed to create the new species

{
    rollingStiffness_ = BaseSpecies::average(S->getRollingStiffness(), T->getRollingStiffness());
    rollingDissipation_ = BaseSpecies::average(S->getRollingDissipation(), T->getRollingDissipation());
    rollingFrictionCoefficient_ = BaseSpecies::averageInf(S->getRollingFrictionCoefficient(), T->getRollingFrictionCoefficient());
    rollingFrictionCoefficientStatic_ = BaseSpecies::averageInf(S->getRollingFrictionCoefficientStatic(),
                                                T->getRollingFrictionCoefficientStatic());
    torsionStiffness_ = BaseSpecies::average(S->getTorsionStiffness(), T->getTorsionStiffness());
    torsionDissipation_ = BaseSpecies::average(S->getTorsionDissipation(), T->getTorsionDissipation());
    torsionFrictionCoefficient_ = BaseSpecies::averageInf(S->getTorsionFrictionCoefficient(), T->getTorsionFrictionCoefficient());
    torsionFrictionCoefficientStatic_ = BaseSpecies::averageInf(S->getTorsionFrictionCoefficientStatic(),
                                                T->getTorsionFrictionCoefficientStatic());
}

References BaseSpecies::average(), BaseSpecies::averageInf(), getRollingDissipation(), getRollingFrictionCoefficient(), getRollingFrictionCoefficientStatic(), getRollingStiffness(), getTorsionDissipation(), getTorsionFrictionCoefficient(), getTorsionFrictionCoefficientStatic(), getTorsionStiffness(), rollingDissipation_, rollingFrictionCoefficient_, rollingFrictionCoefficientStatic_, rollingStiffness_, torsionDissipation_, torsionFrictionCoefficient_, torsionFrictionCoefficientStatic_, and torsionStiffness_.

read()

void FrictionSpecies::read

(

std::istream &

is

)

Reads the species properties from an input stream.

Parameters

[in]

is

input stream (typically the restart file)

{
    SlidingFrictionSpecies::read(is);
    std::string dummy;
    is >> dummy >> rollingStiffness_;
    is >> dummy >> rollingDissipation_;
    is >> dummy >> rollingFrictionCoefficient_;
    is >> dummy >> rollingFrictionCoefficientStatic_;
    is >> dummy >> torsionStiffness_;
    is >> dummy >> torsionDissipation_;
    is >> dummy >> torsionFrictionCoefficient_;
    is >> dummy >> torsionFrictionCoefficientStatic_;
}

References SlidingFrictionSpecies::read(), rollingDissipation_, rollingFrictionCoefficient_, rollingFrictionCoefficientStatic_, rollingStiffness_, torsionDissipation_, torsionFrictionCoefficient_, torsionFrictionCoefficientStatic_, and torsionStiffness_.

setRollingDissipation()

void FrictionSpecies::setRollingDissipation

(

Mdouble

new_dispt

)

Allows the tangential viscosity to be changed.

{
    if (new_dispt >= 0)
        rollingDissipation_ = new_dispt;
    else
    {
        logger(ERROR, "Error in setRollingDissipation");
    }
}

References ERROR, logger, and rollingDissipation_.

setRollingFrictionCoefficient()

void FrictionSpecies::setRollingFrictionCoefficient

(

Mdouble

new_mu

)

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

{
    if (new_mu >= 0)
    {
        rollingFrictionCoefficient_ = new_mu;
        rollingFrictionCoefficientStatic_ = rollingFrictionCoefficient_;
    }
    else
        logger(ERROR, "[FrictionSpecies::setRollingFrictionCoefficient(Mdouble)] The coefficient of friction must be nonnegative.");
}

References ERROR, logger, rollingFrictionCoefficient_, and rollingFrictionCoefficientStatic_.

setRollingFrictionCoefficientStatic()

void FrictionSpecies::setRollingFrictionCoefficientStatic

(

Mdouble

new_mu

)

Allows the static Coulomb rolling friction coefficient to be changed.

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

{
    if (new_mu >= 0)
    {
        rollingFrictionCoefficientStatic_ = new_mu;
    }
    else
        logger(ERROR, "[FrictionSpecies::setRollingFrictionCoefficientStatic(Mdouble)] The coefficient of friction must be nonnegative.");
}

References ERROR, logger, and rollingFrictionCoefficientStatic_.

setRollingStiffness()

void FrictionSpecies::setRollingStiffness

(

Mdouble

new_kt

)

Allows the spring constant to be changed.

{
    if (new_kt >= 0)
    {
        rollingStiffness_ = new_kt;
    }
    else
    {
        logger(ERROR, "Error in setRollingStiffness");
    }
}

References ERROR, logger, and rollingStiffness_.

setTorsionDissipation()

void FrictionSpecies::setTorsionDissipation

(

Mdouble

new_dispt

)

Allows the torsion viscosity to be changed.

Allows the tangential viscosity to be changed.

{
    if (new_dispt >= 0)
        torsionDissipation_ = new_dispt;
    else
    {
        logger(ERROR, "Error in setTorsionDissipation");
    }
}

References ERROR, logger, and torsionDissipation_.

setTorsionFrictionCoefficient()

void FrictionSpecies::setTorsionFrictionCoefficient

(

Mdouble

new_mu

)

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

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

{
    if (new_mu >= 0)
    {
        torsionFrictionCoefficient_ = new_mu;
        torsionFrictionCoefficientStatic_ = torsionFrictionCoefficient_;
    }
    else
    {
        logger(ERROR, "Error in setSlidingFrictionCoefficient");
    }
}

References ERROR, logger, torsionFrictionCoefficient_, and torsionFrictionCoefficientStatic_.

setTorsionFrictionCoefficientStatic()

void FrictionSpecies::setTorsionFrictionCoefficientStatic

(

Mdouble

new_mu

)

Allows the static Coulomb torsion friction coefficient to be accessed.

