Rolled Plate analysis.
Rolled Plate analysis.
(OP)
If you take a cylinder, capped at both ends, made from .25in 304SS, and cut it in half. Does ASME Section VIII criteria for external pressure still apply? The half cylinder would be fully welded to a flat plate. How does one analyze the stresses in the rolled plate? The plate is rolled to a 24in radius. The whole assembly is welded together then welded to a larger flat plate. The length of the cylinder is 36 inches.
I used Roark's, bent beam analysis, but since my R/d is much greater than 8, I am having trouble believing the results. I am trying to determine the amount of external pressure the half cylinder can withstand. I am also interested in the reactionary loads at the welds.
Any suggestions would be greatly appreciated. Thanks.
I used Roark's, bent beam analysis, but since my R/d is much greater than 8, I am having trouble believing the results. I am trying to determine the amount of external pressure the half cylinder can withstand. I am also interested in the reactionary loads at the welds.
Any suggestions would be greatly appreciated. Thanks.
There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.





RE: Rolled Plate analysis.
I am absolutely confused by your post above. Is the original cylinder a pressure vessel? Was it designed for internal pressure or external pressure? Are you sectioning along the meridional or circumferential direction?
RE: Rolled Plate analysis.
RE: Rolled Plate analysis.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rolled Plate analysis.
I have no idea how to deal with a short tube, or a short half tube.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rolled Plate analysis.
There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.
RE: Rolled Plate analysis.
at the ends, the pressure will be reacted by shear into the endplates (rather than hoops stress in the plate).
RE: Rolled Plate analysis.
The 5/8 holes are to bolt down the flat 2" inch strips down each side?
The rolled plate isn't a half-cylinder since its drawn considerably "flatter" than that, but the load will be greatest at the sharp bend between the flat 2 inch strips and the rolled upper cover as the cover is resisting a force "blowing off" the cover. The wall itself will be strong enough for this light a pressure, but the cover might leak around the bolt holes.
I'd analyze the cover as if it were flat. That's conservative, but not too far off.
RE: Rolled Plate analysis.
The way the drawing calls out the 5/8" holes suggests that the material is perforated, but gives no details that would allow analysis.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rolled Plate analysis.
RE: Rolled Plate analysis.
First, the original post is valid. I have what is essentially a half cylinder as stated and the original data is correct.
Second, the previous drawing, is wrong. Close, but useless for what I am trying to convey. Sorry about that. We see so many ambiguous questions and posts, there's no need to add any more.
Third, the attached drawing is what I am dealing with.
Finally, as stated before I analized this using Roark's, bent beam criteria. Since, it seemed applicable. However, after reviewing the results and thickness. I am wondering if I can use ASME Section VIII or basic pressure vessel theory. Which would help me generate a sound methodology.
I hope this clarifies what I am asking. Thanks.
There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.
RE: Rolled Plate analysis.
Mike Halloran
Pembroke Pines, FL, USA
RE: Rolled Plate analysis.
Good catch. Sorry about that.
There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.
RE: Rolled Plate analysis.
When analyzing a cylinder with internal pressure, the assumption is made that loading is uniform around the perimeter, which means there is no bending in the cylinder, just hoop tension. If you start putting attachments on the pressure side of the cylinder wall, that is no longer true, and you need to start looking at what kind of bending you are inducing.
RE: Rolled Plate analysis.
RE: Rolled Plate analysis.
in any case, given Steel, 1/4" thk, R = 24", p = 13.7psi ...
pR/t = 1.3 ksi, conservative allowable stress (assuming 50" long) = 2.2 ksi (and that's conservative by a factor of something like 5) ... reference NACA TN 3783 (available online)
RE: Rolled Plate analysis.
thanks for the reference. It will come in handy.
There are days when I wake up feeling like the dumbest man on the planet, then there are days when I confirm it.