FEAP User Forum

FEAP => FEAPpv => Topic started by: pierre on April 15, 2014, 11:26:25 AM

Title: Large strain compatibility of reduced integration hexaedral element?
Post by: pierre on April 15, 2014, 11:26:25 AM

Hi,

I would like to know if the reduced integration (one point) hexahedral of FEAP program is compatible with large strain applications, and if yes, on what theory is it based?

I thank you in advance for your help!
Best regards,

Pierre

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: FEAP_Admin on April 16, 2014, 09:22:57 AM

You can request one-point integration when defining a material but FEAP does not implement any stabilization so you computation will be unstable;
see for example section 6.1 of the manual.

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: pierre on April 16, 2014, 11:36:42 AM

Hi,

Thank you very much for your quick answer!
Best greetings,

Pierre

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: Prof. R.L. Taylor on April 16, 2014, 12:27:21 PM

fld3d1u is a finite deformation element.  Based on paper by Bonet & Bhargava, IJNME, vol 38, 1995, pp 2809--2828.

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: pierre on April 18, 2014, 03:31:30 AM

Hi,

Thank you very much for this hint.

Best greetings,

Pierre

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: pierre on April 19, 2014, 01:51:27 PM

Dear prof. R.L. Taylor,
I could read the very interesting reference you indicate.
Please, i am curious to know how is managed the hourglass parameter k?
Is it a user parameter, set by default to 0, 01 which is the value given in the reference, or do you think a value expressed in terms of material or element geometry can be derived?
I thank you in advance for your helpful comments.
Best greetings,
Pierre

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: Prof. R.L. Taylor on April 19, 2014, 04:11:53 PM

Yes, you can set the parameter using

   DISP UNIF alpha

where alpha is your parameter.  If zero it is reset to 0.001 and the stabilized tangent is proportional to the initial tangent.  See the file fld3d1u.f in /elements/solid3d

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: pierre on April 20, 2014, 09:04:58 AM

Dear Prof. R. L. Taylor,

Thank you very much for your reply.
I fear this element is not part of FEAPpv source files that I could download here (http://www.ce.berkeley.edu/projects/feap/feappv/feappv31.zip) (version 3.1).
In /elements/solid3d.f, I sould successfully identify  fld3d1 subroutine, but no fld3d1u.
I guess that the u in fld3d1u stands for under-integraiton, right?
Is there perhaps any possibility to have a copy of this soure file?

Thank you again very much for your help.
Have a very good day.
Best greetings.

Pierre

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: FEAP_Admin on April 20, 2014, 06:56:09 PM

I think this routine is only available in the full version of FEAP.  If you want to do this in FEAPpv you will
need to program it yourself.

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: pierre on April 21, 2014, 12:49:02 PM

Hi,

Thanks for the inputs.
I'm about to look into this.
Thanks again.
Best regards,

Pierre

Title: Re: Large strain compatibility of reduced integration hexaedral element?
Post by: Prof. R.L. Taylor on April 22, 2014, 11:46:09 AM

The element integrates volume by 2x2x2 quadrature but evaluates material at only none point.  You can modify the fld3d1 element for most of it.