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Meaning of equation in solid mechanics and stationary study

Posted Jun 15, 2018, 3:42 a.m. EDT 3 Replies

DoWon Heo
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hello In my model, i used solid mechanics and stationary solver.

in solid mechanics, i can see the eqauion, but i cannot understand the meaning of that.

the equation is 0= del FS + Fv , F = I + del u in document, there is no mention about S and v, where can i get the information of this value?

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3 Replies Last Post Jun 19, 2018, 11:16 a.m. EDT
Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Jun 15, 2018, 9:59 a.m. EDT
Updated: 6 years ago Jun 16, 2018, 2:28 a.m. EDT

Hi,

'S' is the stress. Basically this is the equation of motion: divergence of stress equals the volume force. If you look at the equation in the Linear Elastic node, you will see the definition of 'S'.

To be more specific, 'S' is the 2nd Piola-Kirchhoff stress, so 'FS' (where F is the deformation gradient) is the 1st Piola-Kirchhoff stress.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi, 'S' is the stress. Basically this is the equation of motion: divergence of stress equals the volume force. If you look at the equation in the Linear Elastic node, you will see the definition of 'S'. To be more specific, 'S' is the 2nd Piola-Kirchhoff stress, so 'FS' (where F is the deformation gradient) is the 1st Piola-Kirchhoff stress. Regards, Henrik
DoWon Heo
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Posted: 6 years ago Jun 18, 2018, 8:22 p.m. EDT

Thank you for your reply.

Can I ask about more detail?

In equation view, dotted line is under the equation. what is the mening of this line? and i cannot find the meaning of v.

Thank you for your reply. Can I ask about more detail? In equation view, dotted line is under the equation. what is the mening of this line? and i cannot find the meaning of v.
Henrik Sönnerlind COMSOL Employee

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Posted: 6 years ago Jun 19, 2018, 11:16 a.m. EDT

Hi,

The dotted line indicates the part of the equation which is mainly affected by the inputs in a certain feature. If you add a Body Load node, you will find Fv underlined, because that is where the volume force is added. In that case 'v' stands for 'volume', but such decorators must be understood in their own context.

The equations shown in the Equation sections should be considered as conceptual at best. They are just an indication of what a certain feature does, not a complete description of it. For that, you should refer to the documentation.

Regards,
Henrik

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Henrik Sönnerlind
COMSOL
Hi, The dotted line indicates the part of the equation which is mainly affected by the inputs in a certain feature. If you add a Body Load node, you will find Fv underlined, because that is where the volume force is added. In that case 'v' stands for 'volume', but such decorators must be understood in their own context. The equations shown in the Equation sections should be considered as conceptual at best. They are just an indication of what a certain feature does, not a complete description of it. For that, you should refer to the documentation. Regards, Henrik

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