// void AbaqusCreepMaterial::modifyStrain(const unsigned int qp,
// const Real /*scale_factor*/,
// SymmTensor & strain_increment,
// SymmTensor & /*dstrain_increment_dT*/)
void AbaqusCreepMaterial::computeStress()
{
// Recover "old" state variables
for (unsigned int i=0; i<_num_state_vars; i++)
_STATEV[i]=_state_var_old[_qp][i];
// Initialize DECRA and DESWA arrays
for (unsigned int i=0; i<5; i++)
{
_DECRA[i] = 0.0;
_DESWA[i] = 0.0;
}
// Calculate stress array components
_stress_component[0] =
(_elasticity_tensor[0]*_strain_increment.component(0)) +
(_elasticity_tensor[1]*_strain_increment.component(1)) +
(_elasticity_tensor[1]*_strain_increment.component(2));
_stress_component[1] =
(_elasticity_tensor[1]*_strain_increment.component(0)) +
(_elasticity_tensor[0]*_strain_increment.component(1)) +
(_elasticity_tensor[1]*_strain_increment.component(2));
_stress_component[2] =
(_elasticity_tensor[1]*_strain_increment.component(0)) +
(_elasticity_tensor[1]*_strain_increment.component(1)) +
(_elasticity_tensor[0]*_strain_increment.component(2));
_stress_component[3] = (_elasticity_tensor[2]*_strain_increment.component(3));
_stress_component[4] = (_elasticity_tensor[2]*_strain_increment.component(4));
_stress_component[5] = (_elasticity_tensor[2]*_strain_increment.component(5));
// Calculate trial stress and deviatoric trial stress
SymmTensor trial_stress(_stress_component[0], _stress_component[1], _stress_component[2],
_stress_component[3], _stress_component[4], _stress_component[5]);
_trial_stress[_qp] = trial_stress;
_trial_stress[_qp] += _stress_old[_qp];
_dev_trial_stress[_qp] = _trial_stress[_qp];
_dev_trial_stress[_qp].addDiag(-_trial_stress[_qp].trace()/3.0);
// Calculate effective trial stress (_ets)
Real dts_squared = _dev_trial_stress[_qp].doubleContraction(_dev_trial_stress[_qp]);
if (dts_squared >= 0.)
_ets[_qp] = std::sqrt(1.5 * dts_squared);
else
mooseError("Attempted to take square root of a negative number!\n");
// Calculate gradient of dev stress potential (grad_dts)
// grad_dts = d(qtild)/d(dev_trial_stress)
SymmTensor delta_dts = _dev_trial_stress[_qp] - _dev_trial_stress_old[_qp];
Real delta_ets = _ets[_qp] - _ets_old[_qp];
Real grad_dts_potential[6];
for (unsigned int i=0; i<6; i++)
{
if (delta_dts.component(i) == 0.0)
grad_dts_potential[i] = 0.0;
else
grad_dts_potential[i] = delta_ets / delta_dts.component(i);
}
SymmTensor grad_dts(grad_dts_potential[0], grad_dts_potential[1], grad_dts_potential[2],
grad_dts_potential[3], grad_dts_potential[4], grad_dts_potential[5]);
// Pass variables in for information
_KSTEP = _t_step; //Step number
_TIME[0] = _dt; //Value of step time at the end of the increment - Check
_TIME[1] = _t; //Value of total time at the end of the increment - Check
_DTIME = _dt; //Time increment
_EC[0] = _total_creep_old[_qp]; //Metal and Drucker-Prager creep at the start of the increment
_EC[1] = _total_creep[_qp]; //Metal and Drucker-Prager creep at the end of the increment
_ESW[0] = _total_swell_old[_qp]; //Metal swell at the start of the increment
_ESW[1] = _total_swell[_qp]; //Metal swell at the end of the increment
