chrono::fea::ChElementBase Class Referenceabstract

## Description

Base class for all finite elements, that can be used in the ChMesh physics item.

#include <ChElementBase.h>

Inheritance diagram for chrono::fea::ChElementBase:

## Public Member Functions

virtual int GetNnodes ()=0
Get the number of nodes used by this element.

virtual int GetNdofs ()=0
Get the number of coordinates in the field used by the referenced nodes. More...

virtual int GetNdofs_active ()
Get the actual number of active degrees of freedom. More...

virtual int GetNodeNdofs (int n)=0
Get the number of coordinates from the specified node that are used by this element. More...

virtual int GetNodeNdofs_active (int n)
Get the actual number of active coordinates from the specified node that are used by this element. More...

virtual std::shared_ptr< ChNodeFEAbaseGetNodeN (int n)=0
Access the nth node.

virtual void GetStateBlock (ChVectorDynamic<> &mD)=0
Fill the D vector with the current field values at the nodes of the element, with proper ordering. More...

virtual void ComputeMmatrixGlobal (ChMatrixRef M)=0
Calculate the mass matrix, expressed in global reference.

virtual void ComputeNodalMass ()
Compute element's nodal masses.

virtual void ComputeKRMmatricesGlobal (ChMatrixRef H, double Kfactor, double Rfactor=0, double Mfactor=0)=0
Set H as the stiffness matrix K, scaled by Kfactor. More...

virtual void ComputeInternalForces (ChVectorDynamic<> &Fi)=0
Compute the internal forces. More...

virtual void ComputeGravityForces (ChVectorDynamic<> &Fi, const ChVector<> &G_acc)=0
Compute the gravitational forces. More...

virtual void Update ()
Update, called at least at each time step. More...

virtual void EleDoIntegration ()
This is optionally implemented if there is some internal state that requires integration.

virtual void EleIntLoadResidual_F (ChVectorDynamic<> &R, const double c)
Add the internal forces (pasted at global nodes offsets) into a global vector R, multiplied by a scaling factor c, as R += forces * c.

virtual void EleIntLoadResidual_Mv (ChVectorDynamic<> &R, const ChVectorDynamic<> &w, const double c)
Add the product of element mass M by a vector w (pasted at global nodes offsets) into a global vector R, multiplied by a scaling factor c, as R += M * w * c.

virtual void EleIntLoadResidual_F_gravity (ChVectorDynamic<> &R, const ChVector<> &G_acc, const double c)=0
Add the contribution of gravity loads, multiplied by a scaling factor c, as: R += M * g * c Note that it is up to the element implementation to build a proper g vector that contains G_acc values in the proper stride (ex. More...

virtual void InjectKRMmatrices (ChSystemDescriptor &mdescriptor)=0
Indicate that there are item(s) of type ChKblock in this object (for further passing it to a solver)

virtual void KRMmatricesLoad (double Kfactor, double Rfactor, double Mfactor)=0
Add the current stiffness K and damping R and mass M matrices in encapsulated ChKblock item(s), if any. More...

virtual void VariablesFbLoadInternalForces (double factor=1.0)
Add the internal forces, expressed as nodal forces, into the encapsulated ChVariables. More...

virtual void VariablesFbIncrementMq ()
Add M*q (internal masses multiplied current 'qb'). More...

class ChMesh

## ◆ ComputeGravityForces()

 virtual void chrono::fea::ChElementBase::ComputeGravityForces ( ChVectorDynamic<> & Fi, const ChVector<> & G_acc )
pure virtual

Compute the gravitational forces.

Set values in the provided Fi vector (of size equal to the number of dof of element).

## ◆ ComputeInternalForces()

 virtual void chrono::fea::ChElementBase::ComputeInternalForces ( ChVectorDynamic<> & Fi )
pure virtual

Compute the internal forces.

Set values in the provided Fi vector (of size equal to the number of dof of element).

## ◆ ComputeKRMmatricesGlobal()

 virtual void chrono::fea::ChElementBase::ComputeKRMmatricesGlobal ( ChMatrixRef H, double Kfactor, double Rfactor = 0, double Mfactor = 0 )
pure virtual

Set H as the stiffness matrix K, scaled by Kfactor.

