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Hardness: the Knoop test falls within standards
It’s official. The Knoop hardness test is now part of the standardised test available to industrial manufacturers to characterise the hardness of their parts. As a matter of fact, it is covered by Standard NF EN ISO 4545 published in March 2018. The Knoop test applied to metallic materials was developed as an alternative to the Vickers hardness test, primarily to avoid the cracking of brittle materials and simplify tests in thin layers. In fact, this process serves to half the depth of penetration into the material with respect to the Vickers test. This hardness measurement method is therefore suited to very thin parts which often undergo complex machining that are made with the additive manufacturing technologies. The NF EN ISO 4545 standard published in March is divided into four parts. The first part defines the designation of the hardness number, the testing machine, the test piece, the procedure, the uncertainties of the results, the content of the test report, the periodic check of the diagonal length measuring system and of the indenter. The second part covers two methods for verification and calibration of testing machines. The third part specifies the method for calibration of the reference blocks to be used when carrying out the indirect verification in accordance with Part 2 of the standard. Finally, the last part gives a table of the Knoop hardness values calculated based on the calculation formula established in the 1 st part of the standard.
Find more information on the “UNM website”.
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