Charpy V-notch vs. keyhole 1

[MotorMan12]

For a pressure casing, we are looking at using a Copper-Aluminum Bronze (UNS C95300). The design is to be certified by a 3rd party verifying body for use on a ship. The standard to which we certify demands a minimum Charpy V-Notch value of 27 J. We have performed a rather extensive search for Charpy V-Notch values for the given material, but all references to Charpy are given as "keyhole". The certifying body is not too keen on "keyhole" and would like V-notch values. In the TQ50 temper condition, MatWeb has a data sheet with the Charpy keyhole value as 37 J, way in excess of the required 27 J. I have a suspicion, that the use of keyhole instead of V-notch for these materials is related to the failure mode, as these bronzes do not exhibit a ductile to brittle transition.

So, my questions:
1: Does anybody have experience with how the keyhole and V-notch values compare for a material (as the keyhole value indicates that I have a 37% margin)? Can I expect the V-notch value to come out above 27 J?
2: Any suggestions for where I should look to find V-notch values for the given material.

Any help would be much appreciated!

 

[metengr]

Perstens;
If correlations are developed between Charpy notch geometry differences, they are developed and compared for specific materials. A general assumption or correlation cannot be used or defended.

I would suggest you run actual CVN tests on this material for qualification. They are inexpensive tests to conduct and can be defended regarding the specific standard.

 

[TVP]

I agree with metengr, you need to perform actual CVN tests on your specific material/manufcturing process combination. Keyhole values will definitely be higher than V-notch, for a given material. I am almost certain that 37 J Charpy keyhole is going to be a lot less than 27 J Charpy V-notch, but don't have any specific data for this combination. For what it's worth, my gut says 10-15 J.

 

[MotorMan12]

I have also been under the impression that there is a non-precictable difference between the U and V notch values. Looking through the datasheets I have, however, also found materials where the U-notch value was higher than for the V-notch.

Anyway, the certifying agency has informed me that we do not require Charpy testing for Bronze materials (mainly relevant for steel in this context) and the problem has gone away.

Thanks for your resonses.