SphereMaterial.h

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// SPDX-FileCopyrightText: Copyright (c) Stanford University, The Regents of the
// University of California, and others. SPDX-License-Identifier: BSD-3-Clause
 
/**
 * @file SphereMaterial.h
 * @brief Material models for the ChamberSphere block
 */
 
#ifndef SVZERODSOLVER_MODEL_SPHEREMATERIAL_HPP_
#define SVZERODSOLVER_MODEL_SPHEREMATERIAL_HPP_
 
#include <map>
#include <memory>
#include <string>
#include <vector>
 
#include "Parameter.h"
 
/**
 * @brief Return type for SphereMaterial::compute
 *
 * Bundles the nonlinear residual contribution and its derivatives that
 * appear in the spherical-stress equation of ChamberSphere.
 */
struct SphericalStressResult {
  double C_val;         ///< Residual contribution to C vector
  double dC_dy_radius;  ///< Derivative w.r.t. radius
};
 
/**
 * @brief Base class for spherical chamber wall materials
 *
 * Subclasses implement the material-specific elastic stress term in the
 * spherical stress equation:
 * \f[
 * -S + \tau + S_\text{sl}(r, r_0) = 0
 * \f]
 */
class SphereMaterial {
 public:
  /**
   * @brief Properties of the input parameters for this material
   * [(name, InputParameter), ...]
   */
  const std::vector<std::pair<std::string, InputParameter>> input_param_properties;
 
  /**
   * @brief Construct a SphereMaterial
   *
   * @param props Parameter name/spec pairs for this material type
   */
  SphereMaterial(
      const std::vector<std::pair<std::string, InputParameter>>& props);
 
  virtual ~SphereMaterial() = default;
 
  /**
   * @brief Compute material stress contributions at the current state
   *
   * @param radius     Radius perturbation \f$r\f$
   * @param radius0    Reference radius \f$r_0\f$
   * @return SphericalStressResult
   */
  virtual SphericalStressResult compute(double radius,
                                        double radius0) const = 0;
 
  /**
   * @brief Factory: create a material from a type string
   *
   * @param type_str One of: "mooney_rivlin", "exponential"
   * @return Unique pointer to the created material
   */
  static std::unique_ptr<SphereMaterial> create(const std::string& type_str);
 
  /**
   * @brief Set a scalar parameter value by name
   *
   * @param name  Parameter name
   * @param value Parameter value
   */
  void set_param(const std::string& name, double value);
 
 protected:
  /**
   * @brief Map of parameter names to their values
   */
  std::map<std::string, double> params_;
};
 
/**
 * @brief Mooney–Rivlin material (reduces to neo-Hookean for W2=0)
 *
 * Implements:
 * \f[
 * f = 4(1 - C^{-3})(W_1 + C W_2)
 * \f]
 *
 * Parameters: `W1`, `W2`
 */
class MooneyRivlinMaterial : public SphereMaterial {
 public:
  MooneyRivlinMaterial()
      : SphereMaterial({{"W1", InputParameter()},
                        {"W2", InputParameter()}}) {}
 
  SphericalStressResult compute(double radius,
                                double radius0) const override;
};
 
/**
 * @brief Exponential material
 *
 * Implements the exponential strain-energy density:
 * \f[
 * W_1(r) = C_0 \exp(C_1 [I_{1,\text{iso}}]^2),\quad
 * W_4(r) = C_2 \exp(C_3 [I_{4,\text{iso}}]^2)
 * \f]
 *
 * Parameters: `C0`, `C1`, `C2`, `C3`
 */
class ExponentialMaterial : public SphereMaterial {
 public:
  ExponentialMaterial()
      : SphereMaterial({{"C0", InputParameter()},
                        {"C1", InputParameter()},
                        {"C2", InputParameter()},
                        {"C3", InputParameter()}}) {}
 
  SphericalStressResult compute(double radius,
                                double radius0) const override;
};
 
#endif  // SVZERODSOLVER_MODEL_SPHEREMATERIAL_HPP_