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Deflection in a Membrane due to Stress

Sanjay Mukuntha Madhava

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Hi Everyone,
I have a circular membrane ( made of Single crystal silicon Si(c) ) of 6mm diameter and 5 um thickness. The Membrane is fixed through the sides with a residual/intrinsic/internal stress of about 1Mpa.
COMSOL either runs out of memory while performing this calculation ( i have a 6gb RAM) or gives a solver error, however it works when the diameter is 3mm.

I have to calculate the Maximum deflection due to the stress, without any external load

Can someone please help me with this and also later i would be fixing the membrane with the help of Beams, is there any function (like array) where i can create one Beam and replicate it?

Thanks in Advance
Sanjay


7 Replies Last Post 26 avr. 2013, 11:56 UTC−4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 14 nov. 2011, 03:04 UTC−5
Hi

why not use 3D shell or 2D plate physics, your model will be lighter, then once you know all the details of your membrane behaviour you could try a 3D case in full solid, perhaps by using a section and symmetry to study a detail case and to verify that your 3D is equivalent to the simpler 2D and 2.5D cases

--
Good luck
Ivar
Hi why not use 3D shell or 2D plate physics, your model will be lighter, then once you know all the details of your membrane behaviour you could try a 3D case in full solid, perhaps by using a section and symmetry to study a detail case and to verify that your 3D is equivalent to the simpler 2D and 2.5D cases -- Good luck Ivar

Sanjay Mukuntha Madhava

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Posted: 1 decade ago 14 nov. 2011, 04:35 UTC−5
Hi Ivar,
Thanks for your reply. I could try in 2D but how to define a Circle in it and also
1) later i will be fixing the membrane with Beams (now it is completely clamped), is there any function to vary the number of beams (like i could draw it once and use it as a template later)
2) Is there an option to view the model out of scale (when the thickness is only 5um, i have to zoom in a lot to select the edges. It would be much easier if i could represent the model out of scale)

Regards
Sanjay
Hi Ivar, Thanks for your reply. I could try in 2D but how to define a Circle in it and also 1) later i will be fixing the membrane with Beams (now it is completely clamped), is there any function to vary the number of beams (like i could draw it once and use it as a template later) 2) Is there an option to view the model out of scale (when the thickness is only 5um, i have to zoom in a lot to select the edges. It would be much easier if i could represent the model out of scale) Regards Sanjay

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 14 nov. 2011, 08:13 UTC−5
Hi

1) take care with beam and solid as beams , shell and 2D plates have rotational DoF, while Solid have only spatial displacements, this means some additional model writing to link these DoFs

2) there is in the Definition View ... sub node a "Preserve aspect ratio" check box to change for MES high aspect ratio views

--
Good luck
Ivar
Hi 1) take care with beam and solid as beams , shell and 2D plates have rotational DoF, while Solid have only spatial displacements, this means some additional model writing to link these DoFs 2) there is in the Definition View ... sub node a "Preserve aspect ratio" check box to change for MES high aspect ratio views -- Good luck Ivar

Sanjay Mukuntha Madhava

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Posted: 1 decade ago 17 nov. 2011, 05:51 UTC−5
Thanks for the help..I really appreciate it

Regards
Sanjay
Thanks for the help..I really appreciate it Regards Sanjay

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Posted: 1 decade ago 25 avr. 2013, 15:41 UTC−4
Hi Ivar,

I am working on a model to analyze the deflection of a thin polymer layer. I wish to have a pressure boundary load on each face of the layer. The model works until another boundary is added that should be designed to stop the displacement of the polymer layer; however, originally the polymer layer went through the lower limit prescribed by the box. I tried to add a prescribed displacement condition that would stop displacement when the layer hits the lower boundary. But when this condition was added the maximum number of iterations were reached without finding a solution. I was wondering if I was using the Prescribed displacement condition correctly. Essentially I want the layer to stop deforming once it reaches a deformation of -2.5 in the z direction. The input that I am currently using in the w0 field is -2.5*(w>-2.5).
Hi Ivar, I am working on a model to analyze the deflection of a thin polymer layer. I wish to have a pressure boundary load on each face of the layer. The model works until another boundary is added that should be designed to stop the displacement of the polymer layer; however, originally the polymer layer went through the lower limit prescribed by the box. I tried to add a prescribed displacement condition that would stop displacement when the layer hits the lower boundary. But when this condition was added the maximum number of iterations were reached without finding a solution. I was wondering if I was using the Prescribed displacement condition correctly. Essentially I want the layer to stop deforming once it reaches a deformation of -2.5 in the z direction. The input that I am currently using in the w0 field is -2.5*(w>-2.5).

Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 26 avr. 2013, 02:20 UTC−4
Hi

if you do not want to add contact physics (often require some tweaking to get running smoothly, I would propose that you use rather a "model Definition Function step() because this is a "smooth function, your Boolean operator there is a very sharp edges function and that often gives problems to the solver.

The solver works best on smooth continuous functions, so try to use all driving equations that are continuous and check carefully initial conditions particularly for time or transient analysis

--
Good luck
Ivar
Hi if you do not want to add contact physics (often require some tweaking to get running smoothly, I would propose that you use rather a "model Definition Function step() because this is a "smooth function, your Boolean operator there is a very sharp edges function and that often gives problems to the solver. The solver works best on smooth continuous functions, so try to use all driving equations that are continuous and check carefully initial conditions particularly for time or transient analysis -- Good luck Ivar

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Posted: 1 decade ago 26 avr. 2013, 11:56 UTC−4
Thank you very much. It worked wonderfully
Thank you very much. It worked wonderfully

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