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

$$\text{HB} = \frac{2F}{\pi D h}$$

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

Note

Angle between the diamond faces is $136$ degrees. $$

$$HV= \frac{1.854\,F}{d^2}$$

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.

Type	Load	Indenter
HRA	60kg	Cone-shaped indenter. Made of diamond.
HRD	100kg	Cone-shaped indenter. Made of diamond.
HRC	150kg	Cone-shaped indenter. Made of diamond.
HRF	60kg	1/16” diameter (1.5mm approx.) ball made of steel
HRB	100kg	1/16” diameter (1.5mm approx.) ball made of steel
HRG	150kg	1/16” diameter (1.5mm approx.) ball made of steel
HRE	100kg	1/8” diameter (3mm approx.) ball

Note

No need to remember the above data.