Creating local stop conditions

A local stop condition is an optional setting that indicates to the Optimization module when your optimization has converged on a solution. For example, you can specify that an optimization is complete when the change in an optimization function drops below a specified value between iterations. You can choose the variable that will be compared, such as displacement or equivalent stress. You can choose the comparison operator—greater than, equal, to, less than, etc. The change in optimization function can be calculated from the previous iteration (default) or from the first iteration.

In addition, when you create an optimization process in the Job module, you can enter the global stop condition—the maximum number of optimization cycles that should be completed before the optimization process ends. For more information, see Creating and editing optimization processes. In most optimization problems you will use only the global stop condition. Local stop conditions are supported by only shape optimization and are rarely required.

  1. From the main menu bar, select Stop ConditionCreate.

    The Create Stop Condition dialog box appears.

    Tip: You can initiate the Create procedure in two other ways:

    • Click Create in the Stop Condition Manager. (You can display the Stop Condition Manager by selecting Stop ConditionManager from the main menu bar.)

    • Click the tool in the Optimization module toolbox.

  2. From the Create Stop Condition dialog box that appears, enter the name of the stop condition and click Continue.

  3. From the viewport, select the region to which the stop condition will be applied or click Done to apply the stop condition to the entire model.

    By default, Abaqus/CAE allows you to select all of the model. To select faces or cells, use the Selection toolbar to change the type of object that you can select to Face or Cells. For more information, see Filtering your selection based on the type of object.

    If you would rather select from a list of existing sets, do the following:

    1. Click Sets on the right side of the prompt area.

      Abaqus/CAE displays the Region Selection dialog box containing a list of available sets.

    2. Select the set of interest, and click Continue.

    Note:

    The default selection method is based on the selection method you most recently employed. To revert to the other method, click the button—Select in Viewport or Sets—on the right side of the prompt area.

  4. When you have finished selecting the stop condition region, click Done in the prompt area. For more information on selecting objects, see Selecting objects within the viewport.”

    The Edit Stop Condition dialog box appears.

  5. Choose one of the following operators for calculating the objective function:

    • Maximum value

    • Minimum value

    • Sum of values

    • Number of values

  6. Select the variable that will be used by the stop condition. You can choose either a displacement or an equivalent stress for a shape optimization.

    • The displacement of each node from the original shape. You can select the overall displacement, only the displacement due to the addition of material, or only the displacement due to the reduction of material. In addition, you can select the relative value of the displacement or the absolute value.

    • The equivalent stress in a shape optimization. You can select the equivalent stress of the whole model or the equivalent stress calculated from the following:

      • Only the nodes in the region selected for the task.

      • Only restricted nodes in the region selected for the task. Restricted nodes are restrained by a constraint or an Abaqus boundary condition.

      • Only free or unrestricted nodes in the region selected for the task. Free or unrestricted nodes are unconstrained.

      • Only surface nodes.

  7. Select the comparison operator.

  8. Select the iteration that will be used to define the reference value. The Optimization module compares the current value of the optimization function with the reference value.

  9. If desired, enter a value and the operation that will be used to modify the reference value. In effect, you are normalizing the value of the variable that is defining the stop condition. For a discussion of the reference value, see Objectives and constraints.

  10. Click OK to save your data and to exit the editor.