Inconel 625 screw

[symphony123]

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,

 

[jte]

I’d use the green structural engineering book: ASD or Allowable Stress Design put out by the American Institute of Steel Construction. It’s a bit outdated, most new SE’s will probably have a copy of the silver LRFD instead. Just find an SE who started working in the early to mid- ‘90s or earlier.

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

 

[rneill]

The book "An Introduction to the Design and Behavoir of Bolted Joints" by John Bickford presents the same data as given by jte for the stress area and the root area of a 3/8"-16 bolt.

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.

 

[SnTMan]

Machinery's Handbook

 

[jte]

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.

rneill- If you could find where VIII says this, I'd appreciate it.

jt

 

[rneill]

My reference book made this comment but I've taken a look at ASME VIII and if you look at Appendix 2 for bolted flange calculations, it does indicate that the bolt area to be used in the calculations is based on the root diameter of the thread (look at the definition of Ab in Appendix 2).

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.

 

[ColonelSanders83]

FED-STD-H28A may have what you need.

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.

 

[jte]

rneill-

Thanks, I'll look up Ab in App 2.

jt