# Goals and Constraints

In the Goals and Constraints PropertyManager, you set the optimization goal and the geometric constraints that drive the mathematical formulation of the optimization algorithm.

To access the Goals and Constraints PropertyManager:

• In a Topology study tree, right-click Goals and Constraints, and select one of the three optimization goals: Best Stiffness to Weight Ratio, Minimize Mass, or Minimize Maximum Displacement.

## Select Goal

 Best Stiffness to Weight ratio (default) The optimization algorithm yields the shape of a components with the largest stiffness considering the given amount of mass that will be removed from the initial maximum design space. When you select Best Stiffness to Weight ratio, the algorithm seeks to minimize the global compliance of the model which is a measure of the overall flexibility (reciprocal of stiffness). Compliance is defined by the sum of strain energies of all elements. Minimize Maximum Displacement The optimization algorithm yields a shape that minimizes the maximum displacement on a single node (calculated from a static study). With a given percentage of material to remove from a component, optimization yields the stiffest design that weighs less than the initial design and minimizes the maximum observed displacement. Minimize Mass with Displacement Constraint The optimization algorithm yields a shape that weighs less than the maximum size model and does not violate the given target for the displacement constraint. The algorithm seeks to reduce the mass of a component while restricting the displacement (max observed value of component or user-defined at a single node) under a certain limit.

## Constraints

Constraints limit the design space solutions by enforcing the percentage of mass that can be eliminated to be under a certain value, or by setting performance targets for the maximum displacement observed in your model. You can define up to two constraints for one optimization goal. The User Interface filters the type of constraints you can apply based on the goal you select.
Mass constraint Set the targeted mass that the part will be reduced by during optimization. Select one of the following:
 Reduce mass by (percentage) Type the targeted percentage of mass reduction Reduce mass by (absolute value) Type the exact value of the mass to remove from the part's maximum design space.
The optimization algorithm will attempt to reach the targeted mass reduction for the final shape through an iterative process.
Displacement constraint Sets the upper limit for the selected displacement component. In Component, select the desired displacement variable. Select one of the following:
 Specified value Type the targeted value for the selected displacement variable, and set the desired units in Units. Specified factor Type a factor to multiply the maximum displacement calculated from a static study.
Select one of the following for a reference vertex location for the displacement constraint:
 Automatic (single max point) The program selects by default the vertex of the maximum displacement observed in the model. User defined Select in the graphics area the reference vertex for the displacement constraint.