EEPA Model Implementation

See this page for the documentation of this contact model.

contactmodeleepa.h

  1#pragma once
  2// contactmodeleepa.h
  3
  4#include "contactmodel/src/contactmodelmechanical.h"
  5
  6#ifdef EEPA_LIB
  7#  define EEPA_EXPORT EXPORT_TAG
  8#elif defined(NO_MODEL_IMPORT)
  9#  define EEPA_EXPORT
 10#else
 11#  define EEPA_EXPORT IMPORT_TAG
 12#endif
 13
 14namespace cmodelsxd {
 15    using namespace itasca;
 16
 17    class ContactModelEEPA : public ContactModelMechanical {
 18    public:
 19        // Constructor: Set default values for contact model properties.
 20        EEPA_EXPORT ContactModelEEPA();
 21        // Destructor, called when contact is deleted: free allocated memory, etc.
 22        EEPA_EXPORT virtual ~ContactModelEEPA();
 23        // Contact model name (used as keyword for commands and FISH).
 24        virtual QString  getName() const { return "eepa"; }
 25        // The index provides a quick way to determine the type of contact model.
 26        // Each type of contact model in PFC must have a unique index; this is assigned
 27        // by PFC when the contact model is loaded. This index should be set to -1
 28        virtual void     setIndex(int i) { index_ = i; }
 29        virtual int      getIndex() const { return index_; }
 30        // Contact model version number (e.g., MyModel05_1). The version number can be
 31        // accessed during the save-restore operation (within the archive method,
 32        // testing {stream.getRestoreVersion() == getMinorVersion()} to allow for
 33        // future modifications to the contact model data structure.
 34        virtual uint32     getMinorVersion() const;
 35        // Copy the state information to a newly created contact model.
 36        // Provide access to state information, for use by copy method.
 37        virtual void     copy(const ContactModel *c);
 38        // Provide save-restore capability for the state information.
 39        virtual void     archive(ArchiveStream &);
 40        // Enumerator for the properties.
 41        enum PropertyKeys {
 42            kwShear = 1
 43            , kwPoiss
 44            , kwFric
 45            , kwEepaF
 46            , kwEepaS
 47            , kwRGap
 48            , kwDpNRatio
 49            , kwDpSRatio
 50            , kwDpMode
 51            , kwDpF
 52            , kwResFric
 53            , kwResMoment
 54            , kwResS
 55            , kwOverlapMax
 56            , kwPlasRat
 57            , kwLuExp
 58            , kwPullOff
 59            , kwAdhExp
 60            , kwSurfAdh
 61            , kwKsFac
 62            , kwFmin
 63        };
 64        // Contact model property names in a comma separated list. The order corresponds with
 65        // the order of the PropertyKeys enumerator above. One can visualize any of these
 66        // properties in PFC automatically.
 67        virtual QString  getProperties() const {
 68            return "eepa_shear"
 69                ",eepa_poiss"
 70                ",fric"
 71                ",eepa_force"
 72                ",eepa_slip"
 73                ",rgap"
 74                ",dp_nratio"
 75                ",dp_sratio"
 76                ",dp_mode"
 77                ",dp_force"
 78                ",rr_fric"
 79                ",rr_moment"
 80                ",rr_slip"
 81                ",overlap_max"
 82                ",plas_ratio"
 83                ",lu_exp"
 84                ",pull_off"
 85                ",adh_exp"
 86                ",surf_adh"
 87                ",ks_fac"
 88                ",f_min";
 89        }
 90        // Enumerator for the energies.
 91        enum EnergyKeys {
 92            kwEStrain = 1
 93            , kwERRStrain
 94            , kwESlip
 95            , kwERRSlip
 96            , kwEDashpot
 97        };
 98        // Contact model energy names in a comma separated list. The order corresponds with
 99        // the order of the EnergyKeys enumerator above.
100        virtual QString  getEnergies() const {
101            return "energy-strain-eepa"
102                ",energy-rrstrain"
103                ",energy-slip"
104                ",energy-rrslip"
105                ",energy-dashpot";
106        }
107        // Returns the value of the energy (base 1 - getEnergy(1) returns the estrain energy).
108        virtual double   getEnergy(uint32 i) const;
109        // Returns whether or not each energy is accumulated (base 1 - getEnergyAccumulate(1)
110        // returns whether or not the estrain energy is accumulated which is false).
111        virtual bool     getEnergyAccumulate(uint32 i) const;
112        // Set an energy value (base 1 - setEnergy(1) sets the estrain energy).
113        virtual void     setEnergy(uint32 i, const double &d); // Base 1
114        // Activate the energy. This is only called if the energy tracking is enabled.
115        virtual void     activateEnergy() { if (energies_) return; energies_ = NEW Energies(); }
116        // Returns whether or not the energy tracking has been enabled for this contact.
117        virtual bool     getEnergyActivated() const { return (energies_ != 0); }
118
119        // Enumerator for contact model related FISH callback events.
120        enum FishCallEvents {
121            fActivated = 0
122            , fSlipChange
123        };
124        // Contact model FISH callback event names in a comma separated list. The order corresponds with
125        // the order of the FishCallEvents enumerator above.
126        virtual QString  getFishCallEvents() const {
127            return
128                "contact_activated"
129                ",slip_change";
130        }
131
132        // Return the specified contact model property.
133        virtual QVariant getProperty(uint32 i, const IContact *) const;
134        // The return value denotes whether or not the property corresponds to the global
135        // or local coordinate system (TRUE: global system, FALSE: local system). The
136        // local system is the contact-plane system (nst) defined as follows.
137        // If a vector V is expressed in the local system as (Vn, Vs, Vt), then V is
138        // expressed in the global system as {Vn*nc + Vs*sc + Vt*tc} where where nc, sc
139        // and tc are unit vectors in directions of the nst axes.
140        // This is used when rendering contact model properties that are vectors.
141        virtual bool     getPropertyGlobal(uint32 i) const;
142        // Set the specified contact model property, ensuring that it is of the correct type
143        // and within the correct range --- if not, then throw an exception.
144        // The return value denotes whether or not the update has affected the timestep
145        // computation (by having modified the translational or rotational tangent stiffnesses).
146        // If true is returned, then the timestep will be recomputed.
147        virtual bool     setProperty(uint32 i, const QVariant &v, IContact *);
148        // The return value denotes whether or not the property is read-only
149        // (TRUE: read-only, FALSE: read-write).
150        virtual bool     getPropertyReadOnly(uint32 i) const;
151
152        // The return value denotes whether or not the property is inheritable
153        // (TRUE: inheritable, FALSE: not inheritable). Inheritance is provided by
154        // the endPropertyUpdated method.
155        virtual bool     supportsInheritance(uint32 i) const;
156        // Return whether or not inheritance is enabled for the specified property.
157        virtual bool     getInheritance(uint32 i) const { assert(i < 32); uint32 mask = to<uint32>(1 << i);  return (inheritanceField_ & mask) ? true : false; }
158        // Set the inheritance flag for the specified property.
159        virtual void     setInheritance(uint32 i, bool b) { assert(i < 32); uint32 mask = to<uint32>(1 << i);  if (b) inheritanceField_ |= mask;  else inheritanceField_ &= ~mask; }
160
161        // Prepare for entry into ForceDispLaw. The validate function is called when:
162        // (1) the contact is created, (2) a property of the contact that returns a true via
163        // the setProperty method has been modified and (3) when a set of cycles is executed
164        // via the {cycle N} command.
165        // Return value indicates contact activity (TRUE: active, FALSE: inactive).
166        virtual bool    validate(ContactModelMechanicalState *state, const double &timestep);
167        // The endPropertyUpdated method is called whenever a surface property (with a name
168        // that matches an inheritable contact model property name) of one of the contacting
169        // pieces is modified. This allows the contact model to update its associated
170        // properties. The return value denotes whether or not the update has affected
171        // the time step computation (by having modified the translational or rotational
172        // tangent stiffnesses). If true is returned, then the time step will be recomputed.
173        virtual bool    endPropertyUpdated(const QString &name, const IContactMechanical *c);
174        // The forceDisplacementLaw function is called during each cycle. Given the relative
175        // motion of the two contacting pieces (via
176        //   state->relativeTranslationalIncrement_ (Ddn, Ddss, Ddst)
177        //   state->relativeAngularIncrement_       (Dtt, Dtbs, Dtbt)
178        //     Ddn  : relative normal-displacement increment, Ddn > 0 is opening
179        //     Ddss : relative  shear-displacement increment (s-axis component)
180        //     Ddst : relative  shear-displacement increment (t-axis component)
181        //     Dtt  : relative twist-rotation increment
182        //     Dtbs : relative  bend-rotation increment (s-axis component)
183        //     Dtbt : relative  bend-rotation increment (t-axis component)
184        //       The relative displacement and rotation increments:
185        //         Dd = Ddn*nc + Ddss*sc + Ddst*tc
186        //         Dt = Dtt*nc + Dtbs*sc + Dtbt*tc
187        //       where nc, sc and tc are unit vectors in direc. of the nst axes, respectively.
