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Stress gradient

Posted 11 gen 2010, 04:25 GMT-5 Version 4.2a 6 Replies

Andres Vasquez
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Hello,
I am trying to simulate the deflection of a cantilever due to stress gradient, how can I define an uniform stress gradient through the cantilever thickness??
Thanks for your help!
Andres
6 Replies Last Post 27 gen 2014, 15:32 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 14 gen 2010, 00:12 GMT-5
Hi

In V3.5a Structural module OR mems (smsld in 3D) (not the SLD standard multiphysics section) you can define directly your initial stress, and off you go.
i.e. Sx = STx*(z-z0) where Sx is the x component of the initial stress, z is the mesh coordinate and z0 the height of your neutral axis (for a beam shape deflection equivalent to a bending moment Mx

If you are stuck in SLD you would have to complete the equations to add the initial stress.

Try it out on a simple beam first, to you get full crontrol of your coordinate "transform" of the s tensor

Good luck
Ivar
Hi In V3.5a Structural module OR mems (smsld in 3D) (not the SLD standard multiphysics section) you can define directly your initial stress, and off you go. i.e. Sx = STx*(z-z0) where Sx is the x component of the initial stress, z is the mesh coordinate and z0 the height of your neutral axis (for a beam shape deflection equivalent to a bending moment Mx If you are stuck in SLD you would have to complete the equations to add the initial stress. Try it out on a simple beam first, to you get full crontrol of your coordinate "transform" of the s tensor Good luck Ivar
Andres Vasquez
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Posted: 1 decade ago 14 gen 2010, 04:08 GMT-5
Hi,
Thanks a lot for your help!
I tried it that way and it worked fine.

Best regards,
Andres
Hi, Thanks a lot for your help! I tried it that way and it worked fine. Best regards, Andres
M M
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Posted: 1 decade ago 17 mag 2012, 17:05 GMT-4
how can I apply stress gradient in 4.2a? This method doesn't work in 4.2a
how can I apply stress gradient in 4.2a? This method doesn't work in 4.2a
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 18 mag 2012, 10:41 GMT-4
Hi

why cant you apply stress as initial conditions in v4 ?
(you need to know the tensor form, not that trivial)

or easier just run a stationary load case to build up a natural stress, and then solve from there ?

--
Good luck
Ivar
Hi why cant you apply stress as initial conditions in v4 ? (you need to know the tensor form, not that trivial) or easier just run a stationary load case to build up a natural stress, and then solve from there ? -- Good luck Ivar
Alan Paterson
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Posted: 1 decade ago 18 dic 2013, 10:14 GMT-5
I'm also having problems with stress gradients in 4.2A. I've done the calculations manually and the results of the model in no way resemble these calculations. I've attached my model to this post. The z-displacement for the calculated results I have should be approximately 0.127 microns for the 700um diameter sample (corresponds to a curvature of 2.083/m). Not 0.04 microns which I achieve from the model.

Is there something different about the way this initial stress is simulated now?
I'm also having problems with stress gradients in 4.2A. I've done the calculations manually and the results of the model in no way resemble these calculations. I've attached my model to this post. The z-displacement for the calculated results I have should be approximately 0.127 microns for the 700um diameter sample (corresponds to a curvature of 2.083/m). Not 0.04 microns which I achieve from the model. Is there something different about the way this initial stress is simulated now?

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José Mauricio Urbano Caguasango
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Posted: 1 decade ago 27 gen 2014, 15:32 GMT-5
Hi Ivar!

I am working on a linear static structural analysis. I want to perform an incremental analysis. I have a spherical pressure vessel with an interior pressure. My pressure vessel will deform. How do I perform a second analysis using as a starting point the last state of the previous stage (i.e. deformed stressed pressure vessel)?

Thanks in advance!
Mauricio
Hi Ivar! I am working on a linear static structural analysis. I want to perform an incremental analysis. I have a spherical pressure vessel with an interior pressure. My pressure vessel will deform. How do I perform a second analysis using as a starting point the last state of the previous stage (i.e. deformed stressed pressure vessel)? Thanks in advance! Mauricio

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