For those who have studied structural dynamics or mechanical vibrations, it is highly probable that they have come across the dramatic story of Tacoma Narrows Bridge which has collapsed on November 7, 1940, four months after its opening to the public. The famous video is a proof of what might happen to a large structure under certain wind conditions: the bridge bended and twisted in such a way that in a couple of minutes, it sunk in the river.
This was the example that our professor used during the first lesson of mechanical vibrations course to stress how important it is to understand the behavior of structures under dynamic loads. Today, after seven years, I am joining the GVT Master Class in order to understand the dynamics behind a phenomena called “flutter”. Moreover I will learn how modal analysis is used to obtain in-depth knowledge of the structural dynamics and how structural testing is performed on full aircraft structures to avoid flutter.
I am a fresh starter at Siemens and I have worked as a test engineer before. Therefore, it is interesting to be present in a training this time as an insider, not as a customer as I did five years ago. While I am writing those lines, around 40 people from 10 countries are listening to my colleague’s presentation which explains the six steps of complete GVT. This edition of the Master Class hosts the largest number of participants ever in its history. What a success! But this event goes beyond a regular training. Guest speakers and other fresh starters from Siemens PLM Software are also here in Saffraanberg, Belgium.
But what is GVT? If you have ever heard of modal testing, you might be wondering why people came up with this terminology. GVT itself is modal testing of an entire airframe on the “ground” but the results are used to validate the structural Finite Element Model which will later on be used to predict “flutter”. For certification purposes, airplanes need to be free from flutter within their flight envelopes. But performing GVT requires special expertise: determining the correct number of accelerometers and shakers and their locations is not a piece of cake. One needs to be also very careful about the test setup as the number of accelerometers can go up to 500! And beyond that, the type of excitation signal is not straightforward to decide. Stressful, right? But I am not worried at all, because I know that after three days of intensive training, I will be ready to apply what I have learned on a small setup on the last training day.
Looking forward to attend the hands-on session on Friday!