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Volume/Surface of a deformed medium

Posted 12.02.2014, 11:16 GMT-5 Results & Visualization, Structural Mechanics Version 4.4 4 Replies

Hans Gennerich
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I used a simple 2-D geometry of a solid material.
I used "solid mechanics" module and applied different external pressures to the material.
As expected the material was deformed under ther external pressure.

But .....
I now I try to calculated the changed volume of material.
An interpretation in the postprocessing indicates constant surface of the material.
I used "Results/DeriveValues/line integration" and applied it to the expression "1". I expected the integral to be the length of the way = the surface of the body.
But it result sticks to the original length without pressure, independend of the applied external pressure.

Any ideas?
4 Replies Last Post 18.02.2014, 14:26 GMT-5
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago 12.02.2014, 12:38 GMT-5
Hi,

Note that unless geometric nonlinearity is used in the study, there is no difference between the material coordinates (X, Y, Z) and the spatial coordinates (x, y, z). Also, there is no difference between the material frame and the spatial frame.

So in order to integrate a deformed length, you should integrate '1' along an edge on the spatial frame in a study solved with geometric nonlinearity on.

Regards,
Henrik
Hi, Note that unless geometric nonlinearity is used in the study, there is no difference between the material coordinates (X, Y, Z) and the spatial coordinates (x, y, z). Also, there is no difference between the material frame and the spatial frame. So in order to integrate a deformed length, you should integrate '1' along an edge on the spatial frame in a study solved with geometric nonlinearity on. Regards, Henrik
Hans Gennerich
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Posted: 1 decade ago 13.02.2014, 05:07 GMT-5
OK, I now understand that I need to observe two points:
... 1) I need to tag the "include geometric nonlinearity" in the node: "Study/Stationary/"
... 2) I need to change the integration way of the linear integral from "material frame" to the "spacial frame".

But how do I select the frame for the line integration?

- I go to the node: "Results/Derived Values/Line integration".
- There I choose "All Boudaries" to complete the circle as the integration way.
- I set the "Expression" to be "1".
- In the Parameters section I see but cannot modify "solid.refpntx,solid.refpnty,solid.refpntz".
___So: I don't see how and where I can choose between "material frame" to the "spacial frame" for the integration way.___

OK, I now understand that I need to observe two points: ... 1) I need to tag the "include geometric nonlinearity" in the node: "Study/Stationary/" ... 2) I need to change the integration way of the linear integral from "material frame" to the "spacial frame". But how do I select the frame for the line integration? - I go to the node: "Results/Derived Values/Line integration". - There I choose "All Boudaries" to complete the circle as the integration way. - I set the "Expression" to be "1". - In the Parameters section I see but cannot modify "solid.refpntx,solid.refpnty,solid.refpntz". ___So: I don't see how and where I can choose between "material frame" to the "spacial frame" for the integration way.___
Henrik Sönnerlind COMSOL Employee

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Posted: 1 decade ago 13.02.2014, 07:19 GMT-5
Hi,

You select the frame in the settings for the data set under Results->Data Sets->Solution ...

If you add an integration operator under definitions, then there is an explicit frame choice.

Regards,
Henrik
Hi, You select the frame in the settings for the data set under Results->Data Sets->Solution ... If you add an integration operator under definitions, then there is an explicit frame choice. Regards, Henrik
Hans Gennerich
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Posted: 1 decade ago 18.02.2014, 14:26 GMT-5
Thank You, that works. It's easy, if one knows the right places :-)
Thank You, that works. It's easy, if one knows the right places :-)

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