Introduction
Is the material appropriate for manufacturing? If it can achieve the necessary outcomes when treated in the manufacturing process? Only if the value of characteristics of materials is known can you achieve more sustainable and quality products. To answer these questions one of the characteristics is hardness which can be determined by the hardness test.
In this article, we will discuss the hardness test, its importance, applications, etc.
I. What is Hardness?/ How can Hardness be Defined?
Hardness is a characteristic of the material that is measured to show the mechanical resistance of a test specimen. It is the mechanical penetration of the material on any other harder body. While performing the tests, the harder body is called the intender.
Diamond is used as the intender in the most tests as it is the hardest material in nature. Strength and hardness are not the same as strength is the resistance to separation and deformation.
II. What is Hardness Testing?
Hardness tests make it possible to quickly determine the resistance of a material to being damaged, scratched, or penetrated by a piece of another different material and its hardening state, being able, for example, to estimate its state of heat treatment. In this way, we can know the hardness of a material, and therefore, its resistance to deformation, and separation.
Keep in mind these points while drawing a conclusion of measurements outcomes of any hardness tests:
- Test force of the indenter
- The geometry of the indenter
- Loading time profile
- Test load duration
III. How Important and Useful is Material and Hardness Testing?
Hardness testing is a common test method used for material testing. These tests are significant because of their key features of being nondestructive tests, easy to perform and relatively inexpensive set of instruments are used during the process than other verification methods. Moreover, the test is performed without any alteration and directly on the sample material. With the technology advancement, hardness tests are becoming more simple to use but with modern, more reliable equipment.
Hardness testing is also used for quality management. The quality of products and materials is checked at goods in and out. In fields such as architecture, metallurgy, and automotive production, among others, tests must be carried out to help choose the appropriate materials. If a metal that is not hard enough to support the structure is used in the construction, a collapse could occur. Therein lies the importance of knowing exactly the level of hardness of the materials.
IV. What Determines Hardness?
Hardness is not a physical property but is the characteristic of materials that change with their surroundings. The hardness of the object can lie in different ranges. For example, the hardness of the material can be changed when heated. Hardness tests have no strict rules but the following are the points that should be determined while performing the hardness tests to get accurate and precise results.
- Choose the method according to the material characteristics.
- The load is employed on the indenter.
- Time duration of the load in the specimen.
- Indenter and specimen geometry.
V. How to Measure Hardness?/ How is Hardness Measured?
Following are the tests or methods which can help in determining the hardness of materials.
- Static application methods. In these methods, the test force is applied in a static way. The hardness is measured through the indentation size, or the penetration depth created by an indenter.
- Depth measurement methods. In these test methods, hardness is measured through the depth of residual indentation. There are three methods for depth measurement:
- Rockwell methods, which are on standard methods, are approved by ISO 6508 and ASTM E18.
- Brinell HBT and Vickers HVT test methods are non-standardized methods.
- Optical measurement methods. In these test methods, hardness is measured by residual size. Optical hardness testing methods are all standardized through ISO and ASTM: Brinell, Knoop, and Vickers hardness tests.
- Dynamic force methods, in these test methods, hardness is measured with the ball height of rebound. Leeb’s rebound method comes in this category.
VI. How to Ensure Accuracy and Repeatability in Hardness Testing?
The hardness test is only useful if you apply it correctly. Focus on proper execution, preparation, and choice of instrument in the tests. By ensuring these factors, you can get accurate and reliable results with repeatability.
Generally, if you are applying a hardness test with low test force then you need to control more factors to make certain precision of the outcomes is accurate in the hardness tests.
Following are the crucial factors that impact the results of hardness testing:
- Characteristics of surrounding or outside aspects should be controlled for example brightness, dust, sensations, the temperature of the place, and moisture.
- The test should be performed on a solid surface where the tester and equipment should be placed firmly
- Also, the specimen should be kept in a holder tightly.
- The position of the indenter should be perpendicular to the surface on which the test is under process.
- Correct setting of Illumination is also required and should remain the same during the whole process of the test.
- The placement of the tester should be verified again and again. Especially, when the indenter or objective lens is replaced.
Conclusion
Without the calculated hardness of the material used, no quality manufacturing can be done. Factories should have special departments to inspect their materials and then results also. The article clearly explained all the factors and points related to hardness and its testing, still if you have any concerns about hardness testing or you want to know about methods of hardness test then visit our website and solve your queries.