Optionally, also superimposes global damping matrix R, scaled by Rfactor, and mass matrix M, scaled by Mfactor. Matrices are expressed in global reference. Corotational elements can take the local Kl & Rl matrices and rotate them.

## ◆ EleIntLoadResidual_F_gravity()

 virtual void chrono::fea::ChElementBase::EleIntLoadResidual_F_gravity ( ChVectorDynamic<> & R, const ChVector<> & G_acc, const double c )
pure virtual

Add the contribution of gravity loads, multiplied by a scaling factor c, as: R += M * g * c Note that it is up to the element implementation to build a proper g vector that contains G_acc values in the proper stride (ex.

tetahedrons have 4x copies of G_acc in g). Note that elements can provide fast implementations that do not need to build any internal M matrix, and not even the g vector, for instance if using lumped masses.

Implemented in chrono::fea::ChElementGeneric.

## ◆ GetNdofs()

 virtual int chrono::fea::ChElementBase::GetNdofs ( )
pure virtual

Get the number of coordinates in the field used by the referenced nodes.

This is for example the size (number of rows/columns) of the local stiffness matrix.

## ◆ GetNdofs_active()

 virtual int chrono::fea::ChElementBase::GetNdofs_active ( )
inlinevirtual

Get the actual number of active degrees of freedom.

The default implementation returns the full number of DOFs for this element, but some elements may have nodes with fixed variables.

## ◆ GetNodeNdofs()

 virtual int chrono::fea::ChElementBase::GetNodeNdofs ( int n )
pure virtual

Get the number of coordinates from the specified node that are used by this element.

Note that this may be different from the value returned by GetNodeN(n)->GetNdofW().

## ◆ GetNodeNdofs_active()

 virtual int chrono::fea::ChElementBase::GetNodeNdofs_active ( int n )
inlinevirtual

Get the actual number of active coordinates from the specified node that are used by this element.

The default implementation returns the full number of DOFs for this element, but some elements may have nodes with fixed variables.

## ◆ GetStateBlock()

 virtual void chrono::fea::ChElementBase::GetStateBlock ( ChVectorDynamic<> & mD )
pure virtual

Fill the D vector with the current field values at the nodes of the element, with proper ordering.

If the D vector size is not this->GetNdofs(), it will be resized. For corotational elements, field is assumed in local reference!

## ◆ KRMmatricesLoad()

 virtual void chrono::fea::ChElementBase::KRMmatricesLoad ( double Kfactor, double Rfactor, double Mfactor )
pure virtual

Add the current stiffness K and damping R and mass M matrices in encapsulated ChKblock item(s), if any.

The K, R, M matrices are added with scaling values Kfactor, Rfactor, Mfactor.

Implemented in chrono::fea::ChElementGeneric.

## ◆ Update()

 virtual void chrono::fea::ChElementBase::Update ( )
inlinevirtual

Update, called at least at each time step.

If the element has to keep updated some auxiliary data, such as the rotation matrices for corotational approach, this should be implemented in this function.

## ◆ VariablesFbIncrementMq()

 virtual void chrono::fea::ChElementBase::VariablesFbIncrementMq ( )
inlinevirtual

Add M*q (internal masses multiplied current 'qb').

Update fb. For example, if qb is initialized with v_old using VariablesQbLoadSpeed, this method can be used in timestepping schemes that do: M*v_new = M*v_old + forces*dt. WILL BE DEPRECATED

Reimplemented in chrono::fea::ChElementGeneric.

## ◆ VariablesFbLoadInternalForces()

 virtual void chrono::fea::ChElementBase::VariablesFbLoadInternalForces ( double factor = 1.0 )
inlinevirtual

Add the internal forces, expressed as nodal forces, into the encapsulated ChVariables.

Update the 'fb' part: qf+=forces*factor WILL BE DEPRECATED - see EleIntLoadResidual_F

Reimplemented in chrono::fea::ChElementGeneric.

The documentation for this class was generated from the following file:
• /builds/uwsbel/chrono/src/chrono/fea/ChElementBase.h