188        //       [see {Table 1: Contact State Variables} in PFC Model Components:
189        //       Contacts and Contact Models: Contact Resolution]
190        // ) and the contact properties, this function must update the contact force and
191        // moment.
192        //   The force_ is acting on piece 2, and is expressed in the local coordinate system
193        //   (defined in getPropertyGlobal) such that the first component positive denotes
194        //   compression. If we define the moment acting on piece 2 by Mc, and Mc is expressed
195        //   in the local coordinate system (defined in getPropertyGlobal), then we must use the getMechanicalContact()->updateResultingTorquesLocal(...) method to
196        // get the total moment.
197        // The return value indicates the contact activity status (TRUE: active, FALSE:
198        // inactive) during the next cycle.
199        // Additional information:
200        //   * If state->activated() is true, then the contact has just become active (it was
201        //     inactive during the previous time step).
202        //   * Fully elastic behavior is enforced during the SOLVE ELASTIC command by having
203        //     the forceDispLaw handle the case of {state->canFail_ == true}.
204        virtual bool    forceDisplacementLaw(ContactModelMechanicalState *state, const double &timestep);
205        // The getEffectiveXStiffness functions return the translational and rotational
206        // tangent stiffnesses used to compute a stable time step. When a contact is sliding,
207        // the translational tangent shear stiffness is zero (but this stiffness reduction
208        // is typically ignored when computing a stable time step). If the contact model
209        // includes a dashpot, then the translational stiffnesses must be increased (see
210        // Potyondy (2009)).
211        //   [Potyondy, D. 'Stiffness Matrix at a Contact Between Two Clumps,' Itasca
212        //   Consulting Group, Inc., Minneapolis, MN, Technical Memorandum ICG6863-L,
213        //   December 7, 2009.]
214        virtual DVect2  getEffectiveTranslationalStiffness() const { return effectiveTranslationalStiffness_; }
215        virtual DAVect  getEffectiveRotationalStiffness() const { return effectiveRotationalStiffness_; }
216
217        // Return a new instance of the contact model. This is used in the CMAT
218        // when a new contact is created.
219        virtual ContactModelEEPA *clone() const { return NEW ContactModelEEPA(); }
220        // The getActivityDistance function is called by the contact-resolution logic when
221        // the CMAT is modified. Return value is the activity distance used by the
222        // checkActivity function.
223        virtual double              getActivityDistance() const { return rgap_; }
224        // The isOKToDelete function is called by the contact-resolution logic when...
225        // Return value indicates whether or not the contact may be deleted.
226        // If TRUE, then the contact may be deleted when it is inactive.
227        // If FALSE, then the contact may not be deleted (under any condition).
228        virtual bool                isOKToDelete() const { return !isBonded(); }
229        // Zero the forces and moments stored in the contact model. This function is called
230        // when the contact becomes inactive.
231        virtual void                resetForcesAndMoments() {
232            eepa_F(DVect(0.0)); dp_F(DVect(0.0));
233            res_M(DAVect(0.0));
234            if (energies_) {
235                //energies_->estrain_ = 0.0;
236                energies_->errstrain_ = 0.0;
237            }
238            Moverlap_ = 0.0;																// reset the history dependend variables
239            Poverlap_exp_ = 0.0;
240            branch_ = 1;
241        }
242        virtual void     setForce(const DVect &v, IContact *c);
243        virtual void     setArea(const double&) { throw Exception("The setArea method cannot be used with the EEPA contact model."); }
244        virtual double   getArea() const { return 0.0; }
245        // The checkActivity function is called by the contact-resolution logic when...
246        // Return value indicates contact activity (TRUE: active, FALSE: inactive).
247        // A contact with the arrlinear model is active if the surface gap is less than
248        // or equal to the attraction range (a_d0_).
249        virtual bool     checkActivity(const double &gap) { return  gap <= rgap_; }
250
251        // Returns the sliding state (FALSE is returned if not implemented).
252        virtual bool     isSliding() const { return eepa_S_; }
253        // Returns the bonding state (FALSE is returned if not implemented).
254        virtual bool     isBonded() const { return false; }
255
256        // Both of these methods are called only for contacts with facets where the wall
257        // resolution scheme is set the full. In such cases one might wish to propagate
258        // contact state information (e.g., shear force) from one active contact to another.
259        // See the Faceted Wall section in the documentation.
260
261        // Return the total force that the contact model holds.
262        virtual DVect    getForce(const IContactMechanical *) const;
263
264        // Return the total moment on 1 that the contact model holds
265        virtual DAVect   getMomentOn1(const IContactMechanical *) const;
266
267        // Return the total moment on 1 that the contact model holds
268        virtual DAVect   getMomentOn2(const IContactMechanical *) const;
269
270        // Methods to get and set properties.
271        const double & shear() const { return shear_; }
272        void           shear(const double &d) { shear_ = d; }
273        const double & poiss() const { return poiss_; }
274        void           poiss(const double &d) { poiss_ = d; }
275        const double & fric() const { return fric_; }
276        void           fric(const double &d) { fric_ = d; }
277        const DVect &  eepa_F() const { return eepa_F_; }
278        void           eepa_F(const DVect &f) { eepa_F_ = f; }
279        bool           eepa_S() const { return eepa_S_; }
280        void           eepa_S(bool b) { eepa_S_ = b; }
281        const double & rgap() const { return rgap_; }
282        void           rgap(const double &d) { rgap_ = d; }
283        const double & Moverlap() const { return Moverlap_; }
284        void           Moverlap(const double &d) { Moverlap_ = d; }
285        const double & Poverlap_exp() const { return Poverlap_exp_; }
286        void           Poverlap_exp(const double &d) { Poverlap_exp_ = d; }
287        const double & plas_ratio() const { return plas_ratio_; }
288        void           plas_ratio(const double &d) { plas_ratio_ = d; }
289        const double & lu_exp() const { return lu_exp_; }
290        void		   lu_exp(const double &d) { lu_exp_ = d; }
291        const double & pull_off() const { return pull_off_; }
292        void           pull_off(const double &d) { pull_off_ = d; }
293        const double & adh_exp() const { return adh_exp_; }
294        void	       adh_exp(const double &d) { adh_exp_ = d; }
295        const double & surf_adh() const { return surf_adh_; }
296        void           surf_adh(const double &d) { surf_adh_ = d; }
297        const double & lu_exp_inv() const { return lu_exp_inv_; }
298        void           lu_exp_inv(const double &d) { lu_exp_inv_ = d; }
299        const double & k1() const { return k1_; }
300        void           k1(const double &d) { k1_ = d; }
301        const double & k2() const { return k2_; }
302        void           k2(const double &d) { k2_ = d; }
303        const double & kadh() const { return kadh_; }
304        void           kadh(const double &d) { kadh_ = d; }
305        const double & ks() const { return ks_; }
306        void           ks(const double &d) { ks_ = d; }
307        const double & r_hertz() const { return r_hertz_; }
308        void           r_hertz(const double &d) { r_hertz_ = d; }
309        const double & ks_fac() const { return ks_fac_; }
310        void           ks_fac(const double &d) { ks_fac_ = d; }
311        const double & f_min() const { return f_min_; }
312        void           f_min(const double &d) { f_min_ = d; }
313        const int    & branch() const { return branch_; }
314        void           branch(const int &d) { branch_ = d; }
315        const double & rbar_square() const { return rbar_square_; }
316        void           rbar_square(const double &d) { rbar_square_ = d; }
317
318        bool     hasDamping() const { return dpProps_ ? true : false; }
319        double   dp_nratio() const { return (hasDamping() ? (dpProps_->dp_nratio_) : 0.0); }
320        void     dp_nratio(const double &d) { if (!hasDamping()) return; dpProps_->dp_nratio_ = d; }
321        double   dp_sratio() const { return hasDamping() ? dpProps_->dp_sratio_ : 0.0; }
322        void     dp_sratio(const double &d) { if (!hasDamping()) return; dpProps_->dp_sratio_ = d; }
323        int      dp_mode() const { return hasDamping() ? dpProps_->dp_mode_ : -1; }
324        void     dp_mode(int i) { if (!hasDamping()) return; dpProps_->dp_mode_ = i; }
325        DVect    dp_F() const { return hasDamping() ? dpProps_->dp_F_ : DVect(0.0); }
326        void     dp_F(const DVect &f) { if (!hasDamping()) return; dpProps_->dp_F_ = f; }
327
328        bool    hasEnergies() const { return energies_ ? true : false; }
329        double  estrain() const { return hasEnergies() ? energies_->estrain_ : 0.0; }
330        void    estrain(const double &d) { if (!hasEnergies()) return; energies_->estrain_ = d; }
331        double  errstrain() const { return hasEnergies() ? energies_->errstrain_ : 0.0; }
332        void    errstrain(const double &d) { if (!hasEnergies()) return; energies_->errstrain_ = d; }
333        double  eslip() const { return hasEnergies() ? energies_->eslip_ : 0.0; }
334        void    eslip(const double &d) { if (!hasEnergies()) return; energies_->eslip_ = d; }
335        double  errslip() const { return hasEnergies() ? energies_->errslip_ : 0.0; }
336        void    errslip(const double &d) { if (!hasEnergies()) return; energies_->errslip_ = d; }
337        double  edashpot() const { return hasEnergies() ? energies_->edashpot_ : 0.0; }
338        void    edashpot(const double &d) { if (!hasEnergies()) return; energies_->edashpot_ = d; }
339
340        uint32 inheritanceField() const { return inheritanceField_; }
341        void inheritanceField(uint32 i) { inheritanceField_ = i; }
342
343        const DVect2 & effectiveTranslationalStiffness()  const { return effectiveTranslationalStiffness_; }
344        void           effectiveTranslationalStiffness(const DVect2 &v) { effectiveTranslationalStiffness_ = v; }
345        const DAVect & effectiveRotationalStiffness()  const { return effectiveRotationalStiffness_; }
346        void           effectiveRotationalStiffness(const DAVect &v) { effectiveRotationalStiffness_ = v; }
347
348        // Rolling resistance methods
349        const double & res_fric() const { return res_fric_; }
350        void           res_fric(const double &d) { res_fric_ = d; }
351        const DAVect & res_M() const { return res_M_; }
352        void           res_M(const DAVect &f) { res_M_ = f; }
353        bool           res_S() const { return res_S_; }
354        void           res_S(bool b) { res_S_ = b; }
355        const double & kr() const { return kr_; }
356        void           kr(const double &d) { kr_ = d; }
357        const double & fr() const { return fr_; }
358        void           fr(const double &d) { fr_ = d; }
359
360    private:
361        // Index - used internally by PFC. Should be set to -1 in the cpp file.
