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Stress.h
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Wed, Aug 7, 17:27

Stress.h
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#ifndef STRESS_H
#define STRESS_H
#include <map>
#include <string>
#include <vector>
#include <fstream>
#include "MatrixLibrary.h"
#include "ATC_TypeDefs.h"
#include "ATC_TypeDefs.h"
#include "NonLinearSolver.h"
namespace ATC {
enum ElasticityTensorType {FIRST_ELASTICITY_TENSOR=0, SECOND_ELASTICITY_TENSOR};
/**
* @class Stress
* @brief Base class that defines interface for a constitutive law
* @brief that computes stress given all field and gradient information.
*/
class Stress
{
public:
Stress() {};
virtual ~Stress() {};
virtual void initialize(void){};
//* Returns parameter values, (Nothing uses this).
virtual void parameters(std::map<std::string,double> &parameters) {}
//* Computes stress given a displacement gradient.
//* Units: mvv/L^3 (i.e. for units Real: g/(mol ps^2 A^2) )
virtual void stress(const FIELD_MATS &fields,
const GRAD_FIELD_MATS &gradFields,
DENS_MAT_VEC &stress)=0;
//* Computes free (T>0)/potential(T=0) energy density
//* Units: mvv/L^3 (i.e. for units Real: g/(mol ps^2 A^2) )
virtual void elastic_energy(const FIELD_MATS &fields,
const GRAD_FIELD_MATS &gradFields,
DENS_MAT &energy) const;
//* Returns the material tangent at a given deformation gradient.
virtual void tangent(const MATRIX &F, MATRIX &C) const
{throw ATC_Error("Stress::tangent: unimplemented function");}
};
/**
* @class StressCubicElastic
* @brief Class for computing stress for a cubic elastic material
*/
class StressCubicElastic : public Stress
{
public:
StressCubicElastic():c11_(0),c12_(0),c44_(0){};
StressCubicElastic(std::fstream &matfile);
StressCubicElastic(double c11, double c12, double c44)
: c11_(c11), c12_(c12), c44_(c44) { }
void stress(const FIELD_MATS &fields,
const GRAD_FIELD_MATS &gradFields,
DENS_MAT_VEC &flux);
virtual void elastic_energy(const FIELD_MATS &fields,
const GRAD_FIELD_MATS &gradFields,
DENS_MAT &energy) const;
virtual void tangent(const MATRIX &F, MATRIX &C) const {C=C_;}
protected:
double c11_, c12_, c44_;
DENS_MAT C_;
void set_tangent();
};
/**
* @class StressCubicElasticDamped
* @brief Class for computing stress for a cubic elastic material w/ damping
*/
class StressCubicElasticDamped : public StressCubicElastic
{
public:
StressCubicElasticDamped(std::fstream &matfile);
StressCubicElasticDamped(double c11, double c12, double c44, double gamma)
: StressCubicElastic(c11,c12,c44), gamma_(gamma) { }
void stress(const FIELD_MATS &fields,
const GRAD_FIELD_MATS &gradFields,
DENS_MAT_VEC &flux);
protected:
double gamma_;
};
/**
* @class StressLinearElastic
* @brief Class for computing stress for a linear elastic material
*/
class StressLinearElastic : public StressCubicElastic
{
public:
StressLinearElastic(std::fstream &matfile);
void stress(const FIELD_MATS &fields,
const GRAD_FIELD_MATS &gradFields,
DENS_MAT_VEC &flux);
protected:
double E_, nu_;
double mu_, lambda_;
};
// forward declarations needed by StressCauchyBorn
class CbPotential;
class CBLattice;
/**
* Structure of lattice properties needed by StressCauchyBorn.
*/
struct CbData {
double e2mvv; //*> Energy conversion factor (1/mvv2e).
double boltzmann; //*> Boltzmann constant (in LAMMPS units)
double hbar; //*> Planck's constant (in LAMMPS units)
double inv_atom_volume; //*> Volume of atom.
double atom_mass; //*> Mass of an atom.
