You can apply constraints to seeds at the same time you define them by using the Constraints tabbed page of the Local Seeds dialog box that appears during the edge seeding procedures.
Caution: Use care when constraining mesh seeds; overconstraint can make automatic mesh generation impossible if you are trying to generate a mesh that contains quadrilateral- or hexahedral-shaped elements.
To apply constraints:
From the main menu bar, select Seed
Edges. Then select the edges that you want to seed, and click mouse button 2. For more information on performing these tasks, see the following sections:
“Seeding an edge by prescribing the number of elements,” Section 17.16.2
“Seeding an edge by prescribing element size,” Section 17.16.3
Note: If you selected edges that you previously seeded using a combination of constraints, Abaqus/CAE provides an As Is option that allows you to retain the constraints on the selected edges.
Abaqus/CAE displays prompts in the prompt area to guide you through the procedure.
Click the Constraints tabbed page of the Local Seeds dialog box.
Choose the desired constraint. The choices are:
Allow the number of elements to increase or decrease
This option leaves the seeds totally unconstrained. Therefore, the number of elements that Abaqus/CAE creates along an edge can be greater or smaller than the number of elements dictated by the seeds; however, the mesh generator tries to adhere to the requested seed pattern as much as possible. This option provides the greatest flexibility to the automatic mesh generator and, therefore, gives the greatest chance of success when generating the mesh.
Allow the number of elements to increase only
This option (default) partially constrains the seeds so that the number of elements along an edge can only be greater than or remain the same as that dictated by the seeds. Unconstrained seeds that are located near partially constrained seeds tend to behave as though they are partially constrained.
Do not allow the number of elements to change
This option fully constrains the seeds so that the exact number of elements that you have specified with your seeds is maintained.
Use this option with care, since adjustment of the number of elements along the boundary of a region is usually required to generate a mesh; preventing such adjustments can make mesh generation impossible.
Note: The constraint options described above allow you to control only the number of elements along an edge, not the positions of the nodes along the edge. Abaqus/CAE creates meshes that adhere to the seeds as closely as possible.
Click OK.
The mesh seeds change shape to indicate the constraint you have chosen:
Circle: unconstrained seed.
Triangle: partially constrained seed. The triangle points upward, indicating that the number of elements along the edge can only increase.
Square: fully constrained seed.
