To test or not to test

  • 27-Oct-2011 03:42 EDT
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Simulations of components, such as bearings, are frequently used to replace extensive testing. (Timken)

With the growing power of computers and sophistication of CAE software, is it getting harder to decide when to use CAE simulation vs. physical testing?

For certain applications, such as bearings, Timken uses CAE throughout the product development process. Its engineers use the company’s Syber Bearing Program, according to Matthew Eckels, Chief Engineer for Applications Engineering for Timken. He believes using it early in the development process is most effective, to quickly evaluate design alternatives and weed out unlikely candidates.

“With CAE, the accuracy of analysis has dramatically improved,” he said. It provides the means to efficiently analyze and understand multiple variables simultaneously. Prior to CAE, engineers calculated by hand, limiting the ability to analyze key factors like misalignment, load zone, lubrication, and debris.

“Thanks to robust analytical tools such as Syber, Timken engineers help minimize cost and time [in] physical testing,” he said. “In fact, customers rely on Timken analytical capabilities and performance predictions.”

He related that customers would sometimes forego testing based on prior experience and actual field performance correlation, though final validation testing remains key to ensuring quality and performance.

“We also test to reinforce our analytical algorithms in our bearing analysis software,” he added.

Dan Kline, Manager of Business Development for Defiance Testing and Engineering, makes a distinction between components, such as bearings, and systems, such as vehicle suspensions, cooling systems, and towing packages.

“We used to physically test components, now components are mostly evaluated using CAE simulations [for fatigue and NVH],” said Kline. “However, when it comes to systems of components, physical testing tends to be more accurate. Modeling interfaces is difficult—things like bushings, welds, and joints.”

As an example of how CAE simulation is improving even in systems, he cites that analysis of trailer hitch fatigue systems is “on the cusp” of transitioning from physical test to CAE simulation. Fatigue and durability analysis is another area where CAE is becoming more powerful.

“CAE is typically used for ultimate tensile strength and static or peak load stress while physical testing is typically for fatigue and NVH— however, that is changing as well,” he noted.

He also observed that the business is changing as CAE improves and test cell equipment becomes a hybrid of simulation and hardware.

“The question for us is how we transition our business most effectively,” he said. A part of the vision for that transition is to have CAE and test engineers in close proximity, to give CAE analysts that crucial “gut feeling” for the accuracy of their results. Separating test engineers and modeling engineers leads to surprises.

“We have seen where CAE modeled a situation, and because they did not understand the proper boundary conditions, that caused analysis issues,” he said. The challenge becomes one of skill set balance and then selecting the appropriate evaluation method.

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