Partitioning the unmeshable region and meshing the top-down regions

The example part (bottomup_mesh_example_part.sat) is imported from an ACIS file.

Context:

The file is included with the Abaqus installation, and you can use the following utility to obtain a copy: 

abaqus fetch job=bottomup_mesh_example_part.sat

For more information about ACIS files, see Importing parts from an ACIS-format file.

Figure 1 shows the original part. There are three solid regions; the regions colored green and yellow can be meshed using the top-down structured and swept meshing techniques, respectively, and the orange region is unmeshable with the automated top-down techniques and hexahedral elements.

Figure 1. Default mesh color coding on the imported part.

To mesh the part, we will first create three partitions. The first two partitions create another top-down swept meshable region near the outer edge of the unmeshable region. The third partition is a face partition that you will use later as a vector for the bottom-up extrude method. You could apply bottom-up meshing techniques to the entire unmeshable region without partitioning. However, the resulting mesh would contain some poorly formed elements near the outer edge. In practice, you may create several bottom-up meshes before you make a satisfactory mesh for the entire region. Especially for more complex parts, you may want to save copies of a part with different meshing approaches until you decide which approach yields the best mesh.

  1. Rotate the part so that you are viewing the bottom of the part, as shown in Figure 2.

    Figure 2. Creating an offset partition on the bottom face.

  2. Complete the following steps to partition the face:
    1. From the partition face tools in the module toolbox, select the sketch method tool .
    2. Select the bottom face of the part, and select one of the straight edges to be vertical and on the right.

      Abaqus/CAE opens the Sketcher.

    3. From the Sketcher toolbox, select the offset tool .
    4. Select the curved edge, and click mouse button 2 to accept the selected edge.
    5. Enter 2.5 in the prompt area as the offset distance.

      Abaqus/CAE displays a preview of the offset partition.

    6. Click OK if the offset is shown correctly (toward the interior of the part), or click Flip if the offset is shown outside the part.
    7. Click mouse button 2 or click Done in the prompt area to partition the face.

    Abaqus/CAE returns to the Mesh module and displays the partitioned face as shown in Figure 2.

  3. Extrude the face partition through the region.
    1. From the partition cell tools in the module toolbox, select the extrude/sweep method tool .
    2. Select the face partition created in Step 1 as the edge to extrude.
    3. Click Extrude Along Direction in the prompt area, and pick the edge shown in Figure 3.

      Figure 3. Extruding the face partition through the cell.

    4. Click OK if the extrusion direction is shown correctly (through the region), or click Flip to change the direction.
    5. Click Create Partition to partition the cell.

      Abaqus/CAE displays the outer region of the part in yellow, indicating that it can now be meshed using top-down swept meshing.

  4. Partition the front face of the unmeshable region as shown in Figure 4.

    Figure 4. Creating face partitions.

    1. From the partition face tools in the module toolbox, select the sketch method tool .
    2. Select the front face of the unmeshable region, and select an edge to be vertical and on the right.

      Abaqus/CAE opens the Sketcher.

    3. Use the vertical construction line tool to create a construction line as shown in Figure 5.

      Figure 5. Using a vertical construction line to partition the face.

    4. Use the connected lines tool to create a line connecting the two points where the vertical construction line intersects the face of the part.
    5. Create a second line connecting the upper point of the vertical line to the point where the fillet ends on the front face—the line should be nearly horizontal.
    6. Click mouse button 2 or click Done in the prompt area to partition the face.

    There are now three regions in the part that you can mesh using the top-down meshing techniques.

  5. Assign global edge seeds to the entire part using an approximate size of 0.9 and the default settings for curvature control.
  6. Select MeshPart from the main menu bar to mesh the top-down regions.

    Abaqus/CAE highlights the unmeshable region and displays a warning that you cannot mesh it automatically.

  7. Click OK to mesh the three top-down regions. Figure 6 shows the resulting partial mesh.

Figure 6. Automatic meshing of the top-down regions.