Brinell Hardness?

[Jeff82]

I was wondering about how Brinell hardness numbers should be interpreted. For instance, is the numbering linear. So, when comparing a BHN of say 16 to another reading of 20, is the reading of 20 actually 25% harder than the reading of 16? I was comparing two different bullets with the above BHN numbers and the BHN 20 bullets seemed much harder than the BHN 16 bullets, much moreso than I expected.

[Defcon-One]

Not likely!

As the ball is pressed deeper into the metal the resistance will increase as it is required to displace a greater and greater amount of metal as it progresses. This would lead me to believe that there is not a linear relationshsip between the numbers, (ie. 20 would not be exactly twice as hard as 10).

These test are comparitive to allow a metal samples hardness to be compared to another samples and reproduced through the exact same testing. Pressure, dwell time and ball size are critical and must be identical for comparison of results between samples.

I could find nothing on the internet that answered your question at all. I searched on, "Are Brinell Hardness Test Outputs Linear?" and "Is Brinell Hardness Test a Linear scale?".

However, I am just guessing based on what I know! Good luck!

[Pepe Ray]

I would agree with Defcon-One's conclusion and for the same reasons.
Pepe Ray

[btroj]

More Important than is it linear is how the bullet got that hard.

A straight Linotype bullet maybe 18 BHn. A 50/50 WW/lead bullet can be heat treated to the same BHN. How they behave is very different. The linotype bullet is brittle and could fracture on impact. The 50/50 heat treated bullet can expand easily yet hold together.

BHn alone is not the entire story. It is A measure of bullet strength/ behavior but many other things are important too.

[williamwaco]

It is most definitely not linear . . .

http://en.wikipedia.org/wiki/Brinell_scale


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[mehavey]

Since Brinell numbers are literally the metal's yield strength in "pounds per square inch", they ARE linear.
Double the brinell number and you have double the strength ("hardness") of the alloy.

(If you don't believe this, check the chart HERE (http://www.frfrogspad.com/miscellm.htm) )

The only thing that all the "squares & square root" terms do in the Brinell equation is convert the diameter
of the impression made by the steel ball into spherical surface area.

http://www.gordonengland.co.uk/hardness/brinell.gif