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Note: This discussion is about an older version of the COMSOL Multiphysics® software. The information provided may be out of date.

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question regarding PDE and MEMS module

Posted 08.10.2012, 14:31 GMT-4 Low-Frequency Electromagnetics, MEMS & Nanotechnology, MEMS & Piezoelectric Devices, Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 3.5a 3 Replies

Nishant Patel
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I would like to solve some piezoelectric problems, but I do not currently have MEMS module.

I do have ac/dc module and the structural mechanics module that came with the software.

i want to attempt using pde module to try to solve the problems i can't currently solve without the MEMS module.

Is this possible to do or will I be missing information for the model?

3 Replies Last Post 15.10.2012, 11:07 GMT-4
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 08.10.2012, 16:41 GMT-4
Hi

this is certainly possible, but it is some work to set up fully the PZT stress strain - electric - constitutive equations. But it's a very good exercicie to understand COMSOl in details ;)

You have the "physics builder" too nowtodays to help (in v4 sorry)

--
Good luck
Ivar
Hi this is certainly possible, but it is some work to set up fully the PZT stress strain - electric - constitutive equations. But it's a very good exercicie to understand COMSOl in details ;) You have the "physics builder" too nowtodays to help (in v4 sorry) -- Good luck Ivar
Nishant Patel
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Posted: 1 decade ago 09.10.2012, 02:25 GMT-4
ok, thanks for the prompt response.

would it best to make the constitutive relations global expressions or scalar expressions?

is there a "best practices" approach to relating the global/scalar expressions to the built in PDE coefficient form equations?

I ask because the piezoelectric wave equation will contain both the potential and the strain tensor components, so this

connection needs to be made somehow.

what other things will i need to consider besides boundary conditions?

my actual model geometrically is just a rectangular piece of piezo material . i want to see how it changes with AC voltage.

thanks for your time.

Nishant
ok, thanks for the prompt response. would it best to make the constitutive relations global expressions or scalar expressions? is there a "best practices" approach to relating the global/scalar expressions to the built in PDE coefficient form equations? I ask because the piezoelectric wave equation will contain both the potential and the strain tensor components, so this connection needs to be made somehow. what other things will i need to consider besides boundary conditions? my actual model geometrically is just a rectangular piece of piezo material . i want to see how it changes with AC voltage. thanks for your time. Nishant
Nishant Patel
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Posted: 1 decade ago 15.10.2012, 11:07 GMT-4
Ivar,

I have a simple question.

If i wanted to create the constitutive equation

Strain = compliance*Stress -piezocoupling matrix*Electric field

so my syntax in the global expressions box is:

variable: hooke1

expression: cE*sx_ps-e*Ex_dc

(focusing on just 1-d right now)
i am using 3.5a with plane stress (static), plane strain (static), and electrostatics (conductive media dc)

is this correct?

I then apply a constant dc voltage on the top boundary.

how can i look post applied voltage cE values?
Ivar, I have a simple question. If i wanted to create the constitutive equation Strain = compliance*Stress -piezocoupling matrix*Electric field so my syntax in the global expressions box is: variable: hooke1 expression: cE*sx_ps-e*Ex_dc (focusing on just 1-d right now) i am using 3.5a with plane stress (static), plane strain (static), and electrostatics (conductive media dc) is this correct? I then apply a constant dc voltage on the top boundary. how can i look post applied voltage cE values?

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