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What Is a Hardness Test?

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  • Written By: Felicia Dye
  • Edited By: Heather Bailey
  • Last Modified Date: 13 October 2014
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There are some material properties that are precisely defined. Hardness is not one of them. A hardness test can assess several things, such as a material’s resistance to bending, scratching, abrasion, or cutting. These tests can be conducted in numerous ways. Test methods generally depend upon the type of material being tested, such as a mineral, metal, or rubber.

Geology is a field where a hardness test can refer to an assessment of the resistance of scratching. It is common for geologists to use hard items to try to scrape rocks and minerals with an unknown hardness. There is a scale, known as the Mohs scale, which spans from one to ten. The softest materials are ranked at the lower end of the scale and the hardest items at the highest end.

A hardness test that utilizes the Mohs scale is considered a relative test. This is because the information that is attained about one material is related to that of another. Relative tests are often insufficient since they do not provide much individual information.

The Rockwell hardness test is one that is considered more accurate. This test also deals with scratching but focuses more on the indention than confirming whether one item can scratch another. This test is more complex and uses varying degrees of pressure. Since there are several measurable factors, this test provides specific numerical data.

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The Vickers hardness test also deals with indention. Numerical data can also be attained from this test. First, a diamond indenter is used to mar the surface of an item. Then, the force is divided by the area of the indention to produce the result.

A test that measures hardness in the terms of elasticity is known as the Scleroscope hardness test. The results of this test are based on hardness units. The test is performed by allowing a diamond-tipped hammer to fall onto the test material. The hammer should bounce back to some degree. This rebound determines the hardness.

Some people attempt the convert the results from one test to another or to compare them. This can be done in some cases but the results are not likely to be exact. This is because the factors that surround each test can be so different, making it very difficult to accurately convert one set of numerical terms into another.

The decision of which testing method is best is often based on the material being tested. Each method can have advantages and disadvantages. In some cases, it may be necessary to conduct more than one type of test on a single item.

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