MercuryDPM  Beta
SlidingFrictionInteraction Class Reference

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

#include <SlidingFrictionInteraction.h>

Inheritance diagram for SlidingFrictionInteraction:

## Public Types

typedef SlidingFrictionSpecies SpeciesType
An alias name for SlidingFrictionSpecies data type. More...

## Public Member Functions

SlidingFrictionInteraction (BaseInteractable *P, BaseInteractable *I, Mdouble timeStamp)
Constructor. More...

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

virtual ~SlidingFrictionInteraction ()
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...

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

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

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

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

Mdouble getTangentialOverlap () const
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
Returns the sliding friction force vector. More...

const SlidingFrictionSpeciesgetSpecies () const
Returns a const pointer of type SlidingFrictionSpecies*. More...

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

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...

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

InteractionHandlergetHandler () const
Gets a point to the interaction handlers to which this interaction belongs. More...

const Vec3DgetForce () const
Gets the current force (vector) between the two interacting objects. More...

const Vec3DgetTorque () const
Gets the current torque (vector) between the two interacting objects. More...

const Vec3DgetNormal () const
Gets the normal vector between the two interacting objects. More...

const Vec3DgetContactPoint () 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...

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 ()

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

BaseInteractablegetI ()

const BaseInteractablegetP () const

const BaseInteractablegetI () 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 Vec3DgetRelativeVelocity () 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 BaseInteractioncopy () const =0
Makes a copy of the interaction and returns a pointer to the copy. 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...

## Private Attributes

Vec3D slidingSpring_
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(). More...

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...

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

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

add an force increment to the total force. More...

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

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

## Detailed Description

Computes the forces corresponding to sliding friction.

Definition at line 39 of file SlidingFrictionInteraction.h.

## Member Typedef Documentation

An alias name for SlidingFrictionSpecies data type.

Definition at line 45 of file SlidingFrictionInteraction.h.

## Constructor & Destructor Documentation

 SlidingFrictionInteraction::SlidingFrictionInteraction ( BaseInteractable * P, BaseInteractable * I, Mdouble timeStamp )

Constructor.

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

Definition at line 39 of file SlidingFrictionInteraction.cc.

References Vec3D::setZero(), and slidingSpring_.

40  : BaseInteraction(P, I, timeStamp)
41 {
43 #ifdef DEBUG_CONSTRUCTOR
44  std::cout<<"SlidingFrictionInteraction::SlidingFrictionInteraction() finished"<<std::endl;
45 #endif
46 }
void setZero()
Sets all elements to zero.
Definition: Vector.cc:52
BaseInteraction(BaseInteractable *P, BaseInteractable *I, Mdouble timeStamp)
A constructor takes the BaseInteractable objects which are interacting (come into contact) and time t...
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
 SlidingFrictionInteraction::SlidingFrictionInteraction ( const SlidingFrictionInteraction & p )

Copy constructor.

Parameters
 [in] p

Definition at line 50 of file SlidingFrictionInteraction.cc.

References slidingSpring_.

51  : BaseInteraction(p)
52 {
54 #ifdef DEBUG_CONSTRUCTOR
55  std::cout<<"SlidingFrictionInteraction::SlidingFrictionInteraction(const SlidingFrictionInteraction& p) finished"<<std::endl;
56 #endif
57 }
BaseInteraction(BaseInteractable *P, BaseInteractable *I, Mdouble timeStamp)
A constructor takes the BaseInteractable objects which are interacting (come into contact) and time t...
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
 SlidingFrictionInteraction::~SlidingFrictionInteraction ( )
virtual

Destructor.

Definition at line 61 of file SlidingFrictionInteraction.cc.

62 {
63 #ifdef DEBUG_DESTRUCTOR
64  std::cout<<"SlidingFrictionInteraction::~SlidingFrictionInteraction() finished"<<std::endl;
65 #endif
66 }

## Member Function Documentation

 void SlidingFrictionInteraction::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 87 of file SlidingFrictionInteraction.cc.

Referenced by FrictionInteraction::computeFrictionForce().

