J-20 5th Gen Fighter Thread VI

[Deino]

Part 2:

It depends on what the technology is applied to. Remember, the 40% in titanium weight reduction claim came in part from 3D printed bulkheads. It doesn’t seem like that’s what they’re doing for the J-15.

I'm going to go out on a limb and say they are not 3D printing bulkheads on the J-20 either. This is currently the absolute bleeding edge of 3D printing of "large" aerospace structural components elsewhere in the world:

Please, Log in or Register to view URLs content!

Please, Log in or Register to view URLs content!

So, about 1m in the largest dimension is the state of the art. However a fuselage bulkhead on the J-20 ought to be comfortably more than 3m wide and about 1m high, a main wing spar might be north of 4m in length! Sure, China might actually lead the world in 3D printing - absence of evidence is not necessarily evidence of absence, but to such a degree? And even if we accept the idea for argument's sake, where are those comparably incredible weight savings on the C919?

Furthermore I'm still rather skeptical about the material properties achievable in 3D printed parts today. I'm no expert on materials science, but I do know enough to be aware that processing makes a huge difference even when the material is otherwise identical - compare a casting to a machined forging! The immense effort with carefully controlled forging and annealing which billets for machined bulkheads undergo is not done for giggles only (something emphasized in the first of the links above, too).

Last but not least, a bulkhead containing Xm³ of titanium is going to weigh pretty much the same whether it has been machined out of a billet 20 times its final volume or built up to near net-shape in a 3D printer. The only way the weight can be different is for the 3D printed version to be hollow or an integral truss structure, i.e. it in fact contains less than Xm³ of material. While that's absolutely possible with additive manufacturing (seen a remarkably Zeppelin-like truss concept by Airbus at le Bourget in 2015), needless to say it is not what the supposedly 3D printed Chinese bulkhead we were shown a couple of years ago looked like.

All in all, large-scale use of 3D printing to obtain insane weight reductions on the J-20 does not pass my sniff test (as, incidentally, was the case with the more ambitious of the composite content and weight reduction claims on the J-11B, but I digress).

 

[jobjed]

Part 2:

So, about 1m in the largest dimension is the state of the art. However a fuselage bulkhead on the J-20 ought to be comfortably more than 3m wide and about 1m high, a main wing spar might be north of 4m in length! Sure, China might actually lead the world in 3D printing - absence of evidence is not necessarily evidence of absence, but to such a degree? And even if we accept the idea for argument's sake, where are those comparably incredible weight savings on the C919?

Yes, exactly to such a degree. Very large single-piece titanium structures were already known to be in use in China since the FC-31 1.0 was transported on a truck thousands of kilometres across the country.

Also, the C919 is a conservative project with risk-mitigation's being a primary program goal. The extensive use of aluminium and ample cooperation with established Western firms for subsystems are obvious testaments to that. The C919 project cannot be used as benchmark for China's technological accomplishments as it doesn't incorporate the very cutting-edge of Chinese technology.

 

[jobjed]

I also forgot to mention:

The only way the weight can be different is for the 3D printed version to be hollow or an integral truss structure, i.e. it in fact contains less than Xm³ of material.

Or.... additive manufacturing is more precise than traditional methods so parts can be made with less excess material devoted to maintaining safety margins. There's no need to propose some convoluted theory involving obscure geometries like hollow or truss structures. E.g. the J-11B part on the left is made using traditional methods while the right is made using 3D-printing. They serve the exact same role in the exact same position in the exact same aircraft but the right component is obviously slimmer and more refined. I'd expect the same phenomenon with traditionally-made fuselage bulkhead supports vs 3D-printed bulkhead supports.

 

[latenlazy]

On request for a friend from the Key-Forum, who's waiting for his sign-in-confirmation here I already post a first reply here: He is know as "Trident" and he asked me to post this here for him and he would be eager for replies and a honest discussion:
-------------------------------------------------------------------------

I think the photo trident used for cross section might be a bit stretched...plus it's not a perfect head on shot so there's going to be some distortion involved that might affect the height to width ratio.

 

[Air Force Brat]

I now checked this thread from page 120 on, didn't see posted (just the link in case if the article was fishy; it's dated November 24, 2017) PLA admiral rejects talk of J-20 fighters on aircraft carriers

Please, Log in or Register to view URLs content!

The PLA Admiral is "setting things straight", its pure and utter nonsense, not to mention borderline delusional? for people to fancy seeing the J-20 operating off an aircraft carrier.... even a Ford Class!

The J-20 is an air-superiority fighter, like the F-22 it will also function very well in the strike roll as needed! As robust as the F-22 is, the Navy rejected it for carrier ops for the very same reason. So for you otherwise smart guys,,, you're missing something here.....

The FC-31 is perfectly dimensioned and positioned to fill that "niche" very well, and as SAC has designed and built the J-15 to be the PLANAF's premier carrier fighter, a role for which it has proven itself very well suited, SAC will no doubt have the lead in adapting the FC-31 for a Chinese 4 Gen/Western 5 Gen fighter to operate off even the Liaoning.... you watch, and remember,,, there have been many of us who have "kept the Faith!" when it comes to the FC-31...