_QTILD = _ets[_qp]; //Von mises equivalent stress
_P = -_trial_stress[_qp].trace(); //Equivalent pressure stress
// Connection to extern statement
_creep(_DECRA, _DESWA, _STATEV, &_SERD, _EC, _ESW, &_P, &_QTILD, &_TEMP, &_DTEMP, _PREDEF, _DPRED,
_TIME, &_DTIME, &_CMNAME, &_LEXIMP, &_LEND, _COORDS, &_NSTATV, &_NOEL, &_NPT, &_LAYER, &_KSPT, &_KSTEP, &_KINC);
// Update state variables
for (unsigned int i=0; i<_num_state_vars; i++)
_state_var[_qp][i] = _STATEV[i];
// Solve for Incremental creep (creep_inc_used) and/or Incremental Swell (swell_inc_used) based on definition
// NOTE: Below are equations for metal creep and/or time-dependent volumetric swelling materials only
// Drucker-Prager, Capped Drucker-Prager, and Gasket materials have not been included
_creep_inc[_qp] = _DECRA[0];
_total_creep[_qp] = _creep_inc[_qp];
_total_creep[_qp] += _total_creep_old[_qp];
_swell_inc[_qp] = _DESWA[0];
_total_swell[_qp] = _swell_inc[_qp];
_total_swell[_qp] += _total_swell_old[_qp];
Real p = -_trial_stress[_qp].trace();
Real pold = -_trial_stress_old[_qp].trace();
Real creep_inc_used=0.0;
Real swell_inc_used=0.0;
if (_integration_flag == 0 && _solve_definition == 1)
{
creep_inc_used = _DECRA[0];
swell_inc_used = _DESWA[0];
}
else if (_integration_flag == 1 && _solve_definition == 2)
{
creep_inc_used = (_DECRA[1]*(_total_creep[_qp]-_total_creep_old[_qp]))+_creep_inc_old[_qp];
swell_inc_used = (_DESWA[1]*(_total_creep[_qp]-_total_creep_old[_qp]))+_swell_inc_old[_qp];
}
else if (_integration_flag == 1 && _solve_definition == 3)
{
creep_inc_used = (_DECRA[2]*(_total_swell[_qp]-_total_swell_old[_qp]))+_creep_inc_old[_qp];
swell_inc_used = (_DESWA[2]*(_total_swell[_qp]-_total_swell_old[_qp]))+_swell_inc_old[_qp];
}
else if (_integration_flag == 1 && _solve_definition == 4)
{
creep_inc_used = (_DECRA[3]*(p - pold))+_creep_inc_old[_qp];
swell_inc_used = (_DESWA[3]*(p - pold))+_swell_inc_old[_qp];
}
else if (_integration_flag == 1 && _solve_definition == 5)
{
creep_inc_used = (_DECRA[4]*(_ets[_qp]-_ets_old[_qp]))+_creep_inc_old[_qp];
swell_inc_used = (_DESWA[4]*(_ets[_qp]-_ets_old[_qp]))+_swell_inc_old[_qp];
}
// Calculate Incremental Creep Strain (total_effects)
// Incremental creep strain = ((1/3)*(swell_inc_used)*R) + (creep_inc_used*grad_dts)
// R = The matrix with the anisotropic swelling ratios in the diagonal if anisotropic swelling is defined; Otherwise R = Identity
SymmTensor R(1.,1.,1.,0.,0.,0.);
SymmTensor total_effects = (R*(swell_inc_used/3.)) + (grad_dts*(creep_inc_used));
// Modify strain increment
_strain_increment += total_effects;
_stress_component[0] =
(_elasticity_tensor[0]*_strain_increment.component(0)) +
(_elasticity_tensor[1]*_strain_increment.component(1)) +
(_elasticity_tensor[1]*_strain_increment.component(2));
_stress_component[1] =
(_elasticity_tensor[1]*_strain_increment.component(0)) +
(_elasticity_tensor[0]*_strain_increment.component(1)) +
(_elasticity_tensor[1]*_strain_increment.component(2));
_stress_component[2] =
(_elasticity_tensor[1]*_strain_increment.component(0)) +
