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By Chris McAndrew, September 23, 2013
Solid Edge ST has simulation, goal seeking, and model validation functions that are designed to automate what is usually a time-consuming optimization process. Designers and engineers are in an ongoing battle to reduce material usage, maximize efficiency, eliminate waste, and in general find ways to do more with less. When it comes to designs, however, this involves setting up complicated sets of rules to reduce one variable, while maintaining the integrity of others. Solid Edge ST 6 now offers us a host of options to set up multiple simulations. In this First Look article, I'll scratch the tip of the optimization iceberg.
For setting up simulation studies, I am a fan of "wizards" that help me by stepping through the process. Solid Edge does not, unfortunately, have a wizard for simulation, but its ribbon menu lays out actions in the order that they need to be carried out (see figure 1). I found that the ribbon made loads and constraints easy to add - along with the prompt bar that identifies clearly which selection the system is looking for. I was able to setup a basic force study in about a minute. I did this initial setup of a sample part to test the new Optimization function in Solid Edge ST 6.
Figure 1: Simulation ribbon in Solid Edge ST 6
Solid Edge’s simulation is great, but any simulation is unlikely to be used for complete FEA analysis unless it helps in changing the design of parts. In the past, I have even resorted to manual optimization, testing out different wall thicknesses and component sizes to see which one works best. The new optimization function in Solid Edge ST 6 solves this, and does it in a pretty easy way.
(But first I should make this important note: optimizations can only be run after a simulation study has been created. This is because it pulls in all the information from the simulation results and uses the results for variables in the optimization.)
Selecting optimization variables in Solid Edge ST 6 works more like a wizard than do simulations. Here's how it works: After I selected the New Optimization function, Solid Edge presented me with a dialog box listing five fields that I needed to define. Each of the fields came with a prompt window that narrowed the field of selection. The first one is the design objective (see figure 2):
Figure 2: Design objectives as the first step in simulation optimization
At first, the list of possible objectives left me perplexed. In my case, my goal was to define a dimension, such as a wall thickness, and not the mass of the part. Then I realized that this is different type of goal entirely. I found Goal Seek on the Inspect tab that offered some of these capabilities. Ultimately, there are multiple ways to reach answers, but Simulation is used for the ones that relate to the output of a simulation.
At this point, I realized that Solid Edge ST 6 is getting closer to being a full FEA solution. Each of the listed design objectives can be selected to minimize or maximize, and relies on a meshed solution of a complex equation. Solid Edge can also define a target solution.
Of course these three selections cover every possible scenario for one variable, but not all variables. For this, there are design limits, which are limited to the ones shown in the list above. This is a bit misleading, because stress and mass may not be the only limitations. A specific dimension may also be a design constraint, as I first assumed when thinking about the simulation. However, the design variables basically allow the user to select which variables can be used to change the size or shape of the model, such as thickness. The wizard immediately displays the variable table which shows every feature dimension, value, and formula that exists in the model.
The next selections are the control parameters, which is a bit misleading. Really, all that is needed here is a number to define the maximum number of iterations that will be used of the during the optimization. By choosing a ridiculously high number of iterations, I can ensure a more accurate final result of course, but this takes longer to process. In my tests, there seems to be a near linear relationship number of iterations and processing time.
Last up is the job of specifying the convergence parameters. These values define the equation used for optimization, and is one place where I have to admit that I have little idea how to accurately set up the system. For instance, "Design Limits - Max Violation %" presumably defines how far over the design limits a solution will be accepted. In general, I am inclined to keep the default values for everything. Changing any of them, however, did not seem to have an effect on the results, or the time it took to reach the results.
Figure 3: Solid Edge automatically pulling in every available feature variable
There was one additional feature, unrelated to optimization, that I found interesting. The results of simulations can be over whelming but Solid Edge gives a nice variety of viewing styles. Before jumping into optimization and goal seeking I checked out the various viewing options including watching the animation of the part deformation and a new favorite of mine the dynamic ISO contour. Heat maps are the standard way to view stresses but it is difficult to tell any value peaks that are not at the failure point. Having this dynamic has provided the opportunity to view the simulation results in a more detailed fashion. When leaving optimization up to the software I find anything that makes me think of questions helpful.
Figure 4: Dynamic Iso View showing the location of all forces of a certain value
My previous experience with simulation and analysis software is with SolidWorks and Inventor, both CAD systems that have bolt-on solutions. Both allow for some analysis, but I know that the basic packages are just that, basic. Their FEA packages are great for quick checks, but massive assemblies that require failure checks and certifications require a more robust software package.
When it comes to part design and feature optimization, though, Solid Edge ST 6 offers a better selection of options. The optimizer is a powerful tool and in the right hands it certainly saves a lot of time and money for engineers and organizations. Overall, the simulation features I experienced in Solid Edge ST 6 are on par with other systems. Designers looking for ways to enhance their designs and prove the value of a robust CAD system are wise to find out how they can best utilize these simulation features.
|Christopher McAndrew develops and markets toys and children's products. He has a bachelors degree in mechanical engineering from Tulane University. Chris writes the 3 Dimensional Engineer blog. More...|