You can define a nonuniform distribution of elements along selected edges by defining the size of the coarsest and finest element along the edges or the number of elements and the ratio of the two sizes. You can define a single bias that changes the mesh density from one end of the edge to the other. Alternatively, you can define a double bias that changes the mesh density from the center of the edge to each end of the edge. For example, Figure 17–138 shows a combination of edges with single- and double-bias seeding.
All the edge seeding tools generate edge seeds, which are displayed in magenta. Edge seeds override any part or instance seeds you have specified. You should apply seeds to all edges.
To prescribe biased seeding along an edge:
From the main menu bar, select Seed
Edges.
Abaqus/CAE displays prompts in the prompt area to guide you through the procedure.
Tip:
You can also click the 
tool, located with the seed tools in the Mesh module toolbox. (For more information, see “Using the Mesh module toolbox,” Section 17.15.)
Choose the approach for picking from the viewport:
For single-bias seeding, toggle on Use single-bias picking and select the edges you want to seed. You can select only edges for single-bias seeding, and you must select each edge near the end where you expect the mesh to be denser.
For double-bias seeding, toggle off Use single-bias picking and select the edges, faces, or cells you want to seed. The location of your selection does not influence the seeding.
By default, Abaqus/CAE allows you to select only edges to seed. To select faces or cells to seed, use the Selection toolbar to change the type of object that you can select to Face, Cells, or All. For more information, see “Filtering your selection based on the type of object,” Section 6.3.2.
When you have finished selecting edges, faces, or cells, click Done in the prompt area.
From the Local Seeds dialog box that appears, choose the bias control (Single or Double).
Note: If you selected edges that you previously seeded using a combination of bias seeding methods, Abaqus/CAE provides an As Is option that allows you to retain the bias seeding method on the selected edges.
If you selected single-bias seeding, Abaqus/CAE displays arrows on each selected edge indicating the direction in which the element density will increase. If you selected double-bias seeding, Abaqus/CAE displays arrows at the center of each edge indicating the directions in which the element density will increase.
Choose the sizing method (By size or By number).
If you selected By size, enter the minimum and maximum size of the elements—the approximate size of the elements at each end of the biased seeding. You cannot apply curvature control to biased seeding.
If you selected By number, enter the number of elements and the bias ratio. The bias ratio is the approximate ratio of the size of the largest and smallest element on the edge and must be greater than one.
If desired, click Select to reverse the direction of the seeding bias. (When you select an edge to which biased seeding will be applied, the element density increases toward the end of the edge that is closest to the location of your pick.)
Abaqus/CAE reverses the direction of the arrow on each selected edge.
Note: If you selected edges that you previously seeded using a combination of element size or number parameters, Abaqus/CAE provides an As Is option that allows you to retain the size parameters on the selected edges.
If desired, change the default seed constraints by clicking the Constraints button in the prompt area and responding to the dialog box that appears. See “Applying constraints to edge seeds,” Section 17.16.5, for further information on setting seed constraints.
If desired, toggle on Create set with name to create a set containing the edges, faces, and cells you selected and enter the name of the set. If you subsequently want to change the seeding, you can select the set in Step 2 without having to reselect the edges, faces, and cells.
Click Apply to view the seeding that Abaqus/CAE will use.
Magenta seeds appear on the selected edges.
If necessary, adjust the values that you entered in the Local Seeds dialog box.
Click OK to commit the element seeding and to close the dialog box.
