Difference between revisions of "Create a Mesh with Images and Shapes"
Jump to navigation
Jump to search
| Line 9: | Line 9: | ||
<li>Create a standard mesh, which can be done by [[FEA Mesh Generation Commands|generating]] or [[Explicit FEA Mesh Generation|explicitly defining]] a mesh. Each area (in [[FEA Mesh Generation Commands|generated]] meshes) or element (in [[Explicit FEA Mesh Generation|explicitly defined]] meshes) can be assigned to various materials. For sections of the mesh that will be set from image or shape commands, set the material <tt>id</tt> in the [[Area Command]] to <tt>_NONE_</tt> or the <tt>mat</tt> attribute of <tt>XML</tt> commands to 0. The material will be determined later by subsequent image and shape commands.</li> | <li>Create a standard mesh, which can be done by [[FEA Mesh Generation Commands|generating]] or [[Explicit FEA Mesh Generation|explicitly defining]] a mesh. Each area (in [[FEA Mesh Generation Commands|generated]] meshes) or element (in [[Explicit FEA Mesh Generation|explicitly defined]] meshes) can be assigned to various materials. For sections of the mesh that will be set from image or shape commands, set the material <tt>id</tt> in the [[Area Command]] to <tt>_NONE_</tt> or the <tt>mat</tt> attribute of <tt>XML</tt> commands to 0. The material will be determined later by subsequent image and shape commands.</li> | ||
<li>Once the initial mesh is ready, use one or more interspersed [[BMPRegion Command|BMPRegion]], [[Region | <li>Once the initial mesh is ready, use one or more interspersed [[BMPRegion Command|BMPRegion]], [[FEA Region or Hole Commands|Region, or Hole]], commands (in <tt>XML</tt> files, the corresponing commands are [[BMPRegion Command|<tt><BMP></tt>]], [[Region Command|<tt><Body></tt>]], or [[Hole Command|<tt><Hole></tt>]] commands). These commands will map elements covered by the image or by shapes to the material associated with the command. The grid can be regular or irregular. The material will be selected by comparing the centroid of the element to the same location in an image or to see if it is contained in a shape. To resolve complicated structures, the grid has to be fine enough to resolve material boundaries.</li> | ||
<li>When the mesh is done, any elements initialized to <tt>_NONE_</tt> (or <tt>mat=0</tt>) but not assigned to a material by an image or shape command will automatically be removed from the mesh. This feature allows calculations on materials with voids or irregular edges without needing to use complicated [[Area Command|Area commands]] to construct the shape. If these removals cause the mesh to be partitioned into disconnected sections, however, the FEA analysis will fail. A good way to verify connectivity is to attempt to [[Resequence Command|resequence the nodes]].</li> | <li>When the mesh is done, any elements initialized to <tt>_NONE_</tt> (or <tt>mat=0</tt>) but not assigned to a material by an image or shape command will automatically be removed from the mesh. This feature allows calculations on materials with voids or irregular edges without needing to use complicated [[Area Command|Area commands]] to construct the shape. If these removals cause the mesh to be partitioned into disconnected sections, however, the FEA analysis will fail. A good way to verify connectivity is to attempt to [[Resequence Command|resequence the nodes]].</li> | ||
Revision as of 12:58, 13 September 2013
One way to create a complicated FEA mesh, especially composite materials with complex structures of subelements, is to define them with image and shape commands.
Introduction
An advanced method for creating FEA meshes is to create them using image and shape commands. The procedure for using this method is:
- Create a standard mesh, which can be done by generating or explicitly defining a mesh. Each area (in generated meshes) or element (in explicitly defined meshes) can be assigned to various materials. For sections of the mesh that will be set from image or shape commands, set the material id in the Area Command to _NONE_ or the mat attribute of XML commands to 0. The material will be determined later by subsequent image and shape commands.
- Once the initial mesh is ready, use one or more interspersed BMPRegion, Region, or Hole, commands (in XML files, the corresponing commands are <BMP>, <Body>, or <Hole> commands). These commands will map elements covered by the image or by shapes to the material associated with the command. The grid can be regular or irregular. The material will be selected by comparing the centroid of the element to the same location in an image or to see if it is contained in a shape. To resolve complicated structures, the grid has to be fine enough to resolve material boundaries.
- When the mesh is done, any elements initialized to _NONE_ (or mat=0) but not assigned to a material by an image or shape command will automatically be removed from the mesh. This feature allows calculations on materials with voids or irregular edges without needing to use complicated Area commands to construct the shape. If these removals cause the mesh to be partitioned into disconnected sections, however, the FEA analysis will fail. A good way to verify connectivity is to attempt to resequence the nodes.
Using images
An advanced feature of NairnFEA is that you can go directly from a digital image of an object or a CAD drawing to an FEA mesh. The command to handle this feature is the BMPRegion Command.
Using Shapes
To define the mesh using a series of geometric shapes, the two commands are
- Region Command: Generate elements using a series of shape commands.
- Hole Command: Remove elements using a series of shape commands.