<P> The Knoop hardness test / kəˈnuːp / is a microhardness test -- a test for mechanical hardness used particularly for very brittle materials or thin sheets , where only a small indentation may be made for testing purposes . A pyramidal diamond point is pressed into the polished surface of the test material with a known ( often 100g ) load , for a specified dwell time , and the resulting indentation is measured using a microscope . The geometry of this indenter is an extended pyramid with the length to width ratio being 7 : 1 and respective face angles are 172 degrees for the long edge and 130 degrees for the short edge . The depth of the indentation can be approximated as 1 / 30 of the long dimension . The Knoop hardness HK or KHN is then given by the formula : </P>
<P> The Knoop hardness test / kəˈnuːp / is a microhardness test -- a test for mechanical hardness used particularly for very brittle materials or thin sheets , where only a small indentation may be made for testing purposes . A pyramidal diamond point is pressed into the polished surface of the test material with a known ( often 100g ) load , for a specified dwell time , and the resulting indentation is measured using a microscope . The geometry of this indenter is an extended pyramid with the length to width ratio being 7 : 1 and respective face angles are 172 degrees for the long edge and 130 degrees for the short edge . The depth of the indentation can be approximated as 1 / 30 of the long dimension . The Knoop hardness HK or KHN is then given by the formula : </P>
knoop hardness test is used to measure the hardness of
knoop hardness test is used to measure the hardness of
very brittle materials or thin sheets
very brittle materials or thin sheets