Description

Class for hyperelastic materials, that is materials with a constitutive equation of the type S = f(C) , where S is the 2nd Piola-Kirchhoff stress and C is the right Cauchy-Green deformation tensor C=F^T*F (in material space) as in E = 1/2(C -I) where E the Green Lagrange strain tensor.

Or in general, materials for which the stress–strain relationship derives from a strain energy density function.

#include <ChMaterial3DHyperelastic.h>

Inheritance diagram for chrono::fea::ChMaterial3DHyperelastic:

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Collaboration diagram for chrono::fea::ChMaterial3DHyperelastic:

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Public Member Functions
virtual void	ComputeStress (ChStressTensor<> &S_stress, const ChMatrix33d &F, const ChMatrix33d l, ChFieldData data_per_point, ChElementData *data_per_element) override
	Implement interface to lower level stress material. More...

virtual void	ComputeTangentModulus (ChMatrixNM< double, 6, 6 > &C, const ChMatrix33d &F, const ChMatrix33d l, ChFieldData data_per_point, ChElementData *data_per_element) override
	Implement interface to lower level stress material. More...

virtual bool	IsSpatialVelocityGradientNeeded () const override
	Hyperelastic materials do not need info on the spatial velocity gradient l=\nabla_x v , Returning false from this means that the ChDomainXXYY can know that the computation of the "l" parameter could be skipped left to null when calling ComputeStress(...)

virtual void	ComputeElasticStress (ChStressTensor<> &S_stress, const ChMatrix33d &C_def)=0
	Compute elastic stress from the right Cauchy-Green deformation tensor C_def = F^T*F. More...

virtual void	ComputeElasticTangentModulus (ChMatrixNM< double, 6, 6 > &C_tangent, const ChMatrix33d &C_def)
	Computes the tangent modulus for a given deformation. More...

Public Member Functions inherited from chrono::fea::ChMaterial3DStress
virtual void	ComputeUpdateEndStep (ChFieldData data_per_point, ChElementData data_per_element, const double time)
	Update your own auxiliary data, if any, at the end of time step (ex for plasticity). More...

Public Member Functions inherited from chrono::fea::ChMaterial3DDensity
	ChMaterial3DDensity (double density=1000)

virtual void	SetDensity (double density)
	Set the density of the material, in kg/m^2.

virtual double	GetDensity () const
	Get the density of the material, in kg/m^2.

Public Member Functions inherited from chrono::fea::ChMaterial
virtual std::unique_ptr< ChFieldData >	CreateMaterialPointData () const
	Implement this if the material needs custom data per material point, returning a std::make_unique<ChFieldDataCustom>() where ChFieldDataCustom is your custom class with aditional states/properties per-point.

Additional Inherited Members
Protected Attributes inherited from chrono::fea::ChMaterial3DDensity
double	m_density

Member Function Documentation

◆ ComputeElasticStress()

virtual void chrono::fea::ChMaterial3DHyperelastic::ComputeElasticStress	(	ChStressTensor<> &	S_stress,
		const ChMatrix33d &	C_def
	)

pure virtual

Compute elastic stress from the right Cauchy-Green deformation tensor C_def = F^T*F.

Return stress as 2nd Piola-Kirchhoff S tensor, in Voigt notation. Children materials MUST implement this.

Implemented in chrono::fea::ChMaterial3DStressStVenant, chrono::fea::ChMaterial3DStressNeoHookean, and chrono::fea::ChMaterial3DStressOgden.

◆ ComputeElasticTangentModulus()

virtual void chrono::fea::ChMaterial3DHyperelastic::ComputeElasticTangentModulus	(	ChMatrixNM< double, 6, 6 > &	C_tangent,
		const ChMatrix33d &	C_def
	)

inlinevirtual

Computes the tangent modulus for a given deformation.

It takes the right Cauchy-Green deformation tensor C_def, and returns the tangent modulus in 6x6 matrix C_tangent, for dS = C_tangent * dE where S is 2nd Piola-Kirchhoff stress, and E is Green Lagrange strain. A fallback implementation is provided here, that computes C via numerical differentiation by calling 6 times the ComputeElasticStress() function. However, if you are able to compute a custom analytical expression of C_tangent, and the analytical expression is fast to compute, then you SHOULD override this.

Reimplemented in chrono::fea::ChMaterial3DStressNeoHookean, and chrono::fea::ChMaterial3DStressStVenant.

◆ ComputeStress()

virtual void chrono::fea::ChMaterial3DHyperelastic::ComputeStress	(	ChStressTensor<> &	S_stress,
		const ChMatrix33d &	F,
		const ChMatrix33d *	l,
		ChFieldData *	data_per_point,
		ChElementData *	data_per_element
	)

inlineoverridevirtual

Implement interface to lower level stress material.

Parameters

S_stress	output stress, PK2
F	current deformation gradient tensor
l	current spatial velocity gradient (might be nullptr if IsSpatialVelocityGradientNeeded() is false)
data_per_point	pointer to auxiliary data (ex states), if any, per quadrature point
data_per_element	pointer to auxiliary data (ex states), if any, per element

Implements chrono::fea::ChMaterial3DStress.

◆ ComputeTangentModulus()

virtual void chrono::fea::ChMaterial3DHyperelastic::ComputeTangentModulus	(	ChMatrixNM< double, 6, 6 > &	C,
		const ChMatrix33d &	F,
		const ChMatrix33d *	l,
		ChFieldData *	data_per_point,
		ChElementData *	data_per_element
	)