×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Log In

Come Join Us!

Are you an
Engineering professional?
Join Eng-Tips Forums!
  • 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!
  • Students Click Here

*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.

Students Click Here

Jobs

Failure Criteria, FEA

Failure Criteria, FEA

Failure Criteria, FEA

(OP)
Hi,

I want to use failure criteria other than Von Mises in the visualiser or even just post processing.  Normaly the failure theories are quite simple like Coulomb-Mohr theory:
max princ stress divided by materials UTS minus min princ stress divided by UCS. Fracture occurs if the answer is equal or greater than 1 (but you all knew this anyway)

Can i create a result set that applies formula like the one above then display the result set to see if fracture has occured. I have never created any result sets and i got a bit lost when i tried.  I would like to know if i'm on the correct track before diving on in!

Many thanks in advance

Using ideas 9

RE: Failure Criteria, FEA

Hi,

In the I-DEAS postprocessing task, there's a button called "create results", which opens a pop-up menu. Within this menu, you can find some tools that allow you to create your own results. You can directly access the entries of the stress tensor at each node and use standard formulae on them, which should enable you to derive other failure criteria automatically.

If that doesn't satisfy your needs, I would export your FE-model plus results into the Universal format, which is plain ASCII text, and either read it into EXCEL (where you can manipulate the result data) or write a programme that reads the universal file and calculates your failure criterion.

Regards,
Daniel

RE: Failure Criteria, FEA

(OP)
Many thanks, at least i was on the right track.  I'll wade in and have a go at creating a results set now.  Mind you a bit of messing around with the universal file is tempting, i never thought of that.

Cheers

Martin

RE: Failure Criteria, FEA

(OP)
Maybe I'm being a bit slow but how do i access the individual stress tensors when creating the new results set.  I can only apply a formula to whole results set i.e stress and not individual tensors within the results set.

How do i get to the individual stress tensors to apply the formula ??

probably just me having a dense day

Many thanks in advance

RE: Failure Criteria, FEA

You can use the "Reduction" command of the "Create Results" subpanel to derive a scalar value (e.g.a failure criterion) from the entries of a stress tensor of one result set. That should enable you to "programme" your own failure characteristics.

RE: Failure Criteria, FEA

(OP)
I think I’m still being a bit dim!  When using 'reduction' in create results you can only get the normal and shear stress not the principal stresses.  I vaguely remember the graphical Mohr’s circle way for calculating principal stress etc but surely I can get at the principal stress result values for my equation some how without recalculating them!!

Many thanks

Martin

RE: Failure Criteria, FEA

As I know:
In the select result set you can choose the stress data. If you choose Von-Mises stress, Maximum... etc stress you will get in the list these calculated values.
If you choose normal stresses or shear stresses in these case you can list the items of the stress tensor.

Irwin

Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

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!


Resources