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Volumetric strain
Posted Mar 8, 2011, 2:53 p.m. EST 4 Replies
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Hi
I am a new user of COMSOL version 4.1, I want to calculate volumetric strain of a certain aluminium structure after some force is applied on it. in postprocessing when i select the that structure the and select volumetric strain to be computed it comes with a unit "m^3", whereas volumetric strain being ratio shouldnt have any units and also that result doesnt correspond to the strain values plotted on 3D figure after simulation is completed.
Can anybody tell me how to calculate volumetric strain in COSMOL 4.1.
Kind regards
Muhammad Nazar Ul Islam
I am a new user of COMSOL version 4.1, I want to calculate volumetric strain of a certain aluminium structure after some force is applied on it. in postprocessing when i select the that structure the and select volumetric strain to be computed it comes with a unit "m^3", whereas volumetric strain being ratio shouldnt have any units and also that result doesnt correspond to the strain values plotted on 3D figure after simulation is completed.
Can anybody tell me how to calculate volumetric strain in COSMOL 4.1.
Kind regards
Muhammad Nazar Ul Islam
4 Replies Last Post Mar 9, 2011, 7:03 a.m. EST
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Posted:
1 decade ago
Hi
the strain tensor components are unitless (plot solid.eX or solid.eY ...) so how do you calculate your volumic strain. If you integrate solid.eX over a domain you are doing in fact an:
integration_over_domain_of solid.eX *dx*dy*dz
And you will end up with a volume in [m^3] from the *dx[m]*dy[m]*dz[m]
In this case you should use an average operator, which is the combination of the integral oer the domain of your expresion, divided by the integration over the same domain(s) of operand "1" whcih gives the total volume
Do we agree ?
--
Good luck
Ivar
the strain tensor components are unitless (plot solid.eX or solid.eY ...) so how do you calculate your volumic strain. If you integrate solid.eX over a domain you are doing in fact an:
integration_over_domain_of solid.eX *dx*dy*dz
And you will end up with a volume in [m^3] from the *dx[m]*dy[m]*dz[m]
In this case you should use an average operator, which is the combination of the integral oer the domain of your expresion, divided by the integration over the same domain(s) of operand "1" whcih gives the total volume
Do we agree ?
--
Good luck
Ivar
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Posted:
1 decade ago
well, thank you for your response but i am new and didnt get a word of what you tried to xplain. I will xplain what i did so then may be it will be easy for me to understand your response. I right clicked on the derived values tab and selected volume inegration and in volume integration i selected volumetric strain then i selected the domains and tried to calculate it, which resulted in metric cube units, and i know that it is wrong.
So can you make your answer a little bit specific to what i should do.
Muhammad Nazar Ul Islam
So can you make your answer a little bit specific to what i should do.
Muhammad Nazar Ul Islam
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Posted:
1 decade ago
Hi
there are a few conventions in COMSOL, it take some time to get used to them the variable "solid.evol" is in fact a field "solid.evol(x,y,z)" (in 3D and function of the 2D position (x,y) in 2D).
Its not a global variable it is changing its value all over the surface (in 2D or volume in 3D). You observe that when you plot it over your domain. And "evol" has units of [1]
If you integrate this value over the volume you end up with units m^3, that is the units brought in by the volumic integration.
you can get the GLOBAL variable of the average volumic strain, by AVERAGING solid.evol over the volume which is the same as integrating solid.evol over the volume and dividing the results by the total volume (hence units of [1] again). BUT this is the average value of the evol over the full domain (=volume)
Hope this is clearer
--
Good luck
Ivar
there are a few conventions in COMSOL, it take some time to get used to them the variable "solid.evol" is in fact a field "solid.evol(x,y,z)" (in 3D and function of the 2D position (x,y) in 2D).
Its not a global variable it is changing its value all over the surface (in 2D or volume in 3D). You observe that when you plot it over your domain. And "evol" has units of [1]
If you integrate this value over the volume you end up with units m^3, that is the units brought in by the volumic integration.
you can get the GLOBAL variable of the average volumic strain, by AVERAGING solid.evol over the volume which is the same as integrating solid.evol over the volume and dividing the results by the total volume (hence units of [1] again). BUT this is the average value of the evol over the full domain (=volume)
Hope this is clearer
--
Good luck
Ivar
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Posted:
1 decade ago
yes its quiet helpful, Thakn you
Nazar
Nazar