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Brinell hardness
 

Brinell hardness

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    Brinell hardness Brinell hardness Document Transcript

    • Brinell hardness test Theory related to Brinell hardness The first widely accepted and standardized indentation test, was proposed by J.A. Brinell in 1900. Brinell hardness test is mostly regarded as destructive test. This test is widely used in different industries. Brinell hardness test is macro hardness test in which large volume is displaced by hardened steel or tungsten carbide ball. Brinell hardness number is the hardness index, calculated by pressing a hardened steel ball (indenter) into test specimen under standardized load. Brinell hardness tests are used to determine hardness of metallic materials, to check quality level of products, for uniformity of samples of metals, for uniformity of results of heat treatment. The Brinell Hardness Number (BHN) is obtained by dividing the applied force by the spherical surface area of the indentation, Equation: BHN formulae BHN = applied load in kg area of impression or indention in mm2 BHN = P Dtπ Where P = applied load in kilogram D = dia of ball used in mm d = dia of impression produced in mm t = thickness or depth of impression in mm Apparatus  Testing Machine Equipment for Brinell hardness testing usually consists of a testing machine which supports the test specimen and applies an indenting force to a ball in contact with the specimen. The design of the testing machines shall be such that no rocking or lateral movement of the indenter or specimen occurs while the force is being applied. The design of the testing machine shall ensure that the force to the indenter shall be applied smoothly and without impact forces. Page 1 of 5
    • Brinell hardness test  Brinell Balls Table 1 dia and tolerance of Brinell hardness ball Sr. no Ball dia, mm Tolerance, mm 1 10 ±0.005 2 5 ±0004 3 2.5 ±0.003 4 2 ±0.003 5 1 ±0.003  Measuring Device The divisions of the micro meter scale of the microscope or other measuring devices used for the measurement of the diameter of the indentations shall be such as to permit the direct measuring of the diameter to 0.1 mm and the estimation of the diameter to 0.05 mm. Figure 1 Brinell hardness machine Figure 2 Brinell hardness ball Test Specimen There is no standard shape or size for a Brinell test specimen. The specimen upon which the indentation is made shall conform to the following: Thickness Page 2 of 5
    • Brinell hardness test The thickness of the specimen tested shall be such that no bulge or other marking showing the effect of the test force appears on the side of the piece opposite the indentation. As a general rule, the thickness of the specimen shall be at least ten times the depth of the indentation Finish When necessary, the surface on which the indentation is to be made shall be filed, ground, machined or polished with abrasive material so that the edge of the indentation shall be clearly defined to permit the measurement of the diameter to the specified accuracy. Test procedure We were provided steel sample which were heat treated. Rough grinding is done with zero ambry paper. After rough grinding sample was checked either its or thickness and surfaces are flat. Than sample was placed over anvil and adjusted anvil. A steel hardened ball of 10mm dia is used. Applied the load of 3000kg for 10 seconds. Removed the load an impression has been made. Measure the dia of impression with low magnification microscope. Calculation 1st experiment Dia of steel hardened = 10mm Dia of impression = 4.7mm Load applied = 3000kg Dwell time = 10 sec BHN = 163.3 kgf/mm2 2nd experiment Dia of steel hardened = 10mm Dia of impression = 4.65mm Load applied = 3000kg Dwell time = 10 sec BHN = 166.59 kgf/mm2 Advantages of Brinell hardness  Suitable for hardness tests even under rough workshop conditions.  Suitable for hardness tests on inhomogeneous materials.  Simple test procedure.  Simple and cheap penetration element.  Conversion into tensile strength for various materials. Page 3 of 5
    • Brinell hardness test  Nearly All Metals Can Be Tested.  The Brinell Tests a Wider Sample of Material.  Results of the Brinell Test are Force Independent. Disadvantages of Brinell hardness  Restriction of application range to a maximum Brinell hardness of 650 HBW.  Restriction when testing small and thin-walled specimens.  Restriction when testing round specimen if diameter is smaller then 1, 5 x penetrator diameter.  Relatively serious damage to the specimen due to the large test indentation. Page 4 of 5
    • Brinell hardness test References  http://hardnesstesting.info/brinell05.html  http://www.ehow.com/list_7273906_advantages-brinell-hardness test.html#ixzz2gH4HMaSx  E10-01E1 - Brinell Hardness of Metallic Materials  http://www.academia.edu/2158292/Brinell_Hardness_Test_determination_of_hardnes s_of_steel_and_aluminum  http://www.instron.us/wa/applications/test_types/hardness/brinell.aspx  Mechanical metallurgy by dieter  Materials science and engineering by William D Callister Jr eighth edition Page 5 of 5