Axisymmetric Analysis of Long Thin Cylinder

[JuanGarcia]

I am currently doing an axisymmetric analysis of a very large bolted flange connected to a long thin cylinder.

Does anybody in the group know the formulae to find the distance at which the effect of an axisymmetric shear or moment at the end of the cylinder dies away?

In the fea model, I can discontinue the long cylinder at this distance from the joint without any significant effect on the stresses at the joint.

Regards,

Juan Garcia BSc(Hons) Ceng MIMechE DipEM
Pipetech Design & Construction (UK) Ltd.
Engineering Director

 

[prex]

You can take three times the square root of cylinder radius times the thickness. This value is quite sparingly: take the double if you want to exaggerate.
In the site below you find many calculation sheets for thin cylinders under various loadings and restraints.
prex
motori@xcalcsREMOVE.com

http://www.xcalcs.com

Online tools for structural design

 

[butelja]

The local stress dissipates at a rate of:

exp(-1.285*x/sqrt(r*t)), where

exp(x) = e^x; (e=2.71828...)
x = distance along cylinder
r = cylinder radius
t = cylinder thickness

This information comes from eq. 4.5.5 in Theory and Design of Pressure Vessels, 2nd Ed., by John F. Harvey.

 

[juancito]

I´m at home now and dont have the code here, but if you see that code section that deals with location of stiffening rings nearby cilinder-conical intersections, you´ll see that the stif.. ring has to be located within something like 1.8 x (dxt)^1/2 (sorry but I don´t remembre exactly the formula). That is because beyond that distance, the stresses, no matter how high they are, fade away, so the ring has to be located in an are where it is helpfull.
Besides, please have a look in the books of Bednar or Farr (or in Timoshenkos´s Theory of Plates and Shells).