Hi all,

I am trying to create a new Material in the database : the X6CrNiTi18-10 (austenitic Steel, 1.4541 according to German DIN). My stress analysis is based on B31.3 (CAESAR 5.1 database has this material only according to EN 13480). As far as I know in the column “Allowable stresses” I have to put the value Sh, which is calculated according to B31.3 as the lowest of (Ultimate tensile Stress/ 3) and (yield stress / 1.5).

Which value should I use in the place of yield stress for this specific material: The 0.2% or the 1% proof stress? (In literature I found both values).

Is there any general rule when one should use the one or the other value (e.g. depending on the type of material)?

Thanks in advance

Hello HH piper

Austenitic and non austenitic steels are dealt with differently. Austenitic steels base the design stress on the 1% proof stress. B31.3 is not clear on this, but the European codes such as EN 13480 use the 1% proof stress in the case of austenitic steels. The pressure vessel codes such as PD 5500 and EN 13445 also follow this practice.

We are not material experts, but this seems to be the reasonable route to take.

Thank you very much Ray for the very useful answer.

Another thing I noticed: The thermal expansion coefficient in the Material database of CAESAR 5.1 for the material mentioned above (1.4541) is very different of what I find in the literature (in the range from 10 to 12 x E-06 [°C-1] in the former versus 16 to 18 x E-06 in the latter). I thought expansion coefficient is a property of the material and shouldn't depend on the code. Or am I wrong?

Thanks once again

Hello HH Piper

According to EN 13480, the coefficient of thermal expansion is derived from a polynomial with given coefficients. That was the way it was done. We have noticed that the value can very depending on the literature.