Formula for burst pressure of a flat plate or sheet.

Harness the power of precision mixtures of pressurized flammable vapor. Safety first! These are advanced potato guns - not for the beginner.
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Jeeperforlife
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Mon May 10, 2010 9:01 am

I am looking for the formula for burst pressure of steel and aluminum flat plate. I am trying to figure some different burst disks and end plates for my new gun I am building.

Marcus
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Marcus
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Moonbogg
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Mon May 10, 2010 6:52 pm

I made a hybrid with a flat plate at one end of the chamber. I am not a math wizz nor am I an engineer, so I used a software program to calculate the yield for me. If noone gives you equations, I will run the numbers through my program for you if you want. My hybrid has not exploded yet btw :D
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SpudFarm
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Tue May 11, 2010 5:07 am

Jeeperforlife wrote:I am looking for the formula for burst pressure of steel and aluminum flat plate. I am trying to figure some different burst disks and end plates for my new gun I am building.

Marcus
You might get a good answer if you ask "D_Hall"
Try giving him a PM if he dosen't reply here.
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velocity3x
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Tue May 11, 2010 10:32 am

Moonbogg wrote:I used a software program to calculate the yield for me.
@Moonbogg
Did you find COSMOS predictions to be accurate?
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Moonbogg
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Tue May 11, 2010 6:54 pm

velocity3x wrote:
Moonbogg wrote:I used a software program to calculate the yield for me.
@Moonbogg
Did you find COSMOS predictions to be accurate?
If the cannon not failing means anything, then yes, they were accurate. There were some variables in my design that cosmos didn't take into account, such as weld filler material and post weld heat treatment. But the welds are large beads and the filler material is comparable in strength to the base material, so with heat treatment I am assuming that the FOS is at least in the ball park that cosmos predicted, around 4.2 @ 200psi before yield.
I always thought aluminum was a ductile material, but I have noticed that the tensile is not much higher than the yield, so if the cannon approaches the yield at all, then it is also approaching ultimate failure which would not be far behind. What about you? Do you trust cosmos?
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velocity3x
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Tue May 11, 2010 8:46 pm

Moonbogg wrote: What about you? Do you trust cosmos?
I absolutely trust it to determine FOS. I feel very comfortable with its calculations. I've never used it to predict a point of total failure....like a burst disk. Do you think it would would be accurate enough to do it?
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Moonbogg
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Tue May 11, 2010 9:05 pm

velocity3x wrote:
Moonbogg wrote: What about you? Do you trust cosmos?
I absolutely rely on it to determine FOS. My metal of choice is aluminum with normal operating pressure of 1Kpsi. I feel very comfortable with its calculations. Actual, I was wondering if you had every used COSMOS to predict the bursting point of a burst disk design? I only have pneumatics but, it seems to me that COSMOS could be extremely handy for designing burst disks for various pressure ratings. Do you think it would would be accurate enough to do it?
I think it would be accurate enough to at least get you in the ballpark range you want to be. It calculates yield by default thought, right? Yield is different from tensile failure, so thats something that would have to be thought about. You can create your own materials with custom mechanical properties. Perhaps one could use the tensile strength in place of the yield strength, so when the FOS reaches zero, it should actually break. I duno, its worth playing around with. Maybe i'll test it on something easy to duplicate results with, like aluminum foil. Once I get the right numbers down, I would have an idea of how to treat other materials in respect to their tensile/yield strengths.
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Jeeperforlife
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Tue May 11, 2010 10:02 pm

Moonbogg wrote:I made a hybrid with a flat plate at one end of the chamber. I am not a math wizz nor am I an engineer, so I used a software program to calculate the yield for me. If noone gives you equations, I will run the numbers through my program for you if you want. My hybrid has not exploded yet btw :D
Thanks,
But I want to test a long list of ideas, I really don't think you want to go through it. If all else fails I will let you know some ideas and maybe you could do a couple for me. I will see.
SpudFarm wrote:You might get a good answer if you ask "D_Hall"
Try giving him a PM if he doesn’t reply here.
I did think of that, however I know he is busy and would prefer not to bother him if it is not needed. However I probably will if I don't get any other leads.

Thanks
Life is tough, it's even tougher when you're stupid. -John Wayne

Marcus
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