Topic
Knoop hardness test
About: Knoop hardness test is a research topic. Over the lifetime, 2289 publications have been published within this topic receiving 58851 citations.
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TL;DR: In this paper, the authors investigated the properties of indentation hardness on the sub-micrometre scale in nickel, gold and silicon and showed that indent areas and therefore hardness can be determined from penetration depth with reasonable accuracy, and that elastic relaxation can be quantitatively understood.
Abstract: In this paper we investigate the properties of indentation hardness on the sub-micrometre scale in nickel, gold and silicon. Indenter penetration depths as low as 20 nm are used. The area of the indents is determined by electron microscopy, and thus the Meyer hardness calculated. The indenter penetration is monitored continuously during loading and unloading. We show that indent areas, and therefore hardness, may be determined from penetration depth with reasonable accuracy, and that elastic relaxation can be quantitatively understood. We discuss the marked increase of indentation hardness with decreasing indent size on the sub-micrometre scale. Small indents in silicon showed no evidence of cracking, but did show unusual deformation characteristics.
883 citations
TL;DR: Knoop hardness was correlated to degree of conversion (DC) of carbon double bonds, determined by IR, during the setting reaction of three unfilled dental resins, indicating increase in hardness correlates well with increases in DC during setting.
718 citations
TL;DR: In this article, the authors show that the indentation size effect for pyramidal and spherical indenters can be correlated, based on geometrically necessary dislocations and work-hardening.
Abstract: Experimental results are presented which show that the indentation size effect for pyramidal and spherical indenters can be correlated. For a pyramidal indenter, the hardness measured in crystalline materials usually increases with decreasing depth of penetration, which is known as the indentation size effect. Spherical indentation also shows an indentation size effect. However, for a spherical indenter, hardness is not affected by depth, but increases with decreasing sphere radius. The correlation for pyramidal and spherical indenter shapes is based on geometrically necessary dislocations and work-hardening. The Nix and Gao indentation size effect model (J. Mech. Phys. Solids 46 (1998) 411) for conical indenters is extended to indenters of various shapes and compared to the experimental results.
706 citations
TL;DR: In this paper, a simple technique is presented to obtain the characteristic microhardness values of surface coatings that are too thin for the values to be directly measured, using a physical model of film deformation during indentation.
654 citations
TL;DR: Surprisingly, this synthesized polycrystalline diamond is ultrahard and so could be useful in the manufacture of scientific and industrial tools.
Abstract: Polycrystalline diamonds are harder and tougher than single-crystal diamonds and are therefore valuable for cutting and polishing other hard materials, but naturally occurring polycrystalline diamond is unusual and its production is slow. Here we describe the rapid synthesis of pure sintered polycrystalline diamond by direct conversion of graphite under static high pressure and temperature. Surprisingly, this synthesized diamond is ultrahard and so could be useful in the manufacture of scientific and industrial tools.
617 citations