Hello,

I need to calculate the SIFs for a miter bend with a D/t>100 ratio. My question is:

On a FEM analisys, do i need to consider the effects of pression and temperature to calculate the SIFs?, can i do the analisys only with the in plane moments, out of plane moments and geometrical data?

Thanks and Regards

I assume piping code is B31.3.

It seems that large size thin-walled pipe with over 100 D/t ration and the SIF in Appendix D may not be valid…may be unlisted component.

First of all, you need to check if your component is “unlisted component” in B31.3. If so, you need to meet the code compliance of B31.3. i.e. para. 304.7.2(Unlisted Components and Elements).

If you are going to use FE/Pipe to get the SIF and flexibility only, you don’t need pressure and temperature. If other FEA S/W will be used, it is subject to which stress you will take a look.
However, if it is “Unlisted Component” per B31.3, I think, you don’t need to find the SIF because you must evaluate all stresses per ASME VIII.Div.2, Appendix 4.

Let's see other expert's opinion.

Dear all,

In order to obtain conservative results, temperature factor would not be taken into account. The analysis should be performed using the so-called "Cold Elasticity (Young) Modulus" of the basic material.

However, since thin walled piping components are involved, pressure factor should be generally considered. As both B31 piping Codes and speciality literature stipulates, for thin walled elbows/bends, the internal pressure load reduces the cross section distortion/ovalisation during the in-plane and/or out-plane bending process.
Therefore, internal pressure load reduces both the bending SIFs and bending flexibility (i.e. the elbow/bend becomes more rigid).

Therefore, for an accurate analysis purpose, internal pressure load should be taken into account and the geometrical nonlinear behaviour of the elbow/bend should be considered (i.e. the material still behaves linearly/elastically, but the geometrical nonlinear options should be involved during Finite Element Analysis).

For conservative and simplified approach, you may perform a linear-elastic analysis and you can ignore pressure loading effect for Stress Intensification Factors (i.e. in-plane and out-plane SIFs) assessment purpose.
However, the elbow/bend flexibility factor cannot be properly estimated using this simplified (full linear) approach because the actual value would be lower than the theoretical value obtained by linear-elastic analysis.

Regards,