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

Dealing with stress singularity and, evaluation of max equivalent stress

Dealing with stress singularity and, evaluation of max equivalent stress

(OP)
Hello everyone,
I’m engineering student, and I have to perform analyze of stress of street lamp pole. It has octagonal cross-section and rectangular hole on bottom part. I modeled this lamp as a surface body.
Due to geometry I’m facing the problem with stress singularity and I can’t obtain convergence with mesh refinement, and my results depends on mesh density. I’d like to ask you what should I do in this case. I guess results on picture no. 2 are ok, but to get to know exact value of stress in corners I should perform analyze on exact geometry with rounded corners?

[url=https://ibb.co/nQVEwa][/url]
[url=https://ibb.co/kfg9Uv][/url]
[url=https://ibb.co/dCLQ2F][/url]

RE: Dealing with stress singularity and, evaluation of max equivalent stress

This is what stress singularities do. The finite element stress at the sharp corner is infinite. The stress goes up as you refine the mesh because the distance between the integration points and nodes is smaller, making them closer to the corner, so you are averaging two numbers that get progressively closer to infinity.

Your options are:
1. Add a radius and mesh it accordingly. You will not get a perfect sharp corner in the real part. There will be a small radius. Take a look at a part under magnification and estimate the radius. The ease of this will depend on the inspection equipment you have available. This is a workable solution if the radius is not too small. The radius will be determined by how the hole is made, i.e. milling, punching, plasma cutter, etc.
2. Fill in the slot and run an analysis. Take the stress where the corner would be and apply a stress concentration factor. The best resource for those that I have found is Peterson's Stress Concentration Factors. Depending on your loading you may have to interpret your results to determine the stress type (tensile, bending, torsion,tensile+bending, etc) so you can match it up the the correct stress concentration chart.

Rick Fischer
Principal Engineer
Argonne National Laboratory

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