Author Topic: Engineer question... (Read 539 times)

Race · « **on:** October 21, 2008, 04:17:34 PM »

When designing a pressure vessel do longitudinal stress and hoop stress need to be individually calculated? Say hoop stress would need a thickness of .063 and long. being .032. Would the larger figure be used or the sum of each thickness?

If you use an example try to use these numbers:
P=1000 psi (Pressure)
R=2.875 inches (I.R.)
T=.125 inches (Thickness)
S=40,000 psi (Allowable Stress)
E=90% (Weld Eff.)

When considering a tensile strength of 40,00 is the sum of the total stress in all directions? (X+Y+Z=40,00psi) Or 40,000 psi in each direction?

Thanks,
Race

Edit:Changed I.D. to I.R.

RATTFINK · « **Reply #1 on:** October 21, 2008, 04:23:50 PM »

I'll get back to you...

RATTFINK · « **Reply #2 on:** October 21, 2008, 05:22:33 PM »

Ok, I received this information from an Eng. friend.

"you cannot design for the larger and just go with that. The two should be additive in some way but I'm not sure if it is vector addition or not. "

Race · « **Reply #3 on:** October 21, 2008, 05:45:49 PM »

Rattfink,
Thanks for the input from you and your friend. Finding formulas for each stress has been rather easy however the relationship between the two has escaped me. Intution tells me that the two thickness requirements added together should be enough to be at the safety factor I need. Perhaps even higher? Apparently they dont call it rocket science for nothing. I am trying to create a LOX tank thats light enough to fly yet easy enough to fabricate and still let me sleep at night when considering safety margins.

If you or anyone else happens to have any addition info that would be great.

Thanks,
Race

sluggish · « **Reply #4 on:** October 21, 2008, 05:56:18 PM »

Steam or diesel?

caldera · « **Reply #5 on:** October 21, 2008, 07:39:26 PM »

Are you building a Flux Capacitor?

Fulmar · « **Reply #6 on:** October 21, 2008, 07:48:58 PM »

Quote from: caldera on October 21, 2008, 07:39:26 PM

Are you building a Flux Capacitor?

Perhaps taking a hover board over water. But you need to have MORE power for that.

/hijack

Race · « **Reply #7 on:** October 21, 2008, 08:11:29 PM »

Actually, I thought the rocket science bit was enough to give it away. I want to use 6061 T6 aluminum. Its is a fairly common cryogenic material for a LOX (liquid oxygen) and RP-1 (which is basically highly refined kerosene). I haven't decided on whether to use an aerospike nozzle or a conventional bell nozzle. Both represent different challenges, parameters and benefits. I would be glad to discuss them with anyone who has an informed opinion. Not to often I get to bounce things like Isp,C*, DeltaV or L* off people.

Thanks,
Race

RATTFINK · « **Reply #8 on:** October 21, 2008, 10:24:10 PM »

I use 6061 T6 aluminum in the domes I design.

http://conservatek.com/

nirvana · « **Reply #9 on:** October 22, 2008, 05:11:54 PM »

You have anything to do with the "golf balls" at Buckley AFB in Aurora, CO Ratt?

Hangtime · « **Reply #10 on:** October 22, 2008, 05:47:39 PM »

Re: Engineer question...

"Steam or Diesel?"