Linear Buckling Analysis: ERROR 165- Gram-Schmidt reorthogonalization did not converge. This is caused by ill-conditioning of the shifted matrix in Lanczos run.
Altair EmployeeHello,
I am trying to do a linear buckling analysis on a telescopic mast of 12m. The assembly has a blend of 1D, 2D & 3D elements followed by contacts. Anyways i have taken care of all the parameters like element quality, free edges, T connections etc. As usual, I carried out a FREE-FREE Analysis first followed by MODAL & then a STATIC Analysis (Gravity Loading). All the rigid body modes have been eliminated and my modal frequency are as follows 0.676, 0.677, 6.75, 6.78, 19.53, 19.70, 39.55, 39.71, 45.30, 59.39. I don't know why the modal frequency fetched such initial low values and how to interpret the intermediate frequencies occurring in pairs?
The Static Analysis results are also satisfactory with a max displacement of 0.235 mm (Mag) and stress of 11.34 MPa.The stress flow pattern is also satisfactory.
Now when I simulate a linear buckling analysis I get this error:
ERROR 165- Gram-Schmidt reorthogonalization did not converge. This is caused by ill-conditioning of the shifted matrix in Lanczos run.
I have gone through a few other posts in this forum which said to remove rigid body modes, but i don't have any rigid body modes as such. And it is quite evident from the static analysis that my model is well connected and contacts are acting.
Could you please let me know how to resolve this issue?
Thank you.
Answers
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Could you please let us know the type of contact (Freeze ,Sliding or Stick)used for the analysis?If possible share .out file of the run.
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Only Freeze Contact.
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Could you try as per the suggestion mentioned in Help for Error Message Database.Please refer attached screenshot.If still face issue, we request you to share .fem and .out file using secure file transfer link available on my signature.
<?xml version="1.0" encoding="UTF-8"?>
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Hello,
I have shared the required .out file in the secure file dropbox. Kindly let me know what preventive measures to take to successfully run the analysis. The above image shared has decribed measures that has already been taken care of i pressume.
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Thanks for sharing .out files in pdf . Could you please let us know the version of Solver you used for analysis.(Version info is excluded from shared pdf)
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Hypermesh Optistruct 11
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This is very very old version.We have stopped development for this version long ago.Would be nice if you upgrade to 2017 version.Latest version is 2018 with 2018.0.1 patch.
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Does that mean the version is not capable of solving my Buckling case?
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There are several new features added since then.So it is difficult to comment. I guess linear buckling case was available with 11.0.But the order of complexity which you added in terms of contact would make difference.
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Sir,
Linear Buckling is an integral part of Hypermesh 11. And in the past as well I have solved cases with a higher level of complexity (Contact Complexity included). But it is this case that wouldn't solve. But if we see the .out file we can see it has mention of Buckling Modes. Could you please let me know your thoughts regarding the .out file that I have shared.
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