Ftigue Information 3

[cirokos]

Hello there,

I am trying to find Wohlers curves or S-N curves for aluminum 5052. More specifically I want to calculate the fatigue life of a component made from this material with the Miners law but I cannot find fatigue information about the material.

Any help would be appreciated.

Thank you.

 

[JohnRBaker]

Will this help:

Note that the above graph was taken from this item:

https://www.researchgate.net/figure/S-N-curves-obtained-from-fatigue-tests-20_fig28_317713426

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[cirokos]

My structure has very thin walls. So the data must ideally be from foil of a piece with thick < 1 mm. I cannot seem to find this data. I will check want you provided though.

Thank you a lot!

 

[SWComposites]

If your structure is made of foil you probably have more than fatigue problems to worry about.

 

[rb1957]

I'm guessing it's honeycomb core, maybe face sheets.

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

 

[cirokos]

Yes indeed is a honeycomb core. I get extreme high-stress concentration and want to see the fatigue life if these stresses occur.

 

[rb1957]

honeycomb core, carrying tension ... ???

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

 

[cirokos]

Not Tension. Shear but the walls have some tiny holes where stress concentration occurs and want to evaluate the life o the core in fatigue with these holes.

 

[centondollar]

I´m sorry to be the bearer of bad news, but evaluation of fatigue involves a lot of empiricism and is not as rational as many other aspects of structural analysis. Furthermore, aluminum behaves differently and less predictably than steel, and extremely thin-walled materials also have several design aspects (local buckling, distortional buckling, crippling, crushing, warping torsion and Saint-Venant torsion, behavior in the plastic regime, vibration, finite connection stiffness etc.) which likely provide more damning issues than fatigue.

 

[dhengr]

Antonis25:
Yup, that’s what an S-N curve looks like, but it really tells you so little. See where that research came from, what the samples looked like, and what the testing methods were, etc., and it gives you a bit of info. about the bulk material properties. And, you can compare the Al 5052 with other basic materials, and that’s about all. With thin material you problem might as likely be out of plane flutter or vibration causing high stresses at connections or stiffened locations. Your problem probably has as much to do with the product shape or geometry at the critical locations, the bonding methods, manufacturing methods, quality control, etc. Study these in detail at each of the failing locations and see what you can improve. What, of many things, other than base material could be causing stress raisers, concentrations of vibration, maybe bond joint size and shape and stiffness immediately around the joint, etc. Many times, it isn’t the base metal which is the problem, but rather our design, shape and detail which is the killer.

 

[cirokos]

Yes indeed, you are right but fatigue experiments will be performed to evaluate these aspects. What I want to do is in numerical analysis.

 

[cirokos]

Dhengr :

My purpose is not to fully evaluate the fatigue of the material - structure but to determine how much impact some small holes have and compare that with results from experiments

 

[3DDave]

I think that material properties research is typically done either for a graduate degree or because there is a large market for the material in whatever form. If there is no data for foil then either could apply.

Being foil it's likely no longer isotropic - you will have a with-rolling direction, across-rolling direction, and through material direction and these properties will vary considerably with the exact rolling process, the starting thickness, and the final thickness.

Those most likely to have this are companies that did the research for their own products. They might share, but I would not be hopeful. Look for companies that make products from the same foil you are interested in.

(fixed typos)

 

[rb1957]

I've never heard of someone doing fatigue analysis for honeycomb core.

It would be more logical (IMHO) to fatigue test the panel.

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

 

[cirokos]

rb1957 :
No fatigue test happening for the core alone. The whole panel is tested.
I am simply testing a unit cell to see how it behaves and compare the results.

 

[rb1957]

ok, but I don't know what that'll show. In any case, I doubt you'll find fatigue data applicable to your question.

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

 

[cirokos]

If I want to find S-N curve for the material al 5052, where should I look?

 

[JohnRBaker]

Didn't I already provide you an S-N graph showing the curves for AL-5052 based on various types of finishes? I also supplied a link to the source document where that graph was found. What else are you looking for? BTW, I used Google to find what I did. Have you spent any time Googling for the information that you're looking for?

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without

 

[cirokos]

John. Don't be angered by my question. I am simply trying to find answers, of course, I googled it, long before writing this post. I thank you for your help, really do. My field is not mechanical engineering and have no prior work with fatigue, that's why I am trying to find quick answers. Either way, I will continue my search!

 

[JohnRBaker]

If this is a critical application where a failure could threaten life or limb, may I suggest that since you've already admitted that you have little knowledge or experiences with predicting fatigue failure, that your "search" should be for a Mechanical engineering consultant who does.

John R. Baker, P.E. (ret)
Irvine, CA
Siemens PLM:
UG/NX Museum:

The secret of life is not finding someone to live with
It's finding someone you can't live without