Pressure vessel's burst pressure with radioss block

Hi,

I'm working Pressure vessel (a cylindrical shell OD300 mm with 2 torispherical head).

I want to know the burst pressure by using Radioss Block.

I define my pressure as a time fonction from 0 o 1000 bar.

I use th brittle law (/MAT/PLAS_BRIT) to destroy elements reaching ultimate stress.

My results are weird so I want to know if someone already have been using such application with radioss block and if it's possible to help me.

Regards,

Samuel

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Altair Forum User

Hi,

i do not know if you have chekced already, but when i get weird results from pressure loads it is mostly because the normals on the elements are not orientated correctly (pressure on shells should act against the normal direction)

Altair Forum User

Hi,

It's not that kind of problem because I already check the normals on the elements but thank you for the advise.

I'm confident with pressure loads on linear static RADIOSS, my problems come from the non linear modelisation with RADIOSS BLOCK because I'm in plastic domain and reachs the vessel's break.

Do you have just an exemple with pressure loads and plastic domain?

Regards.

Altair Forum User

Hi,

what do you mean with 'weird'?

LAW27 is a elastic-plasic brittle material, including Johnson Cook and damage. Strain rate effects can be also included.

It is only for shells and damage occurs only in tension, but in your case you have only tension.

I'm wondering me a little bet, as you has said you want to destroy elements at ultimate stress. As i see in the help file, that the damage parameters are only strain based.

I would suggest to check:

*do you have right parameters for a,b and n (for the right stress-strain curve)

*make a graph of stress-strain e.g. for one element to check it

*let maximum plasticity stress 1e30

*switch strain rate off

*modify tensile strain, maximum tensil strain, tensile strain for deletion and failure damage for one of the principle directions for checking

Check all the things step by step (e.g. stress - strain without damage)

Regards,

Mario