The formula to calculate the Knoop Hardness (HK) is:
\[ HK = 14.2 \cdot \frac{P}{d^2} \]
Where:
Knoop hardness test comprises of pressing the pyramid-shaped rhombic indenter (longitudinal edge angle 172.5°, transverse edge angle 130°) into a specimen with a defined test load (between 1 gf and 2 kgf).
Indentation Load is the load applied in the microhardness test, typically in the range of 1-1000 grams.
Diagonal Length is the length of the diagonal of the indentation made during the microhardness test, measured in millimeters.
Let's assume the following values:
Using the formula:
\[ HK = 14.2 \cdot \frac{0.9807}{(0.0017)^2} \]
Evaluating:
\[ HK \approx 4818492.388 \, \text{Pascals} \]
The Knoop Hardness is approximately 4818492.388 Pascals.
| Indentation Load (P) (Newtons) | Diagonal Length (d) (meters) | Knoop Hardness (HK) (Pascals) |
|---|---|---|
| 0.9 | 0.0016 | 4,992,187.5000 |
| 0.9 | 0.0017 | 4,422,145.3287 |
| 0.9 | 0.0018 | 3,944,444.4444 |
| 0.9807 | 0.0016 | 5,439,820.3125 |
| 0.9807 | 0.0017 | 4,818,664.3599 |
| 0.9807 | 0.0018 | 4,298,129.6296 |
| 1.1 | 0.0016 | 6,101,562.5000 |
| 1.1 | 0.0017 | 5,404,844.2907 |
| 1.1 | 0.0018 | 4,820,987.6543 |