362        static int index_;
363
364        // Structure to store the energies.
365        struct Energies {
366            Energies() : estrain_(0.0), errstrain_(0.0), eslip_(0.0), errslip_(0.0), edashpot_(0.0) {}
367            double estrain_;   // elastic energy stored in EEPA group
368            double errstrain_; // elastic energy stored in rolling resistance group
369            double eslip_;     // work dissipated by friction
370            double errslip_;   // work dissipated by rolling resistance friction
371            double edashpot_;  // work dissipated by dashpots
372        };
373
374        // Structure to store dashpot quantities.
375        struct dpProps {
376            dpProps() : dp_nratio_(0.0), dp_sratio_(0.0), dp_mode_(0), dp_F_(DVect(0.0)) {}
377            double dp_nratio_;		// normal viscous critical damping ratio
378            double dp_sratio_;		// shear  viscous critical damping ratio
379            int    dp_mode_;		// for viscous mode (0-1) 0 = no cut-offs;    1 = shear damp cut-off when sliding
380            DVect  dp_F_;			// Force in the dashpots
381        };
382
383        bool   updateEndStiffCoef(const IContactMechanical *con);
384        bool   updateEndFric(const IContactMechanical *con);
385        bool   updateEndResFric(const IContactMechanical *con);
386        void   updateStiffCoef(const IContactMechanical *con);
387        void   updateEffectiveStiffness(ContactModelMechanicalState *state);
388        void   setDampCoefficients(const double &mass, double *kn_tangent, double *ks_tangent, double *vcn, double *vcs);
389
390        static const uint32 shearMask = 0x00000002; // Base 1!
391        static const uint32 poissMask = 0x00000004;
392        static const uint32 fricMask = 0x00000008;
393        static const uint32 resFricMask = 0x00004000;
394
395        // Contact model inheritance fields.
396        uint32 inheritanceField_ = shearMask | poissMask | fricMask | resFricMask;
397
398        // Effective translational stiffness.
399        DVect2  effectiveTranslationalStiffness_ = DVect2(0);
400        DAVect  effectiveRotationalStiffness_ = DAVect(0);   // (Twisting,Bending,Bending) Rotational stiffness (twisting always 0)
401
402        // EEPA model properties
403        double      shear_ = 0.0;			// Shear modulus
404        double      poiss_ = 0.0;			// Poisson's ratio
405        double      fric_ = 0.0;			// Coulomb friction coefficient
406        DVect       eepa_F_ = DVect(0);		// Force carried in the eepa model
407        bool        eepa_S_ = false;		// The current slip state
408        double      rgap_ = 0.0;			// Reference gap
409        dpProps *   dpProps_ = nullptr;		// The viscous properties
410        double		Moverlap_ = 0.0;		// Maximum overlap - updated as it evolves
411        double		Poverlap_exp_ = 0.0;	// Plastic overlap raised to the power lu_exp - updated as it evolves
412        double		plas_ratio_ = 0.5;		// plasticity ratio
413        double		lu_exp_ = 1.5;			// load-unload exponent anlong the k1 and k2 brances
414        double		pull_off_ = 0.0;		// constant pull-off force
415        double		adh_exp_ = 1.5;			// adhesive branch exponent
416        double		surf_adh_ = 0.0;		// surface adhesion energy
417        double		lu_exp_inv_ = 0.0;		// inverse of load-unloading exponent
418        double      k1_ = 0.0;				// k1 branch stiffness
419        double		k2_ = 0.0;				// k2 branch stiffness
420        double      kadh_ = 0.0;			// adhesive branch stiffness - updated as the maximum overlap (and plastic overlap) increases
421        double      ks_ = 0.0;				// shear stiffness
422        double      r_hertz_ = 0.0;    		// effective contact radius = (R1*R2)/(R1 + R2)
423        double      ks_fac_ = 0.0;			// shear stiffness scaling factor
424        double		f_min_ = 0.0;			// minimum adhesion force limit
425        int         branch_ = 1;			// 1,2 or 3 for the current branch
426
427        // rolling resistance properties
428        double res_fric_ = 0.0;       // rolling friction coefficient
429        DAVect res_M_ = DAVect(0);          // moment (bending only)
430        bool   res_S_ = false;          // The current rolling resistance slip state
431        double kr_ = 0.0;             // bending rotational stiffness (read-only, calculated internaly)
432        double fr_ = 0.0;             // rolling friction coefficient (rbar*res_fric_) (calculated internaly, not a property)
433        double rbar_square_ = 0.0;	// curvature expression used in calculating the rolling stiffness - stays constant for  given contact where kr_ = rbar_square*ks_tangent
434
435        Energies *   energies_ = nullptr; // The energies
436
437    };
438} // namespace cmodelsxd
439// EoF

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contactmodeleepa.cpp

   1// contactmodeleepa.cpp
   2#include "contactmodeleepa.h"
   3
   4#include "module/interface/icontactmechanical.h"
   5#include "module/interface/icontact.h"
   6#include "module/interface/ipiecemechanical.h"
   7#include "module/interface/ipiece.h"
   8#include "module/interface/ifishcalllist.h"
   9
  10#include "../version.txt"
  11
  12#include "utility/src/tptr.h"
  13#include "shared/src/mathutil.h"
  14
  15#include "kernel/interface/iprogram.h"
  16#include "module/interface/icontactthermal.h"
  17#include "contactmodel/src/contactmodelthermal.h"
  18#include "fish/src/parameter.h"
  19
  20#ifdef EEPA_LIB
  21int __stdcall DllMain(void *, unsigned, void *) {
  22    return 1;
  23}
  24
  25extern "C" EXPORT_TAG const char *getName() {
  26#if DIM==3
  27    return "contactmodelmechanical3deepa";
  28#else
  29    return "contactmodelmechanical2deepa";
  30#endif
  31}
  32
  33extern "C" EXPORT_TAG unsigned getMajorVersion() {
  34    return MAJOR_VERSION;
  35}
  36
  37extern "C" EXPORT_TAG unsigned getMinorVersion() {
  38    return MINOR_VERSION;
  39}
  40
  41extern "C" EXPORT_TAG void *createInstance() {
  42    cmodelsxd::ContactModelEEPA *m = NEW cmodelsxd::ContactModelEEPA();
  43    return (void *)m;
  44}
  45#endif
  46
  47namespace cmodelsxd {
  48
  49    using namespace itasca;
  50
  51    int ContactModelEEPA::index_ = -1;
  52    uint32 ContactModelEEPA::getMinorVersion() const { return MINOR_VERSION; }
  53
  54    ContactModelEEPA::ContactModelEEPA() {  }
  55
  56    ContactModelEEPA::~ContactModelEEPA() {
  57        // Make sure to clean up after yourself!
  58        if (dpProps_)
  59            delete dpProps_;
  60        if (energies_)
  61            delete energies_;
  62    }
  63
  64    void ContactModelEEPA::archive(ArchiveStream &stream) {
  65        // The stream allows one to archive the values of the contact model
  66        // so that it can be saved and restored. The minor version can be
  67        // used here to allow for incremental changes to the contact model too.
