# Metafor

ULiege - Aerospace & Mechanical Engineering

### Sidebar

doc:user:elements:shells:interface

# DG shell interactions

Once shell interactions are defined, they must be completed with (Discontinuous Galerkin) interface interactions, following the well-known material-element-interaction pattern.

## Materials

First, the material is defined as:

materialno = materialset.define (number, type)
materialno = materialset(number)
materialno.put(param, value)
materialno.depend(param, fct, Key(Lock)))
...
 number material number (must be unique with respect to all elements in materialset, not to shells) type shell type (for example DgShellMaterial) param name of the shell parameter (for example STABILIZATION_PARAMETER) value value of the corresponding parameter param fct function which characterizes the dependency of the property (optional: no fct if no dependency) Lock Lock which defines the dependency variable of the property (compulsory if there is a dependency)

### DgShellMaterial

#### Description

DG law for shell interface elements.

### Parameters

Name Metafor Code Dependency
Stabilization parameter (>1) STABILIZATION_PARAMETER

## Elements

After defining the material, it must be associated to an ElementProperties:

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

where

 type desired type of element (for example DgShellFirstDegreeElement) param1 name of the property associated to the element (for example MATERIAL to associate the desired material) 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)

### DgShellFirstDegreeElement

DG interface element to insert between shells. 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.

### DgShellSecondDegreeElement

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

### DgShellNineNodeSecondDegreeElement

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

### DgShellSixteenNodeThirdDegreeElement

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

### Parameters of shell DG interface 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)
-

## Interactions

DG shell interface elements are generated at the start of the simulation by a DgShellInteraction Interaction, defined over desired entities.

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

or

dg = interactionset.add( DgShellInteraction(number) )
dg.push(gObject1)
dg.push(gObject2)
...
dg.addProperty(prp)
 number User number of the interaction gObject1, gObject2 mesh geometric entities where the finite elements are applied prp Properties ofDG interface elements to generate

Careful, for now if two entities have common nodes, to many elements will be generated.