flyingcello
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787 Fatigue Test Frame

Wed Dec 12, 2012 10:25 pm

Quick question...is the fatigue test frame still under test, or has it been retired? How many cycles has it completed?

Also, did Boeing ever break the wing of the static test frame?
 
CM
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 1:31 am

Quoting flyingcello (Thread starter):
is the fatigue test frame still under test, or has it been retired?

Yes, it is still in test.

Quoting flyingcello (Thread starter):
How many cycles has it completed?

I believe Boeing stated some time ago the frame had passed 1xDSO. It will ultimately be tested to 3xDSO

Quoting flyingcello (Thread starter):
did Boeing ever break the wing of the static test frame?

No. But Boeing did break a static test wing (no fuselage attached). They released a video at the time. You may be able to find it on YouTube.
 
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Dreadnought
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 1:57 am

Quoting CM (Reply 1):
No. But Boeing did break a static test wing (no fuselage attached). They released a video at the time. You may be able to find it on YouTube.

It looks from the video that the fuselage was attached. It broke at 154% of design load limit.

http://www.youtube.com/watch?v=Ai2HmvAXcU0
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flyingturtle
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 2:28 am

Quoting Dreadnought (Reply 2):
http://www.youtube.com/watch?v=Ai2HmvAXcU0

Sir, I think your link is showing the 777 wing break test.

The 787 wing break test is here (no fuselage attached): http://www.youtube.com/watch?v=sA9Kato1CxA



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KC135Hydraulics
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 3:40 am

Is 154% about standard for fail rates of wings during testing? I know some of those wings get bent quite high but how did the carbon fiber wing compare to say, the wing on the 777 when it broke?
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CM
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 3:58 am

Quoting KC135Hydraulics (Reply 4):
Is 154% about standard for fail rates of wings during testing? I know some of those wings get bent quite high but how did the carbon fiber wing compare to say, the wing on the 777 when it broke?

Designers shoot for failure with a very small amount of margin above 150% of Limit Load. I doubt it is +4%, which means a great deal more margin than is needed. I would guess the goal is something closer to 151% or 152%. Just enough to remove the risk of failing the test.

You could argue the 787 failed well short of 150%, which was when the side-of-body issue was discovered. The second time around, the test exceeded 150% without breaking. I am unaware of Boeing making the test data public from the wing ultimate load test where they broke a solo 787 wing.

The only other wing where I know of the results from the static test is the A380. That wing broke at 147% of limit load.
 
dynamicsguy
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 4:07 am

Quoting CM (Reply 1):
I believe Boeing stated some time ago the frame had passed 1xDSO. It will ultimately be tested to 3xDSO

I've read that it passed 1xDSO as well. For those not familiar with the jargon, DSO = design service objective and represents one lifetime. The certification requirement is 2xDSO, but in this case Boeing has set a higher standard of 3xDSO.
 
nomadd22
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 12:28 pm

Quoting CM (Reply 5):
You could argue the 787 failed well short of 150%, which was when the side-of-body issue was discovered. The second time around, the test exceeded 150% without breaking. I am unaware of Boeing making the test data public from the wing ultimate load test where they broke a solo 787 wing.

Seems I remember it didn't fail, but showed unexpected damage at that point. It may have passed the break test if they'd kept going, but since it wasn't responding as predicted they needed to wring out the problem to certify the model.
Not trying to contradict the most knowlegable source of Boeing procedures in this asylum. Just meandering.
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Stitch
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 3:47 pm

Boeing chose not to push the 787 wing to the actual breaking point (once Ultimate Load had been achieved) due to the clean-up issues (CFRP shards and dust),
 
CM
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 4:15 pm

Quoting nomadd22 (Reply 7):
Seems I remember it didn't fail, but showed unexpected damage at that point.

It probably depends on how we define the word "fail". The requirement of the ultimate load factor test is to achieve 150% of limit load factor without structural failure. Permenent deformation of the structure is permitted. By the standards of passing the test, the 787 wing failed. It was not, however, a spectacular failure in the sense of the wing breaking, as we've all seen from the 777 video.
 
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Dreadnought
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RE: 787 Fatigue Test Frame

Thu Dec 13, 2012 9:39 pm

Quoting CM (Reply 9):

Bit of a sidenote - Anyone remember the China Airlines flight where a 747SP went into an uncontrolled dive, went briefly supersonic, and recovered with a 5G pullout?

http://en.wikipedia.org/wiki/China_Airlines_Flight_006

The plane continued service for many years and still exists today, and I remember reading that after the incident the wings always had a couple of degrees more dihedral than normal due to the wings having been bent up so hard.

