FEM Modeling > Modify Action > Modify Forms
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Modify Forms
When Modify is the selected action, the following options are available.
 
Object
Type
Description
Mesh
Improve an existing surface mesh with optional hard nodes.
Improve an existing solid mesh with optional hard nodes.
Stitches gaps on a mesh.
Mesh Seed
Allows modification of mesh seed on curves/edges.
Element
Changes attributes such as ID numbering, element topology, or nodal connectivity of selected elements.
Reverses the connectivity definition (and therefore the normal direction) of selected elements.
Adds nodes to specified elements an separates them from the rest of the model.
 
Orients elements in a model in the same direction.
Bar
Splits a bar element in two.
Tria
Splits a tria element into two to four elements.
Quad
Splits a quad element into two to four elements.
Tet
Splits a tet element.
Node
Changes a nodal location.
Moves nodes by an indicated vector distance.
Changes attributes such as ID numbering, associated analysis and reference coordinate frames, or physical location of selected nodes.
Project nodes onto Surfaces, Curves or a constant coordinate plane (e.g X = 5).
 
Changes the attributes of a selected MPC.
Connector
Spot Weld
Changes the attributes of a Spot Weld Connector.
Modifying Mesh
The smoothing algorithm used is the iterative Laplacian-Isoparametric scheme developed by L. R. Herrmann. The final mesh and the execution time for smoothing are controlled by the Smoothing Parameters.
Smoothing Parameters
Figure 13‑1  
Figure 13‑2 Example Meshes with Different Values of Smoothing Factor
Mesh Improvement Form
The purpose of this form is to improve the quality of a solid mesh with respect to the criterion selected.
General Parameters
Process Control
Collapse Ratio
Jacobian Minimum
Modifying Mesh Seed
The modify mesh seed menu allows users to change mesh seed types.
Sew Form
Using Modify/Mesh/Sew form sews gaps on a mesh consisting of all tria3 elements. This program removes interior free edges on a mesh by merging nodes and splitting triangles automatically (see Figure 13‑3 and Figure 13‑4).
Figure 13‑3 Mesh Before Sewing
Figure 13‑4 Mesh After Sewing
The primary purpose of this program is to provide users a useful tool to obtain a congruent mesh which will be used to create a tessellated surface. (See Created Tessellated Surface from Geometry Form (p. 306) in the Geometry Modeling - Reference Manual Part 2.) For this reason, the elements modified or created by this program may not have very good quality.
Modifying Elements
Edit Method
Reverse Method
Separate Method
Shell Orientation
A shell element's orientation and normal are based solely on its connectivity, shape and spatial orientation. There is no element property that affects a shell element's orientation or normal. Therefore, the only model changes made using this functionality will be shell element connectivity.
Since a shell element's connectivity is the only model change that can be made to modify its orientation and normal, the degree of control is limited. Depending on its shape and spatial orientation, there may not be a way to obtain the exact orientation. In these cases, the closest match will be made.
 
Type
Type consists of five options for specifying how to reorient the selected elements.
• Guide Element
Uses the orientation of an element.
• Vector
Uses any valid vector specification. This includes any axis of a selected coordinate frame.
• First Node
Changes the element's connectivity such that the first node is the one specified. A list of first nodes is provided.
• Reverse
The normals of the selected elements will be reversed.
• Rotate
Rotates the element's connectivity by 1, 2 or 3 nodes.
Guide Element
For Guide Element and Vector, the coordinate system or normal may be matched.
• Match System
For Match System a tolerance angle may be specified. If the tolerance angle is exceeded, for any element, that element's orientation is not modified.
Select
Select consists of three options for selecting the elements to be reoriented.
• Elements
The Elements option allows individual shell elements to be selected. Auto Execute may be used to have processing occur immediately after each update of the element list.
• Groups
The Groups option allows any number of groups to be selected. The shell elements in the groups will be processed. The Highlight toggle can be used to turn on/off highlighting of the selected elements.
• Current Group
The Current Group option allows the current group to be selected. The shell elements in the current group will be processed. The Highlight toggle can be used to turn on/off highlighting of the selected elements.
Display Control
The Display control will control the way that elements are displayed. See Display Control for more information.
Show Current Orientation
Displays element orientation and normal as specified in the Display Control form on the selected elements.
Reset Graphics
Removes element orientation and normal graphics.
Apply
Applies the specified changes and updates the element orientation and normal display.
Display Control
 
Display Control
Element system axes (Z = normal) can be drawn as vectors and element normals can be color coded in a fringe plot. Either or both displays can be selected.
Element System Axis Options
Any combination of axes, labels and colors may be selected.
Coordinate System Definition
Either Patran or MSC Nastran conventions can be chosen for displaying the element system. No other analysis code conventions are currently available. Beam axes can include or ignore offsets.
Origin Display Location
The origin of the element system axes can be placed at the element centroid, or the analysis code's (Patran/MSC Nastran) definition.
Color Code Normals Option
Brings up the Fringe Attributes form for controlling the color coded fringe plot attributes. See Fringe Attributes.
Fringe Attributes
This form controls the attributes of the color coded element normal fringe plot.
Modifying Bars
 
Note:  
The new bars will have the same topology as the parent (i.e. a Bar3 will be split into
two Bar3s).
Modifying Trias
Splitting a Tria into Two Trias
 
Note:  
The new trias will have the same topology as the parent (i.e., a Tria6 will be split into
two Tria6s).
Splitting a Tria into Three Trias, Four Trias, or Three Quads
 
Note:  
The new elements will have the same topology as the parent (i.e., a Tria6 will be split into Tria6s or Quad8s).
Splitting a Tria into a Tria and a Quad
 
Note:  
The new elements will have the same topology as the parent (i.e., a Tria6 will be split into a Tria6 and a Quad8).
Splitting Tet Elements
Modifying Quads
Splitting a Quad into Two Quads
 
Note:  
The new quads will have the same topology as the parent (i.e., a Quad8 will be split into two Quad8s).
Splitting a Quad into Three Quads
 
Note:  
The new quads will have the same topology as the parent (i.e., a Quad8 will be split into three Quad8s).
Splitting a Quad into Four Quads or Four Trias or NxM Quads
Figure 13‑5  
Splitting a Quad into Two Trias
Figure 13‑6  
 
Note:  
The new trias will have the same topology as the parent (i.e., a Quad8 will be split into
two Tria6s).
Splitting a Quad into Three Trias
Figure 13‑7  
 
Note:  
The new trias will have the same topology as the parent (i.e., a Quad8 will be split into
three Tria6s).
Modifying Nodes
Move Method
Figure 13‑8  
Offset Method
Edit Method
Project Method
Modifying MPCs
When Modify is the selected Action and MPC is the selected Object, the Modify MPC form is displayed. Use this form to modify the attributes of existing MPCs.
Modify Terms
This form appears when the Modify Terms button is selected on the Modify MPC form. Use this form to modify the dependent and independent terms of a selected MPC.
Modifying Spot Weld Connectors
The form under the Modify action is almost identical to the Create form, except the “Connector ID List” databox becomes a select databox. Connectors may then be selected from the screen, and the values within the form are automatically populated with the values for the selected connector, as are the values for the Connector Properties form. Please see Creating Connectors, 138 for descriptions of all inputs.
 
Connector
A single connector may be selected from the screen, or entered from the keyboard. For keyboard entry, the values are not populated until focus leaves the Connector select databox.