jez-4-bikes-max
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Yeah paperclips are steel? 
Does aluminium degrade over time?
- Thread starter jez-4-bikes-max
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THWANG-666
Senior Retro Guru
russell to the rescue
Stick Legs
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I think the key phrase missing from all of these posts is CYCLES.
Every designed (ie. non organic) item that moves has a number of cycles that it is expected to undergo during it's life time. Your car door handle, the switch on your kettle and, yes indeed, the frame of your bicycle. All these are expected to last a certain number of 'moves' before they enter unknown teritory and probably break.
The designed life of a frame is say 1,000,000 cycles. (aluminum degrades an infintessimaly small amount each time)
Say my Pace RC-200 was NOS. It had a design life of 1,000,000 cycles BUT it has been on LBS wall for 16 years. This was never factored in in the design process and therefore cannot be allowed for. A prudent approach would be to HALVE the number of cycles that that frame can undertake safely before replacing it. (if it was an aeroplane wing spar this is what would happen).
So aluminum does degrade over time. But only so much. I think that too much 'worry' is generated over aluminium, I would be as concerned about the internal corrosion that may or may not have occured inside my Orange frame, or the condition of the epxoy bonding on my Dyna Tech as be concerned about my well used Pace RC-200.
The US airforce are cannabalising B-52 Stratofortress's (mainly B-52D's) that are mothballed in the desert to keep the last 458 B-52H and B-52G's flying. Some interesting facts:
The LAST Boeing B-52 built was an H model in 1967.
The B-52 has new replacement wing spars and skins at 350,000 Cycles (this is measured by stress guages in the wing) but many of the aircraft's stuctural members are original.
EVERY B-52D saw action in Vietnam and none were built later than 1962. These aircraft have useable parts on them today.
Yes aluminium degrades over time, but seriously what is the worst that can happen? Gravel rash? The USAF haven't lost a B-52 since the '70's for ANY REASON!
*The reason I chose the B-52 to illustrate my point is:
It is made almost entirely of aluminium and built with '50's technology. They are all very very old and they have had a serious amount of research done into their future viability by folks far smarter than I! What the USAF do with the B-52 amazes me, just think, every one is older than it's pilot now!
**The US Dept. of Defense (which just retired the F-14 Tomcat) wants to keep the B-52 flying until 2047 :shock: as the cost to design and build a replacement is unthinkable now.
Sorry this got a bit long-winded, I'll go and lie down now
Every designed (ie. non organic) item that moves has a number of cycles that it is expected to undergo during it's life time. Your car door handle, the switch on your kettle and, yes indeed, the frame of your bicycle. All these are expected to last a certain number of 'moves' before they enter unknown teritory and probably break.
The designed life of a frame is say 1,000,000 cycles. (aluminum degrades an infintessimaly small amount each time)
Say my Pace RC-200 was NOS. It had a design life of 1,000,000 cycles BUT it has been on LBS wall for 16 years. This was never factored in in the design process and therefore cannot be allowed for. A prudent approach would be to HALVE the number of cycles that that frame can undertake safely before replacing it. (if it was an aeroplane wing spar this is what would happen).
So aluminum does degrade over time. But only so much. I think that too much 'worry' is generated over aluminium, I would be as concerned about the internal corrosion that may or may not have occured inside my Orange frame, or the condition of the epxoy bonding on my Dyna Tech as be concerned about my well used Pace RC-200.
The US airforce are cannabalising B-52 Stratofortress's (mainly B-52D's) that are mothballed in the desert to keep the last 458 B-52H and B-52G's flying. Some interesting facts:
The LAST Boeing B-52 built was an H model in 1967.
The B-52 has new replacement wing spars and skins at 350,000 Cycles (this is measured by stress guages in the wing) but many of the aircraft's stuctural members are original.
EVERY B-52D saw action in Vietnam and none were built later than 1962. These aircraft have useable parts on them today.
Yes aluminium degrades over time, but seriously what is the worst that can happen? Gravel rash? The USAF haven't lost a B-52 since the '70's for ANY REASON!
