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SE2B (Structural) (OP)
16 Jun 10 8:54
I apologize as I didn't know exactly where to post this, so hopefully it is in the correct forum.

I encountered a situation where a 6061-T6 Aluminum tube [2.5 Dia – Schedule 40 (3/16" wall thickness] supposedly cannot be bent to the 8" radius that was specified.  The contractor has asked to use 6063-T52 aluminum in order to bend it to the specified radius. Based on all the information I could find, the 6063-T52 is more of an "architectural" grade and is not nearly as strong as the 6061-T6.  At the same time, this tube only has to support approximately a 100 lb at the end of this "j-type" configuration so even though 6063-T52 isn't as strong, I don't think using it will be a problem.

Anyone have any thoughts as to substituting one grade for another?  I may be missing something and I only have a few years experience to fall back on so any help would be appreciated.

Thanks in advance.
 
rb1957 (Aerospace)
16 Jun 10 9:37
1) set up a little test with the substitute material

2) bend in O condition and heat treat to T6 or T3
Twoballcane (Mechanical)
16 Jun 10 10:12
From my years of experience, if you need aluminum characteristics and also need to bend it, T53 is the material to use.  For sheets, T6 will crack and break if you try to add a sharp radius.  I use T53 sheets a lot to make electronic boxes and brackets (just to keep circuit cards in place), but never really used it for structural purposes.  However, rb is right, you should make up a test and see what happens, also do some hand calcs to quantify your stress.  Will there be dynamic load (G loads)?

Tobalcane
"If you avoid failure, you also avoid success."  

KENAT (Mechanical)
16 Jun 10 10:22
Have you done any calcs to verify the new material is strong enough?  That would be the first thing I'd think of.

Once that's done and assuming it's OK then you can worry about other factors.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

SE2B (Structural) (OP)
16 Jun 10 10:24
Thank you both for your input.  This pipe will be located outside and there will be some wind gust loading on this "j-pipe" as it is subjected to vehicles passing underneath it as well as general wind loading.
SE2B (Structural) (OP)
16 Jun 10 10:26
I did calcs and the material is definately strong enough.  I just wanted to ask the question because someone else may have had an experience substituting this or another material and I wanted any additional input for a little piece of mind.
KENAT (Mechanical)
16 Jun 10 10:31
So then, given it's external use you might want to check on its propensity to corrode (I'd guess 'architectural' addresses this but I don't know for sure) and given the gust loading you mention you may want to check out its fatigue characteristics.  Afraid I don't know about either though.

Posting guidelines FAQ731-376: Eng-Tips.com Forum Policies http://eng-tips.com/market.cfm? (probably not aimed specifically at you)
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?

Twoballcane (Mechanical)
16 Jun 10 15:04
Sorry, correction I meant T52 not T53

Tobalcane
"If you avoid failure, you also avoid success."  

Ron (Structural)
16 Jun 10 15:47
Substituting 6063-T52 for 6061-T6 is not an issue as long at the stress levels are sufficient for the lower strength material.  The fabricator is correct....the 6063-T52 will bend better and more likely without fracture than the 6061-T6 material.  Check and make sure that the chemistry of the 6063 is adequate for the environment in which it will be installed.  That's usually not an issue with this substitution, but check it anyway.

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