Fbry and Fbru for nickel aluminum bronze

[Joa38]

Can anyone point me to a reliable source for bearing properties for nickel aluminum bronze (QQ-C-465, Alloy 642, Mil-B-6946, or AMS 4640) as used in NAS (76,77,537,538) bushings?

I have a rule of thumb for these numbers but no firm documentation.

Thanks.

Joa

 

[israelkk]

QQ-C-465A gives/requires only yield and tensile properties. Therefore I think you should use those values safely because the bearing Fbry and Fbru rre usually even higher than the tensile and yield in tension.

For alloy 642 the values are vary with bar diameter as follows:

upto 0.5" bar diameter uts=80 ksi and yield=40ksi
0.5" to 1" bar diameter uts=75 ksi and yield=37.5ksi
1" to 3" bar diameter uts=72 ksi and yield=35ksi
over 3" bar diameter uts=70 ksi and yield=30ksi

 

[Joa38]

Thank you for your reply and information.

Wouldn't this be too conservative and result in the bushings being very bearing limited in many instances?

Just for comparison with a material that I do have numbers on (Mil-H-5)... Copper Beryllium Per AMS 4651 has tensile vs bearing values of 180 vs 306 in ultimate and 145 vs 225 in yield. This is quite a bit of difference and can really influence a design.

Anybody ran across hard numbers for this material?

 

[israelkk]

First Copper Beryllium can be heat treated to 42RC while alloy 642 is not treatable. You may use the 1.5 ratio in 642 too. However, be careful to check what is the exact meaning and terms and how the bearing values were determined. It is explained in MIL-HDBK-5. As far as I know there were determined by a static load between a hardened pin against a a very close diameter where the hole diameter to length is very specific.

 

[Lcubed]

Bearing 'brinelling' compressive stress is about 1.81 x Fty, and can be as much as 2 x Fty with friction. I suggest you use 1.8 times tensile yield strength. Reference Nadai and Wahl, "Plasticity", and others. Hope this helps.
Regards