88 {
89  //If tangential forces are absent
90  if (getAbsoluteNormalForce() == 0.0) return;
91
92  const SlidingFrictionSpecies* species = getSpecies();//dynamic_cast
93
94  if (species->getSlidingFrictionCoefficient() != 0.0)
95  {
96  //Compute the tangential component of relativeVelocity_
97  Vec3D tangentialRelativeVelocity = getRelativeVelocity() - getNormal() * getNormalRelativeVelocity();
98
99  if (species->getSlidingStiffness() != 0.0)
100  {
101  //used to Integrate the spring
102  if (dynamic_cast<BaseParticle*>(getI())==0) //if particle-wall
103  slidingSpringVelocity_= tangentialRelativeVelocity;
104  else //if particle-particle
105  slidingSpringVelocity_= (tangentialRelativeVelocity - Vec3D::dot(slidingSpring_, getP()->getVelocity() - getI()->getVelocity()) * getNormal() / getDistance());
106
107  //integrate(getHandler()->timeStep_);
109
110  //Calculate test force acting on P including viscous force
111  tangentialForce_ = - species->getSlidingStiffness() * slidingSpring_ - species->getSlidingDissipation() * tangentialRelativeVelocity;
112
113  //tangential forces are modelled by a spring-damper of elasticity kt and viscosity dispt (sticking),
114  //but the force is limited by Coulomb friction (sliding):
115  Mdouble tangentialForceSquared = tangentialForce_.getLengthSquared();
116  if (tangentialForceSquared <= mathsFunc::square(species->getSlidingFrictionCoefficientStatic() * getAbsoluteNormalForce()))
117  {
118  //if sticking (|ft|<=mu*|fn|), apply the force
120  }
121  else
122  {
123  //if sliding, resize the tangential force such that |ft|=mu*|fn|
124  tangentialForce_ *= species->getSlidingFrictionCoefficient() * getAbsoluteNormalForce() / std::sqrt(tangentialForceSquared);
126  //resize the tangential spring accordingly such ft=-k*delta-nu*relVel
127  slidingSpring_ = -(tangentialForce_ + species->getSlidingDissipation() * tangentialRelativeVelocity) / species->getSlidingStiffness();
128  }
129  }
130  else //if no spring stiffness is set
131  {
132 // if (species->getSlidingDissipation()==0.0)
133 // {
134 // std::cerr << "SlidingFrictionInteraction::getForce(): warning: both sliding stiffness and dissipation are zero" << std::endl;
135 // }
136  Mdouble tangentialRelativeVelocitySquared = tangentialRelativeVelocity.getLengthSquared();
137  if (tangentialRelativeVelocitySquared * mathsFunc::square(species->getSlidingDissipation()) <= mathsFunc::square(species->getSlidingFrictionCoefficientStatic() * getAbsoluteNormalForce()))
138  tangentialForce_=-species->getSlidingDissipation() * tangentialRelativeVelocity;
139  else //if sliding, set force to Coulomb limit
140  tangentialForce_=-(species->getSlidingFrictionCoefficient() * getAbsoluteNormalForce() / std::sqrt(tangentialRelativeVelocitySquared)) * tangentialRelativeVelocity;
141
143  }
144  }
145 // else
146 // {
147 // std::cerr << "SlidingFrictionInteraction::getForce(): warning: sliding friction is zero" << std::endl;
148 // }
149 }
static Mdouble getLengthSquared(const Vec3D &a)
Calculates the squared length of a Vec3D: .
Definition: Vector.cc:304
Mdouble getSlidingFrictionCoefficientStatic() const
Allows the static Coulomb friction coefficient to be accessed.
Vec3D slidingSpringVelocity_
Stores the rate at which the sliding spring compressed or relaxed. Set in the member function compute...
InteractionHandler * getHandler() const
Gets a point to the interaction handlers to which this interaction belongs.
const Vec3D & getRelativeVelocity() const
Returns a constant reference to a vector of relative velocity.
double Mdouble
static Mdouble dot(const Vec3D &a, const Vec3D &b)
Calculates the dot product of two Vec3D: .
Definition: Vector.cc:187
T square(T val)
squares a number
Definition: ExtendedMath.h:91
Vec3D tangentialForce_
Computes the tangential force such that . Set and computed in computeFrictionForce().
Mdouble getNormalRelativeVelocity() const
Returns a double which is the norm (length) of the relative velocity vector.
const SlidingFrictionSpecies * getSpecies() const
Returns a const pointer of type SlidingFrictionSpecies*.
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
const Vec3D & getNormal() const
Gets the normal vector between the two interacting objects.
add an force increment to the total force.
SlidingFrictionSpecies contains the parameters used to describe sliding friction. ...
BaseInteractable * getI()
Mdouble getDistance() const
Returns an Mdouble which is the norm (length) of distance vector.
Mdouble getSlidingStiffness() const
Allows the spring constant to be accessed.
Mdouble getSlidingDissipation() const
Allows the tangential viscosity to be accessed.
BaseInteractable * getP()
Returns a pointer to first object involved in the interaction (normally a particle).
Implementation of a 3D vector (by Vitaliy).
Definition: Vector.h:45
DPMBase * getDPMBase()
Gets the problem that is solved using this handler.
Definition: BaseHandler.h:512
Mdouble getTimeStep() const
Allows the time step dt to be accessed.
Definition: DPMBase.cc:368
Mdouble getSlidingFrictionCoefficient() const
Allows the (dynamic) Coulomb friction coefficient to be accessed.
Mdouble getAbsoluteNormalForce() const
Returns the absolute value of the norm (length) of the Normal force vector.
 std::string SlidingFrictionInteraction::getBaseName ( ) const

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

Returns
std::string

Definition at line 189 of file SlidingFrictionInteraction.cc.

190 {
191  return "SlidingFriction";
192 }
 Mdouble SlidingFrictionInteraction::getElasticEnergy ( ) const
virtual

Returns the amount of elastic energy stored in sliding spring.

Returns
Mdouble

Reimplemented from BaseInteraction.

Definition at line 160 of file SlidingFrictionInteraction.cc.

Referenced by FrictionInteraction::getElasticEnergy().