  68        stream & shear_;
  69        stream & poiss_;
  70        stream & fric_;
  71        stream & eepa_F_;
  72        stream & eepa_S_;
  73        stream & rgap_;
  74        stream & res_fric_;
  75        stream & res_M_;
  76        stream & res_S_;
  77        stream & kr_;
  78        stream & fr_;
  79        stream & Moverlap_;
  80        stream & Poverlap_exp_;
  81        stream & plas_ratio_;
  82        stream & lu_exp_;
  83        stream & pull_off_;
  84        stream & adh_exp_;
  85        stream & surf_adh_;
  86        stream & lu_exp_inv_;
  87        stream & k1_;
  88        stream & k2_;
  89        stream & kadh_;
  90        stream & ks_;
  91        stream & r_hertz_;
  92        stream & ks_fac_;
  93        stream & f_min_;
  94        stream & branch_;
  95        stream & rbar_square_;
  96
  97        if (stream.getArchiveState() == ArchiveStream::Save) {
  98            bool b = false;
  99            if (dpProps_) {
 100                b = true;
 101                stream & b;
 102                stream & dpProps_->dp_nratio_;
 103                stream & dpProps_->dp_sratio_;
 104                stream & dpProps_->dp_mode_;
 105                stream & dpProps_->dp_F_;
 106            }
 107            else
 108                stream & b;
 109
 110            b = false;
 111            if (energies_) {
 112                b = true;
 113                stream & b;
 114                stream & energies_->estrain_;
 115                stream & energies_->errstrain_;
 116                stream & energies_->eslip_;
 117                stream & energies_->errslip_;
 118                stream & energies_->edashpot_;
 119            }
 120            else
 121                stream & b;
 122        }
 123        else {
 124            bool b(false);
 125            stream & b;
 126            if (b) {
 127                if (!dpProps_)
 128                    dpProps_ = NEW dpProps();
 129                stream & dpProps_->dp_nratio_;
 130                stream & dpProps_->dp_sratio_;
 131                stream & dpProps_->dp_mode_;
 132                stream & dpProps_->dp_F_;
 133            }
 134            stream & b;
 135            if (b) {
 136                if (!energies_)
 137                    energies_ = NEW Energies();
 138                stream & energies_->estrain_;
 139                stream & energies_->errstrain_;
 140                stream & energies_->eslip_;
 141                stream & energies_->errslip_;
 142                stream & energies_->edashpot_;
 143            }
 144        }
 145
 146        stream & inheritanceField_;
 147        stream & effectiveTranslationalStiffness_;
 148        stream & effectiveRotationalStiffness_;
 149
 150    }
 151
 152    void ContactModelEEPA::copy(const ContactModel *cm) {
 153        // Copy all of the contact model properties. Used in the CMAT
 154        // when a new contact is created.
 155        ContactModelMechanical::copy(cm);
 156        const ContactModelEEPA *in = dynamic_cast<const ContactModelEEPA*>(cm);
 157        if (!in) throw std::runtime_error("Internal error: contact model dynamic cast failed.");
 158        shear(in->shear());
 159        poiss(in->poiss());
 160        fric(in->fric());
 161        eepa_F(in->eepa_F());
 162        eepa_S(in->eepa_S());
 163        rgap(in->rgap());
 164        res_fric(in->res_fric());
 165        res_M(in->res_M());
 166        res_S(in->res_S());
 167        kr(in->kr());
 168        fr(in->fr());
 169        Moverlap(in->Moverlap());
 170        Poverlap_exp(in->Poverlap_exp());
 171        plas_ratio(in->plas_ratio());
 172        lu_exp(in->lu_exp());
 173        pull_off(in->pull_off());
 174        adh_exp(in->adh_exp());
 175        surf_adh(in->surf_adh());
 176        lu_exp_inv(in->lu_exp_inv());
 177        k1(in->k1());
 178        k2(in->k2());
 179        kadh(in->kadh());
 180        ks(in->ks());
 181        r_hertz(in->r_hertz());
 182        ks_fac(in->ks_fac());
 183        f_min(in->f_min());
 184        branch(in->branch());
 185        rbar_square(in->rbar_square());
 186
 187        if (in->hasDamping()) {
 188            if (!dpProps_)
 189                dpProps_ = NEW dpProps();
 190            dp_nratio(in->dp_nratio());
 191            dp_sratio(in->dp_sratio());
 192            dp_mode(in->dp_mode());
 193            dp_F(in->dp_F());
 194        }
 195        if (in->hasEnergies()) {
 196            if (!energies_)
 197                energies_ = NEW Energies();
 198            estrain(in->estrain());
 199            errstrain(in->errstrain());
 200            eslip(in->eslip());
 201            errslip(in->errslip());
 202            edashpot(in->edashpot());
 203        }
 204        inheritanceField(in->inheritanceField());
 205        effectiveTranslationalStiffness(in->effectiveTranslationalStiffness());
 206        effectiveRotationalStiffness(in->effectiveRotationalStiffness());
 207    }
 208
 209    QVariant ContactModelEEPA::getProperty(uint32 i, const IContact *) const {
 210        // Return the property. The IContact pointer is provided so that
 211        // more complicated properties, depending on contact characteristics,
 212        // can be calcualted.
 213        QVariant var;
 214        switch (i) {
 215        case kwShear:     return shear_;
 216        case kwPoiss:     return poiss_;
 217        case kwFric:      return fric_;
 218        case kwEepaF:     var.setValue(eepa_F_); return var;
 219        case kwEepaS:     return eepa_S_;
 220        case kwRGap:      return rgap_;
 221        case kwDpNRatio:  return dpProps_ ? dpProps_->dp_nratio_ : 0;
 222        case kwDpSRatio:  return dpProps_ ? dpProps_->dp_sratio_ : 0;
 223        case kwDpMode:    return dpProps_ ? dpProps_->dp_mode_ : 0;
 224        case kwDpF: {
 225            dpProps_ ? var.setValue(dpProps_->dp_F_) : var.setValue(DVect(0.0));
 226            return var;
 227        }
 228        case kwResFric:    return res_fric_;
 229        case kwResMoment:  var.setValue(res_M_); return var;
 230        case kwResS:       return res_S_;
 231        case kwOverlapMax: return Moverlap_;
 232        case kwPlasRat:	   return plas_ratio_;
 233        case kwLuExp:	   return lu_exp_;
 234        case kwPullOff:	   return pull_off_;
 235        case kwAdhExp:	   return adh_exp_;
 236        case kwSurfAdh:	   return surf_adh_;
 237        case kwKsFac:	   return ks_fac_;
 238        case kwFmin:	   return f_min_;
 239        }
 240        assert(0);
 241        return QVariant();
 242    }
 243
 244    bool ContactModelEEPA::getPropertyGlobal(uint32 i) const {
 245        // Returns whether or not a property is held in the global axis system (TRUE)
 246        // or the local system (FALSE). Used by the plotting logic.
 247        switch (i) {
 248        case kwEepaF:
 249        case kwDpF:
 250        case kwResMoment:
 251            return false;
 252        }
 253        return true;
 254    }
 255
 256    bool ContactModelEEPA::setProperty(uint32 i, const QVariant &v, IContact *) {
 257        // Set a contact model property. Return value indicates that the timestep
 258        // should be recalculated.
