# Talk:Cylinder stress

WikiProject Physics (Rated Start-class, Low-importance)
This article is within the scope of WikiProject Physics, a collaborative effort to improve the coverage of Physics on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
Start  This article has been rated as Start-Class on the project's quality scale.
Low  This article has been rated as Low-importance on the project's importance scale.
WikiProject Technology (Rated C-class)
This article is within the scope of WikiProject Technology, a collaborative effort to improve the coverage of technology on Wikipedia. If you would like to participate, please visit the project page, where you can join the discussion and see a list of open tasks.
C  This article has been rated as C-Class on the project's quality scale.

We seem to be acquiring a series of paragraphs extolling individual engineering firms and engineers - these seem out of place to me. I intend to remove these unless the OPs justify here. Bob aka Linuxlad 13:19, 4 June 2006 (UTC)

## Set by

The article says A and B are "set by" the pressure inside and outside pressures. Does this mean that A is the inside pressure and B is the outside pressure? If so, shouldn't the article say so? If not, what does "set by" mean? Rwflammang 12:51, 27 October 2006 (UTC)

I don't think this explanation and equation are accurate. For one thing the units don't work out.

## Errors

As the previous discussion says, the equation is incorrect as it stands on the basis of dimensional analysis and vagueness. The equation should be of the form sigma h = pressure x inner radius/wall thickness, where sigma h is the hoop stress. The axial stress is half the hoop stress. MattiMattik 23:40, 5 December 2006 (UTC)

Is there a way to change sigma_h to sigma_θ? its the more commonly accepted form but when i tried the equations wouldnt render. Also the introductory text uses the term axial whereas the equations use longitudinal shouldn't that be set to one or the other (preferebly axial). As a final point this page seems to be incorrectly named...'thin-walled cylinders' or something of that type would seem to more accuarately describe the content Sam Lacey (talk) 12:32, 7 January 2009 (UTC)

## The hoop stress equations are swapped.

You've got the equations for hoop stress in a cylinder and in a sphere interchanged, as a quick search for "hoop stress" will confirm (or just work through the derivation: it isn't hard).

John G. Hasler —Preceding unsigned comment added by 174.124.23.248 (talk) 16:14, 7 April 2011 (UTC)

No, I'm wrong. Sorry.

John G. Hasler —Preceding unsigned comment added by 174.124.23.248 (talk) 17:52, 7 April 2011 (UTC)

## Lead and redirects are poor

• I got to this page by searching for hoop stress. I found that term used in the lead paragraph but not defined until the next section.
• The first sentence of the lead begins by introducing the term circumferential stress, even though the article's title is "Cylinder stresses." Indeed, the next paragraph continues the discussion of circumferential stress. I infer that all of this is a yet-to-be-cleaned-up artifact of the article's history: presmuably, it was at one point titled "Circumferential stress."

Anyway, if we have to have so many other articles redirecting here (axial stress, circumferential stress, hoop stress, and wall tension), then we should show mercy to those innocents who find themselves dumped on a page that is not obviously what they'd gone searching for. Would somebody please revise the lead to clarify that this article subsumes an assortment of topics—and, optimally, mention those topics. That would provide a much more hospitable welcome to the beleaguered readers who've arrived via redirection.—PaulTanenbaum (talk) 16:45, 7 March 2012 (UTC)

Actually from the history, we find that the article was originally "hoop stress". Rmhermen (talk) 02:24, 10 March 2012 (UTC)

## Hoop stress is largest when r is smallest?

For isolated hoops this is backwards: for a given pressure and wall thickness, a large hoop will obviously experience a larger stress than a small one. However it does not obviously follow that a single hoop experiences more circumferential stress at its outside than its inside. In fact I would guess that since in strain the outer circumference will gain the same additional diameter and hence circumference as the inner, it will experience less stress than the inner by having that increment in strain distributed over a greater circumference, suggesting perhaps some sort of quadratic law governing distribution of strain over stress in a thick-walled hoop.

While this is pure guesswork on my part, if correct it would seem well worth clarifying in this article, as it certainly took me by surprise when I first read it. Does someone have a more authoritative source than guesswork on this point, along with the appropriate formulas making it obvious what's going on? --Vaughan Pratt (talk) 19:01, 10 March 2012 (UTC)

## Guessed definition

I tried to provide a definition in the head section (which was lacking as another reader pointed out) but I am not sure I understood the concept correctly. Is it just cylindrical symmetry of the stress field, or is it more restrictive than that? Is hoop stress the stress across any longitudinal section of the object, or just the normal (tangential) component of that stress? Imagine a cylinder with opposite torques applied to the two ends: is the stress inside the cylinder a "cylinder stress" too? Imagine two concentric steel pipes with a layer of rubber in between, and a torque applied to the inner tube: is the stress in the rubber layer a "cylinder stress" too? --Jorge Stolfi (talk) 23:33, 24 February 2013 (UTC)

## Here's a short derivation. Why refer to complicated Young-Laplace equation?

The derivation of the hoop stress in cylinders and spheres is easy enough that I think it should be included rather than vaguely referring the comparatively obscure Young-Laplace equation. Here's my short derivation if someone agrees this is good and would like to include it: "If a free-body "cut" is made along the axis and through the middle of a cylindrical vessel, the wall stress perpendicular to the cut will be the force in that direction divided by its area, σθ= F/(L*2*t) where L is length of the cylinder and 2*t is the total thickness of the "top" and "bottom" wall sections of the cut. This force F has to be equal to the total force in the opposite direction which is the pressure times the area projected (in the opposite direction) by the half-cylinder which is F=P*L*d where d is the diameter=2*r. The wall stress is therefore σθ=P*r/t. A similar cut in a spherical vessel gives σθ=F/(2*π*r) and F=P*π*r^2, so σθ=P*r/(2*t)." The cut can be made to isolate the wall or it is understood that the internal liquid can exert compression but not tension. Ywaz (talk) 08:11, 3 April 2013 (UTC)