Question

Projected area rather than surface area of the indentation is used in

• A. Brinell test
• B. Rockwell test
• C. Vickers test
• D. Meyer test

Hint:

Remember the key calculation basis for major hardness tests: Brinell & Vickers use surface area, Meyer uses projected area, and Rockwell uses depth.

Answer 1

The Correct Option is D

Step 1: Recall how each hardness test defines its number.
Hardness numbers are generally load divided by some measure of the indentation, and the tests differ in exactly which area or depth they use.
Step 2: Go through the tests one by one.
Brinell hardness divides load by the curved surface area of the spherical impression, Vickers hardness divides load by the surface area of the pyramidal impression's sloped faces, and Rockwell hardness skips area altogether and instead reads the depth of penetration.
Step 3: Isolate the one that uses projected area.
Meyer hardness is defined differently, it takes the load and divides it by the flat, projected circular area of the indentation as seen looking straight down, giving $H_M = \dfrac{4P}{\pi d^2}$, which is the only one of these four tests built around projected rather than true surface area.
\[ \boxed{\text{Meyer test}} \]