 259        dpProps dp;
 260        switch (i) {
 261        case kwShear: {
 262            if (!v.canConvert<double>())
 263                throw Exception("eepa_shear must be a double.");
 264            double val(v.toDouble());
 265            if (val <= 0.0)
 266                throw Exception("zero or negative eepa_shear not allowed.");
 267            shear_ = val;
 268            return true;
 269        }
 270        case kwPoiss: {
 271            if (!v.canConvert<double>())
 272                throw Exception("eepa_poiss must be a double.");
 273            double val(v.toDouble());
 274            if (val < 0.0 || val > 0.5)
 275                throw Exception("eepa_poiss must be in the range [0, 0.5].");
 276            poiss_ = val;
 277            return true;
 278        }
 279        case kwFric: {
 280            if (!v.canConvert<double>())
 281                throw Exception("fric must be a double.");
 282            double val(v.toDouble());
 283            if (val < 0.0)
 284                throw Exception("negative fric not allowed.");
 285            fric_ = val;
 286            return false;
 287        }
 288        case kwEepaF: {
 289            if (!v.canConvert<DVect>())
 290                throw Exception("eepa_force must be a vector.");
 291            DVect val(v.value<DVect>());
 292            eepa_F_ = val;
 293            return false;
 294        }
 295        case kwRGap: {
 296            if (!v.canConvert<double>())
 297                throw Exception("reference gap must be a double.");
 298            double val(v.toDouble());
 299            rgap_ = val;
 300            return false;
 301        }
 302        case kwDpNRatio: {
 303            if (!v.canConvert<double>())
 304                throw Exception("dp_nratio must be a double.");
 305            double val(v.toDouble());
 306            if (val < 0.0)
 307                throw Exception("negative dp_nratio not allowed.");
 308            if (val == 0.0 && !dpProps_)
 309                return false;
 310            if (!dpProps_)
 311                dpProps_ = NEW dpProps();
 312            dpProps_->dp_nratio_ = val;
 313            return true;
 314        }
 315        case kwDpSRatio: {
 316            if (!v.canConvert<double>())
 317                throw Exception("dp_sratio must be a double.");
 318            double val(v.toDouble());
 319            if (val < 0.0)
 320                throw Exception("negative dp_sratio not allowed.");
 321            if (val == 0.0 && !dpProps_)
 322                return false;
 323            if (!dpProps_)
 324                dpProps_ = NEW dpProps();
 325            dpProps_->dp_sratio_ = val;
 326            return true;
 327        }
 328        case kwDpMode: {
 329            if (!v.canConvert<int>())
 330                throw Exception("the viscous mode dp_mode must be 0 or 1");
 331            int val(v.toInt());
 332            if (val == 0 && !dpProps_)
 333                return false;
 334            if (val < 0 || val > 1)
 335                throw Exception("the viscous mode dp_mode must be 0 or 1.");
 336            if (!dpProps_)
 337                dpProps_ = NEW dpProps();
 338            dpProps_->dp_mode_ = val;
 339            return false;
 340        }
 341        case kwDpF: {
 342            if (!v.canConvert<DVect>())
 343                throw Exception("dp_force must be a vector.");
 344            DVect val(v.value<DVect>());
 345            if (val.fsum() == 0.0 && !dpProps_)
 346                return false;
 347            if (!dpProps_)
 348                dpProps_ = NEW dpProps();
 349            dpProps_->dp_F_ = val;
 350            return false;
 351        }
 352        case kwResFric: {
 353            if (!v.canConvert<double>())
 354                throw Exception("res_fric must be a double.");
 355            double val(v.toDouble());
 356            if (val < 0.0)
 357                throw Exception("negative res_fric not allowed.");
 358            res_fric_ = val;
 359            return true;
 360        }
 361        case kwResMoment: {
 362            DAVect val(0.0);
 363#ifdef TWOD
 364            if (!v.canConvert<DAVect>() && !v.canConvert<double>())
 365                throw Exception("res_moment must be an angular vector.");
 366            if (v.canConvert<DAVect>())
 367                val = DAVect(v.value<DAVect>());
 368            else
 369                val = DAVect(v.toDouble());
 370#else
 371            if (!v.canConvert<DAVect>() && !v.canConvert<DVect>())
 372                throw Exception("res_moment must be an angular vector.");
 373            if (v.canConvert<DAVect>())
 374                val = DAVect(v.value<DAVect>());
 375            else
 376                val = DAVect(v.value<DVect>());
 377#endif
 378            res_M_ = val;
 379            return false;
 380        }
 381        case kwPlasRat: {
 382            if (!v.canConvert<double>())
 383                throw Exception("plas_ratio must be a double.");
 384             double val(v.toDouble());
 385             if (val <= 0.0 || val >= 1.0)
 386                 throw Exception("plas_ratio must be larger than zero and smaller than 1 (0,1).");
 387             plas_ratio_ = val;
 388             return true;
 389        }
 390        case kwLuExp: {
 391            if (!v.canConvert<double>())
 392                throw Exception("loading-unloading branch exponent must be a double.");
 393            double val(v.toDouble());
 394            if (val < 1.0)
 395                throw Exception("lu_exp must be 1 or larger. For lu_exp = 1, use the linear contact model 'eepa_lin'.");
 396            lu_exp_ = val;
 397            return true;
 398        }
 399        case kwPullOff: {
 400            if (!v.canConvert<double>())
 401                throw Exception("constant pull-off force must be a double.");
 402            double val(v.toDouble());
 403            if (val > 0.0)
 404                throw Exception("pull_off must be a negative value or zero.");
 405            pull_off_ = val;
 406            return false;
 407        }
 408        case kwAdhExp: {
 409            if (!v.canConvert<double>())
 410                throw Exception("adhesion branch exponent must be a double.");
 411            double val(v.toDouble());
 412            if (val < 1.0)
 413                throw Exception("adh_exp must be equal to or greater than 1.");
 414            adh_exp_ = val;
 415            return true;
 416        }
 417        case kwSurfAdh: {
 418            if (!v.canConvert<double>())
 419                throw Exception("surface adhesion energy must be a double.");
 420            double val(v.toDouble());
 421            if (val < 0.0)
 422                throw Exception("negative surf_adh not allowed.");
 423            surf_adh_ = val;
 424            return false;
 425        }
 426        case kwKsFac: {
 427            if (!v.canConvert<double>())
 428                throw Exception("shear stiffness factor must be a double.");
 429            double val(v.toDouble());
 430            if (val <= 0.0)
 431                throw Exception("zero or negative ks_fac not allowed.");
 432            ks_fac_ = val;
 433            return true;
 434        }
 435
 436        }//switch
 437        return false;
 438    }
 439
 440    bool ContactModelEEPA::getPropertyReadOnly(uint32 i) const {
 441        // Returns TRUE if a property is read only or FALSE otherwise.
 442        switch (i) {
 443        case kwDpF:
 444        case kwEepaS:
 445        case kwResS:
 446        case kwOverlapMax:
 447        case kwFmin:
 448            return true;
 449        default:
 450            break;
 451        }
 452        return false;
 453    }
 454
 455    bool ContactModelEEPA::supportsInheritance(uint32 i) const {
 456        // Returns TRUE if a property supports inheritance or FALSE otherwise.
 457        switch (i) {
 458        case kwShear:
 459        case kwPoiss:
 460        case kwFric:
 461        case kwResFric:
 462            return true;
 463        default:
 464            break;
 465        }
 466        return false;
 467    }
 468
 469    double ContactModelEEPA::getEnergy(uint32 i) const {
 470        // Return an energy value.
 471        double ret(0.0);
 472        if (!energies_)
 473            return ret;
 474        switch (i) {
 475        case kwEStrain:    return energies_->estrain_;
 476        case kwERRStrain:  return energies_->errstrain_;
 477        case kwESlip:      return energies_->eslip_;
 478        case kwERRSlip:    return energies_->errslip_;
 479        case kwEDashpot:   return energies_->edashpot_;
 480        }
 481        assert(0);
 482        return ret;
 483    }
 484
 485    bool ContactModelEEPA::getEnergyAccumulate(uint32 i) const {
 486        // Returns TRUE if the corresponding energy is accumulated or FALSE otherwise.
 487        switch (i) {
 488        case kwEStrain:   return true;
 489        case kwERRStrain: return false;
 490        case kwESlip:     return true;
 491        case kwERRSlip:   return true;
 492        case kwEDashpot:  return true;
 493        }
 494        assert(0);
 495        return false;
 496    }
 497
 498    void ContactModelEEPA::setEnergy(uint32 i, const double &d) {
 499        // Set an energy value.
 500        if (!energies_) return;
 501        switch (i) {
 502        case kwEStrain:    energies_->estrain_ = d;   return;
 503        case kwERRStrain:  energies_->errstrain_ = d; return;
 504        case kwESlip:      energies_->eslip_ = d;     return;
 505        case kwERRSlip:    energies_->errslip_ = d;   return;
 506        case kwEDashpot:   energies_->edashpot_ = d;  return;
 507        }
 508        assert(0);
 509        return;
 510    }
 511
 512    bool ContactModelEEPA::validate(ContactModelMechanicalState *state, const double &) {
 513        // Validate the / Prepare for entry into ForceDispLaw. The validate function is called when:
 514        // (1) the contact is created, (2) a property of the contact that returns a true via
 515        // the setProperty method has been modified and (3) when a set of cycles is executed
 516        // via the {cycle N} command.
 517        // Return value indicates contact activity (TRUE: active, FALSE: inactive).
