Inconel 625 screw
Inconel 625 screw
(OP)
Hi
I am trying to get the information for B446 mechanical propterties. I could get these from the ASME codes but I am looking for the bolt stress area of a 3/8-16 UNC 13/4 SCKHD cap screws.
Where can i get this information. Which standard do i need to refer to.
Any help in this regards is greatly appreciated.
thanks,
I am trying to get the information for B446 mechanical propterties. I could get these from the ASME codes but I am looking for the bolt stress area of a 3/8-16 UNC 13/4 SCKHD cap screws.
Where can i get this information. Which standard do i need to refer to.
Any help in this regards is greatly appreciated.
thanks,





RE: Inconel 625 screw
In my copy, 9th ed copyright 1989, rev 1991, the tensile stress area of a 3/8 dia 16 tpi fastener is listed as 0.078 sq.in. That's the value I'd use. Others prefer a more conservative approach and calculate the area based on the min root – this is listed as being 0.068 sq.in if that's the value you prefer.
jt
RE: Inconel 625 screw
However, it does provide a little bit more detailed background as follows:
The conventional formula for stress area (as presented in ASME B1.1) is:
As=0.785(D-(0.09743/n))^2
where D = nominal diameter and n = threads per inch.
However, this book presents an alternative formula that they suggest is more appropriate for materials having an ultimate strength in excess of 100,000 psi (as determined from test coupons):
As = 3.14((Esmin/2)-(0.16238/n))^2
where Esmin is the "mean of the minimum pitch diameter" permitted by thread tolerances and the nominal root diameter.
With regards to the subject of stress area vs. root area, I believe that ASME Section VIII requires the more conservative root area be used.
RE: Inconel 625 screw
RE: Inconel 625 screw
rneill- If you could find where VIII says this, I'd appreciate it.
jt
RE: Inconel 625 screw
I do know that ASME is working on new bolted flange procedures based upon the work by the PVRC so perhaps this will change in the near future when the new requirements are introduced.
RE: Inconel 625 screw
It is important to not that I have come accross design rules forcing the use of the root thread area rather than the tensile stress area when calculating stress in the fastener. Make sure to check you requirements.
RE: Inconel 625 screw
Thanks, I'll look up Ab in App 2.
jt