*The reason I chose the B-52 to illustrate my point is:
It is made almost entirely of aluminium and built with '50's technology. They are all very very old and they have had a serious amount of research done into their future viability by folks far smarter than I! What the USAF do with the B-52 amazes me, just think, every one is older than it's pilot now!
**The US Dept. of Defense (which just retired the F-14 Tomcat) wants to keep the B-52 flying until 2047 :shock: as the cost to design and build a replacement is unthinkable now.
Sorry this got a bit long-winded, I'll go and lie down now 
jez-4-bikes-max
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yeah but....
oh never mind
oh never mind
Russell":1xl3kq41 said:
That was just a simple example of fatigue. A paperclip made of aluminium would break almost immediately if you tried to bend it the same amount as a steel paperclip.
Sticklegs: What you're saying is true but aircraft don't just have fatigue life but 'X' amount of flying hours as well.
mikedesign
Dirt Disciple
if hes talking about sports cars then thats different
am i an expert and do i talk crap before i became a composites guy i had lots to do with aluminium most of it capable of being pushed along by afterburners
in my day job im an expert
down the local pub i talk crap if its to get in a birds nickers i definitely talk crap
i believe the question original question was regarding aluminium degrading then white powder(not columbian) appearance on the surface was mentioned before lots of people mentioned fatigue
aeroplanes are mothballed in that desert because its dry and not humid meaning parts will remain relatively free of any atmospheric degradation however remember most parts used in aircraft are given various anodic and galvanic resistive treatments, these parts can then be brought back in the case of b52
and most of the f111 fleet which are sent to our good freinds down under for their ageing aircraft which are undergoing the same kind of refurbishment
we in the bicycle world neither need or have cost allowance to under go such treatments and so its either polished anodized or painted
the anodizing on frames is sometimes hard or soft hard anodizing used on frames isnt really full depth anodizing as its not good for fatigue resistance and alloys which readilyaccept hard anodizing cannot really be welded into bicycle frames due to the fact that they stress corrosion crack
The white powder which appears on aluminium is also a precursor of stress corrosion cracking which is not really the sameas a crack caused by fatigue though does share certain mechanical causes
even in space where there is no air aluminium degrades by other mechanisms including the fact that its in the abscence of the harsh realities of the earths atmosphere
so if the structure is just sat unpolished or protected for 10 years then yes there is a risk of the aluminium being more succeptible to cracking based on chemical processes alone but this depends on a vast range of variables the main being what type of aluminium it is
am i an expert and do i talk crap before i became a composites guy i had lots to do with aluminium most of it capable of being pushed along by afterburners
in my day job im an expert
down the local pub i talk crap if its to get in a birds nickers i definitely talk crap
i believe the question original question was regarding aluminium degrading then white powder(not columbian) appearance on the surface was mentioned before lots of people mentioned fatigue
aeroplanes are mothballed in that desert because its dry and not humid meaning parts will remain relatively free of any atmospheric degradation however remember most parts used in aircraft are given various anodic and galvanic resistive treatments, these parts can then be brought back in the case of b52
and most of the f111 fleet which are sent to our good freinds down under for their ageing aircraft which are undergoing the same kind of refurbishment
we in the bicycle world neither need or have cost allowance to under go such treatments and so its either polished anodized or painted
the anodizing on frames is sometimes hard or soft hard anodizing used on frames isnt really full depth anodizing as its not good for fatigue resistance and alloys which readilyaccept hard anodizing cannot really be welded into bicycle frames due to the fact that they stress corrosion crack
The white powder which appears on aluminium is also a precursor of stress corrosion cracking which is not really the sameas a crack caused by fatigue though does share certain mechanical causes
even in space where there is no air aluminium degrades by other mechanisms including the fact that its in the abscence of the harsh realities of the earths atmosphere
so if the structure is just sat unpolished or protected for 10 years then yes there is a risk of the aluminium being more succeptible to cracking based on chemical processes alone but this depends on a vast range of variables the main being what type of aluminium it is
mikedesign
Dirt Disciple
ps all you pace owners out there
be afraid
be very afraid
be afraid
be very afraid
