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Created: 2024/05/09 01:21

Experiment No.: 02

NAME OF EXPERIMENT: HARDNESS TEST OF METALS

Objective

The objective of this experiment is to,

1. Study the Rockwell Hardness Tester machine.
2. Determine the hardness of high-carbon steel using Rockwell method.
3. Assess the resistance of the steel to indentation to gain valuable insights into its mechanical properties.

Significance

Hardness testing is crucial in evaluating the suitability of materials for various industrial applications. It,

1. Is an index property of metals.
2. Has correlation with other properties.
3. Has an wider application being a non-destructive test.

Apparatus

1. Rockwell Hardness Tester
2. High-carbon steel specimen
3. Diamond brale indenter

Data sheet

Calculation

Result

Based on our experimentation, the Rockwell hardness number (HRC) of the high-carbon steel specimen was found to be approximately 20 HRC with an equivalent Brinell hardness number of 235 HBW and tensile stress of 788 $Nm{m}^{-2}$.

Discussion

Hardness refers to the ability of a material to resist deformation, indentation, scratching, mechanical wearing, and cutting when subjected to external loads. There are various methods to measure the hardness of metals including Brinell Hardness and Rockwell Hardness test. Brinell hardness can be obtained by:

$$H=\frac{F}{S}=\frac{2F}{\pi D(D-\sqrt{D^2-d^2})}$$

Where, $S$ is the surface area of indenter and $F$ is the pressing load. Similarly, Rockwell hardness can be obtained by:

$$H=N-\frac{h}{R}$$

Where, $N$ is a specific factor often to be 100 or 130, $h$ is the depth of penetration (mm), and $R$ is the radius of indenter tip (mm).

For our experiment, we used the Rockwell Hardness Tester machine. We applied a minor load to:

1. Compensate any clearances.
2. Eliminate the unevenness of the surface. The maximum accepted roughness is $1.6\mu m$.

We also observed that, both Rockwell and Brinell hardness tests are non-destructive. We have seen that there are limited deformations and the deformations are partially reversed, no material removals occurred. As a result, the material's integrity was preserved leading to reusability and cost effectiveness.