Contact US

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.

Students Click Here

Fatigue process using FEM with BS standard

Fatigue process using FEM with BS standard

Fatigue process using FEM with BS standard

Hi everyone,
I am conducting a simulation to calculate stress in order to estimate fatigue of a 3D structure.
In Bs code standard I used, they use nominal stress or hot spot principle stress to calculate stress range and then use it to s-n curve, however, as far as I know, FEM cannot calculate nominal stress (tensor stress, principle stress, .. are ok).
Is that right?
The second question is whether the hot spot principle stress relates to principle stress ?.
I am a very new guy in FEM, thank you so much.

RE: Fatigue process using FEM with BS standard

What do you mean by nominal stress ?

RE: Fatigue process using FEM with BS standard

Hi Rothers,
Thanks for your reply.
"Nominal stress" I said is the type of stress Bs 7608 Standard used to get stress range (nominal stress = F/A Link).
However, using the FEM method, I get only stress tensor, principal tensor but nominal stress.
So how can I pass this obstacle?

RE: Fatigue process using FEM with BS standard

I don't know this code but if they mean nominal stress as opposed to true stress, in FEA you will get the latter which takes the deformation into account. Nominal stress is based on the initial state of the geometry. Up to some point on the stress-strain curve they won't differ that much.

RE: Fatigue process using FEM with BS standard


I think that "nominal stress" in this context (fatigue) is the same as principal stress. It is a pure tensile or compressive stress. Is is not the same as von Mises stress where shear also in included.

Edit: Shear can also be a nominal stress. But then it is pure shear.


RE: Fatigue process using FEM with BS standard

"nominal" stress seems to be like "gross section" stress.

This can be a problem with FEA, in that it'll give you the stress peak due to the stress concentration (or something like it). So you need to look at elements near the point of interest, say an element away from the concentration.

"Hoffen wir mal, dass alles gut geht !"
General Paulus, Nov 1942, outside Stalingrad after the launch of Operation Uranus.

RE: Fatigue process using FEM with BS standard

If I don't remember it wrong the "nominal stress method" and the "hot spot method" both have specific requirements regarding the FEM-modelling. There are requirements regarding meshing and where exactly you should pick the stresses in the model. The models are typically made with volume elements.

I have never used them myself but I had a colleague who used them. And he had done research on fatigue.


RE: Fatigue process using FEM with BS standard

Hi ankhen

One additional comment. You refered to BS code Standard. I assumed that you mean British Standard and that means Eurocode. If your reference is something else some parts of my comments may be incorrect. Even if it is Eurocode I won't bet my life on it but I think my comments are correct smile.


RE: Fatigue process using FEM with BS standard

Hi ankhen,

There should be some sort of guidance or annex in you code about using this method, and if not there should be some sort of example problems available. You didn't name the exact code you are using so couldn't search for any example problems, but here are some articles on the Eurocode hotspot method that I did find. I hope they are helpful to you endeavors.


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! Already a Member? Login


Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Design for Additive Manufacturing (DfAM)
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a part’s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

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