Yep... it's that time again. Time to discuss the one of the best tools Inventor has in its bag of simulation goodies. I have personally waxed philosophic on Optimization several times, and thought with the new release it may be time to speak in glowing terms about the usefulness of this process yet again. So, what is Parametric Optimization and why is it important?

Consider the following example...

This is one of two rear wing support struts from an open wheel (F1, CART, etc...) race car. Under max load, determined with a Single Point analysis, there is a little more than 1.3mm of displacement of the structure. How can I determine what is the best combination of changes that will allow me to minimize this movement, while maintaining an acceptable factor of safety as well as keeping the overall mass to a minimum?

This is a simplified example of the exact problem that Optimization was designed to solve. Now the first thing I need to do is to either change or copy the existing Simulation and set the Design Objective to "Parametric Dimension".

Once this is done the Parametric Table function is used to build optimization criteria. Basically, this entails selecting any of the results that we normally get in the course of a single point simulation, and using those results as design target drivers. Check it out...

With the Parametric Table open a right click in one of the Design Constraint columns allows me to select any of the simulation results...

As I stated previously, I am trying to minimize the deflection of the wing structure, so I select "Displacement" as my first Design Constraint. The same process allows me to add Mass and Von Mises Stress as the other two criteria that I will monitor to help drive the changes to the model.

Now I have to select a single or combination of parametric dimension or user parameters to manipulate and facilitate the geometric change to the model as a function of the Design Constraints. As I have a specific feature in mind to change, I use Feature Priority as my select mode, pick the face of one of the pockets on the strut, right click and select "Show Parameters".

All of the model and user parameters for the selected feature will be displayed in a dialog box, and the one(s) used to drive parametric change is(are) selected.

The current value for this parameter is 7.5mm. I am going to use a set of three configurations from which to select the best to meet the objectives set by the Design Constraints.

Adding two new values for parameter d2... 4.5mm and 6mm I now need to generate temporary geometric configurations that will be used during the optimization.

As you can see there are several options available, as this is a small set of configurations I am going to generate all of them. Once that is done all that is left to do is run the simulation. Now, based on the size of the configuration matrix there are a couple of options to think about when running. Keeping in mind that these are linear static stress and strain problems that are being solved, if there is a large enough matrix the "Smart set of configurations" can be used to reduce solution times.

Consider for example if I had selected three different parameters to drive, with three values for each parameters, and of course the three Design Constraints. That matrix consists of 27 total configurations, but Smart set can be used to reduce that number to 7, with interpolated results for the other 20... a much faster way to solve for a large numbers of configurations.

In any case, once the simulation is run, the best combination of changes can be selected either manually by moving the slider for each set of parameter values, or an optimal configuration can be selected by driving one of the Design Constraints. For example, I noted before that I wanted to minimize deflection of the strut. By selecting that "Constraint Type" from the Design Constraints, and then selecting Minimize for both Mass and Von Mises Stress, the best combination of settings is selected to meet that set of design criteria.

This tool allowed me to significantly reduce the amount of deflection, while meeting the rest of the requirements set by the Design Constraints. At this point, right clicking in the Parametric Table dialog box allows the user to "Promote" this new configuration back to the model.

I realize that is a LOT to take in, but I think you will find that if you try this functionality on a small scale to begin with, you will quickly realize just how powerful a design tool it actually is.

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