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brinell number

Posted on 2011-03-08
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i am reading about brinell number the and hardening test... so what does the brinell number relates to the hardness of a metal ?? is this a way of expressing hardness ?
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Question by:c_hockland
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TommySzalapski earned 2000 total points
ID: 35075741
The Brinell number relates to how deeply the metal (or other substance) was penetrated under pressure. A small ball is pressed into the material and the diameter of the dent is measured.

The wikipedia article is fairly good for this
http://en.wikipedia.org/wiki/Brinell_scale
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by:c_hockland
ID: 35075772
ok so it does express hardness in a way... so is it proportional to tensile strength , modulus of elasticity and ductility ???
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by:mwochnick
ID: 35077474
you should really read the artilcle your answers are in there.
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by:TommySzalapski
ID: 35078029
Just in case you are still wondering, no it is not proportional to any of those things all the time. In general, harder things are usually stronger, but that is not always the case. For example, by weight, live wood is one of the strongest substances known to man, but it's not hard at all.
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by:c_hockland
ID: 35078109
but as the brinel number increases so does the tensile strength
http://www.unified-eng.com/scitech/hardness/hardness.html

did i miss something ?
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by:TommySzalapski
ID: 35078487
If you read it carefully, you'll see that it's an approximation based on experimental data. Not all the data fits the function well, but most of it is close.
The most important thing to note is where it says "The conversions are intended for carbon and alloy steels in the annealed, normalized, and quenched-and-tempered conditions."
So in that very specific case, they are somewhat proportional.
I would expect that if you took several types of maple wood and did the same thing, you would find that they are also proportional, but not at all related to the formula for the steel.
So if you restrict yourself to a very limited, specific subset of materials, they may be proportional, but overall they are not.
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by:c_hockland
ID: 35078530
Hi Tommy ,
thanks for the input... I just have to make a choice between directly proportional and inversely proportional.... so between the two i would choose " directly proportional "...At least they are  for sure NOT inversely proportional , right ?
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by:TommySzalapski
ID: 35078655
I would agree with that. In general.
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by:c_hockland
ID: 35078665
ok , thanks much Tommy for all your help tonight !!
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