Structural Simulation

Prototypes are an invaluable part of the product development process. The question is how many prototypes do you need to build before you get it right? The answer may depend on how many of your design problems can be accurately simulated using finite element analysis or other techniques. Structural problems are present in one way or another in most everything that gets designed and finite element analysis can be a significant knowledge building tool.

It may be as simple as a quick dynamic strain analysis to make sure a plastic snap doesn't fail on assembly. Or it could be as complicated as a large statically indeterminate structural analysis composed of multiple parts, fasteners, material nonlinearity and contact regions.

Finite element analysis really comes into its own on projects where building multiple rounds of prototypes is prohibitively expensive or time consuming. On a recent project it was going to take 7 weeks just to get a piece of plastic large enough to CNC machine the structural plastic parts we were designing. With that kind of time on the line you need to know that the parts will be strong enough when they show up.

How many stress cycles can a given part take before failing? Fatigue analysis is another great application of finite element analysis because laboratory fatigue testing can take weeks or months to complete. For a recent power generation project there was simply no way to test the fatigue performance of critical components before the pilot run of parts. Finite element analysis was used to give confidence that the power shaft would last the life of the unit.

Modal simulation is another type of finite element analysis that can be invaluable. If a component has a natural frequency that is close to the forcing frequency from a motor or external vibration, it's better to know up front than have to deal with the problem once the design is in production. When designing a GLS tracking system for over the road trucking use, it was important that internal components such as batteries and antennas did not resonate due to vibrations typically present in that application.

Sometimes you don't need a stress analysis to know that a part is strong enough, but the question is will it "feel strong enough" to the end user. Often the key issue here is the stiffness of the part, more than the ultimate strength. Finite element analysis can easily be used to determine the stiffness of a part or assembly in a given direction. Then an equivalently stiff piece of stock material can be used to get an understanding of how ridged the part will feel once manufactured.

Much of our work involves judgment calls, especially when considering qualitative factors like perception of quality. We work closely with our colleagues on the design and research side and provide the team with results from finite element analysis and other methodologies to build confidence for solutions. Finite element analysis also helps us optimize the part for efficient manufacturing. Sustainability is a growing part of our design practice. Tools like finite element analysis help us to provide the right function and feel while driving down material usage and waste.

In our finite element analysis consultant work, we try to break out the individual issues that can be quickly and accurately simulated early in the design consulting process.

For instance, it's not uncommon during concept generation to come up with a wide range of materials and manufacturing methods that could be used in the design of a given product. We ran into exactly this situation with the semi trailer tracking unit. We wanted to replace existing die cast aluminum housing with polycarbonate, but needed to be confident up front that it would be both strong and durable enough.

Finite element analysis of very simple design models gave us that confidence within the first few weeks of the project. Ultimately the polycarbonate enclosure helped reduce the casework cost by over 50% and passed its rigorous 10 ft drop, submersion and vibration tests on the first try.

Since structural simulations are generally some of the more straight forward types of finite element analysis they frequently get examined on the front end as we get into our finite element analysis consultant projects.

We use these analysis tools in our consulting practice to answer "big picture" questions as soon as possible: How big does an element need to be? How much material will it take? How heavy will each element be? What material should an element be made of etc... The more of these items that get locked down in the beginning phases of a consulting project, the more efficiently the rest of the project can run.