A small amount of test data can go a long way to reducing the analysis effort. And it can be easy and inexpensive to acquire.
For example, this could be the temperature of electronic components within a circuit card, or wind loads on a structure. The methods by which electronic component manufacturers provide heat dissipation data can vary widely. These can be anywhere from mounting the component on a small circuit card and applying power, to suspending the component in midair and applying power to it. Quite obviously, the heat dissipation characteristics are going to vary considerably under these two scenarios. Neither one of these scenarios will accurately reflect the installation of the component on a custom board.
Using the electronic component as an example, the temperature of a component on a circuit card can be acquired in several ways. A thermocouple can be attached to the component in question, or an infrared scanning device could be used to pull the temperature at several places surrounding the component, as well as on the component itself. This could also be done with the thermocouples, however using an infrared sensor makes this task quite simple, effective, and quick. Thermocouples have the advantage of being able to provide temperatures inside an assembly.
The best way forward is to acquire test data from a functioning prototype where acquiring this information by computer simulation would be difficult to do accurately. The general idea here is to extrapolate over the shortest “distance” possible. This will undoubtedly shorten the time and therefore costs involved in generating an accurate simulation.
One of the areas that comes to mind is in fluid flow simulations combined with heat transfer interactions with natural or forced convection. Fluid flow simulations can be computationally expensive. Not only does the actual assembly model have to be simulated, but also the fluid flow-usually air-throughout the assembly model must be simulated. If a fairly simple and inexpensive test can provide temperature information under real-world conditions, the simulation effort can be greatly sped up.
Aerodynamic analysis is another key area where test data can be combined with finite element analysis – specifically computational fluid dynamics (CFD). Having designed and conducted many wind tunnel and other aerodynamic-related tests over the years, I have come to appreciate having some real-world data available to calibrate a CFD analysis effort. Test results likely do not exist for the exact simulation that you may be after, but using test results as a way to get a “sanity check” on your CFD model – or a portion of it – can provide a real boost in confidence that you are on the right track. Literally thousands of aerodynamic tests were conducted by our military, universities and corporations that are available at no charge just for the asking, if internet searches can be called that. Often it is possible to combine the results of several tests along with a basic understanding of fluid mechanics to arrive at a pretty good estimate of the results you need. From there, running the final CFD analysis becomes much faster along with having the confidence to back up your FEA/CFD results with actual data.
Norman T. Neher, P.E.
Analytical Engineering Services, Inc.
Elko New Market, MN
www.aesmn.org
AES takes a practical, straightforward approach to engineering analysis and problem-solving.
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