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[xenon]

ORIGINAL: Hilux

Or alu plate of thicker gauge

Not good, ally fatigues v quickly with vibration/movement, I`d stick to steel if I were you.

[:-] Considering I'm getting on a 747 tomorrow that's largely comprised of aluminium you've got me worried! I wasn't aware that aluminium was more susceptible to vibration damage than steel -are you sure about that? Jet aircraft are built virtually entirely from aluminium, aside from the titanium and ceramics in the engine, and they vibrate quite a bit!

 

[TTM]

Aluminium is like carbon, you don't want to use it in any given form.

 

[John Sims]

Aluminium has a far lower modulus of elasticity. Provided this isn't exceeded there is no reason not to use ali - most modern GT cars have bonded aluminium monocoqus (? spelling), mountain bikes are made from aluminium, masts are made from aluminium, our front wishbones and rear trailing links are made of aluminium, planes are made from aluminium.

However, aluminium comes in various grades (it is an alloy after all) so you can't grantee what your bit in the shed is. Some aluminium will bend nicely others just tear.

 

[Diver944]

ORIGINAL: xenon
[:-] Considering I'm getting on a 747 tomorrow that's largely comprised of aluminium you've got me worried!

I aint getting on no plane ! []

 

[hotblack944]

Aluminium is an element. Too reactive to use "neat" though []

Jim.

 

[sawood12]

ORIGINAL: xenon

ORIGINAL: Hilux

Or alu plate of thicker gauge

Not good, ally fatigues v quickly with vibration/movement, I`d stick to steel if I were you.

[:-] Considering I'm getting on a 747 tomorrow that's largely comprised of aluminium you've got me worried! I wasn't aware that aluminium was more susceptible to vibration damage than steel -are you sure about that? Jet aircraft are built virtually entirely from aluminium, aside from the titanium and ceramics in the engine, and they vibrate quite a bit!

Aircraft airframes have a finite life measured in cycles - one cycle being one flight. The pressurisation/depressurisation cycle is what causes fatigue in the skin of the fuselage (the interior of the fuselage is pressurised at 8000ft so you can imagine the immense pressure differencial between 8000ft inside the a/c and 35000ft+ outside). The mechanism of Fatigue in aluminium alloys is very well understood thanks to the tragic Comet accidents in the 50's which Boeing benefitted from greatly, so I wouldn't worry about it. Thankfully cases of explosive decompression are very low in the history of pressurised flight and the vast majorit resulted in the aircraft landing safely with no casualties. Sit back, enjoy the G&T's and the in-flight movie. It is by a very large margin the safest form of transport. You are putting yourself at far more risk playing with your 944 than taking a commercial airliner flight.

 

[Hilux]

Basically the main difference with ally as against steel is that it work hardens quicker when bent back and forth which leads to cracks. Admittedly different alloys lessen this tendency but generally is fact. If you keep steel beneath its yeald point (furthest point before it stetches and will not return to original shape/form) it will absorb vibration etc indefinitely.

I`m bound to be corrected but thats always been my understanding [8|]

 

[sawood12]

All aluminium alloys have a fatigue life irrespective of how close to the yeild point the material gets. The key parameter for cyclic fatigue is stress, and higher stresses will fatigue the material more quickly. Aluminium Alloys will eventually fatigue no matter how small the stress levels in the material - it may be many many millions of cycles before failure, however there is a finite limit and the material will eventually fail. Steel and alloys of Steel is different in that it does have a limit below which you have an infinate fatigue life.

 

[Hilux]

What Scott said........................[8D]

 

[sawood12]

Sorry Paul, after 5 yrs as an aircraft apprentice and a further 5 in the design office you pick up a few nuggets! As another useless peice of info the highest stressed parts of an aircraft fuselage are around the windows and doors. Here the thickness of the skin is thicker. The new Boeing 787 Dreamliner (to go into service in 2008) has an all CF fuselage and as a result the windows are 75% larger as the airframes can be made substantially stronger without gaining too much weight, an there are no issues with fatigue.