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MEMS Cantilever Beam

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Hello COMSOL Community,

I am trying to simulate a very basic MEMS Cantilever beam. I simply want to see a deformation plot and and electrostatic plot. Once I figure this one out, I will move on to my actual MEMS Micro Mirror. But have to get this basic one down first.

I have the structural mechanics, moving mesh, and Electrostatics module used for this.

I am continually getting this error when solving a stationary:


Failed to evaluate variable.
- Variable: dnTEx_es
- Geometry: 1
- Boundary: 4
Failed to evaluate expression.
- Expression: d((mod1.smpn.d*(dnTEx_es*test(mod1.u)+dnTEy_es*test(mod1.v)))*(dvol),{test@1})

Could someone let me know what I've done wrong. Once I figure this, I can actually move to my own micro mirror, but since I'm fairly new, going past this hurdle is taking a lot of time. I've attached my model for your review.

-Dibya


1 Reply Last Post 2012年6月2日 GMT-4 03:54
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago 2012年6月2日 GMT-4 03:54
Hi

indeed I got a strange error message so something has got wrong in your model, anyhow v4.0 was not very stable in such cases, I would suggst that you remake the model from scratch

Anyhow I have a few other suggestions:
- for the ES force calculation, select only the canteliever domain "3"
- call the ES force variable only Fes (not the full name I beleive this is the confusion)
- add a Prescribed dispalcement on Bondaries 6 8 10 and use u,v respectively for the deformation
- change your domain "3" prescrived displacement to u,v and not "0,0"
- in the solid Force replace the User defined by the link to the ES in the drop down list, if it is not there use "es.Forcex_Fes" and "es.Forcey_Fes" variable names for x and y

currently your ALE is not drive by the "solid" deformation so you do not have a coupled model

The error message has something to do with the link of the ES force to the solid boundary load, but probably its your full "doted" name of the force in the ES Force calculation node, just use "Fes"


--
Good luck
Ivar
Hi indeed I got a strange error message so something has got wrong in your model, anyhow v4.0 was not very stable in such cases, I would suggst that you remake the model from scratch Anyhow I have a few other suggestions: - for the ES force calculation, select only the canteliever domain "3" - call the ES force variable only Fes (not the full name I beleive this is the confusion) - add a Prescribed dispalcement on Bondaries 6 8 10 and use u,v respectively for the deformation - change your domain "3" prescrived displacement to u,v and not "0,0" - in the solid Force replace the User defined by the link to the ES in the drop down list, if it is not there use "es.Forcex_Fes" and "es.Forcey_Fes" variable names for x and y currently your ALE is not drive by the "solid" deformation so you do not have a coupled model The error message has something to do with the link of the ES force to the solid boundary load, but probably its your full "doted" name of the force in the ES Force calculation node, just use "Fes" -- Good luck Ivar

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