BRINELL HARDNESS TEST

Brinell Test

The fig shows the Brinell hardness testing machine.  It consist of pressing a harden steel ball into a test specimen.  According to ASTM specification a 10mm diameter ball is used for the purpose.  Lower loads are applied for measuring hardness of soft material and vice verse

Procedure for hardness testing:-

1.  Specimen is placed on the anvil the hand wheel is rotated, so that the specimen along with the anvil moves up and contact with the ball.
2. The desired load is applied mechanically or hydraulically and ball presses into the specimen.
3. The diameter of the indention made in the specimen by press ball is measured by the use of a micrometer microscope having a transparent engraved scale in the field of view.
4. The indention diameter is measured at two places at right angle to each other and the average of the two reading is taken.
5. The Brinell hardness number [BHN] which is the pressure per unit surface area of the indention is kg/m² is calculated as follows

BHN =                     W                        
                   (Π D/ 2)  (D - √ D²-d²)
 

                  Where       D is diameter of steel ball in mm

                                    W is the load on the indentor in Kg

                                    d is the average measured diameter of indention in mm

Brinell hardness testing is the best for measuring hardness of Grey iron casting and consisting of soft flake graphite iron and hard iron carbide.