For shaker- and flight test in aircraft development, replacement bodies with similar physical properties as the real body (like a black box) have to be created.
A body like this is called DUMMY and the meant properties are mass, center of gravity in x-, y- and z-direction, as well as inertias (in total 10 components).
These dynamic tests are essential to generate adequate mountings/bearings or to reproduce the real behaviour of an airplane or a subsystem in flight.
Dummies are used when the exact part is not (yet) available or the part is too expensive to destroy it by testing.
To produce dummies, results within 10% deviation (per component) are necessary for dynamic similarity. By trial and error it is possible to create such a body, but it is either time intensive or the precision is not very high. The higher the accuracy of all 10 components of mass properties, the better is the similarity and the better will be the results for mountings and bearings.
Based on an inertia program with shape code calculation capability, an iterative process to create a dummy was developed. By variation of at least 4 bodies it is possible to get first results in all components. Up to a variation of 8 bodies and more is possible. To get good results in acceptable time and effort, a well-thought-out code is essential.
This iteration process produces a lot of data, but with effective code and modern computing hardware it is possible to create more than 100.000 iterations per hour, where one of it is a best fit within 5% deviation or better.

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