Hardness Testing Lab Report

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  • Topic: Rockwell scale, Carbon steel, Vickers hardness test
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  • Published : November 17, 2012
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1. INTRODUCTION

The purpose of the following experiments is to study the hardness of different types of materials, and to understand the significance of this property in materials. The materials and the aforesaid property have significant use in civil engineering. Hardness is defined as a measure of a material’s resistance to localised plastic deformation (i.e. small dents or scratches). As said above, a variety of metal alloys were used in the experiments to understand how each of these metals is characterised as a hard metal and to compare the hardness of different metal alloys. A study of how the molecular structure and the carbon content affects the hardness of each metal alloy used is also done during the course of the experiment. Three different tests are used, namely:

(i) Vicker’s Hardness test
(ii) Rockwell Hardness test
(iii) Brinell Hardness test
A further experiment, known as the Charpy Impact Test is conducted to study the toughness of some specimens of steel. Toughness is the measure of the ability of a material to absorb energy up to fracture. It has been discovered that the larger the area under a material’s stress-strain curve, the tougher it is. Therefore a more ductile material is tougher. An impact test is used to ascertain the fracture characteristics of the material, and it merely offers a relative sense of a material’s toughness.

2. APPARATUS
(i) Vicker’s Hardness Tester is shown in Figure 1.

Figure 1
(ii) Rockwell Hardness Tester, as shown in Figure 2.

Figure 2
(iii) Brinell’s Hardness Tester, as shown in Figure 3.

Figure 3
(iv) Mild steel specimen
(v) Carbon steel specimen
(vi) High carbon steel specimen
(vii) ASSAB steel specimen

3. TESTS

4.1 VICKER’S HARDNESS TEST

4.2.1 Experimental Procedure

i. We used a mild steel specimen and a carbon steel specimen for this experiment. ii. We placed the specimen on the stand under the lens.
iii. We then ensured that the image of the specimen could be clearly seen on the screen. iv. We then ensured that the indenter touched the surface of the specimen. v. We turned on the machine, and an indentation was made on the surface of the specimen. vi. We then adjusted two lines on the screen, and recorded the horizontal and diagonal distances of the indentation made. vii. We were also able to obtain the Vicker’s Hardness, HV, for the specimens used. viii. We conducted the test three times for each specimen. ix. The data is recorded in Tables 1a and 1b.

Table 1a Indentation on mild steel specimen

Dimension/value| Data | Mean|
| x1| x2| x3| x|
Horizontal diagonal, DH (mm)| 362.1| 367.1| 356.2| 361.8| Vertical Diagonal, DV (mm)| 366.0| 367.1| 357.6| 363.6| Vicker’s Hardness, HV| 140| 138| 146| 141|

Table 1b Indentation on carbon steel specimen

Dimension/value| Data | Mean|
| x1| x2| x3| x|
Horizontal diagonal, DH (mm)| 263.6| 294.10| 312.7| 290.1| Vertical Diagonal, DV (mm)| 263.1| 290.3| 316.6| 290|
Vicker’s Hardness, HV| 267| 217| 181| 222|

4.2 ROCKWELL’S HARDNESS TEST

4.3.2 Experimental Procedure

1. We used a high carbon steel specimen and an ASSAB specimen for this experiment. 2. We placed the specimen on the stand.
3. We turned the lever until the tip of the indenter touched the surface of our specimen. 4. We turned on the machine, and an indentation was made on the surface of the specimen. 5. We then obtained the Rockwell’s Hardness value of the specimens from the machine. 6. We conducted the test three times for each specimen.

7. The data is recorded in Tables 2a and 2b.

Table 2aHardness values for the high carbon steel specimen

Hardness| x1| x2| x3|
Rockwell’s Hardness, HRC| 28.0| 28.0| 27.8|
Vicker’s Hardness, HV| 286| 286| 284.6|

Table 2bHardness values for ASSAB specimen

Hardness| x1| x2|...
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