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plane strain model. Parameter thickness

Posted 17.12.2010, 10:30 GMT-5 Modeling Tools & Definitions, Parameters, Variables, & Functions, Structural Mechanics Version 3.5a 4 Replies

Joaquim Lloberas
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Hi,

I'm a beginner in COMSOL and I don't understand about the parameter in a plane strain model, subdomain physics of THICKNESS.
If one of the hypotesis of plane strain is large thickness why there is this option?
I have high different results with different thickness, probably i don't understand this parameter.
Someone can hel me?
4 Replies Last Post 28.02.2017, 15:00 GMT-5
Ivar KJELBERG COMSOL Multiphysics(r) fan, retired, former "Senior Expert" at CSEM SA (CH)
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Posted: 1 decade ago 17.12.2010, 10:50 GMT-5
Hi

are you in 2D ? if o you must understand that COMSOl is working in 3D and the third direction "z" out of the plane is by default set to 1[m] but you can redefine this value. Like this your 2D view including this thickness value gives you a true 3D representation and COMSOl can resolve it correctly.

--
Good luck
Ivar
Hi are you in 2D ? if o you must understand that COMSOl is working in 3D and the third direction "z" out of the plane is by default set to 1[m] but you can redefine this value. Like this your 2D view including this thickness value gives you a true 3D representation and COMSOl can resolve it correctly. -- Good luck Ivar
Joaquim Lloberas
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Posted: 1 decade ago 17.12.2010, 11:04 GMT-5
Thank you, for the reponse.

Quim
Thank you, for the reponse. Quim
DoWon Heo
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Posted: 7 years ago 28.02.2017, 00:01 GMT-5
hi i have some question about plane stress condition.
i'm in 2D rectangle model 10mm*80um and thickness is 2.5mm,
some answer in forum say that 'z' direction is 'out-of-plane' direction.
but in my model i think 'out-of-plane' direction is 'y' direction.

what i wonder is that comsol fixed out-of-plane direction as z-direction in 2D
please answer about my question.
hi i have some question about plane stress condition. i'm in 2D rectangle model 10mm*80um and thickness is 2.5mm, some answer in forum say that 'z' direction is 'out-of-plane' direction. but in my model i think 'out-of-plane' direction is 'y' direction. what i wonder is that comsol fixed out-of-plane direction as z-direction in 2D please answer about my question.
Jeff Hiller COMSOL Employee

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Posted: 7 years ago 28.02.2017, 15:00 GMT-5
Hello Joaquim,
You are correct that in most cases the thickness does not appear in the equations for a plane strain analysis. However, should you want to specify the total force applied to a boundary, the thickness allows the software to convert that total force into the force per-unit-length that matters in such a situation. Along those same lines, the fact that you provide a thickness allows you to specify a body load in terms of the total force, with the software converting that for you into the force per unit area. I believe the thickness also features in the expression for some of the post-processing quantities (such as reaction forces).

The same ideas apply to 2D modeling in other engineering areas. For instance, in a 2D electric currents model, the fact that you supply a thickness allows you to supply the software with the total current at a terminal.
Best,
Jeff
Hello Joaquim, You are correct that in most cases the thickness does not appear in the equations for a plane strain analysis. However, should you want to specify the total force applied to a boundary, the thickness allows the software to convert that total force into the force per-unit-length that matters in such a situation. Along those same lines, the fact that you provide a thickness allows you to specify a body load in terms of the total force, with the software converting that for you into the force per unit area. I believe the thickness also features in the expression for some of the post-processing quantities (such as reaction forces). The same ideas apply to 2D modeling in other engineering areas. For instance, in a 2D electric currents model, the fact that you supply a thickness allows you to supply the software with the total current at a terminal. Best, Jeff

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