XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX''"> Finite Elements
By choosing the Finite Elements toggle located on the application selections for MSC Patran, the Finite Elements form will appear. This permits definition of basic finite element constructs, including the creation of nodes, element topology, and multi-point constraints.
The form below is displayed when Create is selected as the action and Node as the object on the Finite Elements form. Nodes created will be translated to .NOE commands in the Banque file.
Elements
Finite elements in MSC Patran simply assigns element topology, such as Quad/4, for standard finite elements. The type of element to be created is not determined until the element properties are assigned. See
Element Properties Form for details concerning the SAMCEF element types. Elements can be created either directly using the
Element object, or indirectly using the
Mesh object. The form below appears when the Object is set on Mesh and the Type is set on Surface
Multi-Point Constraints
Multi-point constraints (MPCs) can also be created from the Finite Elements menu. These are special element types which define a rigorous behavior between several specified nodes. The forms for creating MPCs are found by selecting MPC as the Object on the Finite Elements form. The full functionality of the MPC forms are defined in
Create Action (FEM Entities) (p. 95) in the Reference Manual - Part III.
MPC Types
To create an MPC, first select the type of MPC you want to create from an option menu. The types that will appear in this option menu are dependent on the current settings of the Analysis Code and Analysis Type preferences. The following table summarizes the MPC types that are supported for SAMCEF.
MPC Types | Analysis Type | Description |
| Structural | Explicit linear constraint equations between degrees‑of-freedom (dof) using the .MCE CNLI command. |
| Structural | Creates a rigid body between an independent node and several dependent nodes using the .MCE RIGI command. |
| Structural | Creates an equality relationship between groups of dofs using .LIA GROUPE. |
| Structural, Thermal | Creates an equality relationship between 2 dofs using the .LIA command. |
Comments:
1. Sliding surfaces are not treated as MPC types. They can be treated as Loads/BCs, using conditions defined in
Loads and Boundary Conditions. To create a sliding surface, define an analysis coordinate system with one axis as the surface outward normal. Then enforce a zero translation (displacement), in that direction, for all nodes on the surface.
2. The BACON command .STICK, which can be used for non-homogeneous linking of two meshed parts of a model, is supported as an LBC type.
Degrees-of-Freedom
Whenever a list of degrees-of-freedom is expected for an MPC term, a listbox containing the valid degrees-of-freedom is displayed on the form. A degree‑of‑freedom is valid if:
1. It is valid for the current Analysis Code Preference.
2. It is valid for the current Analysis Type Preference.
3. It is valid for the selected MPC type.
In most cases, all degrees-of-freedom which are valid for the current Analysis Code and Analysis Type preferences are valid for the MPC type.
The following degrees-of-freedom are supported by the MSC Patran SAMCEF MPCs for the various analysis types:
Degrees-of-Freedom | Equivalent Loads/BCs | Analysis Type |
UX | T1 | Structural |
UY | T2 | Structural |
UZ | T3 | Structural |
RX | R1 | Structural |
RY | R2 | Structural |
RZ | R3 | Structural |
TEMP | TEMP | Thermal |
The above table defines the equivalence between degrees-of-freedom and LBC directions when the LBC coordinate is Coord 0 (Global).
Explicit MPCs
Creates a BACON .MCE CNLI construct defining a linear relationship between DOFs (Structural only).
Rigid Fixed MPCs
Creates a BACON .MCE RIGI construct that inserts a rigid body between an independent node and several other dependent nodes (Structural only).
Rigid Bar MPCs
Creates a BACON .LIA GROUPE construct that defines an equality relationship between a group of nodes and up to six (6) degrees-of-freedom of an independent node (Structural only).
Note: | There is no difference between the dependent and independent term in the treatment
of .LIA. |
Cyclic Symmetry MPCs
Note: | This feature is obsolete and is replaced by the Cyclic Symmetry LBC. |
LIA MPCs (Structural and Thermal)
Creates an equality between two DOFs. The .LIA construct is used to define the boundaries.
Note: | This MPC type is only available for explicit nodes. Special care is required when using hybrid elements. |
