Can anybody give me any WEB BASED FREE references for curve fitting of factors "A" and "B" used in ASME Sec VIII external pressure calculations?

Any type of reference used to "digitalise" the curves by curve fitting or any other methods would be helpful.

I already have prepared a spreadsheet (about 3 yrs back) which does interpolation based on the equivalent tabular values of Fig G and the Fig B charts. I have run SOME cases and compared it with software outputs and the results are fairly comparable. However, the current spreadsheet performs LINEAR INTERPOLATION for the tabulated values. Is that correct?

From ASME Sec II-D Appendix 3, para 3-800, I have obtained a reference to "Michalopoulos, E., A New Method for the Development of External Pressure Charts, ASME PVP-Vol.312-2, pp. 293–301, 1995". However, I have not been able to obtain the same online. Any idea if the same is available online?

Thanks in advance.

Vishal,

The ASME codes permit any type of interpolation provided it is reasonable. A change was made to all of the codes a couple of years back to permit this. In the external pressure charts linear interpolation is not necessarily the correct value but it will get you results in the general range.

When calculating external pressure it should be noted that the code does not consider axial compression, bending, or torsion their effects on the collapse pressure. That is my personal reasoning for always being conservative with external pressure.

Regards,
EJL