Smart questions
Smart answers
Smart people
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Member Login




Remember Me
Forgot Password?
Join Us!

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips now!
  • Talk With Other Members
  • Be Notified Of Responses
    To Your Posts
  • Keyword Search
  • One-Click Access To Your
    Favorite Forums
  • Automated Signatures
    On Your Posts
  • Best Of All, It's Free!

Join Eng-Tips
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.
Jobs from Indeed

Link To This Forum!

Partner Button
Add Stickiness To Your Site By Linking To This Professionally Managed Technical Forum.
Just copy and paste the
code below into your site.

Difference between Plane Stress & Plane Strain in 2D FEM formulation??

MarkH123 (Mechanical) (OP)
10 Mar 10 8:32
Hi guys,

I am writing my own MATLAB code for 2D linear quadrilateral finite elements. The code is complete and when I compare the values of nodal displacement I get from a problem with the values from the same problem in ABAQUS, they are the exact same for Plane Stress problems but different for Plane Strain problems!

As far as I can see the only difference in the formulation is the material stiffness matrix which I have inputted correctly and tested by hand for plane strain. Is there anywhere else I could be going wrong? The type of element I use for plane stress in abaqus is CPS4 and for plane strain CPE4. Does ABAQUS formulte plane strain in a different manner?

Any help would be greatly appreciated.

Mark.
flash3780 (Mechanical)
10 Mar 10 10:04
Plane strain assumes that the thing you're modeling is infinitely thick. An example of a analytical solution that uses a plane strain assumption is the stresses thick walled tubes.

Careful with plane strain elements in FEA as they're prone to "locking" or acting excessively stiff.
MarkH123 (Mechanical) (OP)
10 Mar 10 10:23
Thanks for the reply.

The examples I tried have been similar to say a 1x1 block with a thickness of 20. I am only comparing the results from my FEA code and ABAQUS results so shouldnt the over-stiffening affect both results?
persan (Mechanical)
24 Jun 10 17:21
Hello Mark,

Did you solve your problem?. I got a similar one: I want to turn a plane strain code into plane stress. It seems that in some plane strain formulations, four stress components (Sxx,Syy,Szz,Sxy) are included while in others, Szz is not.

In the plane strain code refered, the C matrix looks like: C=(E/((1+v)(1-2v)))[1-v, v, v, 0; v, 1-v, v, 0; v, v, 1-v, 0; 0,0,0,(1-2v)/2]
while the results compare very well with those of Ansys for a thick wall cylinder.

Regards,

Rogelio

Reply To This Thread

Posting in the Eng-Tips forums is a member-only feature.

Click Here to join Eng-Tips and talk with other members!

Close Box

Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

Register now while it's still free!

Already a member? Close this window and log in.

Join Us             Close