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• Added “Suppress Short Edges” option to Mesh, Mesh Control, Size on Surface.

• Removed “Quad Mesh Layer Options” option from Mesh, Mesh Control, Size on Surface. This capability was improved and is now the Quad Edge Layers “mesh attribute” which can be specified before meshing using Mesh, Mesh Control, Attribute on Surface or during the meshing process using Mesh, Geometry, Surface.

• Added and updated many options found in the Mesh, Geometry, Surface command. All of the options set when the surface is initially meshed are now automatically specified as “mesh attributes”. Additions include the new

“3-D Tri” triangle mesher, new mapped meshing options, the ability to specify mesh offsets on the surface, automatic node merging when meshing surfaces connected to surfaces which have already been meshed, and a

“Post-Meshing Cleanup” option which improves the mesh by eliminating certain patterns and collapsed holes.

Automesh Surfaces dialog box

When you select the Mesh, Geometry, Surface command, you must select the surfaces to mesh. After they are selected, the Automesh Surfaces dialog box appears.

After choosing the appropriate property, you can decide to press OK to accept default options or click the More Options button to set up additional meshing controls. See More Options section below.

The Mesher section allows you to choose between meshing the surfaces with quadrilateral surface elements, where possible (Quad option), or all triangular surface elements (Tri option). When using the Tri option, you may choose to use Auto, which will examine each surface one at a time and attempt to choose the Tri mesher which will create the best overall triangular mesh on each individual surface. If you want FEMAP to use a particular Tri mesher, uncheck Auto and choose one of the three triangle meshers. See the "Element Shape" section below for details.

Checking the Midside Nodes option will create parabolic surface elements instead of linear surface elements, while turning the Mapped Meshing Options will attempt to create a mapped mesh on the surface, if possible using the options currently set.

Node and Element Options

These options control parameters that are assigned to the nodes and elements that you will create. The CSys option does not control the mesh in any way. It is just assigned as the definition coordinate system of each node. The prop-erty is most important. You must choose a propprop-erty which corresponds to a planar element.

Using Meshing Attributes

If the surfaces that you are meshing have mesh attributes defined, you will see an additional property (0..Use Mesh-ing Attributes) in the list. If you choose that “property”, FEMAP will use the attributes to define the property, type of elements that will be created, and which meshing options will be used during the meshing process. If you wish to ignore the attributes, simply pick a different property from the drop-down list or create a new property.

If you wish to use the property specified in the attribute, but set different meshing options, check the Use Property Attribute Only option, which is only available when Property is set to “0..Use Meshing Attributes”.

When the More Options... button has been pressed, the Automesh Surfaces dialog box will expand to offer many more meshing options. Depending on which options are selected in the Mesher section, certain portions of the dia-log will “gray” and “un-gray” to only allow you to choose appropriate options for the selected Mesher.

Mesher

The Mesher section allows you to choose between meshing the surfaces with quadrilateral surface elements, where possible (Quad option), or all triangular surface elements (Tri option). When using the Tri option, you may choose to use Auto, which will examine each surface one at a time and attempt to choose the Tri mesher which will create the best overall triangular mesh on each individual surface. If you want FEMAP to use a particular Tri mesher, uncheck Auto and choose one of the three triangle meshers. See the "Element Shape" section below for details.

Pre-v10 Meshing

The surface meshing in FEMAP has dramatically changed for version 10. This switch allows you to use the “pre-v10” surface meshing if you feel more comfortable with pre-version 10 meshers. This box will be checked by default if you have “Pre-v10 Surface Meshing” checked on the “Geometry/Model” tab in the “Preferences” dialog box (See Section 2.6.2.6, "Geometry/Model").

Node Options Midside Nodes

Checking the Midside Nodes option will create parabolic surface elements instead of linear surface elements. By default, “midside nodes” are created along the element edge between the corner nodes of an element. You project the midside nodes onto the geometry by using the Move to Geometry option. In some cases, you may want to limit the distortion of elements created by projecting the midside nodes. If this is the case, check Max Distortion Angle and enter the max allowable distortion angle.

