Hardness test

HARDNESS TESTEngr. 3451 Lab: 2

Hardness

• One if the mechanical properties that may be important to consider is hardness which is a measure of material’s resistance to localized plastic deformation

• Moha( Minerals)• Vikers• Knoop• Scleroscope• Brinell• Rockwell

Moha

• Moha based the scale on ten minerals that are all readily available.

• The hardest of material is measured against the scale by finding the hardest material that the given material can scratch, and / or the softest material that can scratch the given material

Vickers hardness test

• Vickers Hardness is an alternative to the Brinell method to measure the hardness of materials.

• The Vickers test is often easier to use than other hardness tests since the required calculations are independent of the size of the indenter, and the indenter can be used for all materials irrespective of hardness.

Knoop hardness test

• The Knoop hardness test is a micro hardness test - a test for mechanical hardness used particularly for very brittle materials or thin sheets, where only a small indentation may be made for testing purposes.

• A Diamond indenter point is pressed into the polished surface of the test material with a known force

Scleroscope Hardness• A scleroscope is a device used to measure rebound hardness . It

consists of a diamond-tipped hammer dropped from a fixed height.

Brinell scale • The Brinell scale characterizes the indentation Hardness of materials

through the scale of penetration of an indenter, loaded on a material test-piece. It is one of several definitions of hardness in material science.

• The typical test uses a 10 millimetres (0.39 in) diameter steel ball as an indenter

• Standard Load: 500Kg, 1500Kg, 3000 Kg• Time: 15 sec. Ferrous metal, 30 sec. Non Ferrous , 120 sec. Magnesium

Rockwell scale

• The Rockwell scale is a hardness scale based on the indentation hardness of a material.

• There are different scales, denoted by a single letter, that use different loads or indenters.

HR = E - e F0 = preliminary minor load in kgfF1 = additional major load in kgfF = total load in kgfe = permanent increase in depth of penetration due to major load F1 measured in units of 0.002 mmE = a constant depending on form of indenter: 100 units for diamond indenter, 130 units for steel ball indenterHR = Rockwell hardness numberD = diameter of steel ball

End OF Presentation