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
Gets the number of nodes used by this element.

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

virtual int GetNodeNdofs (int n)=0
Get the number of coordinates from the n-th 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
Fills the D vector with the current field values at the nodes of the element, with proper ordering. More...

virtual void ComputeMmatrixGlobal (ChMatrixRef M)=0
Sets M as the mass matrix. More...

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

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

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

virtual void ComputeGravityForces (ChVectorDynamic<> &Fi, const ChVector<> &G_acc)=0
Computes the gravitational forces and set values in the Fi vector, with n.rows = n.of dof of element.

virtual void Update ()
Update: this is 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)
Adds 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)
Adds 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
Adds 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
Tell to a system descriptor that there are item(s) of type ChKblock in this object (for further passing it to a solver) Basically does nothing, but inherited classes must specialize this.

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

Adds the internal forces, expressed as nodal forces, into the encapsulated ChVariables, in the 'fb' part: qf+=forces*factor WILL BE DEPRECATED - see EleIntLoadResidual_F.

virtual void VariablesFbIncrementMq ()
Adds M*q (internal masses multiplied current 'qb') to Fb, ex. More...

class ChMesh

## ◆ ComputeInternalForces()

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

Computes the internal forces (ex.

the actual position of nodes is not in relaxed reference position) and set values in the Fi vector, with n.rows = n.of dof of element.

## ◆ ComputeKRMmatricesGlobal()

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

Sets 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.

## ◆ ComputeMmatrixGlobal()

 virtual void chrono::fea::ChElementBase::ComputeMmatrixGlobal ( ChMatrixRef M )
pure virtual

Sets M as the mass matrix.

The matrix is expressed in global reference.

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

Adds 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

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

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

## ◆ GetNodeNdofs()

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

Get the number of coordinates from the n-th node that are used by this element.

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

## ◆ GetStateBlock()

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

Fills 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!

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

Adds 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: this is 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 is the proper place.

## ◆ VariablesFbIncrementMq()

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

Adds M*q (internal masses multiplied current 'qb') to Fb, ex.

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.

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