During Vickers Diamond test, an 800 kg load was applied to the square pyramid indenter. If the average length of diagonals and angle between opposite faces of diamond were 300 cm and 120°, respectively, determine the Vickers Hardness Number (VHN).
Answer (1)
The Vickers Hardness test is used to measure the hardness of materials by pressing a diamond-shaped indenter into the material and measuring the diagonal of the indentation left behind. Here's how you can calculate the Vickers Hardness Number (VHN):
Formula for Vickers Hardness Number : V H N = d 2 2 F sin ( θ /2 ) where
F is the load applied in kilograms-force (kgf). Since the standard unit is kgf, and given the load as 800 kg, we can use it as it is assuming kgf is intended.
θ is the angle between the opposite faces of the indenter. This is given as 120°.
d is the average length of the diagonals of the indentation, which needs to be converted from cm to mm as this is the standard practice. Thus, 300 cm is 3000 mm.
Calculating the VHN :
Let's plug in the values: θ = 120° , F = 800 kgf, and d = 3000 mm.
First, calculate sin ( θ /2 ) : sin ( 2 120° ) = sin ( 60° ) = 2 3 ≈ 0.866
Now substitute these values into the VHN formula: V H N = 300 0 2 2 × 800 × 0.866 V H N = 9000000 1385.6 V H N ≈ 0.000154
This result, considering the typical hardness values, seems anomalously low. Thus, the typical Vickers Hardness values are expressed in much larger magnitudes. It highlights the importance of unit consistency and real-world procedural adjustments.
This calculation demonstrates how the sharpness and accuracy of the indenter, alongside measurement precision, critically influence calculated hardness values.
