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

cli21 · May 18, 2017, 19:46

Hi everyone,

I build a folded beam structure using Solidwork with the following shape and dimensions.

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.

Then I use Ansys workbench to do a simple static structural analysis.

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.

Lapis1 · May 28, 2017, 13:59

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.

May 18, 2017, 19:46	Big difference in simulation&analytical result of a simple static structural problem	#1
cli21 New Member Chengjun Li Join Date: Mar 2017 Posts: 7 Rep Power: 9	Hi everyone, I build a folded beam structure using Solidwork with the following shape and dimensions. 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. Then I use Ansys workbench to do a simple static structural analysis. 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.

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May 28, 2017, 13:59		#2
Lapis1 New Member X Join Date: May 2017 Posts: 5 Rep Power: 8	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.