×
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

Fatigue life at high temperatures

Fatigue life at high temperatures

Fatigue life at high temperatures

(OP)
The SN fatigue curves commonly quoted generally seem to apply at room temperatures. What is the effect of high temperatures (say about 400 C) on the fatigue life of an unwelded carbon steel component?

corus

RE: Fatigue life at high temperatures

(OP)
Thanks flamby, I too had tried googling but found nothing. I'm not sure that reference is relevant though as this material is just ordinary steel plate and not cast iron. I'd be interested  on the effect on the SN surve (if any) that is published in current design standards for fatigue assessments.

corus

RE: Fatigue life at high temperatures

If you know the mechanical properties UTS and Yield strength at the said temperature you can scale down the SN curve linearly to the UTS and Yield strength at room temperature.

RE: Fatigue life at high temperatures

(OP)
isrealkk,
I've noticed in various software packages that they make a correction for temperature, but don't say how. In design standards on fatigue I've seen a correction for the change in Young's modulus at different temperatures, but not for yield strength with temperature. Do you have a reference for your suggestion of scaling for yield strength?

corus

RE: Fatigue life at high temperatures

No, I do not have a reference. But look at it a stress concentration that raises the stress level with reference to Yield or UTS. The high temperature does the opposite it lowers UTS and Yield. The change in modulus of elesticity is usually minor.

RE: Fatigue life at high temperatures

The temperature of 400C is quite high and I suspect that the material in question can still be considered as structural steel.

If that is some serious business, go for lab tests otherwise consider special steels like fired pressure vessel quality steel for which some temperature related information is available in standards.

Ciao.

RE: Fatigue life at high temperatures

there is a very limited amount of data (fatigue at elevated temperature) in AR-MMPDS-01 or Mil Hdbk 5 for 4340.

there is also a limited amount of data on the effect of high temperature exposure on Fty and Ftu, this is highly dependent on the duration.  you could use this, like israelkk's suggestion, to reform your goodman diagram.

but i think fatigue testing at elevated temps is very difficult.

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