Hardness is the testing of the specific material; it is not the permanent physical property.
The resistance to the indentation is measured by determining the depth of the indentation.
The fundamental physical hardness of the material is not for permanent time, you can their physical properties by applying different types of pressure or heating them.
The hardness test gives you the chance you determine the properties of the specific material. The physical properties include three different things such as strength, ductility, and resistance.
These properties are different for the different materials; they can help you to select the best suitable treatment for the specific material.
The basic definition of hardness testing is ‘’ it is the test in which you can determine the resistance of the specific material that exhibits the permanent deformation by applying pressure or penetrate it with another hard material”.
It is very important when drawing conclusions about the hardness test to evaluate the quantitative values.
The quantitative values must be evaluated by keeping these few things, what is the given load on the indenter, a certain loading time with the duration of loading, and the indenter geometry.
Hardness Testing Considerations
There are some important things that should be considered before selecting the hardness testing method. These are the simple characteristics of the material or things required to perform the testing.
- Material- what is the type of material you are using for performing the hardness test and what are its physical properties.
- Thickness- the thickness of the material is very important because the thickness of the material will suggest you the testing method. The test is performing according to the thickness of the specific material.
- Sample size- what is your sample size, the sample size is very important for the testing purpose. You can make conclusions according to the sample size.
- The shape of the sample- there are many different types of material and every material has a different shape or size. Identifying the shape of the particular material is necessary before performing the test because the test type depends on the shape of the sample.
- Scale- the scale you are using in the testing process will affect your results. So choosing the right scale for measuring the sample is very important.
- Gage R&R- it is the measuring method used to measure the accuracy of the sample results. It is the statistical tool used for the amount of variation in the measurement device.
How the hardness test works
A hardness test is basically performed by pressing the material with the help of the heavy or dimensioned objects. The loaded object is placed on the surface of the material that you want to test.
After some resistance, the sample material will be started deforming.
The hardness is typically measured by the depth of the indenter or by measuring the impression left by the indenter.
The hardness test is performed by the different tests, for measuring the depth of the indenter penetration the instrumented indentation testing, Rockwell and ball indentation hardness testing is used.
And for measuring the depth of the impression left by the indenter are Knoop, Brinell and Vickers used.
Selection of the test method
Before going to perform the test you have to select the test method according to the physical properties of your sample.
The hardness of the material is determined by the microstructure of the material, its shape, size, Thickness, and many other things.
In all tests for the hardness of the material, the one sample under the indent is the representative of the whole population. If you want to perform the test of different materials at a time than you need the impression in a larger amount.
There are four main types of hardness tests used to measure the hardness of any material. Every test has its own requirement with different benefits.
There are different standards for performing each test. There are some important things that must be considered before selecting the specific hardness test.
What type of material is used for hardness testing?
The material you choose for the testing is up to the mark. As you know every test has some rules or standards, so your sample should be according to it.
- The maximum hardness of the material is known before selecting the test.
- Whether your sample is homogeneity or heterogeneity, you should select the most suitable test for it.
- The size of the material on which the test is performed should be calculated.
- The number of available samples to be tested is mentioned.
- The accuracy of the results is very important in selecting the test.
The Rockwell hardness test
Rockwell hardness test is known to be the very quickest test among other tests. It is commonly used for metallic materials. It is developed to control the production of the specific material. The Rockwell hardness test is determined by measuring the depth of the indent. It is measured when the indenter forcefully hit in the sample material with a certain load on it. The Rockwell is commonly used for large sample materials. It is also used for performing advanced tests like HRC.
The Vickers hardness test
Vickers hardness test is used to check the hardness of the solid material especially for the metallic.
It is measured by the diagonal lengths of the indent sample left by applying the force on the diamond pyramid indenter with a specific load on it. The hardness is measured by the diagonal indents with the help of the formulas or tables.
The Knoop hardness test
Knop is the alternative test to the Vickers; it is used for measuring the hardness of the micro materials. I am commonly used for the brittle material and testing the hardness of thin objects. The indenter used in this test is the asymmetrical diamond and it is measured by the optical long diagonal.
The Brinell hardness test
The Brinell hardness test is used for testing the larger samples. The samples used in the test are in homogenous grain structures. The indentation will leave a large impression on the sample with the help of the carbide ball.