NO BUCKLING MODES FOUND
Altair EmployeeI am trying to optimize a wing box with all components set with composite laminates. The objective is to minimize the weight, the buckling factor should be bigger than 1. However, sometimes the iteration shows that there are no buckling modes found. How this happens? What is this mean? And it seems that the iteration goes to a wrong direction when it can't find the buckling mode.
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Answers
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could you share us .out file?Is the meshing done on outer surface?
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Hi,
I think the problem setup has some problem. Have you defined a EIGRL card which defines the number of modes. This has to be refered by METHOD entry in Buckling subcase.
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Here, I attached the .out file and the .fem file for optistruct. The first 4 iterations go well, but at the 5th time there are no bulking modes found. And the iteration goes to a wrong direction, actually, there are only 6 variables for the top and bottom skin of the wing box.
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I am able to run without any errors so far and the optimization is in 13th iteration.
I just changed number of modes to 6
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Thank you very much, I also have another problem: I added the composite strain constraints for three directions normal 1, normal 2 and shear12 as 0.01933, 0.05333 and 0.01. When I run the optistruct, it often reports this error:
*** ERROR # 1831 ***
Stress/strain/force/fatigue response does not reference any valid elements.
DRESP1 ID = 3
*** ERROR # 1831 ***
Stress/strain/force/fatigue response does not reference any valid elements.
DRESP1 ID = 4
*** ERROR # 1831 ***
Stress/strain/force/fatigue response does not reference any valid elements.
DRESP1 ID = 5
How to solve this problem? I attached my model file.0 -
Select the properties after adding the CSTRAIN
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Hi, where to change the number of modes?
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EIGRL card.ND is for no of modes.
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Thank you very much!
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Hello: would you mind to send me the revised file? I changed the modes to 6, it seems that this problem still exists.
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Hello:
What makes that the buckling mode not found? Please see this message at iteration 9, then the optimization process goes in a wrong direction; However, this problem has feasible solutions. I attach the new model and .out file, this time it has 18 variables.
ITERATION 9
Note: No buckling mode is found for subcase 2.
***** Warning for buckling loadcase 2:
- Quit after 5 factorizations with no new information.
the 1st satisfied convergence ratio = 3.0950E-03Objective Function (Minimize MASS ) = 3.69650E-01 % change = -0.31
No active constraints
Volume = 2.33956E+08 Mass = 3.69650E-01
Subcase Compliance
1 7.664165E+07*** NO BUCKLING MODES FOUND ***
Thank you for your patience.
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Maybe a bug. Update to the latest patch for 14.0 and try again.
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Anyway, thank you very much.
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Your model worked for me with ND 6 on OptiStruct 12.0.
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