SaintVenantElasticity.hpp

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#pragma once
 
#include <polyfem/assembler/Assembler.hpp>
#include <polyfem/assembler/MatParams.hpp>
#include <polyfem/utils/AutodiffTypes.hpp>
#include <polyfem/utils/ElasticityUtils.hpp>
 
namespace polyfem::assembler
{
    // Similar to HookeLinear but with non-linear stress strain: C:½(F+Fᵀ+FᵀF)
    class SaintVenantElasticity : public NLAssembler, ElasticityAssembler
    {
    public:
        SaintVenantElasticity();
 
        using NLAssembler::assemble_energy;
        using NLAssembler::assemble_gradient;
        using NLAssembler::assemble_hessian;
 
        double compute_energy(const NonLinearAssemblerData &data) const override;
        Eigen::VectorXd assemble_gradient(const NonLinearAssemblerData &data) const override;
        Eigen::MatrixXd assemble_hessian(const NonLinearAssemblerData &data) const override;
 
        VectorNd compute_rhs(const AutodiffHessianPt &pt) const override;
 
        void set_size(const int size) override;
 
        void set_stiffness_tensor(int i, int j, const double val);
        double stifness_tensor(int i, int j) const;
 
        void add_multimaterial(const int index, const json &params, const Units &units) override;
 
        std::string name() const override { return "SaintVenant"; }
        std::map<std::string, ParamFunc> parameters() const override;
 
        void assign_stress_tensor(const OutputData &data,
                                  const int all_size,
                                  const ElasticityTensorType &type,
                                  Eigen::MatrixXd &all,
                                  const std::function<Eigen::MatrixXd(const Eigen::MatrixXd &)> &fun) const override;
 
    private:
        ElasticityTensor elasticity_tensor_;
 
        template <typename T, unsigned long N>
        T stress(const std::array<T, N> &strain, const int j) const;
 
        template <typename T>
        T compute_energy_aux(const NonLinearAssemblerData &data) const;
    };
} // namespace polyfem::assembler