 518        assert(state);
 519        const IContactMechanical *c = state->getMechanicalContact();
 520        assert(c);
 521        //
 522        if (state->trackEnergy_)
 523            activateEnergy();
 524        //
 525        if ((inheritanceField_ & shearMask) || (inheritanceField_ & poissMask))
 526            updateEndStiffCoef(c);
 527        if (inheritanceField_ & fricMask)
 528            updateEndFric(c);
 529        if (inheritanceField_ & resFricMask)
 530            updateEndResFric(c);
 531        //
 532        if (shear_ <= 0.0) {
 533            throw Exception("'eepa_shear' must be specified using a value larger than zero in the 'eepa' model.");
 534        }
 535        //
 536        updateStiffCoef(c);												// calculate the stiffness values based on the material properties - specified directly or via inheritance
 537        updateEffectiveStiffness(state);								// effective stiffness for translation and rotation used in the time step estimation
 538        //
 539        return checkActivity(state->gap_);
 540    }
 541
 542    void ContactModelEEPA::updateStiffCoef(const IContactMechanical *con) {
 543        //
 544        double c12 = con->getEnd1Curvature().y();
 545        double c22 = con->getEnd2Curvature().y();
 546        r_hertz_ = c12 + c22;
 547        if (r_hertz_ == 0.0)
 548            throw Exception("eepa contact model undefined for 2 non-curved surfaces");
 549        r_hertz_ = 1.0 / r_hertz_;										// R1*R2/(R1 + R2)
 550        k1_ = 4.0 / 3.0 * (shear_ / (1 - poiss_)) * sqrt(r_hertz_);	    // k1 loading branch
 551        double shear_effective = shear_ / (4.0 - 2.0*poiss_);			// effective shear modulus for contact assuming the two contact pieces are identical in properties
 552        ks_ = ks_fac_ * 8.0*shear_effective*sqrt(r_hertz_);				// shear stiffness
 553        k2_ = k1_ / (1.0 - plas_ratio_);								// k2 loading branch
 554        lu_exp_inv_ = 1.0 / lu_exp_;									// inverse of load-unloading exponent - stored with contact
 555        // rolling resistance
 556        kr_ = 0.0;
 557        fr_ = 0.0;
 558        if (res_fric_ > 0.0) {
 559            rbar_square_ = r_hertz_ * r_hertz_;							// store this value with contact - used again when 'ks_tangent' is updated during loading-unloading to calculate the rolling stiffness
 560            fr_ = res_fric_ * r_hertz_;									// store this value with contact - used in force-displacement calculation
 561            kr_ = ks_ * rbar_square_;									// based on 'ks_' for now, this is updated and based on the shear tangent stiffness during loading-unloading
 562        }
 563    }
 564
 565    bool ContactModelEEPA::endPropertyUpdated(const QString &name, const IContactMechanical *c) {
 566        // The endPropertyUpdated method is called whenever a surface property (with a name
 567        // that matches an inheritable contact model property name) of one of the contacting
 568        // pieces is modified. This allows the contact model to update its associated
 569        // properties. The return value denotes whether or not the update has affected
 570        // the time step computation (by having modified the translational or rotational
 571        // tangent stiffnesses). If true is returned, then the time step will be recomputed.
 572        assert(c);
 573        QStringList availableProperties = getProperties().simplified().replace(" ", "").split(",", Qt::SkipEmptyParts);
 574        QRegularExpression rx(name, QRegularExpression::CaseInsensitiveOption);
 575        int idx = availableProperties.indexOf(rx) + 1;
 576        bool ret = false;
 577
 578        if (idx <= 0)
 579            return ret;
 580
 581        switch (idx) {
 582        case kwShear: { //Shear
 583            if (inheritanceField_ & shearMask)
 584                ret = true;							// return 'true' to ensure 'validate()' is called to affect the change in Shear Modulus through 'updateEndStiffCoef()' and effective (tangent) stiffnesses
 585            break;
 586        }
 587        case kwPoiss: { //Poisson's
 588            if (inheritanceField_ & poissMask)
 589                ret =true;							// return 'true' to ensure 'validate()' is called to affect the change in Poisson's ratio through 'updateEndStiffCoef()' and effective (tangent) stiffnesses
 590            break;
 591        }
 592        case kwFric: { //fric
 593            if (inheritanceField_ & fricMask)
 594                updateEndFric(c);					// friction does not influence any of the other parameters or time step size, so directly update the contact model friction
 595            break;
 596        }
 597        case kwResFric: { //rr_fric
 598            if (inheritanceField_ & resFricMask)
 599                ret = true;							// return 'true' to ensure 'validate()' is called to affect the change in rolling friction through 'updateEndResFric()' and 'fr_'
 600            break;
 601        }
 602        //
 603        }
 604        return ret;
 605    }
 606
 607    static const QString gstr("eepa_shear");
 608    static const QString nustr("eepa_poiss");
 609    bool ContactModelEEPA::updateEndStiffCoef(const IContactMechanical *con) {
 610        assert(con);
 611        double g1 = shear_;
 612        double g2 = shear_;
 613        double nu1 = poiss_;
 614        double nu2 = poiss_;
 615        QVariant vg1 = con->getEnd1()->getProperty(gstr);
 616        QVariant vg2 = con->getEnd2()->getProperty(gstr);
 617        QVariant vnu1 = con->getEnd1()->getProperty(nustr);
 618        QVariant vnu2 = con->getEnd2()->getProperty(nustr);
 619        if (vg1.isValid() && vg2.isValid()) {
 620            g1 = vg1.toDouble();
 621            g2 = vg2.toDouble();
 622            if (g1 <= 0.0 || g2 <= 0.0)
 623                throw Exception("Negative or zero shear modulus not allowed in eepa contact model");
 624        }
 625        if (vnu1.isValid() && vnu2.isValid()) {
 626            nu1 = vnu1.toDouble();
 627            nu2 = vnu2.toDouble();
 628            if (nu1 < 0.0 || nu1 > 0.5 || nu2 < 0.0 || nu2 > 0.5)
 629                throw Exception("Poisson ratio should be in range [0,0.5] in eepa contact model");
 630        }
 631        if (g1*g2 == 0.0) return false;
 632        double es = 1.0 / ((1.0 - nu1) / (2.0*g1) + (1.0 - nu2) / (2.0*g2));
 633        double gs = 1.0 / ((2.0 - nu1) / g1 + (2.0 - nu2) / g2);
 634        poiss_ = (4.0*gs - es) / (2.0*gs - es);
 635        shear_ = 2.0*gs*(2 - poiss_);
 636        if (shear_ <= 0.0)
 637            throw Exception("Negative or zero shear modulus not allowed in eepa contact model");
 638        if (poiss_ < 0.0 || poiss_ > 0.5)
 639            throw Exception("Poisson ratio should be in range [0,0.5] in eepa contact model");
 640        return true;
 641    }
 642
 643    static const QString fricstr("fric");
 644    bool ContactModelEEPA::updateEndFric(const IContactMechanical *con) {
 645        assert(con);
 646        QVariant v1 = con->getEnd1()->getProperty(fricstr);
 647        QVariant v2 = con->getEnd2()->getProperty(fricstr);
 648        if (!v1.isValid() || !v2.isValid())
 649            return false;
 650        double fric1 = std::max(0.0, v1.toDouble());
 651        double fric2 = std::max(0.0, v2.toDouble());
 652        double val = fric_;
 653        fric_ = std::min(fric1, fric2);
 654        if (fric_ <= 0.0)
 655            throw Exception("Negative friction not allowed in eepa contact model");
 656        return ((fric_ != val));
 657    }
 658
 659    static const QString rfricstr("rr_fric");
 660    bool ContactModelEEPA::updateEndResFric(const IContactMechanical *con) {
 661        assert(con);
 662        QVariant v1 = con->getEnd1()->getProperty(rfricstr);
 663        QVariant v2 = con->getEnd2()->getProperty(rfricstr);
 664        if (!v1.isValid() || !v2.isValid())
 665            return false;
 666        double rfric1 = std::max(0.0, v1.toDouble());
 667        double rfric2 = std::max(0.0, v2.toDouble());
 668        double val = res_fric_;
 669        res_fric_ = std::min(rfric1, rfric2);
 670        if (res_fric_ <= 0.0)
 671            throw Exception("Negative rolling friction not allowed in eepa contact model");
 672        return ((res_fric_ != val));
 673    }
 674
 675    void ContactModelEEPA::updateEffectiveStiffness(ContactModelMechanicalState *state) {
 676        //
 677        double overlap = rgap_ - state->gap_;
 678        //
 679        double kn_tangent = 0.0;
 680        double ks_tangent = 0.0;
 681        //
 682        if (overlap <= 0.0) {													// inactive contact
 683            // The assumption below is based on the Hill contact model in PFC
 684            // 0.01% of Diameter = 0.0001*D
 685            // For monodisperse system, r_hertz_ = 0.5*R where R is the particle radius
 686            // r_hertz_ = 0.5*(0.5*D) = 0.25*D where D is the particle diameter
 687            // D = 4*r_hertz_
 688            // 0.01%*D = 0.0001*D = 0.0001*4*r_hertz_ = 0.0004*r_hertz_
 689            overlap = 0.0004*r_hertz_;
 690            kn_tangent = lu_exp_ * k1_*pow(overlap, lu_exp_ - 1.0);				// k1 loading branch assumed for inactive contacts
 691            ks_tangent = ks_ * sqrt(overlap);									// tangent stiffness in the shear direction
 692        }
 693        else {																	// active contact
 694            switch (branch_) {
 695            case 1: {
 696                kn_tangent = lu_exp_ * k1_*pow(overlap, lu_exp_ - 1.0);
 697                break;
 698            }
 699            case 2: {
 700                kn_tangent = lu_exp_ * k2_*pow(overlap, lu_exp_ - 1.0);
 701                break;
 702            }
 703            case 3: {
 704                kn_tangent = adh_exp_ * kadh_*pow(overlap, adh_exp_ - 1.0);
 705                break;
 706            }
 707            }//switch
 708            ks_tangent = ks_ * sqrt(overlap);
 709        }
 710        //
 711        DVect2 retT(kn_tangent, ks_tangent);
 712        if (res_fric_ > 0.0) {													// rolling
 713            kr_ = ks_tangent * rbar_square_;									// based on the tangent shear stiffness (Wensrich and Katterfeld, 2012)
 714        }
 715        //
 716        // correction if viscous damping active
 717        if (dpProps_) {
 718            DVect2 correct(1.0);
 719            if (dpProps_->dp_nratio_)
 720                correct.rx() = sqrt(1.0 + dpProps_->dp_nratio_*dpProps_->dp_nratio_) - dpProps_->dp_nratio_;
 721            if (dpProps_->dp_sratio_)
 722                correct.ry() = sqrt(1.0 + dpProps_->dp_sratio_*dpProps_->dp_sratio_) - dpProps_->dp_sratio_;
 723            retT /= (correct*correct);
 724        }
 725        //
 726        effectiveTranslationalStiffness_ = retT;									// set
 727        effectiveRotationalStiffness_ = DAVect(kr_);								// Effective rotational stiffness (bending only)
 728#if DIM==3
 729        effectiveRotationalStiffness_.rx() = 0.0;
 730#endif
 731    }
 732
 733    bool ContactModelEEPA::forceDisplacementLaw(ContactModelMechanicalState *state, const double &timestep) {
 734        assert(state);
 735        //
 736        // Current overlap
 737        double overlap = rgap_ - state->gap_;
 738        // Relative translational increment
 739        DVect trans = state->relativeTranslationalIncrement_;
 740        //
 741        // The contact was just activated from an inactive state
 742        if (state->activated()) {
 743            // The contact just got activated, set the initial normal force equal to the pull-off force
 744            eepa_F_.rdof(0) = pull_off_;
 745            //
 746            // Trigger the FISH callback if one is hooked up to the
 747            // contact_activated event.
