Hardness Testing

Topics: Rockwell scale, Tensile strength, Vickers hardness test Pages: 5 (1472 words) Published: February 7, 2012
This experiment will explain what the Rockwell hardening test is and why it is used, how the experiment was conducted, data that was found, and the importance of testing the hardness of materials. This experiment explains and proves how the hardness of materials can be increased by alloying and heat treating. Intro – Rockwell Hardness Testing

Soft and hard qualities exist in materials. In materials, hardness measures the ability of a material to resist scratching, indentation, or penetration. Hardness cannot be expressed in terms of defined units; it is the result of a defined measurement procedure. It is a complex material property which cannot be related to basic properties. Tests measuring resistance to bending, cutting, and scratching have been used to assess the hardness of materials. Three separate but standard test methods are used to express the relationship between hardness and the size of the indentation: Brinell, Vickers, and Rockwell. Hardness tests are one of the most commonly used measuring devices to measure mechanical properties because they are relatively easy to perform and typically do not cause destruction. Figure 2: The above figure shows the principle of the Rockwell Hardness Test. Figure 2: The above figure shows the principle of the Rockwell Hardness Test. The objective of this experiment was to test the hardness of various materials. The Rockwell Hardness Test was used in this experiment and consisted of indenting each of the materials with a steel ball indenter or diamond cone. The indenter is fixed in the testing machine and is forced into the material at a preliminary load that corresponds to the scale in use. When equilibrium has been achieved, the testing machine follows the movement of the indenter and responds to the change in depth of penetration. On top of the preliminary load there is the major load. Together the loads create the total load that causes a permanent increase in depth of penetration from the initial load. Removal of the additional load allows for partial recovery, reducing the depth of penetration. Resulting from the addition as well as removal of the additional major load is a permanent depth allows the Rockwell hardness number to be calculated by the testing machine.

Figure1: The above figure shows the Rockwell hardness testing machine used. The Rockwell Hardness Test is the best to use when it comes to determining mechanical properties. This being because this test is the easiest to perform and the hardness value is calculated whereas in the Brinell Hardness Test, the hardness is calculated. A downside to this test is if a material were needed to be tested in between scales; a proper hardness value would not be outputted. Procedure

When it comes to testing the hardness of materials, two main tests called upon are the Brinell and Rockwell hardness tests. For our experiment, the Rockwell hardness test was used. This method consists of using a machine to calculate the hardness number. This machine has a variety of scales that can be used to test a wide range of materials whether they are soft or hard. For our experiment, scales C and F were used. Scale C uses a diamond cone and it used for steels, hard cast irons, case hardened steel and other materials harder that 100 HRB. HRB refers to the hardness test scale B which consists of copper alloys, soft steels, aluminum alloys, etc. Scale F uses a 1/16” steel ball indenter and is typically used for annealed copper alloys and thin soft sheet metals. Each scale has its own minor, major, and total load and needed to be set before beginning. If not set, the machine would know the material did not categorize in the currently set scale and would not continue until the correct setting was achieved. When everything was set as it needed to be, the various materials were placed in the machine and tested for hardness values.

Steel Alloy Results:
Material| Value| Average|
Stainless Steel CB7...
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