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

{
    if (new_mu >= 0)
    {
        torsionFrictionCoefficientStatic_ = new_mu;
    }
    else
    {
        logger(ERROR, "Error in setSlidingFrictionCoefficientStatic");
    }
}

References ERROR, logger, and torsionFrictionCoefficientStatic_.

setTorsionStiffness()

void FrictionSpecies::setTorsionStiffness

(

Mdouble

new_kt

)

Allows the torsion stiffness to be changed.

Allows the spring constant to be changed.

{
    if (new_kt >= 0)
    {
        torsionStiffness_ = new_kt;
    }
    else
    {
        logger(ERROR, "Error in setTorsionStiffness");
    }
}

References ERROR, logger, and torsionStiffness_.

write()

void FrictionSpecies::write

(

std::ostream &

os

)

const

Writes the species properties to an output stream.

Parameters

[out]

os

output stream (typically the restart file)

{
    SlidingFrictionSpecies::write(os);
    os << " rollingStiffness " << rollingStiffness_;
    os << " rollingDissipation " << rollingDissipation_;
    os << " rollingFrictionCoefficient " << rollingFrictionCoefficient_;
    os << " rollingFrictionCoefficientStatic " << rollingFrictionCoefficientStatic_;
    os << " torsionStiffness " << torsionStiffness_;
    os << " torsionDissipation " << torsionDissipation_;
    os << " torsionFrictionCoefficient " << torsionFrictionCoefficient_;
    os << " torsionFrictionCoefficientStatic " << torsionFrictionCoefficientStatic_;
}

References rollingDissipation_, rollingFrictionCoefficient_, rollingFrictionCoefficientStatic_, rollingStiffness_, torsionDissipation_, torsionFrictionCoefficient_, torsionFrictionCoefficientStatic_, torsionStiffness_, and SlidingFrictionSpecies::write().

Member Data Documentation

rollingDissipation_

Mdouble FrictionSpecies::rollingDissipation_

private

rolling dissipation coefficient.

Typically set to 2/5 of the normal force dissipation, as both the tangential and the normal spring have the same restitution coefficients (if the rolling and normal stiffnesses also have a ratio of 2/5).

Referenced by FrictionSpecies(), getRollingDissipation(), mix(), read(), setRollingDissipation(), and write().

rollingFrictionCoefficient_

Mdouble FrictionSpecies::rollingFrictionCoefficient_

private

(dynamic) Coulomb rolling friction coefficient.

Referenced by FrictionSpecies(), getRollingFrictionCoefficient(), mix(), read(), setRollingFrictionCoefficient(), and write().

rollingFrictionCoefficientStatic_

Mdouble FrictionSpecies::rollingFrictionCoefficientStatic_

private

static Coulomb rolling friction coefficient
(by default set equal to the dynamic one).

Referenced by FrictionSpecies(), getRollingFrictionCoefficientStatic(), mix(), read(), setRollingFrictionCoefficient(), setRollingFrictionCoefficientStatic(), and write().

rollingStiffness_

Mdouble FrictionSpecies::rollingStiffness_

private

rolling stiffness.

Typically set to 2/5 of the stiffness of the normal force, as
both the rolling and the normal spring have the same oscillation
frequency (and thus require the same timeStep)in this case.

Referenced by FrictionSpecies(), getRollingStiffness(), mix(), read(), setRollingStiffness(), and write().

torsionDissipation_

Mdouble FrictionSpecies::torsionDissipation_

private

rolling dissipation coefficient.

Typically set to 2/5 of the normal force dissipation, as both the tangential and the normal spring have the same restitution coefficients (if the rolling and normal stiffnesses also have a ratio of 2/5).

Referenced by FrictionSpecies(), getTorsionDissipation(), mix(), read(), setTorsionDissipation(), and write().

torsionFrictionCoefficient_

Mdouble FrictionSpecies::torsionFrictionCoefficient_

private

(dynamic) Coulomb torsion friction coefficient.

Referenced by FrictionSpecies(), getTorsionFrictionCoefficient(), mix(), read(), setTorsionFrictionCoefficient(), and write().

torsionFrictionCoefficientStatic_

Mdouble FrictionSpecies::torsionFrictionCoefficientStatic_

private

static Coulomb torsion friction coefficient
(by default set equal to the dynamic one).

Referenced by FrictionSpecies(), getTorsionFrictionCoefficientStatic(), mix(), read(), setTorsionFrictionCoefficient(), setTorsionFrictionCoefficientStatic(), and write().

torsionStiffness_

Mdouble FrictionSpecies::torsionStiffness_

private

rolling stiffness.

Typically set to 2/5 of the stiffness of the normal force, as
both the rolling and the normal spring have the same oscillation
frequency (and thus require the same timeStep)in this case.

Referenced by FrictionSpecies(), getTorsionStiffness(), mix(), read(), setTorsionStiffness(), and write().

---

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

• FrictionSpecies.h
• FrictionSpecies.cc