 748            if (cmEvents_[fActivated] >= 0) {
 749                // The contact was just activated from an inactive state
 750                // Trigger the FISH callback if one is hooked up to the
 751                // contact_activated event.
 752                auto c = state->getContact();
 753                std::vector<fish::Parameter> arg = { fish::Parameter(c->getIThing()) };
 754                IFishCallList* fi = const_cast<IFishCallList*>(state->getProgram()->findInterface<IFishCallList>());
 755                fi->setCMFishCallArguments(c, arg, cmEvents_[fActivated]);
 756            }
 757        }
 758        //
 759        // Angular dispacement increment.
 760        DAVect ang = state->relativeAngularIncrement_;
 761        //
 762        // EEPA NORMAL FORCE ==============================================================================================================
 763        //
 764        double overlap_exp = pow(overlap, lu_exp_);										// current overlap raised to the power "lu_exp"
 765        double eepa_Fn = eepa_F_.dof(0);												// current normal force value
 766        DVect eepa_F_old = eepa_F_;														// store for energy computations
 767        //
 768        // The updates below only occur when the maximum overlap is exceeded
 769        if (overlap > Moverlap_) {														// the current overlap is exceeding the maximum it has ever been
 770            Moverlap_ = overlap;														// update the maximum overlap
 771            //
 772            double radius = sqrt(pow(Poverlap_exp_,lu_exp_inv_)*2.0*r_hertz_);			// contact patch radius at plastic overlap
 773            f_min_ = pull_off_ - 1.5*M_PI*surf_adh_ *radius;							// update the minimum force based on the surface adhesion energy and the current contact surface area
 774            //
 775            double f_min_limit = eepa_Fn - k2_ * overlap_exp;							// the limit of Fmin that can be reached at zero overlap for the current force value
 776            if (f_min_ < f_min_limit) {
 777                f_min_ = 0.5*(pull_off_ + f_min_limit);									// if Fmin is less than the limit, set it to half the limit (Morissey, 2013)
 778            }
 779            //
 780            double overlap_min_exp = overlap_exp - (eepa_Fn - f_min_) / k2_;			// the minimum overlap raised to the power lu_exp - the overlap where the k2 unloading branch goes over into the adhesion branch
 781            kadh_ = (pull_off_ - f_min_) / (pow(overlap_min_exp, adh_exp_*lu_exp_inv_));// stiffness of the adhesion branch
 782        }
 783        //
 784        double F1 = pull_off_ + k1_ * overlap_exp;								// k1 loading branch force for this overlap
 785        double F2 = pull_off_ + k2_ * (overlap_exp - Poverlap_exp_);			// k2 loading-unloading branch force for this overlap
 786        double Fadh = pull_off_ - kadh_ * pow(overlap, adh_exp_);				// adhesion branch force for this overlap
 787        //
 788        double kn_tangent = 0.0;												// tangent stiffness in the normal direction - used for time step calculation
 789        //
 790        if (F2 >= F1) {															// the k1 loading branch should be followed
 791            eepa_Fn = F1;														// set the EEPA force to that of the k1 loading branch
 792            Poverlap_exp_ = overlap_exp - (F1 - pull_off_) / k2_;				// for the current force (F1), calculate the plastic overlap [not the usual equation based on maximum overlap, but the same result]
 793            kn_tangent = lu_exp_ * k1_*pow(overlap, lu_exp_ - 1.0);				// set the tangent stiffness in the normal direction
 794            branch_ = 1;
 795        }
 796        else {																	// will only enter if F2 < F1
 797            if (F2 > Fadh) {													// on the k2 loading-unloading branch
 798                eepa_Fn = F2;													// set the EEPA force to that of the k2 loading-unloading branch
 799                kn_tangent = lu_exp_ * k2_*pow(overlap, lu_exp_ - 1.0); 		// set the tangent stiffness in the normal direction
 800                branch_ = 2;
 801            }
 802            else {																// only enter if F2 < F1 AND F2 < Fadh
 803                if (trans.x() >= 0.0) {											// contact is unloading along the adhesive branch (can not load along this branch)
 804                    eepa_Fn = Fadh;												// set the EEPA force to that of the adhesive unloading branch
 805                    kn_tangent = adh_exp_ * kadh_*pow(overlap, adh_exp_ - 1.0);	// set the tangent stiffness in the normal direction
 806                    branch_ = 3;
 807                }
 808                else {															// loading on the adhesive branch which is not defined
 809                    eepa_Fn += k2_ * pow(-trans.x(), lu_exp_);					// set the EEPA force by incrementing the force from the previous time-step along the k2 loading branch.
 810                                                                                // The next time step, the updated Poverlap_exp is used and the code will automatically follow the k2 loading branch since F2 is calculated from this updated Poverlap_exp
 811                                                                                // The negative of the increment should be used to ensure a positive value is rasied to the power "lu_exp". The sign is then corrected by adding the force increment to the previous value
 812                    Poverlap_exp_ = overlap_exp + (pull_off_ - eepa_Fn) / k2_;	// update the plastic overlap (raised to the power "lu_exp") which means that the k2 loading-unloading branch has shifted in the unloading direction to start at this point
 813                    kn_tangent = lu_exp_ * k2_*pow(overlap, lu_exp_ - 1.0);		// set the tangent stiffness in the normal direction
 814                    branch_ = 2;
 815                }
 816            }
 817        }
 818        eepa_F_.rdof(0) = eepa_Fn;												//set the updated normal force component
 819        //
 820        // EEPA SHEAR FORCE ==============================================================================================================
 821        //
 822        double ks_tangent = ks_ * sqrt(overlap);						// tangent stiffness in the shear direction
 823        //
 824        DVect sforce(0.0);
 825        // dim holds the dimension (e.g., 2 for 2D and 3 for 3D)
 826        // Loop over the shear components (note: the 0 component is the normal component) and calculate the shear force.
 827        for (int i = 1; i < dim; ++i)
 828            sforce.rdof(i) = eepa_F_.dof(i) - trans.dof(i) * ks_tangent;// shear force update
 829        //
 830        // The canFail flag corresponds to whether or not the contact can undergo non-linear
 831        // force-displacement response. If the SOLVE ELASTIC command is given then the
 832        // canFail state is set to FALSE. Otherwise it is always TRUE.
 833        if (state->canFail_) {
 834            // Resolve sliding. This is the normal force multiplied by the coefficient of friction.
 835            double crit = fric_ * std::abs(eepa_Fn - f_min_);														//take absolute value - contact with very small overlap might result in negative value here due to rounding
 836            // The is the magnitude of the shear force.
 837            double sfmag = sforce.mag();
 838            // Sliding occurs when the magnitude of the shear force is greater than the critical value.
 839            if (sfmag > crit) {
 840                // Lower the shear force to the critical value for sliding.
 841                double rat = crit / sfmag;
 842                sforce *= rat;
 843                // Handle the slip_change event if one has been hooked up. Sliding has commenced.
