Indentation Test

Metal is subjected to indentation with a hard indenter. Depth of the indent is a measure of hardness.

Hardness units differ with the type of indenter used and the load applied.

Units

Brinell (HB)

• $10\,\text{mm}$ diameter steel / WC ball indenter
• Any load can be applied
• Diameter of the indentation is measured instead of the depth

Here:

$F$

applied load (in $\text{kN}$)

$D$

diameter of the indenter (in $\text{mm}$)

$d$

diameter of the indentation (in $\text{mm}$)

$h = (D-\sqrt{D^2 - d^2})$

depth of the indentation (in $\text{mm}$)

Vickers (HV)

• Pyramid shaped indenter made of diamond
• Any load can be applied
• Diagonal lengths $d_1$ and $d_2$ of the diamond-shape indentation are measured
• Average $d$ is used in the calculation

Rockwell (HR)

Not accurate enough to be used in academic level (or where accuracy is important). Industrially preferred because of ease of measurement. Only 3 load options.