Creating a bottom-up mesh

Bottom-up meshing is a manual process that may be time consuming and require some trial and error to produce an acceptable mesh. Bottom-up meshing is intended for use primarily when you need hexahedral elements for an analysis and you cannot generate them using top-down meshing techniques. You can also use bottom-up meshing in cases where extensive partitioning would be required to create a high-quality top-down mesh on geometry or where you want to extend a mesh part. The following procedure includes the basic steps for creating a bottom-up mesh. To create a bottom-up mesh, you must first have either a mesh region or a solid region with the bottom-up meshing technique assigned (for more information, see Assigning mesh controls). You can also create a bottom-up mesh on an assembly containing independent instances of native parts or dependent instances of parts containing any combination of orphan mesh and geometry.

Related Topics
Selecting objects within the viewport
Bottom-up meshing
Selecting parameters for a bottom-up mesh
Using the Mesh module toolbox

  1. From the main menu bar, select MeshCreate Bottom-Up Mesh.

    Tip: You can also click the tool in the Mesh module toolbox. (For more information, see Using the Mesh module toolbox.)

    Abaqus/CAE opens the Create Bottom-Up Mesh dialog box and displays prompts in the prompt area to guide you through the procedure.

  2. Select the Domain for which you want to create the bottom-up mesh.

    If there is only one appropriate domain for the current part or assembly, Abaqus/CAE automatically makes the selection. If there are multiple geometry regions, or cells, with the bottom-up technique assigned, click Select to select the cell that will be associated with the bottom-up mesh that you are creating. Regions that you can select are colored light tan.

    If you work with orphan elements, there is no association between the elements and any geometric region in the part.

    Note:

    After selecting a geometric region for bottom-up meshing, you can use the Edit button to change your selection.

  3. Select one of the following meshing methods:

    • Sweep

    • Extrude

    • Revolve

    • Offset (available only for element face selections)

    For a description of each method, see Bottom-up meshing methods.

  4. If you previously selected bottom-up meshing parameters for the current region, you can click Fetch Last Selections to reuse your previous selections.

    Abaqus/CAE saves your selections for the domain, source side, connecting sides, target side, extrusion vector, and axis of revolution in the session until they are overwritten by new selections.

    Note:

    If you add a partition to the model, you cannot reuse previously selected geometry; however, as long as you have not modified the mesh, you can reuse mesh selections such as element faces and two-dimensional elements.

  5. Click Select next to Source side; and select the region faces, element faces, or two-dimensional elements where you want the mesh to begin.

    Tip: Use ShiftClick to select more than one face.

    If you are creating an offset mesh and you selected two-dimensional elements, Abaqus/CAE prompts you to indicate the side of your selection that will be offset. You can choose the Brown side, the Purple side, or Both sides.

    Abaqus/CAE colors your selection magenta.

  6. When you have finished selecting the source side, click Done in the prompt area.

  7. If you chose the Sweep method, you must select Connecting sides or a Target side or both to complete the mesh definition. Complete the following steps to make your selections:

    1. Toggle on Connecting sides, and click Select to choose one or more sides that connect the source side to the end of the mesh. Connecting geometric sides must be four-sided. You can also select four-sided element faces or two-dimensional elements that form a regular grid pattern. For more information, see Defining connecting sides for a bottom-up swept mesh.
    2. If you are working with geometry, you can toggle on Target side and click Select to choose a single face that Abaqus/CAE uses to end the swept mesh.

  8. If you chose the Extrude method, you must specify an extrusion vector and choose the extrusion depth.

    1. Click Select next to Vector to select two points from the viewport or enter coordinates in the prompt area to define the start and end points of the extrusion vector.

      Abaqus/CAE displays a yellow arrow in the viewport to indicate the extrusion vector.

    2. Select a method to define the extrusion depth:

      • Toggle on Use vector length to extrude by the length of the vector created in the previous step.

      • Toggle on Specify and enter an extrusion depth.

      • Toggle on Project to target and click Select to specify a target side. The target side must lie along the direction prescribed by the extrusion vector.

        Abaqus/CAE uses the target side to set the extrusion distance. The extruded mesh will closely match the shape of the target side, but it will not conform to a mesh on the target side. (For more information, see Bottom-up meshing methods.)

  9. If you chose the Revolve method, you must specify an axis and an angle of revolution.

    1. Click Select next to Axis to select two points from the viewport or enter coordinates in the prompt area to define the start and end points of the axis of revolution.

      Abaqus/CAE displays a yellow arrow in the viewport to indicate the axis.

    2. In the Angle field, enter the desired angle of revolution, in degrees, for the revolved mesh.

  10. If you chose the Offset method, you must specify the total thickness, and you can change the way two-dimensional mesh corners are offset.

    1. In the Total thickness field, enter the thickness for the offset mesh.
    2. For source sides containing shell elements that form sharp corners, toggle on Constant thickness around corners to maintain the same total thickness where the elements meet in the corner as in the rest of the selection. Using the option can reduce element distortion and prevent collapsed elements, especially if elements are offset to the inner side of a corner (for more information, see Reducing element distortion and collapse during mesh offsetting).

  11. Where applicable, enter the Number of layers to define the number of element layers between the source side and the end of the bottom-up mesh.

    Note:

    The Number of layers parameter is required for the Sweep method only if you specify a target side with no connecting sides. It is always required for the Extrude, Revolve, and Offset methods.

  12. If desired, enter a Bias ratio for an extruded bottom-up mesh to skew the thickness of element layers toward or away from the source side. Bias ratio is used in conjunction with Number of layers.

    The bias ratio is the ratio of the thickness of the element layer at the source side to the thickness of the element layer furthest from the source side.

  13. If desired, use the Options area to add the new bottom-up elements to element sets:

    Extend existing sets

    Each new bottom-up element will be added to any mesh sets containing its parent element from the source side.

    Create a set for new elements

    Create a new element set for the bottom-up elements. You can use the default set name or create a name for the set. If you are working with orphan elements, you can also create a separate set for each layer of elements. If you choose this option, Abaqus/CAE increments the base set name with -Layer-n, where n is the layer number.

  14. The Undo field near the bottom of the Create Bottom-Up Mesh dialog box allows you to undo and redo bottom-up mesh changes, mesh-geometry associativity changes, and mesh edits. You can access the same functions in the Edit Mesh toolset. For more information, see Undoing or redoing a change in the Edit Mesh toolset.

  15. Click Mesh in the Create Bottom-Up Mesh dialog box to generate the bottom-up mesh.

  16. Repeat Steps 3 through 15 to create another bottom-up mesh in the same region, or click Cancel to end the procedure.