Note: Only options available is versions of FEMAP before version 10 will be available when Pre-v10 Mesh-ing is checked. Notice, Quad Edge Layers is now set in the Automesh Surfaces dialog box when usMesh-ing the Mesh, Geometry, Surfaces command instead of in the Automatic Mesh Sizing dialog box, which appears when using the Mesh, Mesh Control, Size on Surface command.

Connect Edge Nodes

When this option is turned on, FEMAP will use existing nodes on edges of adjacent surfaces instead of creating new nodes when at least one of the adjacent surfaces has already been meshed. This option is only applicable when the adjacent surfaces are stitched together to form a solid (or sheet solid) or joined together into a “general body”

using Geometry, Surface, Non-Manifold Add .

Smoothing

These options are the same as those described in the Mesh, Smooth command. After an initial mesh is generated, it is automatically smoothed to reduce element distortions. You will usually just want to accept the default values for these options. For more information, see Section 5.3.4, "Mesh, Smooth...".

Offset

Allows you to automatically offset the surface mesh so the Top Face (Face 1) or Bottom Face (Face 2) of shell ele-ments will be aligned with the surface(s) currently being meshed. There is also an option to simply offset the mesh away from the Centerline of the elements (default) a specified amount. Entering a positive number will offset the mesh towards the Top Face (Face 1) of the elements, while entering a negative value will offset towards the Bottom Face (Face 2).

For Example, the “thicker” Black lines represent a Surface. Elements are shown with Normal Vectors “on”.

Mapped Meshing Options

When Mapped Meshing is set to Off, FEMAP will simply mesh the selected surface(s) with a “free mesh”, unless a

“Mapped Meshing Approach” is set. If Mapped Meshing is On, FEMAP will attempt to create a “Mapped Mesh”.

Note: The best way to determine which face is the Top Face and which face is the Bottom Face is to view the normal direction of the elements. This can be accomplished by setting options for the Element - Direc-tion opDirec-tion in the Labels, Entities and Color category of the View, OpDirec-tions command (See SecDirec-tion 6.1.5.3, "View, Options..."). To see the “normal vector” on each element, choose “1..Normal Vectors”

from the Normal Style list, check the box next Show Direction and then click Apply or OK. The arrow representing the normal vector points towards the Top Face of the element.

Three Surfaces stitched together using

Geometry, Solid, Stitch command Surfaces 1 and 3 meshed at the same time Free Edge Plot of existing mesh on

Edges surface 2 shares with previously meshed adjacent surfaces 1 and 3

Surfaces 1 and 3

Free Edge Plot after meshing surface 2 with

“Connect Edge Nodes” turned ON Free Edge Plot after meshing surface 2 with

“Connect Edge Nodes” turned OFF

Mesh with no offsets Mesh Offset so “Top Face” of elements Aligned

attempt a mapped mesh on surfaces.

There are several other options available:

• Equal Sides Only - FEMAP will only attempt a mapped mesh on surface(s) with equal mesh sizing on opposing

“sides” of the surface(s). The “sides” are the curve(s) between the “corners” the mesher locates.

• Map Subdivisions - As the “subdivision” meshers “subdivide” the geometry during the meshing process, the mesher will determine if each “subdivision” can by mapped meshed. If possible, that portion of the surface will be mapped meshed and then “smoothed” using the current Smoothing settings to create the overall surface mesh.

• Split Quad Map - Only available when using the Tri option in the Mesher section. FEMAP will actually create a quad mesh first and then split the quads into the best possible triangles using the same approach as the Modify, Update Elements, Split Quads command.

• Alternate - Only available when using one of the Tri options in the Mesher section. The mesher will attempt to alternate the direction of triangles which are side by side instead of having them all go in one direction.

• Right Bias - Only available when using one of the Tri options in the Mesher section. The mesher uses the oppo-site direction to start when choosing the direction of the triangles.

Subdivision Options (Tri Mesher set to Subdivision, Quad Mesher only)

These options control the size and shape of the mesh inside the boundary. The elements along the boundary edges are defined by the mesh sizes that you choose and are unaffected by these settings. Those mesh sizes also have sub-stantial impact on the interior of the mesh, but these options give you additional control.

