material template
Here we show the build-in material template.
/**
* @class MaterialExample
* @brief A MaterialExample material class.
* @author tlc
* @date 06/07/2018
* @version 0.2.0
* @file MaterialExample.h
* @addtogroup Material-1D
* @ingroup Material
* @{
*/
#ifndef MATERIALEXAMPLE_H
#define MATERIALEXAMPLE_H
#include <Material/Material.h>
/**
* \brief It is recommended to store data, especially constant data, in a simple
* structure. The motivation is to obtain a clear interface so that store and recover
* of objects will be easier.
*/
struct MaterialExampleData {
const double elastic_modulus; // elastic modulus
const double yield_stress; // initial yield stress
const double hardening_ratio; // hardening ratio
const double beta; // isotropic/kinematic hardening factor
const double plastic_modulus; // plastic modulus
};
class MaterialExample final : MaterialExampleData, public Material {
double current_back_stress = 0.;
double current_plastic_strain = 0.;
double trial_back_stress = 0.;
double trial_plastic_strain = 0.;
public:
explicit MaterialExample(unsigned = 0, // tag
double = 2E5, // elastic modulus
double = 400., // initial yield stress
double = .05, // hardening ratio
double = 0., // isotropic/kinematic hardening factor
double = 0. // density
);
void initialize(const shared_ptr<DomainBase>&) override;
unique_ptr<Material> get_copy() override;
int update_trial_status(const vec&) override;
int clear_status() override;
int commit_status() override;
int reset_status() override;
void print() override;
};
#endif#include "MaterialExample.h"
/**
* \brief The constructor of material model depends on the specific model to be
* implemented. But for the base `Material` class, it takes only three input arguments:
*
* - Unique Material Tag
* - Material Type
* - Density
*
* Here we are implementing a uniaxial bilinear hardening model, hence `MaterialType::D1`
* is passed to the base. The material type will be used to validate with associated
* elements/sections to ensure the consistency of the sizes of data passed between objects.
*
* \param T Unique Material Tag
* \param E Elastic Modulus
* \param Y Yield Stress
* \param H Hardening Ratio
* \param B Beta
* \param R Density
*/
MaterialExample::MaterialExample(const unsigned T, const double E, const double Y, const double H, const double B, const double R)
: MaterialExampleData{E, Y, H, B, E * H / (1. - H)}
, Material(T, MaterialType::D1, R) {}
/**
* \brief Unless the target material model involves other material models to compute
* responses, in general, it is not necessary to get additional information from
* other parts of the model.
*
* In general cases, history variables shall be initialised and initial stiffness
* (and initial damping if appropriate) shall be set to proper value.
*
* To enable initial values for history variables, build-in `trial_history` and
* `current_history` shall be used, developers can initialise them via method
* `initialise_history()` so that initial values set by `initial` command will not be
* overwritten.
*
* In this example, instead of using build-in history variables, we manage history
* variables, namely back stress and plastic strain, by ourselves.
*
*/
void MaterialExample::initialize(const shared_ptr<DomainBase>&) {
current_back_stress = trial_back_stress = 0.;
current_plastic_strain = trial_plastic_strain = 0.;
trial_stiffness = current_stiffness = initial_stiffness = elastic_modulus;
}
/**
* \brief The `get_copy()` method should always be implemented with `make_unique`.
* In case the model defines other memory management, developers may need to further
* provide a copy ctor to make `make_unique` work.
*
* **!!!NEVER DO A MANUAL COPY OF DATA IN THIS METHOD!!!**
*
* \return a copy of material model
*/
unique_ptr<Material> MaterialExample::get_copy() { return make_unique<MaterialExample>(*this); }
/**
* \brief There are two states we are managing at any time point.
* The current state is the converged state from the last time substep. Since it is
* converged, all data shall be valid and accurate.
* The trial state stores the response computed based on converged state and new trial
* strain. It may be discarded, committed or overwritten with new trial values.
*
* **WE ALWAYS COMPUTE TRIAL STATE BASED ON CURRENT STATE AND NEW TRIAL STRAIN**
* **NEVER COMPUTE RESPONSE BASED ON ANY INFORMATION FROM UNCONVERGED STATE**
*
* Developers who are not familiar with classic plasticity theory may consult textbooks
* for details.
*
* \param t_strain trial strain
* \return error flag
*/
int MaterialExample::update_trial_status(const vec& t_strain) {
trial_strain = t_strain;
incre_strain = trial_strain - current_strain;
if(fabs(incre_strain(0)) <= tolerance) return 0;
trial_back_stress = current_back_stress;
trial_plastic_strain = current_plastic_strain;
trial_stiffness = initial_stiffness;
trial_stress = current_stress + elastic_modulus * incre_strain;
const auto shifted_stress = trial_stress(0) - current_back_stress;
const auto yield_func = fabs(shifted_stress) - yield_stress - (1. - beta) * plastic_modulus * current_plastic_strain;
if(yield_func > 0.) {
const auto incre_plastic_strain = yield_func / (elastic_modulus + plastic_modulus);
trial_stress -= suanpan::sign(shifted_stress) * elastic_modulus * incre_plastic_strain;
trial_stiffness *= hardening_ratio;
trial_back_stress += suanpan::sign(shifted_stress) * beta * plastic_modulus * incre_plastic_strain;
trial_plastic_strain += incre_plastic_strain;
}
return 0;
}
/**
* \brief Operations are required to achieve the following objective.
*
* current state -> 0
* trial state -> 0
*
* \return error flag
*/
int MaterialExample::clear_status() {
current_strain.zeros();
current_stress.zeros();
current_stiffness = initial_stiffness;
current_back_stress = 0.;
current_plastic_strain = 0.;
return reset_status();
}
/**
* \brief Operations are required to achieve the following objective.
*
* current state <- trial state
*
* \return error flag
*/
int MaterialExample::commit_status() {
current_strain = trial_strain;
current_stress = trial_stress;
current_stiffness = trial_stiffness;
current_back_stress = trial_back_stress;
current_plastic_strain = trial_plastic_strain;
return 0;
}
/**
* \brief Operations are required to achieve the following objective.
*
* current state -> trial state
*
* \return error flag
*/
int MaterialExample::reset_status() {
trial_strain = current_strain;
trial_stress = current_stress;
trial_stiffness = current_stiffness;
trial_back_stress = current_back_stress;
trial_plastic_strain = current_plastic_strain;
return 0;
}
void MaterialExample::print() {
suanpan_info("A material example based on uniaxial J2 bilinear mixed hardening model.\n");
suanpan_info("current strain: %.5E\tcurrent stress: %.5E.\n", current_strain.at(0), current_stress.at(0));
}Last updated