# Metafor

ULiege - Aerospace & Mechanical Engineering

### Sidebar

doc:user:elements:shells:boundary

# DG shell boundary conditions

Since shell formalism only takes displacements into account, rotating boundary conditions are imposed though a DG formulation.

## Materials

As for boundary condition elements, there is no material to associate to an element.

## Elements

Since no material is required, the first stage consists in defining an ElementProperties:

prp = ElementProperties(typeEl)
prp.put(param1, value1)
prp.depend(param1, fct1, Lock1)) #facultatif
...

where

 typeEl desired type of element (for example BoundaryDgShellFirstDegreeElement) param1 name of the property associated to the element (for example STIFFMETHOD) value1 value of the corresponding property fct1 function which characterizes the dependency of the property (optional: no fct if no dependency) Lock1 Lock which defines the dependency variable of the property (compulsory if there is a dependency)

### BoundaryDgShellFirstDegreeElement

DG interface element to insert on shell boundaries to provide BCs. These are 2-nodes linear lines, but they are interfering over all neighboring dofs.

By default, stresses are integrated over dim*2 integration points. The material used is dgShellMaterial.

### BoundaryDgShellSecondDegreeElement

Same as BoundaryDgShellFirstDegreeElement, but 8-nodes second order shell element.

### BoundaryDgShellNineNodeSecondDegreeElement

Same as BoundaryDgShellSecondDegreeElement, but 9-nodes second order shell element.

### BoundaryDgShellSixteenNodeThirdDegreeElement

Same as BoundaryDgShellNineNodeSecondDegreeElement, but 16-nodes third order shell element.

### Parameters of shell boundary conditions elements

Name Metafor Code Dependency
MATERIAL Number of the material to consider -
STIFFMETHOD Method used to compute the stiffness matrix
= STIFF_ANALYTIC : analytic matrix (default)
= STIFF_NUMERIC : numerical matrix
-
BENDING_NPG Number of integration points along one direction for bending solving
= 2 classical solving (second order)
= 3 EAS solving with 22 or 7 added modes (8 or 9-nodes second order)
= 4 solving without EAS (16-nodes third order)
-
NORMAL_PT1 First point governing the element of the shell normal -
NORMAL_PT2 First point governing the element of the shell normal -

## Interactions

Once created, the element is generated by a DgShellInteraction:

dgBound = DgShellInteraction(number)
dgBound.push(gObject1)
dgBound.push(gObject2)
...
interactionset.add(dgBound)  # the interaction is added in InteractionSet

or

dgBound = interactionset.add( DgShellInteraction(number) )
dgBound.push(gObject1)
dgBound.push(gObject2)
...
dgBound.addProperty(prp)
 number Number of the material to consider gObject1, gObject2 mesh geometric entities prp Properties of the DG boundary condition elements to generate

Generally, entities are lines or groups of nodes on a line.