Non-Circular Vessel Design

[PVGuy]

hello,

I am looking for a method to design flat plates under low pressure and some accelerations. The shapes do not fall within the scope of App. 13 in SC 8-1. One shape has an elliptical cross-section, the other is hopper like with an inverted pyramid shape attached to the bottom of a cube shape. The pressures, materials, and inert nature of the contents do not justify the expense of FEA. Any suggestions on a reference? Or just sweat it out with Roark?

Thanks in advance

 

[JStephen]

"Sweat it out with Roark" sounds like a good approach. Actually, you can make some conservative assumptions and check the results- if the results show it's okay, you're all set. If the results are unreasonable, then you know you need to go into more detail.

For example- on ellipse, perhaps consider checking as a circle with both the major and minor diameters, and figure you're results ought to be in between there. For a triangle, figure it ought to be stronger than a square with those dimensions. (assuming triangles and ellipses aren't in there, which they may be).

If you get someone really familiar with FEA, they could probably whip up a flat-plate design of arbitrary shape fairly quickly- about the easiest problem that could be done with FEA.

 

[prex]

Well JStephen, the elliptical section would be calculated based onto the major diameter, as the hoop stress is maximum there (and is easily calculated as Pa/t, a being the major semiaxis). However bending stresses also exist, they cannot be neglected as they are primary, and if I recall correctly they are maximum exactly at the major diameter. Roark does not seem to have the formula for this, but I think that it can be found on the net(a few years ago I had it, but can't find anymore).
Otherwise I concur with the reference to Roark. If the budget does not allow for FEA, then it is also possible to adopt ample margins based onto a rough analysis, and be prepared to add some stiffeners after hydrotest.

prex

http://www.xcalcs.com

Online tools for structural design

 

[PVGuy]

JStephen and Prex,

Thank you both.

 

[arto]

Triotsky has some Hopper Design methods in Ch.7:

https://ssl.lincolnelectric.com/foundation/item.asp?prodnum=TS&PID=16

 

[PVGuy]

Thanks Arto