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[Xansys] [STRUC] Membrane with Static Pressure using Shell41
 
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jose.galan
User


Joined: 21 Oct 2008
Posts: 140

PostPosted: Tue Mar 24, 2009 1:52 pm  Reply with quote

Dear Abe,
have you activated non-linear geometry effects with NLGEOM,ON? Otherwise, your
shell41 would not have any bending stiffness. Yours is a non-linear problem.
Best regards,

Jose M. Galan
Department of Construction Engineering
Escuela Tecnica Superior de Ingenieros
University of Sevilla
Spain

Date sent: Tue, 24 Mar 2009 15:55:32 -0400 (EDT)
From: --email address suppressed--
Subject: [Xansys] [STRUC] Membrane with Static Pressure using Shell41
To: --email address suppressed--
Send reply to: ANSYS User Discussion List <--email address suppressed-->

> Dear all ANSYS experts,
>
> I am trying model a rectangular (or circular like a drum head)
> membrane using shell41 (that has membrane stiffness only no bending
> stiffness), and find its deformation due to a pressure load. I fixed
> all directions on the boundary. And here I have two problems..
>
> First, when I try to run the static analysis with a pressure under the
> membrane, I do not see any deformation at all. I made sure that I
> applied a right tension (prestress) by
>
> S=alphe*t*E*deltaTemp
>
> where S=tension
> alpha = thermal coefficient
> E = young's modulus
> deltaTemp = change of temperature with respect to
> reference tempearture
>
> I could get its mode shapes by the modal analysis. How come.. I do not
> get a deflection of the plate when I do the static. I thought it's
> like putting a force on drum head.
>
> Secondly, is there any better way to give a tension (prestress) in the
> model not by thermal way?
>
> Please help me with thess problems. I have been trying to get this
> done for the past 2 weeks. No progress at all till now..
>
>
> Thanks all
>
>
>
> Abe H. Lee (Master's in ME)
> Department of Mechanical Engineering
> State University of New York
> Vestal Parkway East
> P.O. 6000
> Binghamton, NY 13902
>
> www.me.binghamton.edu
> --email address suppressed--
>
> ^----------------------------------------------------
> | XANSYS web - www.xansys.org |
> | XANSYS blog - xansys.blogspot.com |
> | The Online Community for users |
> | of ANSYS, Inc. Software |
> | Hosted by PADT - www.padtinc.com |
> ^----------------------------------------------------
>

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abe.lee
User


Joined: 24 Mar 2009
Posts: 1

PostPosted: Wed Mar 25, 2009 12:10 pm  Reply with quote

Jose,
I finally see its deformation of a membrane. However, I could not do this with SHELL41. I had to use SHELL63 having both membrane and bending stiffnesses and also turning on NLGEOM,ON.
Thanks much,

Abe H. Lee (Mater's in ME)
Mechanical Department
Binghamton University
State University of New Yrok


-------------------------------------------------------------
Dear Abe,
have you activated non-linear geometry effects with NLGEOM,ON? Otherwise, your
shell41 would not have any bending stiffness. Yours is a non-linear problem.
Best regards,

Jose M. Galan
Department of Construction Engineering
Escuela Tecnica Superior de Ingenieros
University of Sevilla
Spain

Date sent: Tue, 24 Mar 2009 15:55:32 -0400 (EDT)
From: --email address suppressed--
Subject: [Xansys] [STRUC] Membrane with Static Pressure using Shell41
To: --email address suppressed--
Send reply to: ANSYS User Discussion List <--email address suppressed-->

> Dear all ANSYS experts,
>
> I am trying model a rectangular (or circular like a drum head)
> membrane using shell41 (that has membrane stiffness only no bending
> stiffness), and find its deformation due to a pressure load. I fixed
> all directions on the boundary. And here I have two problems..
>
> First, when I try to run the static analysis with a pressure under the
> membrane, I do not see any deformation at all. I made sure that I
> applied a right tension (prestress) by
>
> S=alphe*t*E*deltaTemp
>
> where S=tension
> alpha = thermal coefficient
> E = young's modulus
> deltaTemp = change of temperature with respect to
> reference tempearture
>
> I could get its mode shapes by the modal analysis. How come.. I do not
> get a deflection of the plate when I do the static. I thought it's
> like putting a force on drum head.
>
> Secondly, is there any better way to give a tension (prestress) in the
> model not by thermal way?
>
> Please help me with thess problems. I have been trying to get this
> done for the past 2 weeks. No progress at all till now..
>
>
> Thanks all
>
>
>
> Abe H. Lee (Master's in ME)
> Department of Mechanical Engineering
> State University of New York
> Vestal Parkway East
> P.O. 6000
> Binghamton, NY 13902
>
> www.me.binghamton.edu

