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!

*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

Stress Linearization

Stress Linearization

(OP)
hi Guys

Can be possible that Membrane plus bending stress is higher than stress intensity (Tresca)?

thank!

RE: Stress Linearization

Unfortunately, your question makes absolutely no sense.

The stress intensity (or if you are using an Edition of ASME Section VIII, Division 2 more recent than 2004/2006, the invariant of choice should be equivalent stress or von Mises) is an invariant - a way of collapsing the stress tensor into a single quantity with no direction.

A membrane-plus-bending stress is typically a tensor representation of a stress state from an (pseudo-)elastic analysis along a stress classification line (SCL).

Perhaps some additional information can assist with getting a better answer to what you're actually looking for.

RE: Stress Linearization

(OP)
Ok TGS4

Here we go

I attached a .doc file when you can find what I want to say. There are 2 lines highlighted when it say:

SCL 6:
The Linearized Maximum Combined Membrane and Bending Stress is calculated as 80.187

The Maximum Tresca Stress along the SCL is 75.924

SCL7:
The Linearized Maximum Combined Membrane and Bending Stress is calculated as 101.769

The Maximum Tresca Stress along the SCL is 96.912

Thank!

RE: Stress Linearization

I don't use FEMAP, so I can't comment on what they're doing. Since you have posted this in an ASME forum, I am going to assume that you are performing an analysis in accordance with ASME Section VIII, Division 2 - is that correct?

If so, then your second SCL is completely invalid. Your first is valid.

The proper procedure for calculating primary-plus-secondary membrane-plus-bending equivalent stress (range) is to calculate the tensor of the membrane-plus-bending stress range, and then calculate the equivalent stress from that. You can't state that the membrane is X, and the bending is Y, so the equivalent (von Mises) is X+Y. That's not how tensors work.

Find out the basis of this calculation.

On the topic of membrane-plus-bending stresses - you may find my blog post on the subject enlightening - https://becht.com/blog/asme-section-viii-division-...

RE: Stress Linearization

(OP)
Yes TGS4 Sec VIII and III

I made a sub routine in matlab for calculate membrane, bending, membrane+bendig stress, using stress tensor components and I obtained the same result that in femap. But I have so many doubt about the procedure used for calculate the integrals shown in Sec VIII, Div2 Apendix 5A.

Do you have some papers or guide that estimate these integrals?

Thank!

RE: Stress Linearization

Just so that we're clear, ASME Section VIII, Division 2 uses von Mises (equivalent) as the invariant. Section III use Tresca as the invariant. The difference is important, so you need to ensure that you use the correct one for the appropriate Code.

ASME PTB-2 has sample problems for Section VIII, Division 2.

RE: Stress Linearization

I believe TGS4 is referring to PTB-3 for example problems, not PTB-2.

RE: Stress Linearization

(OP)
I'm using Tresca.

Thanks!!

RE: Stress Linearization

pdiculous963 - you are correct.

DomCattoni - I understand that you are using Tresca. However, if you are using VIII-2, then that is not a permitted invariant. Period.

RE: Stress Linearization

Coming back to your original question, DomCattoni, it is indeed possible that the maximum local stress intensity is lower than the M+b stress intensity. However you should not be concerned with the local stress intensity for verification purposes.

prex
http://www.xcalcs.com : Online engineering calculations
https://www.megamag.it : Magnetic brakes and launchers for fun rides
https://www.levitans.com : Air bearing pads

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


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