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--- doc:user:elements:boundaries:pressure_shear [2013/07/11 18:06] – joris
+++ doc:user:elements:boundaries:pressure_shear [2018/08/16 11:32] – [ContactTraction2DElement, ContactTraction3DElement] boemer
@@ Line 1: / Line 1: @@
+====== 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 ''[[doc:user:elements:general:def_element_properties|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''| [[doc:user:general:locks|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 of a node to zero, when this node is in contact within a specified contact interaction.  To determine the contact status, the contact flag of the previous time step is used.
+=== Parameters ===
+The same than in Traction2DElement and Traction3DElement, with the following additional parameters:
+^  Name  ^  Description  ^  Dependency  ^
+| ''NUM_CONTACT_INTERACTION'' | Number of the contact interaction, which is tested for the contact status |  -  |
+| ''TRACTION_AT_TRANSITION_ON'' | If True (default), the traction of a node belonging to an element at the transition from contact to no contact is not set equal to zero, although the node is in contact  |  -  |
+{{ :doc:user:elements:boundaries:tractionattransition.png?600 |}}
+===== Interaction =====
+The interaction is defined as:
+  load = LoadingInteraction(no)
+  load.push(gObject1)
+  load.push(gObject2)
+  ...
+  load.addProperty(prp)
+  interactionset.add(load)
+where
+| ''no''       | number of the ''Interaction''  |
+| ''gObject1'', ''gObject2''  | meshed geometric entity where the boundary conditions are applied  |
+| ''prp''      | [[doc:user:elements:general:def_element_properties|Properties]] of [[#Element|boundary condition elements]] to generate |
+==== Remark ====
+Traction, pressure and shear is generated by "traction elements". Their definition requires a specific ''[[doc:user:general:glossaire#Interaction]]'' called ''LoadingInteraction'', to which is associated an [[doc:user:elements:general:def_element_properties|ElementProperties]]. These should not be mixed with [[doc:user:conditions:dead_loads|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.
+{{ doc:user:pressure.gif |Elements de pression}}
+:!: Traction element is used backwards in 3D, so a positive value must be applied to generate a pressure. !!