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Forums > COE Forums > CATIA V5
Subject: CATIA V5 Generative Assembly Structural Analysis

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COE-FORUM-USER

21 Jan 2002 07:17 PM
I'm assuming that you are using CATIA V5R7 Generative Assembly Structural Analysis (GAS) for performing an analysis of your assembly. You haven't provided sufficient detail to decipher the exact nature of your problem but you indicate that you believe that you have reached a limit in the number of parts that are allowed in the FE analysis of an assembly. To my knowledge there aren't any limits on the number of parts allowed in an assembly analysis (at least I've not seen any limits documented). I've performed assembly analysis on many assemblies including about 25 part assemblies successfully. Most of the time the problems (errors) encountered in performing GAS are related to the connectivity between the parts. If that sounds a possibility then read on... You must assure that free body motion is eliminated for every part. This is particularly tricky when utilizing the (analysis) contact connection in GAS. As an example: consider a simple case of a bolt and nut (no threads included) used to clamp two flat plates together. You might apply (analysis) contact to five surface connections (1) under side of the bolt head to first plate, (2) first plate to the second plate, (3) nut to second plate, (4) bolt shank to bolt hole in first plate, (5) bolt shank to bolt hole in second plate. Apply fixed analysis connection between the bolt shank and the hole in the nut. Additionally, you'll need to restrain both plates from rotation about the cylindrical axis of their bolt holes and at least one plate from translation in X,Y,Z. Finally the most forgotten restraint =>don't forget to fix the rotation of the bolt about it's own longitudinal axis of the bolt shank (since the analysis contact does not include friction, the bolt and nut will spin about their axis) . Apply your desired loads and run the computation. If you get a singularity in your results then most likely you have free body motion that you've forgotten to restrain. Usually, you can visualize the free body motion causing a singularity by picking the icon to show displacenents and then pick the icon to animate the results. This is where it might be difficult to see a bolt rotation about the axis of the shank unless you focus on the bolt head rotating.

Author: Hans Kraus
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