Post-Meshing Cleanup

This option, which is on by default, attempts to eliminate specific “patterns” in a mesh in an effort to create an overall higher quality mesh. It also does additional element checking in an attempt to eliminate meshing situations which may cause problems with surface and/or solid meshing.

Curved Geometry Default Triangle Mesh Triangle Mesh using Split Quad Map Option

Subdivision

Fast Tri

3-D Tri

Triangle Mesher Mapped Off Mapped On

Mapped On Alternate On

Mapped On Right Bias On

Mapped On Alternate and Right Bias On

Additional clean-up includes inserting extra mesh points on long cylindrical surfaces with course mesh sizing. This eliminates the possibility of elements “bridging the gap” resulting in a “collapsed” hole.

Here are a few examples of mesh patterns which will be recognized and the resulting mesh after the “clean-up”.

Quad Edge Layers

This option specifies the number of layers of quadrilateral elements that FEMAP will attempt to place around every boundary curve on a surface. You can choose to have either 1, 2, or 3 layers of quads around each boundary curve of a surface, including internal curves from the drop-down list. Additionally, you may enter a number higher than 3 directly into the field and the mesher will attempt to create the specified number of quad element layers. If there is not enough room for the requested number of layers based on the mesh size, FEMAP will try to put as many layers of quads in as possible. The process goes one layer at a time, meaning that one layer of quads will be placed around all boundary curves (external curves first, internal curves second) before a second layer of quads will be attempted.

In many cases, more layers will produce a higher quality mesh, but on some pieces of geometry using only 1 or 2 layers may produce better overall mesh quality than using 3 or more layers.

Min Elements Between Boundaries

As a boundary is being meshed, groups of elements are often generated between two opposite edges of a boundary.

Sometimes, the mesh sizes that you have defined are large enough that a single element will span the distance between surfaces. Since this may not be enough refinement for the model that you are creating, you can control this behavior by setting a minimum number of elements that must be created between any boundary edges.

Setting this parameter does not guarantee that you will get that number of elements between every edge. But wher-ever possible (based on compatibility with your surface mesh sizes) that number of elements or greater will be cre-ated.

It is usually best to leave this parameter set to 1 initially, then if the results are undesirable, undo the mesh and try it again with the number increased. Setting this number greater than 1 can greatly increase the number of elements that are generated.

Note: In almost all cases, this option should be turned “on”, as it will usually create a better overall mesh. The only potential drawback to using this option is the possibility that the “clean-up” will replace “patterns”

with less elements and therefore create a slightly courser mesh than expected.

“Diamond” elements eliminated Patterns

Original After Clean-up

2 Layers 1 Layers

0 Layers 3 Layers 5 Layers

surface that is long and thin relative to the mesh size, or one that has long, thin “appendages”, as this example demonstrates.

Max Element Aspect Ratio

Like the Min Elements setting described above, this option controls the elements inside the mesh. In this case however, control over the number of elements is only a secondary effect of this option. Prima-rily, this number is used as a guideline for how “long” elements can be relative to their “width”. You must always specify a value that is greater than or equal to 1.0. Smaller numbers usually create slightly more uniform meshes with elements that are better shaped. Large numbers can lead to severely distorted elements. If you make a mesh that contains long, thin or distorted elements, try again with a smaller aspect ratio.

Quick-Cut boundaries with More Than “n” Nodes (n = 300 by default)

Meshing large non-uniform surfaces can often take some time. Turning this option on shortens the time required while usually having minimal impact on the overall mesh quality. If you want the best possible mesh, and are will-ing to wait, turn this option off. You can also control the threshold by settwill-ing the number of nodes to a smaller or larger number. Do not reduce the number of nodes too much, or mesh quality will substantially decrease.

Cut Quads with Angle Deviation Above “n” deg (n = 60 degress by default)

Typically, quadrilateral elements with an angle deviation above 60 degrees will have poor element quality. Trian-gles are created wherever a quadrilateral would be severely distorted. You can override the default 60 degree allow-able distortion with any value that you want. Lower distortion values will result in more triangles in your mesh.