Let's hear it for good old-fashioned 1960's over-engineering.

http://www.airliners.net/photo/Globa...d=c1afa7b554b907865ab557e3a9c01ef0
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nomadd22
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RE: 787 Fatigue Test Frame

Fri Dec 14, 2012 1:46 pm

I'm guessing the only way you'd survive 5Gs is if it was lightly loaded. I doubt if the wings went to 200%.
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Viscount724
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RE: 787 Fatigue Test Frame

Fri Dec 14, 2012 6:01 pm

Quoting Dreadnought (Reply 10):
Quoting CM (Reply 9):


Bit of a sidenote - Anyone remember the China Airlines flight where a 747SP went into an uncontrolled dive, went briefly supersonic, and recovered with a 5G pullout?

I can't find any reference in the official NTSB accident report stating that the aircraft went supersonic. Where do you see that?
 
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Dreadnought
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RE: 787 Fatigue Test Frame

Fri Dec 14, 2012 9:33 pm

Quoting Viscount724 (Reply 12):
I can't find any reference in the official NTSB accident report stating that the aircraft went supersonic. Where do you see that?

I can't find it either. I believe I recall reading it in one of MacArthur Job's Air Disaster books, but I don't have it in front of me. I could be wrong...

But in looking for it I found this page about the DC-8 that went over Mach 1 on a test flight, in a shallow dive.

http://www.dc-8jet.com/0-dc8-sst-flight.htm
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amccann
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RE: 787 Fatigue Test Frame

Sat Dec 15, 2012 12:27 am

Quoting dynamicsguy (Reply 6):
I've read that it passed 1xDSO as well. For those not familiar with the jargon, DSO = design service objective and represents one lifetime. The certification requirement is 2xDSO, but in this case Boeing has set a higher standard of 3xDSO.

If this is not public information please do NOT post it here. However, if it is public information, does anyone know how Boeing has been handling thermal fatigue on the 787 fatigue test frame? The interaction of two materials with different coefficients of thermal expansion across a wide temperature range, I would imagine, is tested somehow either large scale or small scale.
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bikerthai
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RE: 787 Fatigue Test Frame

Mon Dec 17, 2012 2:22 pm

Quoting amccann (Reply 14):
Boeing has been handling thermal fatigue on the 787 fatigue test frame?

Thermal fatigue is a material dependent property that can be tested in larger batches at smaller scale. In fact, it would have been tested at the beginning of the program when they characterized the material to obtained material properties.

Usually, those testing will result in a "knock-down" factor at is included in the analysis to account for thermal stress/cycling.

FYI: typically, hot wet have more detrimental effect on composite than cold/freezing (unless when you have freezing water in honeycomb cell).

The test frame itself sees only the general environment impact of being out doors at the test facility just north of the main Everett factory. Right now it is seeing driving rain and 40mph wind gusts.   

An no propriety information have been released in the above information.

bt  
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amccann
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RE: 787 Fatigue Test Frame

Tue Dec 18, 2012 1:16 am

Quoting bikerthai (Reply 15):
Thermal fatigue is a material dependent property that can be tested in larger batches at smaller scale. In fact, it would have been tested at the beginning of the program when they characterized the material to obtained material properties.

Usually, those testing will result in a "knock-down" factor at is included in the analysis to account for thermal stress/cycling.

Thanks for the information, I was very curious.   I kind of assumed it was either a coupon test or small assembly test and resulted in an analytical knockdown.

I tried a quick Google search of the issue and found only the following article;

http://www.flightglobal.com/news/art...o-another-787-modification-342219/
What one person receives without working for, another person must work for without receiving. - Ronald Reagan
 
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bikerthai
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RE: 787 Fatigue Test Frame

Tue Dec 18, 2012 2:21 pm

Quoting amccann (Reply 16):

I tried a quick Google search of the issue and found only the following article;

http://www.flightglobal.com/news/art...o-another-787-modification-342219/

I think the issue in the article has more to do with the dissimilar coefficient of thermal expansion between the composite skin and the aluminum shear tie.

This thesis gives you a glimpse of what composite do at lower temperature.

http://scholarworks.uno.edu/cgi/view...ontent.cgi?article=1169&context=td

Shear strength goes up. But I would bet brittleness would also go up which would result in more prone to impact damage. But I guess at 40,000 ft, you are not going to hit a ground cart or have a wrench drop on your wing.

bt
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