[Gmsh] meshing thin membranes in structural analysis

Tue May 7 11:14:56 CEST 2013

Le 2 mai 2013 à 11:50, Matthijs Suijlen <matthijs.suijlen at innoluce.com> a écrit :

> Dear Mr Geuzaine and Mr Remacle,
> 

Hello,

> Please let me introduce myself and the company I am working for (Innoluce). Innoluce is a high-tech starter which has spun off from Royal Philips Electronics three years ago. The core activities of Innoluce are designing and manufacturing micro MEMS mirrors for different markets where miniature and accurate laser scanning is required e.g. laser printers, optical medical devices and laser radar/gesture control. I am responsible for the mechanical (FEM) analysis of these mirror designs. The reason for writing this message to you is that we are facing some mesh generation difficulties/problems and we would appreciate your comments and advice very much.
> 

Great !

> For the finite element analysis we use Elmer FEM from the Finnish institute CSC (www.csc.fi/english/pages/elmer‎).

I know well Elmer, we use it here for education purposes, together with gmsh.

> With the Alibre CAD software we model the actual designs. These design files in STP format are then used as input for the mesh generation in GMSH and NETGEN. For the post-processing we use own programs written in Numerical Python and we use Paraview a lot for inspecting output in 3D projection.
> 
> The typical geometries we are facing have all very thin membranes (~10 μm thick) attached to large anchor blocks (~300 μm thick). Currently we use unstructured mesh element distributions. For the stress calculations we would like to use at least two element layers over the thickness of these thin membranes. The difficulty is to combine coarseness of the mesh with the double element layer over the thickness. I have attached a model file which represents this typical geometry. Currently we use attractor fields to locally refine the mesh but this results in meshes with very large number of nodes. We believe this could be done more smartly and efficiently in GMSH. However we do not know how to proceed.
> 

Gmsh will have 3D boundary layer capabilities in less than a year (we are working on it). For now the best option (as you say) is to generate
extruded meshes in the thin layer and unstructured meshes in the bulk.

Here is an example you can look at that mimics what you need.

JFR

> Our thought about the work flow for generating such a mesh would be:
> Generate 2D mesh of the membrane including refinement at desired areas
> Extrude this 2D mesh in the 10μm thick membrane with at least two element layers over the thickness
> Use this mesh as input for generating the 3D mesh in the rest of the geometry
> We would like to get your advice on our mesh problem and secondly we would like to know if the above work flow is possible with GMSH.
> 
> We thank you for your time and effort in advance and are looking forward to your reaction.
> 
> Best regards,
> 
> Matthijs Suijlen
> 
> 
> 
> Matthijs Suijlen
> Development Engineer
>  
> Telephone	+31-40-8002432	Address	Kerkenbos 1234 unit C
> Mobile	+31-6-41876748	 	6546 BE Nijmegen
> Skype	matthijs.suijlen	 	The Netherlands
> E-mail	matthijs.suijlen at innoluce.com	Internet	http://www.innoluce.com
> Innoluce is an entrepreneurial spin-off of Royal Philips Electronics and is a leading provider of laser scanner modules built around state-of-the-art MEMS mirrors.
> 
> The information contained in this message may be confidential and legally protected under applicable law. The message is intended solely for the addressee(s). If you are not the intended recipient, you are hereby notified that any use, forwarding, dissemination, or reproduction of this message is strictly prohibited and may be unlawful. If you are not the intended recipient, please contact the sender by return e-mail and destroy all copies of the original message. Computer viruses can be transmitted via email. The recipient should check this email and any attachments for the presence of viruses. Any views or opinions presented in this email are solely those of the author and do not necessarily represent those of Innoluce. Any actions taken on the basis of this email are at the reader’s own risk.
> 
> <membrane_part.stp>

------------------------------------------------------------------
Prof. Jean-Francois Remacle
Universite catholique de Louvain (UCL)
Ecole Polytechnique de Louvain (EPL) - Louvain School of Engineering
Institute of Mechanics, Materials and Civil Engineering (iMMC)
Center for Systems Engineering and Applied Mechanics (CESAME)
Tel : +32-10-472352 -- Mobile : +32-473-909930 

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