Expt 2(b) - Hardness Test

ME 218: SOLID MECHANICS LABORATORY

H A R DN E S S TE S T EXPERIMENT NO.2(B)

BATCH: A8 07010042-07010046

HARDNESS TEST EXPERIMENT NO.2(B)

AIM

The aim of this experiment is to determine the Rockwell hardness numbers of metals. E Q U I P M E N T A N D T O OL S THE FOLLOWING HAVE BEEN USED: 1. 2. 3.

Rockwell hardness testing machine. Indenters. Specimen. T H OE RY

Hardness, though difficult to define exactly may be defined as resistance to permanent deformation. It can be determined either statistically or dynamically. Static hardness test can be further classified as follows:1. Those expression the hardness number in terms of the load per unit area of indentations. e.g. Brinell and Vickers test. 2. The Rockwell hardness test in which the Rockwell number depends upon the depth of penetration of the indenting tool. Significant information can be obtained from the hardness number of a specimen. Uniform hardness numbers are nearly always a sufficient guarantee of the uniform quality of the finished products. In this test the depth of the penetration of the given indenture under a specified load is measured. The type of indenter and load used depend upon the material to be tested. Scale B is used for the materials having hardness number upto that of MS and CI. The indenture is then a hardened steel ball of 1/ 16” dia. An initial load of 10 kg is applied on the ball. An additional load of 90 kg in then applied (major load). Scale C is used for alloy steels. The indenture is a diamond cone of 120 deg. included angle. Here 150 kg is used as the major load.

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P RO C E D U R E

The following procedure has been followed:  Keep the specimen on the machine table.  Turn the table upward so that distance between the indenture and specimen will be less than 8mm.  Select the HRC scale with the help of touch screen display buttons.  Press the start button, it will automatically go down in the specimen to make the impression and will display the HRC value.  HRB is used for Copper alloys, soft steels, aluminium alloys, malleable irons, etc.  HRC is used for Steel, hard cast irons, case hardened steel and other materials harder than 100 HRB  Brinnel Hardness Number (BHN) also can find from this after changing the scale.  Take at least 3 reading and take an average to get the final hardness value.

OB S E RVA T I ON S

Copper and Brass has got negative hardness values.

Material

Hardness Test used

Values of hardness

Theoretical Values

R1

R2

R3

Ravg

Aluminium

HRB

62.58

53.91

57.07

57.85

56

Mild Steel

HRB

91.60

87.76

90.56

89.97

71

High Carbon Steel

HRB

126.19

126.69

129.24

128.37

155

Brass

HRC

-14.41

-11.13

-4.25

-9.93

2

Copper

HRC

-55.67

-31.48

95.78

2.87

-20

3

C ON C L U S I O N

Experiment values calculated are almost in coincide with theoretical values. Negative values are due to scale.

D E TA I L S OF T H E S T U D E N T S

ROLL NUMBER

NAME

07010042

Repaka Jyoti Swaroop

07010043

Sharath Chandra Pawar

07010044

Puvvada N V Prudhvi Teja

07010045

J G M V Pramod

07010046

Vishnu Narayanan Suresh

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