Running linear buckling analysis on an assembly

[Anonymous]

We are running linear buckling analysis on a rod made of three different parts in an assembly with varying diameters. When running the FEA, the maximum allowable force before buckling was 40kN. A simplified, single part was made based on the assembly and with the same analysis the result was 63kN. An approximate hand calculation gave a results of 72kN. Is Nastran reliable for buckling rods made in assemblies? Or perhaps we are doing something wrong???

[John_Holtz]

Hi @Anonymous

There should be "no" difference in the result between an assembly and a part. However, the obvious difference is the contact between the parts. That is where you should look at the models to find any differences. For example, are the parts bonded together properly? Is the maximum activation distance large enough, or is it too small and the parts are behaving something between a full bonded and pinned contact.

It may be easier to perform a modal analysis on both models and look for differences in the frequencies and mode shapes.

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