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doc:user:elements:boundaries:pressure_shear

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Pressure and shear

Materials

Since pressure/shear interactions are boundary conditions interactions (LoadingInteraction), no materials must be associated to the element.

Element

Therefore, the first step consist in defining an ElementProperties, as

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

where

 typeEl desired element (for example Traction[2|3]DElement) param1 name of the property associated to the element (for example PRESSURE) 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)

Traction2DElement, Traction3DElement

Traction/shear element for a mesh made of quadrangles in 2D or hexaedra in 3D.

Parameters

Name Description Dependency
STIFFMETHOD Method used to compute the stiffness matrix
= STIFF_ANALYTIC : analytic matrix (default)
= STIFF_NUMERIC : numerical matrix
-
PRESSURE Pressure on the entity on which the propriety is applied time
SHEAR_KSI / SHEAR_ETA Shear along $\xi$ or $\eta$ on the entity on which the propriety is applied time
NPG Number of integration points (default : 2) -

TriangleTraction3DElement

Traction/shear element for a mesh made of tetrahedra

Parameters

Name Description Dependency
STIFFMETHOD Method used to compute the stiffness matrix\\= STIFF_ANALYTIC : analytic matrix (default)
= STIFF_NUMERIC : numerical matrix
Not applicable, only the numerical one exists !
-
PRESSURE Pressure on the entity on which the propriety is applied time
SHEAR_KSI / SHEAR_ETA Shear along $\xi$ or $\eta$ on the entity on which the propriety is applied time
NPG Number of integration points (default : 1) -

ContactTraction2DElement, ContactTraction3DElement

Derivations of Traction2DElement and Traction3DElement with the possibility to set the traction/shear force to zero, when this node is in contact within a specified contact interaction.

Parameters

Name Description Dependency
STIFFMETHOD Method used to compute the stiffness matrix
= STIFF_ANALYTIC : analytic matrix (default)
= STIFF_NUMERIC : numerical matrix
-
PRESSURE Pressure on the entity on which the propriety is applied time
SHEAR_KSI / SHEAR_ETA Shear along $\xi$ or $\eta$ on the entity on which the propriety is applied time
NPG Number of integration points (default : 2) -
NBR_CONTACT_INTERACTION Number of the contact interaction -

Interaction

The interaction is defined as:

load = LoadingInteraction(no)
...
interactionset.add(load)

where

 no number of the Interaction gObject1, gObject2 meshed geometric entity where the boundary conditions are applied prp Properties of boundary condition elements to generate

Remark

Traction, pressure and shear is generated by “traction elements”. Their definition requires a specific Interaction called LoadingInteraction, to which is associated an ElementProperties. These should not be mixed with dead loads. In most cases, traction elements should be chosen over dead loads:

• traction (or pressure/shear) is always defined in local axes, so the direction of the force depends on the orientation of the edge/face on which it is applied.
• traction is divided properly over all edges/faces on which the Interaction is applied. Consequently, the resultant force does not depend on the mesh.

Traction element is used backwards in 3D, so a positive value must be applied to generate a pressure. !!