161 {
163 }
static Mdouble getLengthSquared(const Vec3D &a)
Calculates the squared length of a Vec3D: .
Definition: Vector.cc:304
const SlidingFrictionSpecies * getSpecies() const
Returns a const pointer of type SlidingFrictionSpecies*.
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
Mdouble getSlidingStiffness() const
Allows the spring constant to be accessed.
 const SlidingFrictionSpecies * SlidingFrictionInteraction::getSpecies ( ) const

Returns a const pointer of type SlidingFrictionSpecies*.

Returns
const SlidingFrictionSpecies*

Definition at line 182 of file SlidingFrictionInteraction.cc.

References BaseInteraction::getBaseSpecies().

Referenced by computeFrictionForce(), and getElasticEnergy().

183 {
184  return dynamic_cast<const SlidingFrictionSpecies*>(getBaseSpecies());
185 }
const BaseSpecies * getBaseSpecies() const
Return a constant point to BaseSpecies of the interaction.
SlidingFrictionSpecies contains the parameters used to describe sliding friction. ...
 const Vec3D SlidingFrictionInteraction::getTangentialForce ( ) const
virtual

Returns the sliding friction force vector.

Returns
const Vec3D

Reimplemented from BaseInteraction.

Definition at line 175 of file SlidingFrictionInteraction.cc.

References tangentialForce_.

176 {
177  return tangentialForce_;
178 }
Vec3D tangentialForce_
Computes the tangential force such that . Set and computed in computeFrictionForce().
 Mdouble SlidingFrictionInteraction::getTangentialOverlap ( ) const
virtual

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 167 of file SlidingFrictionInteraction.cc.

References Vec3D::getLength(), and slidingSpring_.

168 {
170  return -slidingSpring_.getLength();
171 }
static Mdouble getLength(const Vec3D &a)
Calculates the length of a Vec3D: .
Definition: Vector.cc:427
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
 void SlidingFrictionInteraction::integrate ( Mdouble timeStep )
virtual

Increments the amount of compression in sliding spring.

Parameters
 [in] timeStep the dt

Reimplemented from BaseInteraction.

Definition at line 153 of file SlidingFrictionInteraction.cc.

References slidingSpring_, and slidingSpringVelocity_.

Referenced by FrictionInteraction::integrate().

154 {
156 }
Vec3D slidingSpringVelocity_
Stores the rate at which the sliding spring compressed or relaxed. Set in the member function compute...
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
 void SlidingFrictionInteraction::read ( std::istream & is )
virtual

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

Parameters
 [in,out] is

Reimplemented from BaseInteraction.

Definition at line 78 of file SlidingFrictionInteraction.cc.

References slidingSpring_.

79 {
81  std::string dummy;
82  is >> dummy >> slidingSpring_;
83 }
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
 void SlidingFrictionInteraction::reverseHistory ( )
virtual

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.

Definition at line 196 of file SlidingFrictionInteraction.cc.

References slidingSpring_, slidingSpringVelocity_, and tangentialForce_.

Referenced by FrictionInteraction::reverseHistory().

197 {
201 }
Vec3D slidingSpringVelocity_
Stores the rate at which the sliding spring compressed or relaxed. Set in the member function compute...
Vec3D tangentialForce_
Computes the tangential force such that . Set and computed in computeFrictionForce().
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
 void SlidingFrictionInteraction::rotateHistory ( Matrix3D & rotationMatrix )
virtual

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.

Definition at line 203 of file SlidingFrictionInteraction.cc.

References slidingSpring_, slidingSpringVelocity_, and tangentialForce_.

Referenced by FrictionInteraction::rotateHistory().

204 {
205  slidingSpring_=rotationMatrix*slidingSpring_;
207  tangentialForce_=rotationMatrix*tangentialForce_;
208 }
Vec3D slidingSpringVelocity_
Stores the rate at which the sliding spring compressed or relaxed. Set in the member function compute...
Vec3D tangentialForce_
Computes the tangential force such that . Set and computed in computeFrictionForce().
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...
 void SlidingFrictionInteraction::write ( std::ostream & os ) const
virtual

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

Parameters
 [in,out] os

Reimplemented from BaseInteraction.

Definition at line 70 of file SlidingFrictionInteraction.cc.

References slidingSpring_.

Referenced by FrictionInteraction::write().

71 {
72  //BaseInteraction::write(os);
73  os << " slidingSpring " << slidingSpring_;
74 }
Vec3D slidingSpring_
Stores the amount of sliding spring ( ) compression from the expression . Set in the member function ...

## Member Data Documentation

 Vec3D SlidingFrictionInteraction::slidingSpring_
private

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 111 of file SlidingFrictionInteraction.h.

 Vec3D SlidingFrictionInteraction::slidingSpringVelocity_
private

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

Definition at line 116 of file SlidingFrictionInteraction.h.

Referenced by computeFrictionForce(), integrate(), reverseHistory(), and rotateHistory().

 Vec3D SlidingFrictionInteraction::tangentialForce_
private

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

Definition at line 120 of file SlidingFrictionInteraction.h.

Referenced by computeFrictionForce(), getTangentialForce(), reverseHistory(), and rotateHistory().

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