 844                if (!eepa_S_ && cmEvents_[fSlipChange] >= 0) {
 845                    auto c = state->getContact();
 846                    std::vector<fish::Parameter> arg = { fish::Parameter(c->getIThing()),
 847                                                         fish::Parameter((qint64)0) };
 848                    IFishCallList* fi = const_cast<IFishCallList*>(state->getProgram()->findInterface<IFishCallList>());
 849                    fi->setCMFishCallArguments(c, arg, cmEvents_[fSlipChange]);
 850                }
 851                eepa_S_ = true;
 852            }
 853            else {
 854                // Handle the slip_change event if one has been hooked up and
 855                // the contact was previously sliding. Sliding has ceased.
 856                if (eepa_S_) {
 857                    if (cmEvents_[fSlipChange] >= 0) {
 858                        auto c = state->getContact();
 859                        std::vector<fish::Parameter> arg = { fish::Parameter(c->getIThing()),
 860                                                             fish::Parameter((qint64)1) };
 861                        IFishCallList* fi = const_cast<IFishCallList*>(state->getProgram()->findInterface<IFishCallList>());
 862                        fi->setCMFishCallArguments(c, arg, cmEvents_[fSlipChange]);
 863                    }
 864                    eepa_S_ = false;
 865                }
 866            }
 867        }
 868        //
 869        // Set the shear components of the total force.
 870        for (int i = 1; i < dim; ++i)
 871            eepa_F_.rdof(i) = sforce.dof(i);
 872        //
 873        // EEPA ROLLING RESISTANCE ==============================================================================================================
 874        //
 875        DAVect res_M_old = res_M_;													// used in energy calculation only
 876        if (fr_ == 0.0) {
 877            res_M_.fill(0.0);
 878        }
 879        else {
 880            DAVect angStiff(0.0);
 881            DAVect MomentInc(0.0);
 882            kr_ = ks_tangent * rbar_square_;										// update rolling stiffness based on the tangent shear stiffness (Wensrich and Katterfeld, 2012)
 883#if DIM==3
 884            angStiff.rx() = 0.0;
 885            angStiff.ry() = kr_;
 886#endif
 887            angStiff.rz() = kr_;
 888            MomentInc = ang * angStiff * (-1.0);
 889            res_M_ += MomentInc;
 890            if (state->canFail_) {
 891                // Account for bending strength
 892                double rmax = std::abs(fr_*(eepa_Fn - f_min_));						// Using the same normal force as in the shear limit
 893                double rmag = res_M_.mag();
 894                if (rmag > rmax) {
 895                    double fac = rmax / rmag;
 896                    res_M_ *= fac;
 897                    res_S_ = true;
 898                }
 899                else {
 900                    res_S_ = false;
 901                }
 902            }
 903        }
 904        //
 905        // EEPA TANGENT STIFFNESS FOR TIME STEP UPDATES ==============================================================================================================
 906        //
 907        // set effective or tangent stiffness in the normal and shear directions for timestep calculation
 908        effectiveTranslationalStiffness_ = DVect2(kn_tangent, ks_tangent);
 909        // set the effective rotational stiffness (bending only)
 910        effectiveRotationalStiffness_ = DAVect(kr_);
 911#if DIM==3
 912        effectiveRotationalStiffness_.rx() = 0.0;
 913#endif
 914        // EEPA DAMPING FORCE ==============================================================================================================
 915        //
 916        // Account for dashpot forces if the dashpot structure has been defined.
 917        if (dpProps_) {
 918            dpProps_->dp_F_.fill(0.0);
 919            double vcn(0.0), vcs(0.0);
 920            // Calculate the damping coefficients.
 921            setDampCoefficients(state->inertialMass_, &kn_tangent, &ks_tangent, &vcn, &vcs);				// this is based on the current tangent loading stiffness
 922            // First damp the shear components
 923            for (int i = 1; i < dim; ++i)
 924                dpProps_->dp_F_.rdof(i) = trans.dof(i) * (-1.0* vcs) / timestep;
 925            // Damp the normal component
 926            dpProps_->dp_F_.rx() -= trans.x() * vcn / timestep;
 927            //
 928            if (eepa_S_ && dpProps_->dp_mode_ == 1) {
 929                // Limit in shear if sliding.
 930                double dfn = dpProps_->dp_F_.rx();
 931                dpProps_->dp_F_.fill(0.0);
 932                dpProps_->dp_F_.rx() = dfn;
 933            }
 934            // Correct effective translational stiffness
 935            DVect2 correct(1.0);
 936            if (dpProps_->dp_nratio_)
 937                correct.rx() = sqrt(1.0 + dpProps_->dp_nratio_*dpProps_->dp_nratio_) - dpProps_->dp_nratio_;
 938            if (dpProps_->dp_sratio_)
 939                correct.ry() = sqrt(1.0 + dpProps_->dp_sratio_*dpProps_->dp_sratio_) - dpProps_->dp_sratio_;
 940            effectiveTranslationalStiffness_ /= (correct*correct);
 941        }
 942
 943        //Compute energies if energy tracking has been enabled.
 944        if (state->trackEnergy_) {
 945            assert(energies_);
 946            // calculate the strain energy increment in the normal direction
 947            energies_->estrain_ -= 0.5*(eepa_F_old.dof(0) + eepa_Fn)*trans.dof(0);
 948            if (ks_tangent) {
 949                DVect u_s_elastic = trans;										// set the elastic displacement increment equal to the total displacement increment
 950                u_s_elastic.rx() = 0.0;											// set the normal component to zero: u_s_elatic = [0, trans_shear_1, trans_shear_2]
 951                DVect shearF = eepa_F_;											// set the shear force equal to the total EEPA force (including the normal component)
 952                shearF.rx() = 0.0;												// set the normal component to zero: shearF = [0, shear_force_1, shear_force_2]
 953                eepa_F_old.rx() = 0.0;											// set normal component of the previous force equal to zero
 954                DVect avg_F_s = (shearF + eepa_F_old)*0.5;						// average shear force vector
 955                if (eepa_S_) {													// if sliding, calculate the slip energy and accumulate it
 956                    DVect u_s_total = u_s_elastic;								// total shear displacement increment
 957                    u_s_elastic = (shearF - eepa_F_old) / ks_tangent;			// elastic shear displacement increment
 958                    energies_->eslip_ -= std::min(0.0, (avg_F_s | (u_s_total + u_s_elastic))); // where (u_s_total + u_s_elatic) is the slip displacment increment (due to the sign convention, the terms are added up)
 959                }
 960                energies_->estrain_ -= avg_F_s | u_s_elastic;
 961            }
 962            // Add the rolling resistance energy contributions.							// done incrementally since the stiffness kr_ changes with the tangent shear stiffness (non-linearly)
 963            if (kr_) {
 964                DAVect t_s_elastic = ang;												// set the elastic rotation increment equal to the total angle increment
 965                DAVect avg_M = (res_M_ + res_M_old)*0.5;								// average moment from this time step and the previous
 966                if (res_S_) {															// if sliding, calculate the slip energy and accumulate it
 967                    t_s_elastic = (res_M_ - res_M_old) / kr_;							// elastic angle increment
 968                    energies_->errslip_ -= std::min(0.0, (avg_M | (ang + t_s_elastic)));// where (ang + t_s_elatic) is the slip rotation increment (due to the sign convention, the terms are added up)
 969                }
 970                energies_->errstrain_ -= avg_M | t_s_elastic;							// add the elastic component (if any - if previous force equals current force, the elastic incrment is zero)
 971            }
 972            // Calculate damping energy (accumulated) if the dashpots are active.
 973            if (dpProps_) {
 974                energies_->edashpot_ -= dpProps_->dp_F_ | trans;
 975            }
 976        }
 977
 978        // This is just a sanity check to ensure, in debug mode, that the force isn't wonky.
 979        assert(eepa_F_ == eepa_F_);
 980        return true;
 981    }
 982
 983    void ContactModelEEPA::setForce(const DVect &, IContact *) {
 984        //
 985    }
 986
 987    DVect ContactModelEEPA::getForce(const IContactMechanical *) const {
 988        DVect ret(eepa_F_);
 989        if (dpProps_)
 990            ret += dpProps_->dp_F_;
 991        return ret;
 992    }
 993
 994    DAVect ContactModelEEPA::getMomentOn1(const IContactMechanical *c) const {
 995        DVect force = getForce(c);
 996        DAVect ret(res_M_);
 997        c->updateResultingTorqueOn1Local(force, &ret);
 998        return ret;
 999    }
1000
1001    DAVect ContactModelEEPA::getMomentOn2(const IContactMechanical *c) const {
1002        DVect force = getForce(c);
1003        DAVect ret(res_M_);
1004        c->updateResultingTorqueOn2Local(force, &ret);
1005        return ret;
1006    }
1007
1008    void ContactModelEEPA::setDampCoefficients(const double &mass, double *kn_tangent, double *ks_tangent, double *vcn, double *vcs) {
1009        *vcn = dpProps_->dp_nratio_ * 2.0 * sqrt(mass*(*kn_tangent));
1010        *vcs = dpProps_->dp_sratio_ * 2.0 * sqrt(mass*(*ks_tangent));
1011    }
1012
1013} // namespace cmodelsxd
1014// EoF

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