MindlinInteraction.h

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#ifndef MINDLININTERACTION_H
#define MINDLININTERACTION_H

#include "Interactions/BaseInteraction.h"
#include "Math/Vector.h"

class BaseParticle;
class MindlinSpecies;
class BaseInteractable;
class MindlinInteraction : public virtual BaseInteraction
{
public:
    typedef MindlinSpecies SpeciesType;
    MindlinInteraction(BaseInteractable* P, BaseInteractable* I, unsigned timeStamp);
    MindlinInteraction(const MindlinInteraction &p);
    MindlinInteraction();
    virtual ~MindlinInteraction();
    void computeFrictionForce();
    void read(std::istream& is) override;
    void write(std::ostream& os) const override;
    void integrate(Mdouble timeStep) override;
    Mdouble getElasticEnergy() const override;
    Mdouble getTangentialOverlap() const override;
    std::string getBaseName() const;

    //setters and getters
    const Vec3D getTangentialForce() const override;
    //k_edit
    //Returns a scalar value letting us know the direction of the tangential force
    //(i.e. positive or negative) so that accurate values can be output to the fstat file
    const Mdouble getTangentialForceDirection() const;

    //k_edit
    Mdouble getAbsoluteNormalForcePrevious() const;

    //k_edit
    void setAbsoluteNormalForcePrevious(Mdouble absoluteNormalForcePrevious);

    const MindlinSpecies* getSpecies() const;
    void reverseHistory() override;

    void rotateHistory(Matrix3D& rotationMatrix) override;

    //k_edit
    //Allows the K_t0 parameter (for Mindlin model) to be set
    void setTangentialStiffnessZero(Mdouble newKt0);

    //k_edit
    //Allows the K_t0 parameter (for Mindlin model) to be accessed
    Mdouble getTangentialStiffnessZero();

    //k_edit
    //...and a similar function for the "normal" K_t
    Mdouble getTangentialStiffness();

    //k_edit
    //A quick way to update the K_t0 parameter when necessary...
    void updateTangentialStiffnessZero(Mdouble rad, double shearMod);
    //k_edit
    //...and a second, similar method by which to update K_t0 for loading curves in which
    //multiple steps are required to increment the tangential force
    //void updateTangentialStiffnessZeroSecondStep(Mdouble rad, double shearMod);

    //k_edit
    //A way to easily update K_t for all possible cases,
    //i.e. initial loading (under constant normal force)...
    void updateTangentialStiffnessInitial(Mdouble fric);
    void updateTangentialStiffnessInitial2(const Mdouble fric, const Vec3D direction);
    //...unloading (under constant normal force)...
    void updateTangentialStiffnessUnloading(const Mdouble fric, const Vec3D direction);
    //...reloading (under constant normal force)...
    void updateTangentialStiffnessReloading(const Mdouble fric, const Vec3D direction);
    //...reloading (i.e. tangential force increasing) and normal force varying (moving from state 1 to 2)...
    void updateTangentialStiffnessReloadingTanUp(const Mdouble fric, const Vec3D direction);
    //...and with increasing normal force and decreasing tangential...
    void updateTangentialStiffnessUnloadingTanDown(const Mdouble fric, const Vec3D direction) ;


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

protected:
    Vec3D slidingSpring_;
    //k_edit
    //Introducing a parameter to store the value of "slidingSpring_" (i.e. delta_t) for a previous timestep
    Vec3D slidingSpringPrevious_;
    Vec3D slidingSpringVelocity_;
    Vec3D tangentialForce_;
    //k_edit
    //adding a parameter to store the tangential force from a previous timestep
    Vec3D tangentialForcePrevious_;
    //a parameter to give the (scalar) DIRECTION of the force, i.e. "with" or "against" the tangential motion!
    Mdouble tangentialForceDirection_;
    //k_edit
    //A pair of parameters to store the force at turning point, for use in calculating unloading/reloading
    //curves using the Mindlin model (see Di Renzo and Di Maio 2004)
    //"UL" and "LU" are used to distinguish between turning points between unloading and loading and
    //those between loading and unloading
    Vec3D tangentialForceTurningPointLU_;
    Vec3D tangentialForceTurningPointUL_;
    //A pair of variables to temporarily store updated versions of these values for use in multi-step
    //Mindlin calculations
    Vec3D tangentialForceTurningPointLUTemp_;
    Vec3D tangentialForceTurningPointULTemp_;
    //a pair of vectors to store the current tangential displacements at each turning point
    Vec3D tangentialDisplacementTurningPointUL_;
    Vec3D tangentialDisplacementTurningPointLU_;


    //k_edit
    // the constant K_t0 used to calculate the tangential stiffness (K_t) for the
    //Mindlin model (see, for example, Di Renzo and Di Maio, 2004)
    Mdouble tangentialStiffnessZero_;
    //...and a variable to save its value from the previous timestep
    Mdouble tangentialStiffnessZeroPrevious_;
    // the constant K_t as used in Di Maio and Di Renzo
    Mdouble tangentialStiffness_;
    //k_edit
    //a simple flag to let functions know whether loading has been performed before or not
    //(0 if no prior loading, 1 if prior loading)
    bool priorLoadingFlag_;

    //k_edit
    //a pair of variables to temporarily store the intermediate values of f_t and delta_t
    //during the multiple-point force calculations necessary when both normal and tangential
    //forces are varying
    Vec3D tangentialForceTemp_;
    Vec3D tangentialDisplacementTemp_;

    //k_edit
    //A second set of temporary vectors for when >2 steps are required.
    //although not technically necessary, helps the clarity of the code GREATLY!
    Vec3D tangentialForceTemp2_;
    Vec3D tangentialDisplacementTemp2_;

    //k_edit
    //the minimal tangential displacement for which the simple loading assumption can be expected to hold
    //in Herz-Mindlin theory
    Mdouble tangentialDisplacementSL_;

    //records the initial tangential velocity such that all subsequent motion can be directly compared to this!
    Vec3D initialTangentialVelocity_;

    //k_edit
    //parameter allowing previous values of the normal force to be stored and used in calculations
    Mdouble absoluteNormalForcePrevious_;

};
#endif