E-N Curves and fatigue failure analysis?

[VelocityGirl]

Hi guys,

 

I'm writing a lab report on fatigue testing and have been asked to discuss methods of predicting fatigue failure. After researching this I came across a method called E-N curves, which we haven't covered in our class (we're using S-N curves) so I was wondering if anyone can explain E-N curves to me simply? Thanks!

[baxtrom]

Hi guys,

 

I'm writing a lab report on fatigue testing and have been asked to discuss methods of predicting fatigue failure. After researching this I came across a method called E-N curves, which we haven't covered in our class (we're using S-N curves) so I was wondering if anyone can explain E-N curves to me simply? Thanks!

 

 

Hi,

E-N curves refer to strain life (from strain = epsilon = "e"), and is mostly used for low-cycle fatigue, i.e. for high loads that lead to more rapid failure. S-N curves are applicable for high cycle fatigue, when nr of cycles exceeds 100,000 or so. Check out this website.

[VelocityGirl]

Hey, thanks for the reply. I actually have seen that website already, I understand that they're strain-life curves, what I wanted to know was if there's a simple explaination of how they're created? The theory seems fairly complicated if you've never covered it. We have to draw an S-N curve so I understand the theory for that (basically what is the lab procedure to draw an E-N curve?), are the two similar?

 

Thanks!

Edited February 24, 2012 by VelocityGirl

[Xittenn]

I have no idea where you are in your education but I find papers like the following helpful in gaining the knowledge I require:

 

Mean Stress Effects in Strain–Life Fatigue by N. E. DOWLING

 

This one builds up through application and specialization.

[VelocityGirl]

I'm in my final year of an ordinary degree in mechanical engineering. Thanks for the help guys, ended up just writing what I could for it in terms of how much I understood. I didn't need to go really in depth but it'd have been nice if the lecturer would've covered it with us to save any confusion!