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04-06-2015 05:50 PM

Good morning / afternoon / night,

I've been working with Femap for 1 year and I'd like to share and ask for help about this case:

Please consider two chambers or tanks, one inside the first one. What I want to simulate is a case about internal pressure inside the first one and an atmospheric pressure on the second one (the one inside). Picture is attached.

The results would be deformations due to pressures, etc.

Could anyone help me with an analysis recommendation for this case? I'd like to use linear static, positioning both tanks and assign pressures on surfaces, usign constraints, assembly contacts, etc... but I don´t know if that is a good choice.

Thanks for any help.

4 REPLIES

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04-07-2015 05:02 AM

Hello!,

I do not see too much complexity here: apply pressure loads as the problem require. You do not need to apply the Atmospheric pressure explicitely (at this state the material strain & stress = 0), you need to apply the pressure load above the atmospheric value.

The only caution is to orient normal vectors for shell elements correctly, having consistent TOP/BOT faces mesh, this way the pressure load will be applied correctley (either inward or outward). This should be done during geometry creation phase, surfaces has it proper normal vector, OK?.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director

IBERISA • 48004 BILBAO (SPAIN)

WEB: http://www.iberisa.com

Blog Femap-NX Nastran: http://iberisa.wordpress.com/

IBERISA • 48004 BILBAO (SPAIN)

WEB: http://www.iberisa.com

Blog Femap-NX Nastran: http://iberisa.wordpress.com/

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04-07-2015 11:46 AM

Thanks a lot Blas !

Just another question, what if I need to apply a pressure below atmospheric? For example a pressure of -14.7 psig ? Would it be fine if I apply it explicitely?

Thank you !

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04-07-2015 04:12 PM

Hello!,

You can apply any pressure you like, positive or negative. Please note the sign will reverse the direction of the pressure normal to element, simply play with the command and you will see: positive value of pressure applied to a shell CQUAD4 elements means that the pressure arrow is in the oposite direction to the normal to the shell element, ie, positive values means INWARD pressure. Please feel free to "experiment", OK?.

By the way, once you apply the pressure load use command MODEL > LOAD > EXPAND, this way FEMAP will expand the pressure symbol to the explicit pressure load element-by-element, this is very interesting when using variable pressure loads, not constant.

Enjoy!.

Best regards,

Blas.

Blas Molero Hidalgo, Ingeniero Industrial, Director

IBERISA • 48004 BILBAO (SPAIN)

WEB: http://www.iberisa.com

Blog Femap-NX Nastran: http://iberisa.wordpress.com/

IBERISA • 48004 BILBAO (SPAIN)

WEB: http://www.iberisa.com

Blog Femap-NX Nastran: http://iberisa.wordpress.com/

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04-10-2015 11:54 AM

Thank you very much Blas !

De hecho estoy revisando tu firma y me doy cuenta que eres de España. Te agradezco mucho tu apoyo nuevamente.

Excelente dia.

Jesus Cordero

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