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Autodesk Sim 360 for On-Demand FEA

By Francis Sebastian, December 10, 2013

Autodesk Sim 360 is a Web-based FEA (finite element analysis) program meant for use early in the design process. It can be used to conduct studies on the effects of static stress, modal frequencies, structural buckling, fatigue, heat transfer, and thermal stresses - these were available at the time of the writing; more analyses may be added later. Autodesk targets the package at smaller engineering firms and independent consultants specifically, those that the company feels may have traditionally shied away from FEA because of either the investment required or time constraints.

What's Special About Sim 360?

There are a few things that are special about Sim 360.

Web-based. To begin with, Sim 360 is Web-based - '360' being Autodesk's moniker for Web-based services. This means that it can resolve a roadblock that prevents FEA tools from being used more widely: it harnessing the seemingly limitless processing power of what is more commonly referred to as "cloud computing."

This has several advantages, the first being that our computers are free to explore more design options even while the simulations are in progress. Another advantage is that the turnaround time afforded by Sim 360 should be faster, meaning more design iterations and incremental improvements within the same developmental cycle. And, Sim 360 has the advantage of storing multiple versions of simulations online.

Recognize that Sim 360 is not a Web-version of Autodesk's existing simulation software, but a product that was designed and then optimized to be used online. In my opinion, I think that Autodesk astutely identified at least one collateral Web advantage when developing this tool: integrating social collaboration with teams.

Faster FEA Results. Traditional desktop-based FEA tools are resource hogs. They typically take up the most powerful computers in the office for the longest period of time. Turn-around times could vary between a few tens of minutes to a few hours. This usually forces engineering teams to use FEA for design verification at the end of the design cycle when the major design decisions have already been made. As we all know, the cost of making last minute changes is far more than if those same changes were made in the beginning. Sim 360 is designed specifically to validate design assumptions early in the design process. (In the future, platform will handle large, complex studies.)

Effective Pricing. Although Autodesk has not announced pricing, Sim 360 will be available on a pay-as-you-go basis. This will allow users to pay for what they need, consuming cloud credits with each simulation solved. Other cloud simulation services consume between two and 20 credits for each simulation; cloud credits themselves are available in 100-unit packs for $100 each. I performed fourteen simulations using five models over a three-week period, so consumed a maximum of about 280 credits in the process.

Learner Friendly. To understanding the underlying principles of FEA and to learn to use the software is equivalent to one or two college-level courses, roughly. Let's take an example of a simple static stress analysis. As engineers, we would need to ascertain whether a part of a given geometry made from a given material will be stressed more - or less - than its yield strength. When the analysis is done early in the design cycle (that's when the specifics are still up-in-the-air), then the last thing that we would want to do is go through an elaborate set-up process.

This is precisely where Sim 360 fits in. Anyone with a basic understanding of statics (analysis where things don't move) can perform this kind of static stress analysis, with a handful of straight-forward variables like geometry, loads, constraints, and materials.

(Here I should disclose that I did not perform any of the other studies available with Sim 360, but going by my experience with static stresses, I believe that the processes for the others are similar.)

Integrated Communications for Design Collaboration. One of the most interesting aspects to Sim 360 is its built-in social networking. For me, this was the first time I worked with an application that could seamlessly integrate communication with design development. Given the current hype about 'social' capabilities in the tech industry, I am skeptical when this buzzword is used.

As it turned out, during my work with Sim 360 I needed help from Autodesk's experts to clarify some aspects of the simulation I was running and so I initiated contact via email, as usual. But then technical experts Jon denHartog and Tyler convinced me to use the in-app social feature for communicating (see figure 1). I found myself being reluctant to switch back to email.

Figure 1: Part of the simulation page indicating the simulation version and all related communication

In hindsight, the decision to integrate collaboration is brilliant (and, sadly, obvious). The in-application communication keeps records where it is relevant, close to the subject of the communication. I no longer have to waste time tracking back conversation strings and matching those strings with design versions or communication contexts. And unlike widely used email clients, the conversations are automatically minimized depending on the how recent and how long the exchange was.

The entire package is completed through an option to receive instant email alerts should someone message you via the application. Implied here is that Sim 360 manages versioning automatically, complete with author, timestamps, and comments if any.

Hands-on Simulation Experience

With the introduction to Sim 360 done, it was time to see how it really works. The first two steps are shown in figure 2:

  1. Select the type of simulation. I tested static stress.
  2. Import a 3D CAD model to test.

Figure 2: The first steps are selecting the simulation type, and then choosing the model source

Importing Geometry. Sim 360 accepts nineteen standard engineering model formats and those of Autodesk's competitors. The results I got from importing models varied according to the file format. Naturally, Sim 360 works very well with part geometry created with Autodesk's own Inventor and Fusion 360 program. But a few models from other MCAD programs caused an application crash, while a few others produced curved surfaces that were segmented (had flats).

