FEA Region and Hole Commands

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When using shapes to define an FEA mesh, use Region commands to define material properties for elements and use Hole commands to remove elements from the mesh.

Region Commands

Once the mesh is ready to use shapes, elements within shapes are assigned to materials by using a series of Region commands (or <Body> commands in XML files). In scripted files, the Region command defines material type, thickness, and angle (needed for some anisotropic materials): 

Region (matid),(thick),<(angle)>
  (any number of shape commands)
EndRegion

In XML files, the <Body> block is: 

<Body mat='(matid)' angle='(angle)' thick='(thick)'>
  (any number of shape commands)    
</Body>

where

  • (matid) is the material ID for a previously defined material.
  • (thick) is the thickness of the region in length units.
  • (angle) is an optional angle for the material which is only relevant for anisotropic materials. It can be entered as a number or as a user-defined function of the coordinates for the element centroid. The units are degrees.

Between the Region command and the subsequent EndRegion command (or within the <Body> block), there can be any number of Rect, Oval, and PolyPt commands to define the geometry whose elements will use this region's material properties.

Hole Commands

Once the mesh is ready to use shapes, elements within shapes can be removed with a series of Hole commands (or <Hole> commands in XML files). In scripted files, the Hole command is: 

Hole
  (any number of shape commands)
EndHole

In XML files, the <Body> block is: 

<Hole>
  (any number of shape commands)    
</Hole>

Between the Hole command and the subsequent EndHole command (or within the <Hole> block), there can be any number of Rect, Oval, and PolyPt commands to define the geometry whose elements should be removed.

Rect Command

A scripted Rect command defines a region to be assigned element materials or to be defined as a hole: 

Rect (xmin),(xmax),(ymin),(ymax),<(arcStart)>,<(arcEnd)>

In XML files, the command is: 

<Rect xmin='(xmin)' xmax='(xmax)' ymin='(ymin)' ymax='(ymax)'>
   <arc start='(arcStart)' end='(arcEnd)'/>
</Rect>

where

  • (xmin),(xmax),(ymin), and (ymax) are the x and y extents of the rectangle (or R and Z extents if axisymmetric). If xmax<xmin or ymax<ymin, they will be automatically switched to define the rectangle. The units are length units (or determined by a units attribute in XML files).
  • (arcStart) and (arcEnd) are optional parameters that limit the shape to an to arc of the rectangle (ccw from start to end in degrees with 0 degrees along the x axis, 0≤(arcStart)<360, and (arcEnd)>(arcStart)).

If the defined rectangle overlaps areas that already has assigned elements, or has been defined as a hole, those areas will be ignored.

Oval Command

A scripted Oval command defines a region to be assigned element materials or to be defined as a hole: 

Oval (xmin),(xmax),(ymin),(ymax),<(arcStart)>,<(arcEnd)>

In XML files, the command is: 

<Oval xmin='(xmin)' xmax='(xmax)' ymin='(ymin)' ymax='(ymax)'>
   <arc start='(arcStart)' end='(arcEnd)'/>
</Oval>

where

  • (xmin),(xmax),(ymin), and (ymax) are the x and y extents of the rectangle (or R and Z extents if axisymmetric) that encloses the oval. If xmax<xmin or ymax<ymin, they will be automatically switched to define the oval. The units are length units (or determined by a units attribute in XML files).
  • (arcStart) and (arcEnd) are optional parameters that limit the shape to an to arc of the oval (ccw from start to end in degrees with 0 degrees along the x axis, 0≤(arcStart)<360, and (arcEnd)>(arcStart)).

If the defined oval overlaps areas that already has assigned elements, or has been defined as a hole, those areas will be ignored.

PolyPt Command

In scripted files, a series of PolyPt commands is used to define a polygonal region to be assigned element materials, or to be defined as a hole: 

PolyPt (x1),(y1)
PolyPt (x2),(y2)
  ...
PolyPt (xn),(yn)
PolyPt

In XML files, a polygon is defined with a <Polygon> block: 

<Polygon>  
  <pt x='(x1)' y='(y1)'/>  
  <pt x='(x2)' y='(x2)'/>
    ...
  <pt x='(xn)' y='(yn)'/>
</Polygon>

where

  • (xi),(yi) (for i = 1 to n) are the x and y coordinates of the each point in the polygon (or R and Z if axisymmetric) with the last point (xn),(yn)) being connected to the first ((x1),(y1)). If the PolyPt arguments are omitted, the polygon is closed. The units are length units (or determined by a units attribute in XML files).

A blank PolyPt command in scripted files is only needed if you need to define more than one polygon in the same region. The blank command will finish the current one and the next one will start with the next PolyPt command. Intervening Rect and Oval commands or the end of a block will also stop the current polygon; in these cases the blank PolyPt is not needed.

Nested Shape Commands

By nesting shapes, you can create many more types of shapes.

Using 2D Images

You can also fill the mesh based on drawings in 2D images by using BMPRegion commands.

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