Big difference in simulation&analytical result of a simple static structural problem
 

Hi everyone,

I build a folded beam structure using Solidwork with the following shape and dimensions.
http://i65.tinypic.com/11wbl2t.jpg
http://i64.tinypic.com/23rv6gg.jpg
the thickness the of structure is 0.025mm.

I want to know the stiffness of the structure, using the analytical equation I got the stiffness is 976N/m. The material is silicon with a Young's modulus of 160Gpa.
http://i63.tinypic.com/2lcbiue.gif

Then I use Ansys workbench to do a simple static structural analysis.
http://i65.tinypic.com/r7p1tk.jpg
1. I import the geometry.
2. I choose material Si with young's modulus 160Gpa.
3. I set the element size 10um, and generate the mesh.
4. I fixed the lower surface and add a 1uN force on the top surface
5. From the displacement, the stiffness from simulation is 792N/m, which is very different from the analytical result.

I think there shouldn't be so large deviation between simulation and analytical result for such a simple problem. I must have done something wrong, could anybody point it out?

Thanks.

1. Are you sure the material's Young's Modulus really is 160GPa? Have you checked it yourself? Are you sure the type of Silicon you're using doesn't have any sort of "directional Young's Modulus" (ie stiffer in one orientation than in another)?

2. Refine the mesh further multiple number of times and see if there's any deviation from your original simulation's result, and whether the results start to converge. If it does, then a finer mesh is needed.