As reality sets in for the the USN, (IT HAS TO HAVE THE F-35!), the Chinese are looking ahead to the FC-31 and SAC to continue their legacy as Naval Aircraft specialists!

 

[Jura The idiot]

The PLA Admiral is "setting things straight", its pure and utter nonsense, not to mention borderline delusional? for people to fancy seeing the J-20 operating off an aircraft carrier.... even a Ford Class!

The J-20 is an air-superiority fighter, like the F-22 it will also function very well in the strike roll as needed! As robust as the F-22 is, the Navy rejected it for carrier ops for the very same reason. So for you otherwise smart guys,,, you're missing something here.....

The FC-31 is perfectly dimensioned and positioned to fill that "niche" very well, and as SAC has designed and built the J-15 to be the PLANAF's premier carrier fighter, a role for which it has proven itself very well suited, SAC will no doubt have the lead in adapting the FC-31 for a Chinese 4 Gen/Western 5 Gen fighter to operate off even the Liaoning.... you watch, and remember,,, there have been many of us who have "kept the Faith!" when it comes to the FC-31...

As reality sets in for the the USN, (IT HAS TO HAVE THE F-35!), the Chinese are looking ahead to the FC-31 and SAC to continue their legacy as Naval Aircraft specialists!

well let's wait and see what further reaction(s) the article from
#1227 Today at 12:44 PM
receives here: I could of course imagine something might get lost in translation, plus now noticed
Deino
questioned the source Today at 1:44 PM

 

[Air Force Brat]

Disingenuously titled report.

All that was said was just plain common sense - that the J20 is unsuited for carrier ops as is.

No one with any basic understanding of carrier ops would ever claim otherwise.

That is completely different from the idea that the J20 cannot be developed into a carrier fighter, as the title strongly implies.

NYET KOMRADE WOLFIE! just a little "reality therapy" by the PLA Admiral, that's very high up, and borderline "OFFICIAL" word, if I'm wrong I will give the official AFB "OFFICIAL APOLOGY!"

but you of all people,,, remember when I used to remind everyone what a "bright lad" you are, and you are brother! but, like the AFB's official "wet dream F-22 back in production", don't let your "dream girl" blind you to the "girl next door"..

the J-20 is an awesome airplane as is, like the F-22 don't compromise her integrity by promising something she won't be able to deliver! let her be her "glorious self!"

 

[latenlazy]

Furthermore I'm still rather skeptical about the material properties achievable in 3D printed parts today. I'm no expert on materials science, but I do know enough to be aware that processing makes a huge difference even when the material is otherwise identical - compare a casting to a machined forging! The immense effort with carefully controlled forging and annealing which billets for machined bulkheads undergo is not done for giggles only (something emphasized in the first of the links above, too).

It depends on the process, and post process treatment. If you can get grain size down, take advantage of the additive process to exercise fine control of the alloying, or treat the part after printing to remove grain deformities you can achieve acceptable levels of structural strength. The strength of the part doesn't need to be the highest you can achieve with the material after all, just what's mechanically required of it for its specific use.

Last but not least, a bulkhead containing Xm³ of titanium is going to weigh pretty much the same whether it has been machined out of a billet 20 times its final volume or built up to near net-shape in a 3D printer. The only way the weight can be different is for the 3D printed version to be hollow or an integral truss structure, i.e. it in fact contains less than Xm³ of material. While that's absolutely possible with additive manufacturing (seen a remarkably Zeppelin-like truss concept by Airbus at le Bourget in 2015), needless to say it is not what the supposedly 3D printed Chinese bulkhead we were shown a couple of years ago looked like.

Except the point is the bulkheads wouldn't be the same volume. When you mill titanium from a forged billet you can't get below a certain part thickness because that increases the risk of cracking during the milling process. You can more or less avoid that with 3D printed bulkheads. The 3D printed bulkheads we saw certainly looks milled, of course, but using milling to clean up a part will involve less mechanical strain than using milling to shape a billet.

This is currently the absolute bleeding edge of 3D printing of "large" aerospace structural components elsewhere in the world:
...


So, about 1m in the largest dimension is the state of the art. However a fuselage bulkhead on the J-20 ought to be comfortably more than 3m wide and about 1m high, a main wing spar might be north of 4m in length! Sure, China might actually lead the world in 3D printing - absence of evidence is not necessarily evidence of absence, but to such a degree? And even if we accept the idea for argument's sake, where are those comparably incredible weight savings on the C919?

Not according to this...

Please, Log in or Register to view URLs content!

 

[Air Force Brat]

Part 2:

as the old Pentecostal Preachers used to intone, "AMEN! and AMEN!" very well stated Trident! and Deino thanks for sharing these rather more "informed and accurate" manufacturing processes analysis.

Looks like we're going to have a new "smart kid" on the block,,, awesome, is "Trident" going to be his SDF identity??

 

[Deino]

as the old Pentecostal Preachers used to intone, "AMEN! and AMEN!" very well stated Trident! and Deino thanks for sharing these rather more "informed and accurate" manufacturing processes analysis.

Looks like we're going to have a new "smart kid" on the block,,, awesome, is "Trident" going to be his SDF identity??

Regrettably not since he made a "Bltzio" again when he signed in he wrote "Tirdent" !