units of vickers,brinell and rockwell . . .

[kafri09]

hello everyone.

a little question...(or mybe two...)...

why does vickers and brinell hardness test have the units of stress ?

and why does rockwell test has no units at all ?


thanks to all !

[Mapes]

Hi kafri09, welcome to PF. Hardness is a measure of resistance to yield (plastic deformation), and the yield strength \sigma_y has units of stress. Thus, the Vickers and Brinell hardness measurements, which are related to \sigma_y, do too. The Rockwell hardness is measured on a calibrated scale, where the calibration points correspond to well-defined tests on well-defined materials (similar to the temperature scale, which is calibrated by certain equilibrium phase change reactions). Does this answer your question?

[kafri09]

yes it does.

thank u Mapes!