Assigning Boundary and Load Conditions

We next add boundary conditions and loading specifications to selected edges and vertices in the geometric model.

8. Add Displacement Constraints

The only boundary conditions used in our MinimalFEM analysis are displacement constraints. For our problem, we will constrain two edges: the bottom edge and the adjacent one to its left. To do this, click on the Constraints tab. The user interface in this tab is an attribute view, in which you create attributes as needed for your specfication. For this problem, only one attribute is needed; to add it, click the New button to the right of the Constraint label, and note that an item labeled constraint-0 appears in a list below the button. You can double click the name to edit it, but the default name is fine.

Below the list of attributes is a Displacement Constraint field with a selection box to choose the direction, with the choices X Direction (default), Y Direction, or X and Y Directions. Choose X and Y Directions from the list.

Below that is a Model Boundary and Attribute Associations widget – this is where you assign the displacement constraint attribute to model entities. For this problem, select edge 01 and edge 02 in the Available list, then click the arrow to move those entities to the left-hand list (Currrent).

_images/constraints-set.png

9. Set Loads

For our problem, we will apply two load conditions, one to the top-most edge and the other to a vertex on the right-hand size. To do this, click on the Loads tab to display its attribute view. In this view, we will create two attributes, one for each load.

  • Click the New button to create the first load attribute. Below that, find the Force (N) fields and set the Y-Force to -3.5. In the Available list, select edge 06 and move it to the Current list.

  • Click the New button to create the second load attribute. For the Force (N) fields set X-Force to -2.0 and Y-Force to -2.0. In the Available list, select vertex 04 and move it to the Current list.

_images/loads-set.png

10. Save the Project

We have now specified all of the information needed for our problem. Save the project once again by going to the CMB2D menu and selecting the Save Project item. The next step is meshing.