(_elasticity_tensor[1]*_strain_increment.component(1)) +
(_elasticity_tensor[0]*_strain_increment.component(2));
_stress_component[3] = (_elasticity_tensor[2]*_strain_increment.component(3));
_stress_component[4] = (_elasticity_tensor[2]*_strain_increment.component(4));
_stress_component[5] = (_elasticity_tensor[2]*_strain_increment.component(5));
// Update Stress
SymmTensor stressnew(_stress_component[0], _stress_component[1], _stress_component[2],
_stress_component[3], _stress_component[4], _stress_component[5]);
_stress[_qp] = stressnew;
_stress[_qp] += _stress_old[_qp];
}
void AbaqusUmatMaterial::computeStress()
{
//Calculate deformation gradient - modeled from "solid_mechanics/src/materials/Nonlinear3D.C"
// Fbar = 1 + grad(u(k))
ColumnMajorMatrix Fbar;
Fbar(0,0) = _grad_disp_x[_qp](0);
Fbar(0,1) = _grad_disp_x[_qp](1);
Fbar(0,2) = _grad_disp_x[_qp](2);
Fbar(1,0) = _grad_disp_y[_qp](0);
Fbar(1,1) = _grad_disp_y[_qp](1);
Fbar(1,2) = _grad_disp_y[_qp](2);
Fbar(2,0) = _grad_disp_z[_qp](0);
Fbar(2,1) = _grad_disp_z[_qp](1);
Fbar(2,2) = _grad_disp_z[_qp](2);
Fbar.addDiag(1);
_Fbar[_qp] = Fbar;
Real myDFGRD0[9] = {_Fbar_old[_qp](0,0), _Fbar_old[_qp](1,0), _Fbar_old[_qp](2,0), _Fbar_old[_qp](0,1), _Fbar_old[_qp](1,1), _Fbar_old[_qp](2,1), _Fbar_old[_qp](0,2), _Fbar_old[_qp](1,2), _Fbar_old[_qp](2,2)};
Real myDFGRD1[9] = {_Fbar[_qp](0,0), _Fbar[_qp](1,0), _Fbar[_qp](2,0), _Fbar[_qp](0,1), _Fbar[_qp](1,1), _Fbar[_qp](2,1), _Fbar[_qp](0,2), _Fbar[_qp](1,2), _Fbar[_qp](2,2)};
for (unsigned int i=0; i<9; ++i)
{
_DFGRD0[i] = myDFGRD0[i];
_DFGRD1[i] = myDFGRD1[i];
}
//Recover "old" state variables
for (unsigned int i=0; i<_num_state_vars; ++i)
_STATEV[i]=_state_var_old[_qp][i];
//Pass through updated stress, total strain, and strain increment arrays
for (int i=0; i<_NTENS; ++i)
{
_STRESS[i] = _stress_old.component(i);
_STRAN[i] = _total_strain[_qp].component(i);
_DSTRAN[i] = _strain_increment.component(i);
}
//Pass through step , time, and coordinate system information
_KSTEP = _t_step; //Step number
_TIME[0] = _t; //Value of step time at the beginning of the current increment - Check
_TIME[1] = _t-_dt; //Value of total time at the beginning of the current increment - Check
_DTIME = _dt; //Time increment
for (unsigned int i=0; i<3; ++i) //Loop current coordinates in UMAT COORDS
_COORDS[i] = _coord[i];
//Connection to extern statement
_umat(_STRESS, _STATEV, _DDSDDE, &_SSE, &_SPD, &_SCD, &_RPL, _DDSDDT, _DRPLDE, &_DRPLDT, _STRAN, _DSTRAN, _TIME, &_DTIME, &_TEMP, &_DTEMP, _PREDEF, _DPRED, &_CMNAME, &_NDI, &_NSHR, &_NTENS, &_NSTATV, _PROPS, &_NPROPS, _COORDS, _DROT, &_PNEWDT, &_CELENT, _DFGRD0, _DFGRD1, &_NOEL, &_NPT, &_LAYER, &_KSPT, &_KSTEP, &_KINC);
//Energy outputs
_elastic_strain_energy[_qp] = _SSE;
_plastic_dissipation[_qp] = _SPD;
_creep_dissipation[_qp] = _SCD;
//Update state variables
for (unsigned int i=0; i<_num_state_vars; ++i)
_state_var[_qp][i]=_STATEV[i];
//Get new stress tensor - UMAT should update stress
SymmTensor stressnew(_STRESS[0], _STRESS[1], _STRESS[2], _STRESS[3], _STRESS[4], _STRESS[5]);
_stress[_qp] = stressnew;
}