So for simple parts I found it easier to simply rebuild the model within Sim 360. The vast majority of Fusion modeling capabilities (see figure 3) are available in Sim 360, so there should not be any need to access it separately, unless you work with industrial design or surfacing.

Figure 3: The model, of which a component will be simulated (sample file provided by Autodesk)

Simplifying and Editing the Model. Simplifying the model is typically done in two steps: suppressing parts that are not currently being analyzed and removing extraneous features such as fillets that may lengthen the simulation time without any meaningful impact on the results (see figure 4).

Figure 4: Suppressing components (left) and features (right)

I found the editing tools just as handy to create parts and modifications on the fly. These editing tools work with both solids and surfaces and are sophisticated enough to create production grade geometry without any of the lag commonly associated with online geometry editing tools. I should note here that while the suppression tool was able to remove most fillets, suppressing continuous fillets that turned corners sometimes caused the application to crash. (If the software cannot adjust geometry, it usually presents a message indicating the problem.) This typically happened when I inadvertently missed a tiny fillet segment in a continuous chain of fillets. In these cases, I had to either let the fillets remain or simply re-create the geometry using native tools.

Figure 5: Direction of work-flow indicating a linear, logical setup before the SOLVE signal turns green when all conditions to perform a simulation are satisfied. Properties for a given part can be accessed either from the ribbon, the browser on the left or from the dynamic right-click selector. The yellow arrows indicate that the material properties can be accessed from the ribbon on the top and the part can be selected from the browser/navigator on the left

Adding Constraints, Loads, and Materials. It appears that once the part is inside Sim 360, the remainder of the setup is fairly sequential and logical. All the tools can be accessed either from the ribbon to top (via drop down menus), or from the browser/navigator on the left via the right-click menu. My favorite is the dynamic right-click menu that varies based on the context and part that I have selected (see figure 6).

Figure 6: The right-click menu gives handy access to almost every tool that you could possibly need for the selected part

As I expected, placing loads and constraints was a breeze. There are both graphical and numerical input options both of which are intuitive because of the helpful visual icons that come with each of the tool-sets.

Solving and Reporting. Once the setup was complete and the geometry mesh generated, I ran the simulation. The application did warn me if the part is not adequately constrained.

Sim 360 can work with assemblies when contact conditions and prescribed displacements are specified. For this article, I simulated the stresses caused by a 10,000 lb-force tensile load on the strut that is part of a larger assembly (see figure 7).

Figure 7: Simulation results showing stress distribution in terms of Von Mises Stress with a customizable legend showing the maximum and minimum stress generated

From the results, I could tell that the current design would not fail under the test load. While the maximum stress generated within the part is 217MPa (mega Pascals), the yield strength of the material is 275MPa (according to the material definition in figure 5). This indicates that my part is safe.

Aside from identifying the maximum and minimum stress locations, the static stress study identifies safety factors, displacement, and strain distributions. One useful feature for further optimization studies is the ability to filter the view based on the stress level. I have shown one such filtered view below that gives a snapshot of all areas within the approximate upper quartile of the stress range (see figure 8).

Figure 8: Parts of the component experiencing higher stresses. This view can be helpful in deciding the course of action to take for part optimization. Obtaining this view is as simple as sliding the legend up to the requisite value as indicated with the red arrow

Once a satisfactory solution is obtained, the results can be reported in a dynamic HTML format, among others. The HTML format includes some options to customize the report, and even include a corporate logo. Also available is the ability to compare pairs of results of separate simulation including variations in geometry, loading, materials and constraints (see figure 9).

Figure 9: Side-by-side comparison of results for two different geometries

Conclusion

I found Autodesk Sim 360 a fascinating tool that made FEA seem deceptively easy for the expert and the novice alike. In the three weeks that I tested this program, I came to see how the application's responses were progressively improving; there were fewer crashes and more comprehensible error messages. This led me to believe that I benefitted from another big advantage of Web-based applications: instant, ongoing product updates.

This product is designed for the initial phases of engineering, where the engineer is very much in the realm of 'possibility' and so the tool does not need to serve the simulation analyst. I am certain that every mechanical engineer will appreciate how it makes some of the most complex engineering analysis accessible, timely, and presentable.

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About the Author

  Francis Sebastian is an architect by training. He teaches, supports and provide implementation services for the AEC industry in the New York tri-state area and writes for his para-analytics blog. More....

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