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.

 

[SWComposites]

He declined to answer my previous questions ………… sigh.

 

[cirokos]

The fatigue is done in half the yield load.
I don’t know if it is a commercial panel (the manufacturer never mentioned)
I will try to get more information about that. If it is a commercial one, the manufacturer et al.
I am as confused as you are.

SWcomposites :
Which one?

 

[SWComposites]

questions posted 10 Oct 22 22:16

 

[cirokos]

The holes as answered above are for ventilating the panel. Their size approx 1/20 of the width of the cell and the spacing seems kind random to me.
Shear force is applied to the panel.
is the document you referred the one called: <Honeycomb Attributes and Properties A comprehensive guide to standard Hexcel honeycomb materials, configurations, and mechanical properties> ?

 

[SWComposites]

Yes. 2016 version:

https://www.hexcel.com/user_area/content_media/raw/HexWebHoneycombAttributesandProperties.pdf

 

[cirokos]

The cores are indeed from Hexcel but I don't know if it a commercial one.

Also, the document from Hexcel provides general information not specific as is the one I am looking for.

 

[rb1957]

ok, but I'd still ask Hexcel if they've ever heard of this failure mode.

A fatigue load of 50% limit (or ultimate) is severe but not too severe.

I suspect that something is happening locally, which could be fixed by a local redesign.

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

 

[Sparweb]

To the OP: This is what it looks like when you "troll" members of a forum, whether you intend to or not.
I haven't hit the "red flag" button yet, but you are inviting it.
You are providing too little information for us to help you.

I believe what the OP is working with is called "foamed aluminum core"

https://duckduckgo.com/?q=foamed+aluminum+core&ia=web

Modeling this should be done as a monolithic set of properties. Modeling in any way other than that is nonsense since the material is basically a sponge.

Fatigue is not applicable to this material in the typical sense of the word. It's not really "fatigue" when it is so vastly full of flaws, inclusions, voids already. Concepts such as "notches" are irrelevant when every surface is as rough as sandpaper. I can't deny that growth of a crack in your material isn't similar to fatigue. The problem is that the stress models that define the behaviour of fatigue mathematically are not based on this kind of geometry, and can't be forced into it either.

I don't see the point of discussing with Hexcel because this isn't a product they make so they wouldn't know anything more about it than a web search I just did. I don't know what it's normally used for. Could be great for sound isolation when you absolutely cannot use a non-metallic barrier (for whatever reason). Just guessing. I would never have heard about it either, except for someone who asked if it would be good for impact energy absorption. "Maybe, but impossible to apply quality control, so not worth trying".

 

[3DDave]

About the holes - they will never allow moisture to escape in a meaningful way. They will serve to allow moisture to enter and degrade the material, but the designers of this must already know that just as they know the tiny holes are stress concentration that will start fatigue cracks.

There are dozens of research papers on the topic of fatigue in the cell material.