FEA helps us shorten the design process and save customers money.
From the beginning, engineering has concerned itself with making sure that a product or structure won’t fail in service because it isn’t strong enough.
VIRTUAL TESTING To create a component design that is reliable, the design team must understand how loading, vibration, fatigue and heat transfer will impact the part in its application. Without a method of virtual testing like FEA, designers must make prototype parts for testing purposes, then revise their designs based on the results of that testing. This can be a slow and costly process. RL Hudson’s Product Design Group uses a powerful FEA software package to analyze component design models and quickly modify designs when changes are indicated.
Since our design engineers are involved in the development of a variety of product types—molded rubber, molded plastic, formed hoses, sealing products, and assemblies—we apply FEA across a variety of products, applications, and design requirements. FEA is valuable in helping to solve production part problems, but more often we use it early in the design cycle to improve and confirm designs so that design-related product issues can be avoided entirely. In addition, FEA is useful in comparing alternate design concepts.
An example of how we use FEA is to predict the minimum wall thickness, or rib structure of molded rubber ducts (see the image at the top right). These ducts must handle vacuum or the relative displacement of the ends without the duct collapsing beyond a safe limit. In this case, we use FEA to predict displacement and are much less concerned about stresses in the duct.
LIMITATIONS Another common use of FEA is to confirm that stresses in a part due to application loads are within acceptable limits. However, we have repeatedly found that application loads are often much lower than installation stresses or accidental loads such as someone stepping on a part (yes, it does happen). And this brings up an important point: FEA is a useful tool, but it must be applied with a thorough understanding of materials and applications.
ADDITIONAL ANALYSES In addition FEA, we often do a DFMEA (Design Failure Modes and Effect Analysis). This basically consists of brainstorming all the ways a design could fail, and making sure we cover those with analysis, testing or both. In addition, we often do a “matrix of analyses” on a project. By running multiple analyses using different materials, different durometers (hardnesses) of rubber, different temperatures, LMC (Least Material Condition) and MMC (Maximum Material Condition), etc., we ensure that, even in the worst case scenario our customers will have a product that still performs well.
In most cases, such as for the molded oil adapter (bottom right), our physical testing confirms that the FEA predictions are within acceptable accuracy. In some instances, the predicted loads at failure may vary, especially when friction is involved. But in general, trouble spots are correctly predicted by FEA.
FEA software, in combination with knowledgeble engineers and complementary testing techniques, is a very useful tool when designing a new component. To paraphrase an old expression, it’s not the quickest way to design a part, but it’s the quickest way to design a part right.