# Discussion Forum

## How can I define an PML in model solids mechanics ?

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Hejer Abd

May 7, 2013 1:04pm UTC

How can I define an PML in model solids mechanics ?

I need a help !

I'm using a model of a small rectangle onto a large rectangle 2D axisymmetric
to denote of wave propagation
I have to put the PML absorbed wave to not be reflects
But when i put it and i do the compute
I don't see a difference => PML like does not work !
can you help me please ? what do I do?

note:
-> Model Wizard -> 2D axisymmetric -> structural mechanics -> solid mechanics -> temporel
-> Definitions -> PML

I have searched through the documents COMSOL a model that contains a sample of the PML but I have not found.

STS

May 13, 2013 10:16am UTC in response to Hejer Abd

Re: How can I define an PML in model solids mechanics ?

beware! PMLs are defined only for harmonic analysis. For transient analysis, please use infinite elements (COMSOL version 4.3 and later).

This is not specific to structural mechanics, but also valid for other physics.

More information may be found in Help > Documentation > Search > infinite elements

--
www.comsol.fr

Hejer Abd

May 13, 2013 10:36am UTC in response to STS

Re: How can I define an PML in model solids mechanics ?

thank you,

But my internship project is "the simulation of wave propagation by finite element method"
can i use Elements infinite in this case?

STS

May 13, 2013 11:38am UTC in response to Hejer Abd

Re: How can I define an PML in model solids mechanics ?

Actually, the search for "infinite elements" returns a lot of information, so my first answer was too general. Here is a more specific answer for structural mechanics: please check the chapter "About the Low-Reflecting Boundary Condition" in the MEMS or Structural Mechanics Module documentation.

Please also not that, under some circumstances, a periodic boundary condition might also be helpful. For instance:
www.comsol.com/showroom/gallery/9903/

--
www.comsol.fr

Hejer Abd

May 13, 2013 1:58pm UTC in response to STS

Re: How can I define an PML in model solids mechanics ?

thank you
I'll try from this model.

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