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residual stress
Posted Sep 7, 2010, 8:18 a.m. EDT 4 Replies
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Hello,
I'am trying to compare the eigenfrequency of a fixed-fixed beam without residual stress and with stress, I enter the value of the residual stress in: physics-subdomains-initial stress and strain-initial normal stress.
But after the eigenfrequency analysis the eigenfrequency value does not change! I think it does not take into account the residual stress value!
4 Replies Last Post Jul 26, 2011, 11:46 a.m. EDT
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Posted:
1 decade ago
Hi
An eigenfreuqnecy analyis is a linear analysis developped around an initial starting point (normally stress free).
To get your case with a preload, you need to tell COMSOL to do a static load case, and THEN to linearise the eigenfrequency around the previously calculated initial values. This is solver setting "tweaking". Take the buclking example to study the link stationary analysis + eigemode one (the buckling is a modified eigenmode analysis)
By the way in 3.5 I believe you need to use Matlab, in V4 it can be done internally in teh GUI
--
Good luck
Ivar
An eigenfreuqnecy analyis is a linear analysis developped around an initial starting point (normally stress free).
To get your case with a preload, you need to tell COMSOL to do a static load case, and THEN to linearise the eigenfrequency around the previously calculated initial values. This is solver setting "tweaking". Take the buclking example to study the link stationary analysis + eigemode one (the buckling is a modified eigenmode analysis)
By the way in 3.5 I believe you need to use Matlab, in V4 it can be done internally in teh GUI
--
Good luck
Ivar
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Posted:
1 decade ago
Ivar,
I am solving an acoustic-structure interaction problem. The analysis type was set as "Frequency response" for solid domains and "Time-harmonic" for the acoustic domain. In this case, if I set a constant value as the initial stress for a solid domain, it is static or dynamic (automatically treat as time-harmonic by COMSOL)? Could you please tell me how to set a static initail stress in a frequency response analysis?
Thanks in advance!
Hongxue
I am solving an acoustic-structure interaction problem. The analysis type was set as "Frequency response" for solid domains and "Time-harmonic" for the acoustic domain. In this case, if I set a constant value as the initial stress for a solid domain, it is static or dynamic (automatically treat as time-harmonic by COMSOL)? Could you please tell me how to set a static initail stress in a frequency response analysis?
Thanks in advance!
Hongxue
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Posted:
1 decade ago
Hi
the way I have understood initial streess issues are that you must first run a static load case to build up the stress i.e. with external forces, then you save this solution and use it as a starting linearisation point for your frequency domain anlysis (which is by definition/design linear and ignores external forces), then you might couple further.
Now I do not have th accoustic module so I cannot check that part.
I know that the initial stress before eigenfrequency can only be done via matlab in V3.5, but is possible fulli within the GUI in V4 (see as example a buckling example case)
--
Good luck
Ivar
the way I have understood initial streess issues are that you must first run a static load case to build up the stress i.e. with external forces, then you save this solution and use it as a starting linearisation point for your frequency domain anlysis (which is by definition/design linear and ignores external forces), then you might couple further.
Now I do not have th accoustic module so I cannot check that part.
I know that the initial stress before eigenfrequency can only be done via matlab in V3.5, but is possible fulli within the GUI in V4 (see as example a buckling example case)
--
Good luck
Ivar
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Posted:
1 decade ago
Hi Ivar,
I can solve the problem using the example in the documentation of COMSOL "Rotating blade" but the same problem in harmonic analysis. In harmonic analysis the resonance frequency do not change, ie without taking into account the initial stress values.
Thank you
I can solve the problem using the example in the documentation of COMSOL "Rotating blade" but the same problem in harmonic analysis. In harmonic analysis the resonance frequency do not change, ie without taking into account the initial stress values.
Thank you