# pressure vessel

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• Last Post 29 May 2018
Mehran posted this 29 May 2018

hi im working with pressure vessel that works in specific working cycle:

1) 4 hours takes that its pressure become from 0 to 103Mpa

2) 4 hours holds its pressure in 103 Mpa

3) 5 hours takes that its pressure become from 103 Mpa to 0

i do not know how simulate this in static structural or other parts, can u help me?

plz explain in simple mode im new with ansys, tnx

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peteroznewman posted this 29 May 2018

ANSYS Static Structural can simulate the stress in the parts when the internal gauge pressure is 103 MPa. In the screen snap above, in the Tabular Data window at the bottom right corner of the screen, in row 2 of the table that lists the Time as 1. you just replace the 0. in the Pressure column with 103e6.  You also need a fixed support. Click a small face that supports the vessel, not the whole outer circumference of the vessel, and under Supports, select Fixed Support. Then you can click the Solve button.

Are you interested in fatigue failure?  If so you have a 13 hour cycle where the pressure goes from 0 to 103 and back to 0.  In fatigue terminology, that is a stress ratio of 0.   If you have S-N (stress-life) curves for the materials in the pressure vessel, you can predict cycles to failure.

Mehran posted this 29 May 2018

you mean it does not necessary to apply whole hours in the tabular?

Mehran posted this 29 May 2018

and how can i predict cycles to failure for 13 hours i mean where i must apply 13 hours?

peteroznewman posted this 29 May 2018

I expect you are interested in the stress at 103 MPa and that this is an elastic material solution, so the stress at 10.3 MPa will be exactly 1/10 of the stress at 103 MPa.

Fatigue only cares about cycles, not hours.  Is the cycle done once a day?  If so, when you calculate the cycles to failure, you can divide by 365 to find out how many years the pressure can cycle like that before failure.

If you have S-N (stress-life) curves for the materials in the pressure vessel, you can predict cycles to failure by adding the Fatigue Tool to the Static Structural Solution and Insert Life.