Hoop Stress Calculation 2

[JW92]

Hello,

Could someone please explain how to go about calculating hoop stress in a steel barrel that is not under pressure, but rather filled with a powder mixture and also rotating.
Thanks,

 

[LittleInch]

If you can work out the surface loading this would equate to pressure and then use the normal formula.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[JStephen]

Treat the powder mixture like a liquid, and calculate pressure at the bottom of the barrel from that effect.
Find the centrifugal/centripetal force at the radius of the barrel, assume that same force acts from zero radius out to the edge, and calculate the resulting pressure from that effect.
Add the two pressures, calculate hoop force (pressure x radius for thin walls).
For an actual barrel, this would probably work fine.
Those first two steps are very conservative, and if you can show that the barrel is 8 times thicker than it needs to be, then you don't need to spend any more time on the analysis.
If it's not actually a barrel or you're spinning it at 10,000 RPM where the extra conservatism won't work, then you can look at it in more details.

 

[chicopee]

I agree with Stephen about treating the content like a fluid but you have not stated how the position of the barrel will be during the rotation. Is it to be rotated about the longitudinal axis of the barrel with the barrel upright or by some other axis with the barrel on its side? I am assuming that the barrel will be full.

 

[JW92]

The barrel will be rotating on its side and will be roughly 75% full.
Thanks,

 

[JStephen]

Now it's sounding like a giant rock tumbler, that's a little different...

 

[dhengr]

JW92:
Boy, it is like pulling teeth to get you guys to answer more than one question at a time and to really flesh out your problem with enough engineering detail and info. so as to generate some real discussion, instead of just more 20 questions. O.k., it’s on its side, about 75% full, by volume, or by height on the vert. dia.? Is it just rolling on the floor? How’s it structured and supported, is it some sort of mixing drum, a kiln, conveying the powder lengthwise, or some such, acting almost like a deep beam btwn. several supports? Let’s see a side view, plan and end view, with some sizes, dimensions, etc. Let’s see some material props. info. on the powder, is it just loosely rolling in the drum, or impacting the other side of the drum as it rolls and falls?

My first tack on the problem would have been just as JStephen explained it, given your OP. Now, it seems that you have some sort of a deep beam, hollow structure (drum), with uniform loading, which varies across the horiz. dia. of the drum, as a function of its depth. This can be converted to normal forces on the inside of the drum to produce some form of hoop stress, but about 1/3rd of the circumference is not loaded by any internal normal forces. Then, there is also an overall beam bending stress component to the problem too. You gotta explain some of this so we know what you are doing. Don’t just keep us guessing and wasting our time.

 

[LittleInch]

Agree with dhengr,

Unless you are rotating your horizontal? barrel fast enough that all the material is pressed against the side then hoop stress is not your issue, but more likely bending between the ends of the drum.

Some drawings / sketches / photos required to make sense of this.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[rb1957]

I think you have a very complicated problem.
how does the "powder mixture" respond to the rotating walls ? does it flow like a fluid, or "climb" up the walls and collapse ? how small are the powder particles ? small like continuum or large like discrete or a combination or any size !?
how fast is the drum rotating ?
etc ...

Are there similar drums in service that you can "copy" ?

another day in paradise, or is paradise one day closer ?