Why not use the allowable stress value in ASME B&PV Code, Section II, Part D, Table 3 for SA 193 Grade B16? At 400 deg C (750 deg F) the allowable stress value is 20-22 Ksi depending on diameter for B16.
Thanks for that suggestion but in this case I am measuring the extension of the B16 stud in order to calculate the load using youngs modulus. I am concerned that if any creep occurs that may introduce error into the calculation. In effect I want to check there is no creep of any significance for a B16 stud operating below 400C so the load calc using youngs modulus remains correct.
Well, the good news is that for this service temperature, time independent properties govern the selection of allowable stress when compared with creep or stress rupture below (see below)
(b) At temperatures in the range where creep and
stress rupture strength govern the selection of stresses,
the maximum allowable stress value for all materials is established
by the Committee not to exceed the lowest of the
following:
(1) 100% of the average stress to produce a creep
rate of 0.01%/1,000 hr
(2) 100Favg% of the average stress to cause rupture
at the end of 100,000 hr
(3) 80% of the minimum stress to cause rupture at
the end of 100,000 hr
Favg = multiplier applied to average stress for rupture
in 100,000 hr. At 1500°F and below, Favg = 0.67.
Above 1500°F, it is determined from the slope of
the log time‐to‐rupture versus log stress plot at
100,000 hr such that log Favg = 1/n, but it may
not exceed 0.67.
