Derivation of ASME Section I formulas

[coolniks37]

Hi

This sounds interesting to me? How the formulas in PG 26, PG 27 etc can be derived?

 

[DSB123]

First principles.

 

[metengr]

The weld strength reduction factor in PG-26 2013 Edition of Section I was established based on creep data associated with comparing weld metal versus base metal creep behavior. The reduction factor reduces the base metal creep strength to that of the weld metal creep strength.

 

[coolniks37]

Thanks metengr for info abt WSRF.
DSB123, i know it is the first principles, but there ought to be reasons for terms like 0.005D etc in the formula?