DENS_MAT cell_vectors; //*> Unit vectors for lattice cells.
DENS_MAT basis_vectors; //*> Positions of atoms within a lattice cell.
};
/**
* @class StressCauchyBorn
* @brief Class for computing the stress and elastic constants for a
* @brief Cauchy-Born material.
*/
class StressCauchyBorn : public Stress
{
public:
StressCauchyBorn(std::fstream &matfile, CbData &cb);
virtual ~StressCauchyBorn();
virtual void initialize(void);
//* Returns the stress computed from a 0K Cauchy-Born approxmation.
virtual void stress(const FIELD_MATS &fields, const GRAD_FIELD_MATS &gradFields,
DENS_MAT_VEC &flux);
//* Computes free (T>0)/potential(T=0) energy density
//* Units: mvv/L^3 (i.e. for units Real: g/(mol ps^2 A^2) )
virtual void elastic_energy(const FIELD_MATS &fields,
const GRAD_FIELD_MATS &gradFields,
DENS_MAT &energy) const;
//* Computes entropic energy density
void entropic_energy(const FIELD_MATS &fields, const GRAD_FIELD_MATS &gradFields,
DENS_MAT &energy) const;
//* Returns the material tangent at a given deformation gradient.
virtual void tangent(const MATRIX &F, MATRIX &C) const;
double stiffness() const;
//* Creates a linearization for a deformation gradient.
DENS_VEC elasticity_tensor(const VECTOR &Fv, MATRIX &C, const ElasticityTensorType type=FIRST_ELASTICITY_TENSOR) const;
DENS_VEC elasticity_tensor(const MATRIX &F, MATRIX &C, const ElasticityTensorType type=FIRST_ELASTICITY_TENSOR) const;
protected:
void linearize(MATRIX *F=NULL);
CBLattice *cblattice_; //*> CbLattice -> makes atom clusters.
CbPotential *potential_; //*> CbPotential -> interatomic forces.
bool makeLinear_;
StressCubicElastic *cubicMat_; //*> Stores optional linear elastic law.
bool initialized_;
double fixed_temperature_; //*> Specifies a uniform temperature.
CbData cbdata_; //*> Lattice & atom volume/mass.
};
// adaptor to NonLinearSolver
class CBElasticTangentOperator : public TangentOperator {
public:
CBElasticTangentOperator (StressCauchyBorn * cauchyBornStress,
DENS_VEC & targetP) :
TangentOperator(),
cauchyBornStress_(cauchyBornStress),
targetP_(targetP) {};
void function(const VECTOR & F, DENS_VEC & R)
{
DENS_MAT B;
tangent(F,R,B);
}
void tangent(const VECTOR & F, DENS_VEC & R, MATRIX & B)
{
cbP_ = cauchyBornStress_->elasticity_tensor(F, B);
R = cbP_ - targetP_;
}
private:
StressCauchyBorn * cauchyBornStress_;
DENS_VEC targetP_, cbP_;
};
// adaptor to NonLinearSolver
class CB2ndElasticTangentOperator : public TangentOperator {
public:
CB2ndElasticTangentOperator (StressCauchyBorn * cauchyBornStress,
DENS_VEC & targetS) :
TangentOperator(),
cauchyBornStress_(cauchyBornStress),
targetS_(targetS) {};
void function(const VECTOR & U, DENS_VEC & r)
{
DENS_MAT C;
tangent(U,r,C);
}
void tangent(const VECTOR & U, DENS_VEC & r, MATRIX & C)
{
cbS_ = cauchyBornStress_->elasticity_tensor(U, C, SECOND_ELASTICITY_TENSOR);
r = cbS_ - targetS_;
}
private:
StressCauchyBorn * cauchyBornStress_;
DENS_VEC targetS_, cbS_;
};
}
#endif

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