Are you having trouble determining the hardness of various materials for application in manufacturing your products? If so, you should consider the Brinell hardness test. The procedure for performing a Brinell hardness test is quite easy, and if you follow this guide, your results should be accurate.
The Brinell hardness test is a standardized test used for measuring the hardness of metals and other hard materials. It is performed by measuring penetration depth into a standardized material with a known hardness, typically steel or copper, when an object with a known force is pressed into it at a standard rate. It is named after Swedish engineer Johan August Brinell who developed it in 1900.
The objective of this post is to teach you how to perform Brinell Hardness tests on various materials.
I. What is the Brinell Hardness Test?
The Brinell hardness test is based on the amount of resistance that a solid material offers when it is pressed into by force. Brinell’s method produces a small depression in the surface of some sample material with a ball of specified diameter, then measures its depth. The difference between the initial and final diameters is multiplied by some factor (which varies from one instrument to another) to estimate penetration depth. Softer materials result in deeper depressions, while harder materials result in shallow depressions.
II. Principle and Theory of Brinell Hardness Test
Brinell hardness testing uses a known-sized ball with a diameter of 10mm and is pressed into the material with a specified amount of force. The smallest indentation made into the material is then measured and recorded. Based on the initial and final diameters of the indentation, the percent of density change can be calculated to determine the material’s hardness value.
The indentation depth, “d”, is called Brinell depth and depends upon both applied load and sample hardness. Since a ball of steel with radius “R” is used as an indenter in this method, the Brinell hardness of the material will be directly proportional to its elastic modulus and inversely proportional to Poisson’s ratio. A tungsten carbide ball is used for harder materials instead of a steel ball. The Brinell method produces the deepest indentation making this method versatile for measuring the hardness of various materials accurately, taking into account the irregularity of material surface and structure of the material.
Generally, the harder the material, the smaller the indentation. Therefore, a large, shallow indentation indicates a softer material, while a small, deep indentation indicates a harder material.
III. Testing Requirements
- Choose a test material with a rough surface that other methods cannot be used to test.
- Select the right indenter: Use the right-sized ball for the material you are testing.
- Uniform Load: You need a known force applied to the indenter during testing that will have a consistent penetration depth.
- Position the indents correctly to ensure sufficient clearance between the sample edge and the individual indents.
IV. Testing Standards
- ASTM E10
- ISO 6506
- JIS Z 2243
V. Brinell Hardness Test Procedure/ How to Perform a Brinell Hardness Test?
Here is a step-by-step guide for performing a Brinell hardness test:
- Pick a ball with an appropriate-sized indenter depending on the type of material you want to test.
- Carefully uniformly position the ball so that its diameter coincides with that of the sample surface, and its circumference leaves it just a bit smaller than the sample surface. Ensure there is enough clearance between the indenter and the test sample edges.
- Turn on the motor and use the hand lever to pull the load into position. Press it down until it creates an indentation in your sample, and wait for 10 to 15 seconds.
- Measure the diameter of the indentation with a micrometer to calculate its depth based on this measurement.
- Repeat this procedure at different positions on the test sample to get the data for calculating the hardness of the material.
VI. Brinell Hardness Formula
The formula used for calculating Brinell hardness is as follows:
Now that you have your indentation depth, multiply it by the known load of your testing machine, so you get a value. Divide this value by the original known radius of your test piece to get penetration depth in inches (this is just the area you measured). Then, divide it by two to determine the force per unit area, which can be expressed as kg/mm^2 (kilograms per square millimeter). Finally, divide this result by some factor that depends on what testing machine or hardness tester you use to determine penetration and Brinell numbers. The factors for each standard are given in the ASTM D1044-06 standard table.
Penetration values are only used when your sample consists of an elastic material such as clay or a stone. Most metals only have a hardness of around 80 to 85 on the Brinell scale. They, therefore, have resistance values close to 0.05–0.1 on the Brinell hardness scale.
The Brinell hardness method is a simple, fast, and reliable method for measuring the hardness of various materials. It does not require any special preparation of the test specimens and can be used for samples that are hard to cut into pieces.
Brinell Hardness tests are widely used in metallurgical, construction materials, and engineering fields. Brinell hardness testing plays an important role in producing steel, aluminum, and other hard metals. It is also used to help determine the breakage behavior of concrete in prestressed concrete structures.