Element Shape Quad Mesher

Although the mesher is called Quad, it is physically impossible on some surfaces with certain mesh sizing to create a mesh using “all quads” without some being highly distorted. The Quad option will generate quadrilateral ele-ments whenever possible using a “subdivision” approach in the “parametric space” of each surface being meshed.

Tri Meshers

These options control the creation of triangular elements in your mesh. If you want to create all triangles (Tri option), you may choose from the Subdivision, Fast Tri, or 3-D Tri options. Use the Auto option to have FEMAP choose which Tri meshing option should be used on each surface.

• Subdivision - FEMAP’s original triangle mesher. It creates triangle elements by making subdivisions of a sur-face based on “parametric space”. It works very similar to the Quad mesher, but instead of making 90 degree

“splits” to create quadrilateral elements, it makes 60 degree “splits” to make triangles. In a few cases, it may produce better quality mesh than the Fast Tri or 3-D Tri meshers.

• Fast Tri - creates large triangles in “2-D parametric space” of a surface (U and V directions) then creates the final mesh through a process of splitting and improving the shape of the triangles based on where they are posi-tioned in each surface’s “parametric space”. The Fast Tri mesher generally produces fewer triangles with better aspect ratios than the Subdivision mesher. This technique works particularly well if you have a long thin surface with holes.

• 3-D Tri - uses the “facets” of each surface as a “triangular seed mesh”, then uses a similar “splitting and improving triangle shape” technique as the Fast Tri mesher, except it evaluates the shape of the triangles in true

“3-D space” instead of the surface’s “parametric space”. Also, the nodes are constantly projected back to each Note: You must always get at least one triangle if you specify an odd number of nodes on the surface.)

Trian-gles are created wherever quadrilaterals cannot meet the specified boundary mesh sizes and wherever a quadrilateral would be severely distorted.

Min Elements = 3 (or 2) Min Elements = 1

surface to match the actual shape of the surface as closely as possible. In many cases, this will produce the best quality mesh and is the recommended option for meshing “boundary surfaces” created from surfaces which are part of a solid or stitched sheet solid.

Meshing a surface which has already been meshed

If you choose a surface to mesh which has already been meshed, FEMAP will give you three options:

•Delete Existing Mesh and Remesh - Simply deletes the mesh and remeshes the surface.

•Skip Meshed Surfaces - If you have chosen a number of sur-faces to mesh, some of which have already been meshed, only the surfaces which currently are not meshed will be meshed.

•Create Duplicate Meshes on Meshed Surfaces - Usually used when you want to “skin” a solid mesh with a shell mesh.

Surface Mesh Attributes dialog box

... is used to assign meshing attributes to one or more surfaces. Simply choose a surface element property to be assigned to the surface(s) and specify the desired mesh options. The mesh options are identical to the ones which can be specified when using the Mesh, Geometry, Surface command (See "Automesh Surfaces dialog box" section for descriptions of the meshing options). Press the New Property “icon button” if you have not already created the property that you need.

Once attributes have been defined, surfaces can be easily meshed with elements, as properties (thicknesses, materi-als...) will be automatically assigned. Attributes are automatically assigned once a surface has been meshed.

Note: One of the only drawbacks to using the 3-D Tri mesher, is when trying to mesh surfaces which “wrap around” with a large amount of curvature over a short distance. When using a relatively course mesh size on this type of surface, the mesher may create elements which do not follow the curvature of the surface properly, as a better shaped element can be created without following the curvature based on the positions of the nodes in 3-D space.

this dialog box. You can offset the mesh to align the “Top Face” (Face 1) of the elements to the surface, align the

“Bottom Face” (Face 2) to the surface, or enter an offset from the “Centerline” directly (Positive values offset the mesh towards Face 1, negative values offset towards Face 2).

By default, both the property and mesh options will be set for all of the selected surfaces. If you only want to change the property of a number of surfaces but leave each surface’s meshing options intact, make sure that Update Property is “checked” and Update Other Attributes is “unchecked”. Vice versa, if you only want to change the

By default, both the property and mesh options will be set for all of the selected surfaces. If you only want to change the property of a number of surfaces but leave each surface’s meshing options intact, make sure that Update Property is “checked” and Update Other Attributes is “unchecked”. Vice versa, if you only want to change the