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# Vonmises and Stress intensity of cylinder w/ internal and external pressure and Compressive load

## Vonmises and Stress intensity of cylinder w/ internal and external pressure and Compressive load

(OP)
Hi All,

Hope somebody could clear my doubts.
I'm looking to calculate the von mises equivalent stress (using distortion energy theory)and primary membrane stress intensity for a cylinder with internal and external pressure and with a compressive load on one sides as shown below.

So, for calculating the von mises equivalent stress using distortion energy theory, I used negative for calculating all three principal streses as the cylinder will be in compression with internal and external pressure. Hope this is right?
Principal stresses:
Longitudinal stress -> negative (-)
Tangential stress -> negative (-)

But for calculating the stress intensity under such compression load, should the stress values be negative as well?
Primary membrane stress intensity:
Longitudinal stress -> ?
Tangential stress -> ?

Stress intensity happens at a localized point unlike Von mises stress, but I'm not sure what to use in the formula + or - to obtain the stress values. Sorry but I am new to pressure vessel design. I appreciate your help.

Thanks,
Hanson

### RE: Vonmises and Stress intensity of cylinder w/ internal and external pressure and Compressive load

Your situation is either extremely theoretical to the point of smelling like a school assignment, or you have a situation that I cannot fathom. Can you provide some additional context to your situation?

### RE: Vonmises and Stress intensity of cylinder w/ internal and external pressure and Compressive load

(OP)
Hi,

A fluid pressure of 10000 psi is acting on the inner and outer wall of the cylinder. The cylinder is fixed at one end as shown and the other end
experiences a compressive force of 95000 lbf.
I just want to know whether,

1) three principal stresses ie., the longitudinal, tangential and radial stresses will be negative as the cylinder is in compression ?
2) how to calculate the stress intensities of the cylinder in compression. i used roarks formula to calculate the stress intensities, Table 13.5, Case 1b
but as the cylinder is in compression, im not sure if the three stress components must be negative?

Thanks.

### RE: Vonmises and Stress intensity of cylinder w/ internal and external pressure and Compressive load

Your situation is either extremely theoretical to the point of smelling like a school assignment, or you have a situation that I cannot fathom. Can you provide some additional context to your situation?

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