Allowable Stress for materials from EN10216-5

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r2user_0790
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Registriert: Do 10. Jan 2013, 08:22
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Allowable Stress for materials from EN10216-5

Beitrag von r2user_0790 » Di 16. Dez 2014, 16:10

Hi

I have a question about the allowable stresses for austenitic materials from EN10216-5.
The allowable stress at the beginning of the creep-range is strange.
There is a strong discontinuity in the allowable stress acc. to EN13480-3 when
using these materials e.e 1.4918 etc.

Here is the allowable stresses plotted with ROHR2:
X6CRNIMO17.PNG
There is a sudden increase in the allowable stress at 550°C.
Is this correct?

Best regards
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rohr2support
Beiträge: 352
Registriert: Mi 14. Sep 2011, 08:23

Re: Allowable Stress for materials from EN10216-5

Beitrag von rohr2support » Di 23. Dez 2014, 08:12

Dear User,

you are right, this looks a little bit odd.
It is caused by the fact, that for some materials the usage of the creep rupture range leads to higher allowable stresses than the usage of the yield strength.
If you compare the yield strength with the creep rupture range, it looks like this:
creep.JPG
In EN13480 the allowable stresses for the mentioned material is calculated according to equation 5.2.2-2 for for temperatures below creep range:
f.JPG
For temperatures above the allowable stresses are calculated according to equation 5.3.2-1:
fcr.JPG
When you display the calculated stresses, it looks like your picture above. Therefore, this is no bug in ROHR2, as the calculation of the allowable stresses are given by the calculation standard.
This question occurred already a few times to our support team and already was questioned and discussed at the helpdesk of the EN13480. Therefore we decided from now on to check, which equation leads to lower allowable stresses. Additionally we are interpolating the allowable stresses at the intersection point, so this will be the new graph:
creep-new.JPG
We think that this procedure is the only sense full way to solve this problem, as the original procedure just doesn’t make sense.

Best regards
ROHR2support
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