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doc:user:elements:boundaries:pressure_shear [2014/10/06 17:57]
joris
doc:user:elements:boundaries:pressure_shear [2021/09/22 11:43]
boman
Line 1: Line 1:
 ====== Pressure and shear ====== ====== Pressure and shear ======
  
-===== Materials=====     +Pressure and shear boundary conditions can be applied using special finite elements defined on the boundary of the mesh. The geometry of these elements are lines in 2D corresponding to the boundary edges of the elements of the 2D mesh. 
 +In 3D, pressure elements are triangles or quads, depending of the shape of the facets of the elements of the mesh near the boundary.
  
-Since pressure/shear interactions are boundary conditions interactions (''LoadingInteraction''), no materials must be associated to the element.+As any finite element, their definition requires an ''ElementProperty'' object and an ''Interaction'' (''LoadingInteraction'')
 +Unlike contact finite elementthere is no "material" associated to this kind of element. 
 + 
 +The ''ElementProperty'' contains the type of element and the values for the pressure and the shear, as well as functions defining the time evolution of these values.  
 + 
 +These elements should not be mixed with [[doc:user:conditions:dead_loads|dead loads]]. In most cases, pressure elements should be chosen over dead loads because: 
 + 
 +    * Pressure and shear are always defined in local axes, so the direction of the resulting force depends on the orientation of the boundary edge/face on which it is applied. 
 +    * Pressure is distributed properly over all edges/faces on which the ''LoadingInteraction'' is applied. Consequently, the total applied force does not depend on the mesh.  
 + 
 +{{ doc:user:pressure.gif |Pressure Elements}}
  
 ===== Element ===== ===== Element =====
  
-Therefore, the first step consist in defining an ''[[doc:user:elements:general:def_element_properties|ElementProperties]]'', as+Therefore, the first step consists in defining an ''[[doc:user:elements:general:def_element_properties|ElementProperties]]'', as
  
   prp = ElementProperties(typeEl)   prp = ElementProperties(typeEl)
-  prp.put(param1value1+  prp.put(paramvalue
-  prp.depend(param1fct1Lock1)) #optional+  prp.depend(paramfctlock)) # optional
   ...   ...
  
 where where
-|''typeEl'' | desired element (for example ''Traction[2|3]DElement'')| +| ''typeEl'' | desired element (for example ''Pressure[2|3]DElement'' - see below 
-|''param1''| name of the property associated to the element (for example ''PRESSURE''+| ''param'' | name of the property associated to the element (e.g. ''PRESSURE''
-|''value1''| value of the corresponding property | +| ''value'' | value of the corresponding property (e.g. value for the pressure  
-|''fct1''| function which characterizes the dependency of the property (optional: no fct if no dependency) | +| ''fct''   | function which characterizes the dependency of the property (optional: no fct if the value is constant) | 
-|''Lock1''| [[doc:user:general:locks|Lock]] which defines the dependency variable of the property (compulsory if there is a dependency) |+| ''lock''  | [[doc:user:general:locks|lock]] which defines the dependency variable of the property (e.g. time-dependence = ''TM'' |
  
-==== Traction[2|3]DElement ==== 
  
-Traction/shear element for a mesh made of quadrangles in 2D or hexaedra in 3D.+==== Pressure2DElement, Pressure3DElement ==== 
 + 
 +Pressure/shear element for a mesh made of triangles/quadrangles in 2D or hexahedra in 3D.
  
 === Parameters === === Parameters ===
 ^   Name                                          ^     Description        Dependency ^ ^   Name                                          ^     Description        Dependency ^
-| ''STIFFMETHOD'' | Method used to calculate the stiffness matrix\\= ''STIFF_ANALYTIC'' : analytic matrix (default)\\ = ''STIFF_NUMERIC''  : numerical matrix \\ Not applicable, only the numerical one exists ! |  -  | +| ''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 | +| ''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 |+| ''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)    |  -  | | ''NPG''    | Number of integration points (default : 2)    |  -  |
  
 +<note tip>Pressure2DElement / Pressure2DElement were named Traction2DElement / Traction3DElement before v3484. The sign of the pressure has also been changed in 2D.  </note>
  
-==== TriangleTraction3DElement ==== 
  
-Traction/shear element for a mesh made of tetrahedra+==== TrianglePressure3DElement ==== 
 + 
 +Pressure/shear element for a mesh made of tetrahedra
  
 === Parameters === === Parameters ===
 ^   Name                                          ^     Description        Dependency ^ ^   Name                                          ^     Description        Dependency ^
-| ''STIFFMETHOD'' | Method used to calculate the stiffness matrix\\= ''STIFF_ANALYTIC'' : analytic matrix (default)\\ = ''STIFF_NUMERIC''  : numerical matrix \\ Not applicable, only the numerical one exists ! |  -  | +| ''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 | +| ''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 |+| ''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)    |  -  | | ''NPG''    | Number of integration points (default : 1)    |  -  |
 +
 +
 +==== ContactPressure2DElement, ContactPressure3DElement ====
 +
 +Derivations of ''Pressure2DElement'' and ''Pressure3DElement'' with the possibility to set the pressure/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 ===== ===== Interaction =====
  
-The interaction is defined as:+The interaction used for pressure/shear element is a ''LoadingInteraction''. It is defined as:
  
   load = LoadingInteraction(no)   load = LoadingInteraction(no)
Line 59: Line 90:
  
 | ''no''       | number of the ''Interaction''  | ''no''       | number of the ''Interaction'' 
-| ''gObject1'', ''gObject2'' mesh geometric entity where the boundary conditions are applied  |  +| ''gObject1'', ''gObject2'' meshed geometric entity where the boundary conditions are applied (one part of the boundary of the mesh)  |  
-| ''prp''      | [[doc:user:elements:general:def_element_properties|Properties]] of [#Element|boundary condition elements]] to generate | +| ''prp''      | [[doc:user:elements:general:def_element_properties|Properties]] of [[#Element|boundary condition elements]] to be generated  |
- +
-==== 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. !! 
doc/user/elements/boundaries/pressure_shear.txt · Last modified: 2021/09/22 11:45 by boman