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Author Topic: How do I calculate the thickess of material required for a container?  (Read 3080 times)

Offline zoz712

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I'm a student in grade 10, and i'm working on a science project.

if i have a spherical liquid container made of an elastomer (rubber), can anybody tell me how to determine the thickness of the rubber which is needed to hold the liquid inside......just a general equation

I need it so much....
« Last Edit: 19/03/2009 09:56:48 by chris »


 

Offline daveshorts

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That is probably not a trivial question, rubber is complex stuff, there are lots of different rubbers, and any non-symmetrical inflation is going to be complex.  What is causing the sphere to fail? Is the liquid under pressure? Is it going to be sitting on a flat surface and the failure is due to its flattening? How spherical do you want the sphere to stay? Gravity is going to always distort it. etc etc etc.

It is probably going to be quicker and easier to work it out empirically - by doing experiments to see when various different - shall we call them balloons - burst.
 

Offline zoz712

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That is probably not a trivial question, rubber is complex stuff, there are lots of different rubbers, and any non-symmetrical inflation is going to be complex.  What is causing the sphere to fail? Is the liquid under pressure? Is it going to be sitting on a flat surface and the failure is due to its flattening? How spherical do you want the sphere to stay? Gravity is going to always distort it. etc etc etc.

It is probably going to be quicker and easier to work it out empirically - by doing experiments to see when various different - shall we call them balloons - burst.
Thanks for your attention.....this rubber container will carry crude oil inside it and it's made of an elastomer called Viton, only this high quality elasomer can resist the chemical components of the oil.....i want a general equation to determine the thickness of the container to be able to contain the oil according to the weight of the oil (quantity)
 

Offline daveshorts

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How is the sphere being supported? It will depend on a huge number of things, and it will be hideous. I doubt that anyone has worked out a general formula for all cases Roughly how large a sphere are you talking about? - this may give some idea of how it is likely to fail. What are you trying to do with the balls of oil? As this may affect how they fail?

Fundamentally I may be able to help you with how a perfectly symmetrical ball will fail, but anything more complex will need hard maths and probably a computer.

Sorry have to go to bed now...
 

Offline zoz712

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How is the sphere being supported? It will depend on a huge number of things, and it will be hideous. I doubt that anyone has worked out a general formula for all cases Roughly how large a sphere are you talking about? - this may give some idea of how it is likely to fail. What are you trying to do with the balls of oil? As this may affect how they fail?

Fundamentally I may be able to help you with how a perfectly symmetrical ball will fail, but anything more complex will need hard maths and probably a computer.

Sorry have to go to bed now...
How is the sphere being supported? It will depend on a huge number of things, and it will be hideous. I doubt that anyone has worked out a general formula for all cases Roughly how large a sphere are you talking about? - this may give some idea of how it is likely to fail. What are you trying to do with the balls of oil? As this may affect how they fail?

Fundamentally I may be able to help you with how a perfectly symmetrical ball will fail, but anything more complex will need hard maths and probably a computer.

Sorry have to go to bed now...
I know that there isn't such an equation, i just want somebody to help me to form one 
The tanker (ship) is divided to smaller tankers.....it's divided like Bingo game (longitudinal and transverse), it's all made of steel....my rubber container will be inside each room in the tanker.....i don't know the weight specifically that's why i just want a general equation ofcourse with variables...
 

Offline Soul Surfer

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I still think you are a long way from describing what you want for any sensible answer to be given to the question that you wish to be answered. for example an elastomer containg a liquid of a density close to that of water suspended in the air will have to be a lot stronger than one suspended in water.  the final shape will probably not be spherical because gravitational or buoyancy forces and contact with tank walls will probably change it.  Also you do not state the intended purpose of this container. if for example it is to provide additional security against leakage in stressful conditions the rupture forces will have to be considered
 

lyner

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I think this is a similar question to the one about the footprint of a car tyre related to the pressure inside it and the load it bears. To a first approximation, you can say the footprint times the area must be the pressure in the tyre. That ignores the support that the fabric of the tyre provides.. The tension in the envelope could be found, I guess, by using the 'virtual work' idea (which I learned at A level but haven't used since).
This question is harder, though, I think.
I have a suspicion that the person who set the question may have not given it a great deal of though - or it would be obvious that you, in 10th grade (what age does that represent?- I am in the UK) might be struggling to answer it. (Comiserations) Go and challenge your tutor about it. If he / she has an answer then we would all be interested.

It is not always a bad thing to ask your teachers just what the hell they mean. They deserve to be put on the spot occasionally. Kids do it to me  all the time and I never label them a troublemakers!
 

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