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Deflection of a microcantilever beam
Posted Feb 3, 2010, 7:52 a.m. EST 1 Reply
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I am a student of mechanical engg (M-tech) in NIT silchar, India. I am designing a microactuator in comsol multiphysics which is basically a cantilever consisting of three layers. Top layer is of 1 micrometer thick titanium layer, middle one is 2 micrometer thick silicon dioxide layer and bottom layer is of 3 micrometer thick polysilicon layer. When a voltage is applied across titanium layer, heat is produced because of joule heating effect and temperature of the cantilever rises. As different layers have different thermal expansion co-efficient, there is a deflection at the tip of free end. I am getting some deflection when applied voltage is less than 1.2 volt. But when is more than 1.2 volt, it doesn't yield any result. I dont under stand what is happening.
All layers having rectangular cross-section and one end of the cantilever is fixed
Length and width of the cantilever are 200 micrometer and 20 micrometer respectively.
All layers having rectangular cross-section and one end of the cantilever is fixed
Length and width of the cantilever are 200 micrometer and 20 micrometer respectively.
1 Reply Last Post Feb 6, 2010, 5:41 a.m. EST
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Posted:
1 decade ago
Hi
as you describe it its "not normal" I agree. To debug such situations that rather indicates you have missed some meterial properties or BC (boundary conditions) you have several posibilities. I usually run a parameter analysis and check a few varaibles, and then look at the response of the others.
And sometimes it's the material parameters, specially if these are from the library and are "T" and "p" dependent: are "T" and "p" well defined, if not add them as constants, and are we within their domain of effect, always test the range for the material parameters, these are not covering systematically T>0[K] and T<3000[K].
You often learn a lot by debugging your models, and its always mandatory to verify and validate a FEM model by a simple hand or analytical calculation and some experiences/tests for a few critical points.
Good luck
Iva
as you describe it its "not normal" I agree. To debug such situations that rather indicates you have missed some meterial properties or BC (boundary conditions) you have several posibilities. I usually run a parameter analysis and check a few varaibles, and then look at the response of the others.
And sometimes it's the material parameters, specially if these are from the library and are "T" and "p" dependent: are "T" and "p" well defined, if not add them as constants, and are we within their domain of effect, always test the range for the material parameters, these are not covering systematically T>0[K] and T<3000[K].
You often learn a lot by debugging your models, and its always mandatory to verify and validate a FEM model by a simple hand or analytical calculation and some experiences/tests for a few critical points.
Good luck
Iva