Because the allowable stress value is controlled by time dependent mechanisms for this material in this temperature range, like creep deformation or stress rupture (whichever is the lowest value). The allowable stress is all that is needed for design by rule.

Afox88, Psrt UHX provides a means to obtain yield strength from external prressure charts, by reference to UG-28(c). Look up in Part UHX nomenclature the definitions for Sy. You are then directed to UG-28(c) Step 3. Start reading at the words "Values of yield strength...", second sentence. Note that it is unrelated to geometry.

Since Chart HA-2 has a temp line for 1500 F, I don't see why you could not apply the procedure.

Regards,

Mike

The problem with sloppy work is that the supply FAR EXCEEDS the demand

Thanks for the responses Sntman and metengr.

I ended up extrapolating the yield strength from the table to 1100F and using that value (17600 psi). When doing UG-28 (c) step 3, as suggested by Sntman, using the 1200F curve, I got a B value of 10,000, doubling it would give a yield strength of 20,000 psi. I ended up using the lower extrapolated number as I do not feel comfortable using a yield strength at 1058F from the curve that is higher than the yield strength from Table Y-1 at 1000F.

At least now I have some ammo in my holster if my AI or customer questions by thinking.

Thanks for your help.