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Help for Modal analysis of a nonuniform beam using COMSOL

Posted Oct 10, 2012, 6:30 p.m. EDT Structural Mechanics Version 4.3 4 Replies

Lin Wang
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Hello,everyone. I want to do modal analysis of composite blade using COMSOL. The blade will be represented as a series of beam element. My question is how to use COMSOL to build nonuniform beam, because the properties of each blade section is different.
I am grateful for any help.
Regards
4 Replies Last Post Oct 11, 2012, 3:22 p.m. EDT
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago Oct 11, 2012, 1:31 a.m. EDT
Hi

can you make a series of adjacent volumes and give properties per layer ? Or do you have any more complex constitutive equations ?

--
Good luck
Ivar
Hi can you make a series of adjacent volumes and give properties per layer ? Or do you have any more complex constitutive equations ? -- Good luck Ivar
Lin Wang
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Posted: 1 decade ago Oct 11, 2012, 8:19 a.m. EDT
Hello. Thanks for your reply.

The blade is divided by 20 cross sections. The cross section properties is show as follows:
mass per unit length EI
90.37 44200000
58.496 27595540
47.192 19615360
49.105 15821054
50.333 12799255
48.912 10427460
45.977 8427317
42.735 6826572
39.243 5550799
36.024 4462882
33.118 3589918
30.272 2821277
27.523 2221759
24.996 1677427
22.991 1264032
20.925 883482
18.628 625509
16.201 382064
12.871 239543
9.536 103000
6.1 103000
I use 20 beam elements in COMSOL to represent the blade. Each beam element is setted different material properties. However, the results for COMSOL do not agree with those from analytical method. I do not understand why.
Hello. Thanks for your reply. The blade is divided by 20 cross sections. The cross section properties is show as follows: mass per unit length EI 90.37 44200000 58.496 27595540 47.192 19615360 49.105 15821054 50.333 12799255 48.912 10427460 45.977 8427317 42.735 6826572 39.243 5550799 36.024 4462882 33.118 3589918 30.272 2821277 27.523 2221759 24.996 1677427 22.991 1264032 20.925 883482 18.628 625509 16.201 382064 12.871 239543 9.536 103000 6.1 103000 I use 20 beam elements in COMSOL to represent the blade. Each beam element is setted different material properties. However, the results for COMSOL do not agree with those from analytical method. I do not understand why.
Nagi Elabbasi Facebook Reality Labs
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Posted: 1 decade ago Oct 11, 2012, 9:36 a.m. EDT
Hi Lin,

You have 21 sections, so you need at least 21 elements not 20, right? In general however, you need multiple beam elements per section to accurately calculate the beam’s frequencies and mode shapes.

Nagi Elabbasi
Veryst Engineering
Hi Lin, You have 21 sections, so you need at least 21 elements not 20, right? In general however, you need multiple beam elements per section to accurately calculate the beam’s frequencies and mode shapes. Nagi Elabbasi Veryst Engineering
Lin Wang
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Posted: 1 decade ago Oct 11, 2012, 3:22 p.m. EDT
Dear Ivar and Nagi, thanks for your help.

Dear Ivar and Nagi, thanks for your help.

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