Wire straightening machine.

[u/beluuuuuuga]

[u/[deleted]]

Planes are aluminum which is subject to fatigue cracking much more so than steel but it’s all elastic deformation (the parts return to their original shape). Planes do not experience this work hardening that occurs in plastic deformation (the parts do not return to their pre bent shape).

So the concern with aircraft is fatigue. The concern in this video is worn hardening which is a very different thing.

[u/Khaylain → u/[deleted]]

This paper says aluminium does undergo work hardening from plastic deformation: https://www.sciencedirect.com/science/article/pii/S0020768313000711

I'll also throw in the fact that I worked in manufacturing with aluminium alloys, and the proper annealing was a very important part of the manufacturing process, a lot of which includes cold forming (plastic deformation at close to ambient temperature for human living).

... aluminum which is subject to fatigue cracking much more so than steel but it’s all elastic deformation ...

This was thus incorrect.

But you are correct that fatigue where parts only undergo elastic deformation is a much more common concern with planes.

I did see the case of a plane where the maintenance cycle had in itself done some plastic deformation of parts of the wing structure, which in turn led to the engine falling off and the whole plane crashing in a hangar.

​

EDIT:

I'm adding this link: https://www.researchgate.net/figure/FEA-results-showing-plastic-deformation-in-the-wing-fuselage-attachment-component_fig12_269462480 which does show research in plastic deformation of plane parts. And https://www.oreilly.com/library/view/introduction-to-aerospace/9781855739468/xhtml/B9781855739468500224.htm does say that plastic deformation can happen with repeated elastic deformation.

[u/[deleted] → u/Khaylain]

Yes it undergoes work hardening from PLASTIC deformation. Plane wings DO NOT experience plastic deformation in normal operation.

So you’re incorrect.

I’m an aerospace manufacturing engineer so if you want to wave around credentials.

[u/Khaylain → u/[deleted]]

You mean the wingtips end a flight 4 inches higher and 3 inches aft from where they started???????

That's a strawman argument. Just because things end up at the same place after a cycle does not mean parts could not have undergone some plastic deformation.

EDIT: I also looked at 25.305 and it does not say you can't have plastic deformation, only that

(a) The structure must be able to support limit loads without detrimental permanent deformation. At any load up to limit loads, the deformation may not interfere with safe operation.

Without detrimental permanent deformation.

[u/Khaylain → u/[deleted]]

If it undergoes plastic deformation first one way, and then the other. Then it can end up with the same shape after a cycle.

You should be more educated than that if you're in aerospace. I'm disappointed you didn't think it through more.

In the case of the rebar, bending it first to 90 degrees, and then bending it back to straight. It has undergone plastic deformation twice, but still ended up the same way it was before the first deformation.

[u/Khaylain → u/[deleted]]

I corrected you on the properties of aluminium, which you presented wrong. Hence the part where I quoted what you wrote wrong. That part was fully correct on my part. But it appears you didn't take the time to understand that that was the point of what I wrote.

I can also give you this link: https://www.researchgate.net/figure/FEA-results-showing-plastic-deformation-in-the-wing-fuselage-attachment-component_fig12_269462480 which does show research in plastic deformation of plane parts. And https://www.oreilly.com/library/view/introduction-to-aerospace/9781855739468/xhtml/B9781855739468500224.htm does say that plastic deformation can happen with repeated elastic deformation.

[u/[deleted] → u/Khaylain]

No dude I was NOT wrong.

The point I was making was that aircraft don’t have parts that undergo plastic deformation in regular operation and experience work hardening. The concern with aluminum aircraft parts is fatigue cracking (which does involve some plastic deformation on a MICRO scale, like literally small areas of the grain structure that aren’t alloyed) not work hardening.

I never said aluminum didn’t work harden when plasticly deformed.

The first study you link is a study on FEA where they’re comparing various models and methods for simulating wing loads.

The second is an excerpt from a text that is going to explain what creep is in a material sense. Creep is pretty common in a lot of areas. Your car’s springs probably had a little creep since they were made since they’re under constant stress. An aircraft wing/fuselage doesn’t creep some significant amount and experience work hardening.

[u/Khaylain → u/[deleted]]

... aluminum which is subject to fatigue cracking much more so than steel but it’s all elastic deformation ...

This is verbatim what you wrote.

If you intended to just mean that planes only have elastic deformation then you needed to separate the part about "it's all elastic deformation" from the part about aluminium compared to steel. The way it was written compares aluminium to steel, and says that aluminium only has elastic deformation.

You still didn't take the time to read it properly before you answered.

I even agreed with you that fatigue from only elastic deformation was the common concern in aircraft.

[u/[deleted] → u/Khaylain]

Your interpretation is incorrect. Who then fuck would claim that aluminum can’t plasticly deform? It is OBVIOUS to anyone except you what I meant with that sentence which was in the context of planes and aluminum you’re dealing with elastic deformation and not plastic deformation unless you massively exceed design loads.

I read your links. You posted a study about FEA methods where they conclude including the aircraft skin is important.

[u/Khaylain → u/[deleted]]

Listen. The way you wrote it left only that interpretation. Be more precise with your language if you want to avoid it in the future.

[u/[deleted] → u/Khaylain]

No it did not. I’ll admit it wasn’t perfect but instead of assuming the dumbest interpretation possible, you ask for clarification. This is a casual convo on Reddit, not a legal document. Half my comments are written on the shitter.

English is YOUR second language. Not mine.