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Hardness. In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by pressing or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and ...
For example, some sources have assigned a Mohs hardness of 6 or 7 to granite but it is a rock made of several minerals, each with its own Mohs hardness (e.g. topaz-rich granite contains: topaz - hardness 8, quartz - hardness 7, orthoclase feldspar - hardness 6, plagioclase feldspar - hardness 6 to 6.5, mica - hardness 2 to 4).
Brinell hardness is sometimes quoted in megapascals; the Brinell hardness number is multiplied by the acceleration due to gravity, 9.80665 m/s 2, to convert it to megapascals. The Brinell hardness number can be correlated with the ultimate tensile strength (UTS), although the relationship is dependent on the material, and therefore determined ...
Digital Shore hardness tester. The Shore durometer is a device for measuring the hardness of a material, typically of polymers. [1] Higher numbers on the scale indicate a greater resistance to indentation and thus harder materials. Lower numbers indicate less resistance and softer materials. The term is also used to describe a material's rating ...
The Vickers test can be used for all metals and has one of the widest scales among hardness tests. The unit of hardness given by the test is known as the Vickers Pyramid Number ( HV) or Diamond Pyramid Hardness ( DPH ). The hardness number can be converted into units of pascals, but should not be confused with pressure, which uses the same units.
HSAB theory. HSAB is an acronym for "hard and soft (Lewis) acids and bases ". HSAB is widely used in chemistry for explaining the stability of compounds, reaction mechanisms and pathways. It assigns the terms 'hard' or 'soft', and 'acid' or 'base' to chemical species. 'Hard' applies to species which are small, have high charge states (the ...
A mineral's hardness is a function of its structure. Hardness is not necessarily constant for all crystallographic directions; crystallographic weakness renders some directions softer than others. An example of this hardness variability exists in kyanite, which has a Mohs hardness of 5 1 ⁄ 2 parallel to but 7 parallel to .
Toughness as defined by the area under the stress–strain curve. In materials science and metallurgy, toughness is the ability of a material to absorb energy and plastically deform without fracturing. [1] Toughness is the strength with which the material opposes rupture. One definition of material toughness is the amount of energy per unit ...