×
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

Formula for estimating endurance limit

Formula for estimating endurance limit

Formula for estimating endurance limit

(OP)
Hello Experts,

I have a test report detailing methods used to estimate the endurance limit of single components in a multiple step fatigue test.

In this test, the component undergoes one million cycles with a maximum load of 2000 N, another million cycles with a max load of 3000 N, and so on, for a total of five million cycles. This makes the graph of maximum load vs number of cycles a stepwise graph. The time of failure of each component tested is marked on this graph.

In estimating the endurance limit, the testers used the following formula:

FDL = Fo,L-1 + [(Fo,L - Fo,L-1) x (nL/del(n))]

where

FDL = endurance limit
L = index of load level at which component fails (1-5)
Fo,L = max load level at which component fails
Fo,L-1 = max load on level L=1
nL = number of cycles to failure at Fo,L
del(n) = number of cycles at one load level of test



This is the protocol outlined in the international standard ISO 7206-8, but I do not own rights to this protocol and would like to avoid having to purchase it if possible. The standard is titled Implants for surgery -- Partial and total hip joint prostheses -- Part 8: Endurance performance of stemmed femoral components with application of torsion.

I am interested in the research or proofs which led to the creation of this formula, as I have never seen it before and currently no indication as to how it was derived. I have been doing a lit search and so far I have not been able to find anything even remotely similar to this formula, though it seems that the part of the equation (nL/del(n)) vaguely resembles the Palmgren-Miner linear damage hypothesis, as it is a ratio involving number of cycles to failure with number of cycles at a given stress magnitude. I am not certain that this correlation is valid, this was only my first guess.


Thank you for your time.

Mike

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