Do you ever wonder what is required to carry out a hardness test using the Rockwell Hardness method? In any case, the Rockwell method offers a plethora of advantages, which makes it one of the most preferred and deployed methods of measuring a material’s strength and durability. Before we delve too deep into the Rockwell method’s advantages, let’s not lose sight of the main topic of this article. So, if you want to know more about the specimen requirements for the Rockwell method, hop on the ride.
I. Rockwell Hardness Test
Rockwell hardness test is one of the easiest and most widely used methods of testing a material’s resistance to permanent deformation. This is mostly due to its ability to estimate the results fast and is commonly used on materials like steel, and hard plastic. Rockwell hardness tests combine the use of about thirty different scales, but the appropriate scale for measurement is determined by the material to be tested.
Related Article: What are the Advantages and Disadvantages of the Rockwell Method?
Related Article: How to Perform a Rockwell Hardness Test?
II. How is the Rockwell Test Performed?
Typically, when measuring any material using the Rockwell hardness method, an initial load or preload is applied to the material’s surface. The preload makes a penetration through the material via a ball or diamond-shaped indenter. The preload is held for a time known as the dwell time, and then measurement of the indentation of the preload is taken. Thereafter, the major load is applied to attain a test load specification. The major load is also allowed a dwell time before it is removed. The depth of indentation after the major load is applied is now measured against the indentation of the preload.
III. What Factors should you Consider for the Precision and Reliability of the Rockwell Test?
Rockwell Hardness Testing Machine
Before delving into the testing of any material, specified guides and requirements on the appropriate Rockwell hardness testing machine to be employed is a very critical consideration. This is to ensure accuracy and precision, and this starts from the material to be tested. Selecting the scale appropriate for testing, and the indenter type (diamond or ball) as well. Ascertaining these requirements aids the operator to execute a reliable test.
Indenter Damage
The type of indenter utilized for any test as earlier stated could as well determine a Rockwell test’s accuracy and reliability. While the diamond indenter is used for harder and stronger metals and steel, the ball indenter is used to create indents on softer metals such as aluminum, copper, alloys, etc. when the wrong indenter is applied, damage to the material is inevitable. And therefore, lead to erroneous results.
Deflection in the Loading Platform
The loading platform of a test machine must be equipped with the right support. A slight disengagement on the loading platform could render test material unusable and test results inconclusive or erroneous. Since Rockwell hardness testing entails the measurement of depth, a stable and steady platform for executing the test is highly recommended for the precision and reliability of the actual results of the test.
The Specimen
Needless to say the most important consideration that holds every other factor in tandem is the specimen. The specimen for measurement and testing determines what Rockwell testing machine to be employed, the type of indenter to use, and the support it needs to fit properly and be stable for testing. All these are reliant on the specimen. Therefore, whether metal, steel, aluminum, or alloy, the precision and reliability of test results has a whole lot to do with the specimen or material.
IV. Specimen Requirements for the Rockwell Method
The specimen requirements for the Rockwell hardness testing method include a selection of a scale applicable to material type. In an instance where there is no specified scale for hardness, the material type should be contrasted with other tables that identify a general scale for the type of material. Furthermore, material thickness also counts as a requirement, thereby allowing the determination of what indenter is appropriate for the material’s thickness and accurate results. Essentially, it is of great importance for the material surface to be perpendicular to the point of impact of the indenter. Ultimately, when testing a specimen, the spacing between the material edge and indent must be maintained.
Conclusion
So, let’s do a recap. The Rockwell hardness test is easy to execute and widely accepted due to its high accuracy. Moreover, because it requires no optical readouts, it assists operators to assess the results easily. Conclusively, the factors to be considered for precise results add to its reliability. You might want to consider adopting the Rockwell method for your material hardness testing, especially when performing large sample tests.