The knoop hardness test is a test which is designed to measure mechanical hardness, a test particularly useful when dealing with thin sheets or brittle materials, such as ceramics. A small indentation may need to be made for testing purposes to ensure it’s suitable to be used for its purpose.
The Test
The test does not necessarily define the bulk hardness, however it is necessary. The pyramid shaped diamond is slowly pressed into the material being tested with a small weight also attached. The indentation made is then looked at with a microscope once the allotted time had been met. The knoop hardness test is then calculated by dividing the load used by the impression area which will provide the result. The knoop hardness is measured along the diagonal indent of the elongated pyramid indentation, an aspect that differentiates this test from the Vickers hardness test.
There are a number of benefits to using the knoop hardness test. When testing, not too much material is required and the results provided are suitable for a wide range of test forces. Of course, using a microscope to provide such accurate results as well as the time needed to measure the load can be time consuming. It’s also worth noting that in order to receive the most accurate results, the surface used should be flat and firm. With all these factors considered, the test certainly is a reliable and effective measurement.
