Vickers pyramid hardness test.

When the Brinell test is used on very hard materials, low values result owing to the spherical shape of the indenter and flattening of the ball. These are eliminated by using a square based diamond pyramid indenter which does not deform easily and gives geometrically similar impressions under various loads. The diamond pyramid with an angle between opposite faces of 136 degree is pressed under a standard load into the surface of the material, and the diagonal of the indentation produced is measured- The load divided by the contact area of impression gives the Vickers Pyramid Number. VPN = Load in kg / Pyramidal area of impression in sq. mm

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