void PLC_LSH::computeStress() { // Given the stretching, compute the stress increment and add it to the old stress. Also update the creep strain // stress = stressOld + stressIncrement // creep_strain = creep_strainOld + creep_strainIncrement if (_t_step == 0 && !_app.isRestarting()) return; if (_output_iteration_info == true) { _console << std::endl << "iteration output for combined creep-plasticity solve:" << " time=" <<_t << " temperature=" << _temperature[_qp] << " int_pt=" << _qp << std::endl; } // compute trial stress SymmTensor stress_new( *elasticityTensor() * _strain_increment ); stress_new += _stress_old; SymmTensor creep_strain_increment; SymmTensor plastic_strain_increment; SymmTensor elastic_strain_increment; SymmTensor stress_new_last( stress_new ); Real delS(_absolute_stress_tolerance+1); Real first_delS(delS); unsigned int counter(0); while (counter < _max_its && delS > _absolute_stress_tolerance && (delS/first_delS) > _relative_tolerance) { elastic_strain_increment = _strain_increment; elastic_strain_increment -= plastic_strain_increment; stress_new = *elasticityTensor() * elastic_strain_increment; stress_new += _stress_old; elastic_strain_increment = _strain_increment; computeCreep( elastic_strain_increment, creep_strain_increment, stress_new ); // now use stress_new to calculate a new effective_trial_stress and determine if // yield has occured and if so, calculate the corresponding plastic strain elastic_strain_increment -= creep_strain_increment; computeLSH( elastic_strain_increment, plastic_strain_increment, stress_new ); elastic_strain_increment -= plastic_strain_increment; // now check convergence SymmTensor deltaS(stress_new_last - stress_new); delS = std::sqrt(deltaS.doubleContraction(deltaS)); if (counter == 0) { first_delS = delS; } stress_new_last = stress_new; if (_output_iteration_info == true) { _console << "stress_it=" << counter << " rel_delS=" << delS/first_delS << " rel_tol=" << _relative_tolerance << " abs_delS=" << delS << " abs_tol=" << _absolute_stress_tolerance << std::endl; } ++counter; } if (counter == _max_its && delS > _absolute_stress_tolerance && (delS/first_delS) > _relative_tolerance) { mooseError("Max stress iteration hit during plasticity-creep solve!"); } _strain_increment = elastic_strain_increment; _stress[_qp] = stress_new; }
void CombinedCreepPlasticity::computeStress( const Elem & current_elem, unsigned qp, const SymmElasticityTensor & elasticityTensor, const SymmTensor & stress_old, SymmTensor & strain_increment, SymmTensor & stress_new ) { // Given the stretching, compute the stress increment and add it to the old stress. Also update the creep strain // stress = stressOld + stressIncrement // creep_strain = creep_strainOld + creep_strainIncrement if(_t_step == 0) return; if (_output_iteration_info == true) { Moose::out << std::endl << "iteration output for CombinedCreepPlasticity solve:" << " time=" <<_t << " temperature=" << _temperature[qp] << " int_pt=" << qp << std::endl; } // compute trial stress stress_new = elasticityTensor * strain_increment; stress_new += stress_old; const SubdomainID current_block = current_elem.subdomain_id(); const std::vector<ReturnMappingModel*> & rmm( _submodels[current_block] ); const unsigned num_submodels = rmm.size(); SymmTensor inelastic_strain_increment; SymmTensor elastic_strain_increment; SymmTensor stress_new_last( stress_new ); Real delS(_absolute_tolerance+1); Real first_delS(delS); unsigned int counter(0); while(counter < _max_its && delS > _absolute_tolerance && (delS/first_delS) > _relative_tolerance && (num_submodels != 1 || counter < 1)) { elastic_strain_increment = strain_increment; stress_new = elasticityTensor * (elastic_strain_increment - inelastic_strain_increment); stress_new += stress_old; for (unsigned i_rmm(0); i_rmm < num_submodels; ++i_rmm) { rmm[i_rmm]->computeStress( current_elem, qp, elasticityTensor, stress_old, elastic_strain_increment, stress_new, inelastic_strain_increment ); } // now check convergence SymmTensor deltaS(stress_new_last - stress_new); delS = std::sqrt(deltaS.doubleContraction(deltaS)); if (counter == 0) { first_delS = delS; } stress_new_last = stress_new; if (_output_iteration_info == true) { Moose::out << "stress_it=" << counter << " rel_delS=" << (0 == first_delS ? 0 : delS/first_delS) << " rel_tol=" << _relative_tolerance << " abs_delS=" << delS << " abs_tol=" << _absolute_tolerance << std::endl; } ++counter; } if(counter == _max_its && delS > _absolute_tolerance && (delS/first_delS) > _relative_tolerance) { mooseError("Max stress iteration hit during CombinedCreepPlasticity solve!"); } strain_increment = elastic_strain_increment; }