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Buckling mode shows for one model, but not for another with different thickness? [COMSOL]

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tugni925

tugni925

Mechanical
Sep 14, 2020
107
I have a linear buckling model where the thickness is t = 0.005 m, here I get a buckling mode shape with the corresponding critical load factor as seen on the right:

1_vwiqni.png


But I change the thickness to 0.035 and run the exact same model again, but dont get a buckling mode or critical load factor:

2_phoyku.png


The only thing that comes to mind is perhaps the prescribed displacement which I have set to -0.01 m in the x-direction. Perhaps as the thickness is larger in the second model I have to pull on it harder to achieve buckling? I am currently trying to increase the displacement to -0.035 but I am not sure this is working. Is there some other reason why my second model might not be giving me the buckling mode I want?
 
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Probably wrong solution/dataset is selected for the plot in the second case. Make sure that proper buckling study results are picked there.
 
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Looked at that too, I have dataset from two previous parametric studies, but this new dataset wont plot. Maybe it didnt finish running somehow, because as I said the two models are exactly the same, I just changed parameter "t" from 0.005 to 0.040 and now I dont get it. Do you think changing the prescribed displacement to be larger could help? Since we have a stiffer system now?

1_xkmtsp.png
 
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I don’t think it’s a solver problem. Most likely something went wrong with plot generation. Copy this file and try clearing the whole results tree. Maybe even prepare the model from scratch if that doesn’t help.
 
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Buckling typically scales with t^2. So you will need to increase load or displacement a lot more than thickness ratio.
 
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So I tried changing the prescribed displacement from -0.01m to -0.05m, and also tried a load rather than a prescribed displacement for this buckling study. Same problem, solver cant find any eigenvalues it seems. Any ideas what I could try to fix this and get those precious buckling modes?

1_l1yhkt.png


2_wlpeyi.png


I get the error message:

"The following feature has encountered a problem:
- Feature: Eigenvalue Solver 1 (sol1/e1)
No eigenvalues found.
- Error on node 1: No eigenvalues found.
- Error on node 2: No eigenvalues found.
- Error on node 3: No eigenvalues found.
- Error on node 4: No eigenvalues found.
- Error on node 5: No eigenvalues found.
- Error on node 6: No eigenvalues found.
- Error on node 7: No eigenvalues found.
- Error on node 8: No eigenvalues found.
- Error on node 9: No eigenvalues found.
- Error on node 10: No eigenvalues found.
- Error on node 11: No eigenvalues found.
- Error on node 12: No eigenvalues found.
- Error on node 13: No eigenvalues found.
- Error on node 14: No eigenvalues found.
- Error on node 15: No eigenvalues found."
 
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