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Linear buckling and eigenfrequency analysis.

Posted 2024年12月5日 GMT-5 11:56 MEMS & Piezoelectric Devices Version 6.2 0 Replies

Lukas Barauskas

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Hi, I am trying to recreate some results in a paper for a structure which undergoes buckling and then an eigenfrequency study. The eigenfrequencies the paper obtains are 24.9, 33.9, 38.2, and 39.6 Hz for the first 4 modes. In my study i am obtaining frequencies of 35.85, 50.66, 55.55 and 58.8 Hz for the first 4 modes. I have attempted a variety of different constraint settings and triple checked my geometry. I have also tried the Solid structural and Shell settings with them both yielding similar frequency values under the same settings (unsupprisingly).

Currently, i am prescribing equal and opposing displacements on the ends of the region to be buckled, with a rigid connector to limit rotation (attempted to use the prescribed displacement for this purpose, but had difficulties with geometrically nonlinear convergence). I am conducting a linear buckling study, with which i declare a buckling imperfection. Using the imperfection i move onto a pre-stressed eigenfrequency study with the geometric non-linearity enabled for the stationary step.

Using these steps, i obtain the right mode shapes for the frequencies, but there is a large discrepancy in the frequencies i am comparing it to.

I have checked all my material settings, my geometry, the declared thickness (in the shell model) and have experimented with the solver settings. I have also explored damping, but trying to recreate the simulation as accurately as possible, i have not included it in my simulation as it is not included in the paper. Its important to note, that the paper in reference uses ABAQUS to analyse the structure, so i expect some differences in results but not this significant. I am unsure as to why i obtain this difference and any help or insight into the possible factors which i have not considered would be valuable.

Additionally, i would like to explore the effect on the eigenfrequencies with increased prescribed displacement. For this i used the auxillary sweep setting for both steps in the pre-stressed eigenfrequency study, setting the displacement within a range. I find that my results give the same eigenfrequencies and modes for the different displacements. How would i go about doing this sweep? As i have realised that with every displacement, a different critical load factor and deformed geometry exists, which i cannot reference in the auxillary sweep settings.

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