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jose.galan
User


Joined: 21 Oct 2008
Posts: 140

PostPosted: Wed Mar 25, 2009 12:34 pm  Reply with quote

I am glad that you made it.
Were you using quadrilateral or triangular shell41 elements? If you look at "Shell41 Assumptions and Restrictions",  the quadrilateral elements are not allowed if there is some warping. For that reason, they also add the following sentence:

"The triangular shape is required for large deflection analyses since a four-node element may warp during deflection."
Best regards,
Jose M. Galan
Department of Construction Engineering
Escuela Tecnica Superior de Ingenieros
University of Sevilla
Spain

Date sent:                  Wed, 25 Mar 2009 15:10:40 -0400 (EDT)
From:                         --email address suppressed--
Subject:                     Re: [Xansys] [STRUC] Membrane with Static Pressure using Shell41
To:                             ANSYS User Discussion List <--email address suppressed-->
Send reply to:            ANSYS User Discussion List <--email address suppressed-->

> Jose,
> I finally see its deformation of a membrane. However, I could not do
> this with SHELL41. I had to use SHELL63 having both membrane and
> bending stiffnesses and also turning on NLGEOM,ON. Thanks much,
>
> Abe H. Lee (Mater's in ME)
> Mechanical Department
> Binghamton University
> State University of New Yrok
>
>
> -------------------------------------------------------------
> Dear Abe,
> have you activated non-linear geometry effects with NLGEOM,ON?
> Otherwise, your shell41 would not have any bending stiffness. Yours is
> a non-linear problem. Best regards,
>
> Jose M. Galan
> Department of Construction Engineering
> Escuela Tecnica Superior de Ingenieros
> University of Sevilla
> Spain
>
> Date sent:      Tue, 24 Mar 2009 15:55:32 -0400 (EDT)
> From:             --email address suppressed--
> Subject:         [Xansys] [STRUC] Membrane with Static Pressure using
> Shell41 To:                 --email address suppressed-- Send reply to:         ANSYS User
> Discussion List <--email address suppressed-->
>
> > Dear all ANSYS experts,
> >
> > I am trying model a rectangular (or circular like a drum head)
> > membrane using shell41 (that has membrane stiffness only no bending
> > stiffness), and find its deformation due to a pressure load. I fixed
> > all directions on the boundary. And here I have two problems..
> >
> > First, when I try to run the static analysis with a pressure under
> > the membrane, I do not see any deformation at all. I made sure that
> > I applied a right tension (prestress) by
> >
> > S=alphe*t*E*deltaTemp
> >
> > where S=tension
> >       alpha = thermal coefficient
> >       E = young's modulus
> >       deltaTemp = change of temperature with respect to
> >                   reference tempearture
> >
> > I could get its mode shapes by the modal analysis. How come.. I do
> > not get a deflection of the plate when I do the static. I thought
> > it's like putting a force on drum head.
> >
> > Secondly, is there any better way to give a tension (prestress) in
> > the model not by thermal way?
> >
> > Please help me with thess problems. I have been trying to get this
> > done for the past 2 weeks. No progress at all till now..
> >
> >
> > Thanks all
> >
> >
> >
> > Abe H. Lee (Master's in ME)
> > Department of Mechanical Engineering
> > State University of New York
> > Vestal Parkway East
> > P.O. 6000
> > Binghamton, NY 13902
> >
> > www.me.binghamton.edu
>
> ^----------------------------------------------------
> |           XANSYS web - www.xansys.org             |
> |        XANSYS blog - xansys.blogspot.com          |
> |          The Online Community for users           |
> |            of ANSYS, Inc. Software                |
> |         Hosted by PADT - www.padtinc.com          |
> ^----------------------------------------------------
>

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