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Anonymous Poster

Thick Shell

09/21/2007 7:29 AM

How to find the strain developed in Spherical Shell & in Cyllindrical tube due to stress in Three Dimensional case?

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Guru

Join Date: Jul 2007
Posts: 4448
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#1

Re: Thick Shell

09/21/2007 11:56 AM

ANSYS, COSMOS, ALGOR, etc. should do this nicely. Or, you could use Roark's Formulas for Stress and Strain book.

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Guru
Engineering Fields - Piping Design Engineering - New Member Egypt - Member - Member since 02/18/2007

Join Date: Feb 2007
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#2

Re: Thick Shell

09/22/2007 8:23 AM

To find the strain, you have to determine the various stresses arising.

Cylindrical shapes are subjected to Longitudinal, Hoop and Radial Stresses, where Spherical shapes are subjected to Longitudinal and Radial stresses only.

In reality, the hoop pressure stress varies thru the thickness of the pipe. This stress variation is defined by Lame's equations which apply equally for thin and thick walled tubes and spheres :

σhoop = (P ri2 + P ri2 ro2 / r2) / (ro2 – ri2)

σlongitudinal = P ri2 / (ro2 – ri2)

σradial = (P ri2 - P ri2 ro2 / r2) / (ro2 – ri2)

where, r = position through the thickness, ri = inside radius, ro = outside radius, P = pressure

Notes.

1. In cylindrical shells, pipes and tubes, the hope stress (circumferential stress which affecting at longitudinal joint) is the most severe stress, and used in design formulas.

2. In spherical and semi-spherical shells, the longitudinal stress (circumferential joints) is the most severe stress, and used in design formulas.

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