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AFM Modelling

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Hello there,

I´m trying to simulate an AFM (Atomic Force Microscopy) model with Comsol 4.1. Specifically I have an indenter modeled as a linear elastic material that indents a cell with a hyperelastic behaviour. I use a prescribed displacement setup for a parametric study.

The model is shown in the attached file GEOMETRY.bmp

I have issues in solving the problem: when I start my analysis with the configuration shown in GEOMETRY 1.bmp I got a result, instead when the initial geometry is the one in GEOMETRY 2.bmp the solver doesn´t converge.
I mainly followed the tutorial model "hyperelastic seal".

I defined the contact between the surfaces like in the file CONTACT 1.bmp and CONTACT 2.bmp

I also attached the entire model. To get the result you have to run it since the file with the solution inside was too heavy. Thank you


3 Replies Last Post Apr 26, 2011, 3:01 p.m. EDT

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Posted: 1 decade ago Apr 8, 2011, 6:13 a.m. EDT
Sorry, use this file for the model
Sorry, use this file for the model


Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)

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Posted: 1 decade ago Apr 9, 2011, 5:18 a.m. EDT
Hi

first of all you have the Geometry "Finish union mode", if you want to do "contact" you need to "duplicate" common boundaries, for this you need the COMSOL geometry "Finish Assembly mode" and define your "contact pairs" accordingly (and select the right ones, unfortunately "loop" selection is not implemented in COMSOL, so you must identify the "loop" yourself (loop = lines that are linked to form a closed solid. The closest you can come is to use the selection settings and change the application items, and then remove the few (mostly) boundaries not desired.

I would also split the glass needle to limit the size of the contact region to a few microns, it always "simplifies" the calculation even if todays PC are really fast ;)

--
Good luck
Ivar
Hi first of all you have the Geometry "Finish union mode", if you want to do "contact" you need to "duplicate" common boundaries, for this you need the COMSOL geometry "Finish Assembly mode" and define your "contact pairs" accordingly (and select the right ones, unfortunately "loop" selection is not implemented in COMSOL, so you must identify the "loop" yourself (loop = lines that are linked to form a closed solid. The closest you can come is to use the selection settings and change the application items, and then remove the few (mostly) boundaries not desired. I would also split the glass needle to limit the size of the contact region to a few microns, it always "simplifies" the calculation even if todays PC are really fast ;) -- Good luck Ivar

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Posted: 1 decade ago Apr 26, 2011, 3:01 p.m. EDT
Using Comsol 4.1 I can not open this model
Could anyone help me on how to open it? since I am doing pretty much the same modeling
Thanks!
Using Comsol 4.1 I can not open this model Could anyone help me on how to open it? since I am doing pretty much the same modeling Thanks!

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