Oh no.
> For example, when vibrating a fuselage on an enormous platform to expose weaknesses - known as fatigue testing - the vast majority of the time the tool itself breaks instead of the airframe, according to a person with knowledge of past tests. Such work is costly and has reliably confirmed engineers’ expectations, he added.
Is this just hubris, or is this real? That's a lot of confidence to place in a software model.
Now probably isn't the best time to put out press releases on this though.
Finite element methods are such a known quantity that we're able to design nuclear weapons without ever testing them in meatspace. If it's good enough for nuclear weapons, I am strongly convinced it's good enough for something as simple as stress analysis.
As for not testing nukes, I'm damn sure they test the relevant non-nuclear parts such as the lensing (conventional) explosives.
> ...for something as simple as stress analysis
Of entire wings? From the article "..such as using machines to bend the wings to extreme angles and shaking the fuselage until it cracks"
Your job isn't in this area I guess. I'm sure of it.
BTW the model is only as good as its inputs so if you have a defective batch of components (and wasn't there very recently a case where a bunch of deliberately below-spec aluminium parts were delivered to various aerospace companies which cost lots to rectify) then your model had better refelect that defect. But how are you going to find out? With pure maths?
I'm a mechanical engineer. My point is that stress analysis is the oldest, simplest, and most well understood application of finite element analysis. I can't even begin to imagine the multiphysics that goes into simulating a nuclear weapon, but if we are willing to bet our entire nuclear deterrent on it, it seems reasonable to skip some additional rounds of physical tests that are mostly a formality at this point.
Also, defective materials are caught much earlier in the manufacturing process through quality assurance methods, before they become airplanes. And then you apply a factor of safety on your calculations for added assurance.
Okay so maybe this is an apple's to oranges comparison, but I thought of the story how NASA was scammed by a supplier passing off shitty aluminium as space grade [1]. Is it reasonable to assume that if it can happen to NASA, it can happen to Boeing?
https://weather.com/news/news/2019-05-02-nasa-launch-failure...
And the company, Sapa, didn't (AFAICT) manufacture the components, they were a third-party testing service!
They provided exactly the tests you say should have picked up the problems.
I am not a mechanical engineer.
My understanding is that some composite materials used in modern aircraft manufacturing can fail in ways unlike classic aircraft aluminum (i.e. suddenly, without prior visible signs of stress/wear).
Is that relevant here?
And we still get it wrong at times; especially with interactions between disparate parts. See the fatigue problems caused as a result of interactions between the engines and fuselage of the C-133 Cargomaster, or how the F/A-18 had a habit of destroying it's vertical stabilizer due to generated turbulence unaccounted for in the original design. All the FEA in the world gives you a good estimate when you abstract away the details. It doesn't give you the 'real story'.
> I can't even begin to imagine the multiphysics that goes into simulating a nuclear weapon, but if we are willing to bet our entire nuclear deterrent on it, it seems reasonable to skip some additional rounds of physical tests that are mostly a formality at this point.
This is a false equivalence. Nuclear weapons testing has been strictly limited by international accord. You cannot physically test these weapons anymore without "waking up the neighbors" and leading to exceedingly difficult to defuse international scrutiny. That's why the copious levels of "in theory" with regard to nuclear weapons is a reasonable route to take. There is literally no other way to advance the state of the Art. Planes thankfully, don't have that issue. Also, while nuclear weapons testing wasn't restricted, test destinations were done with some degree of regularity; so again, the nuclear weapon point fails.
>Also, defective materials are caught much earlier in the manufacturing process through quality assurance methods, before they become airplanes. And then you apply a factor of safety on your calculations for added assurance.
Just like those leading edge slats for 737 NG, MAX 8 right? You know, the ones that lead to a grounding of aircraft that had already been carrying passengers recently? And who is doing that quality assurance? That bunch of "Quality" people Boeing laid off/relocated elsewhere a few months ago?
Not a credentialed engineer, but know more than enough to LARP as one in certain fields. Testing, aviation/aerodynamics, mechanics of materials, and software being some of them.
You simply cannot know what you're dealing with until you actually test it, and it's generally right after you stop doing that one test that just tells you exactly what you think it should that you get that design with a problem that would have manifested if you just did it.
The only people who should be interested in decreasing testing is the sales, accounting, and business departments. As Engineers, we've had upward of 100 years of design driven 'oopsie' to grind into us the fact we are, in fact, not as clever at accounting for the real world as we think we are.
The fact that as a credentialed mechanical engineer, you don't see it this way is concerning. Though again, I've not had my scrutinous edges rounded off by regular business constrained application either. So there is that.
Depends on the plane I guess, Cessna 172 or F-34 or 787 and the nuke (last gen two stage fusion or Little Boy).
The nuke is harder to build because of the requirement for fuel purification but the actual engineering has to be in the same order of complexity as a modern airliner surely.
I mean we built little boy in the 1940's we definitely couldn't have built anything like the F-35 then.
Sorry for the crappy mistake.
That said the engineering on a nuclear warhead is still exquisite (if such a word is accurate for such a horrible device), requiring insane tolerances and timings to ensure everything works properly.
So it’s a different kind of complexity I guess.
Stress analysis isn’t simple.
In aircraft applications, the analysis has to model not only metals, but composite materials that have anisotropic and nonlinear responses, account for acoustic energy distribution and local concentration effects, incorporate static- low- and high-cycle fatigue mechanisms (which differ in the materials imperfections that initiate them and in how the ultimate failures play out), incorporate time varying and differential spatial temperature distributions ranging from -55°C to ~1500°C (hot section, commercial engines) and on and on.
It’s not simple. I really like physical testing to validate analytical models of complex physical systems.
Perhaps you are forgetting about all the nuclear weapons testing that was carried out in the 40's 50's and 60's ? (The last tests by USA and USSR, took place in the early 90's.)
[0] https://en.wikipedia.org/wiki/List_of_nuclear_weapons_tests