×
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

maixmum principal stress greater than von mises stress

maixmum principal stress greater than von mises stress

maixmum principal stress greater than von mises stress

(OP)
hello,
    I ran my static analysis on curved beam subjected to bending loads and found that the maximum principal stress is greater than the vonimises stress at a particular node.Both the stresses below the yield st. Can any one explain what accounted for this differnce.
    meher.

RE: maixmum principal stress greater than von mises stress

Hi Meher,

That is perfectly acceptable. If the 3 principal stresses are S1, S2 and S3, the von Mises stress

   Sv = sqrt( (S1-S2)^2 + (S1-S3)^3 + (S2-S3)^2 )/sqrt(2).

So, the principal stresses can be greater than the von Mises stress. Consider, for example, S1=S2=S3=1000. The von Mises stress in that case is 0!!

Nagi

RE: maixmum principal stress greater than von mises stress

It is hard to concieve of how a beam, albeit curved, can have a high stress triaxiality (all three principal stresses in the same direction, and having relatively similar values).  So, from that respect, you may want to double check your results.  Of course, as nadi explained, you can have principal stresses higher than the von mises stress intensity when the principal stresses are all the same sign (tension or compression).

Note that high stress triaxiality is associated with low ductility behavior, and some codes (e.g. Section VIII, Div 2, Appendix 4) specify limits on the sum of the principal stresses.

RE: maixmum principal stress greater than von mises stress

You're right cb4 the principal stress can't be that much higher than the von Mises stress for a curved beam since it is unlikely that the 3 principal stresses in that case be all comparable in magnitude (and same sign).

Meher, what was the value of the maximum principal stress, the v.Mises stresses and the other 2 principal stresses? They should satisfy the equation I stated earlier.

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