hardness


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hardness,

property of matter commonly described as the resistance of a substance to being scratched by another substance. The degree of hardness is relative, different substances being compared with one another. Mohs's scale of hardness (named for Friedrich Mohs), used commonly in mineralogy, lists certain minerals in order of hardness: talc, 1; gypsum, 2; calcite, 3; fluorite, 4; apatite, 5; orthoclase, 6; quartz, 7; topaz, 8; corundum, 9; diamond, 10. The listing indicates merely that gypsum (hardness=2) is harder than—i.e., capable of scratching—talc (hardness=1). The listing does not indicate that gypsum (2) is twice as hard as talc (1). The hardness of many minerals falls between those included in the list. For example, the hardness of barite is 3.3. Hardness may differ with the direction of the scratch made on the substance. Thus the mineral kyanite has a hardness of 5 parallel to the length of its crystals and of 7 at right angles to this direction. There are several other methods based on the resistance to indentation for testing engineering materials. The solid elements have been thus classified: diamond (an allotropic form of carbon) is hardest and listed as 10, with cesium the softest, rated as 0.2, the same degree of hardness as wax (hardness=0.2 at 0°C;). The hardness numeral of the Brinell scale is based upon the indentation produced when pressure is exerted by a sphere on the substance. The value thus obtained has a direct relation to the tensile strength of the substance. The hardness of a material may be modified by the presence of small quantities of another substance, as in metallic alloys, or by impurities in minerals.

hardness

[′härd·nəs]
(chemistry)
The amount of calcium carbonate dissolved in water, usually expressed as parts of calcium carbonate per million parts of water.
(electromagnetism)
That quality which determines the penetrating ability of x-rays; the shorter the wavelength, the harder and more penetrating the rays.
(engineering)
Property of an installation, facility, transmission link, or equipment that will prevent an unacceptable level of damage.
(materials)
Resistance of a metal or other material to indentation, scratching, abrasion, or cutting.

hardness

1. The resistance of wood, rubber, sealant, plastic, or metal to plastic deformation by compression or indentation; in wood, hardness is generally related to density. Common methods of measurement include the Rockwell, Brinell, Scleroscope, and Vickers tests.
2. A property of a paint or varnish film that is a measure of its ability to withstand damage from marring, abrasion, etc.
3. The degree of hardness, applied to water, based on the amount of calcium and magnesium salts in the water, expressed as grains per gallon or parts per million of calcium carbonate.
References in periodicals archive ?
In 1924, Smith and Sandland introduced the Vickers hardness test method, as an alternative to the Brinell hardness test.
The total hardness of the water sample is obtained using Equation 2.
Figure 2a/b shows the Vickers Hardness HV (calculated from the indentation hardness HIT) and the indentation modulus EIT of two coatings--a hard anodised coating (480 HV) of 11 [micro]m thickness (shown in red) and a soft anodised coating of 14 [micro]m thickness (shown in blue).
Hardness creates many undesirable effects in the wet processing.
Similarly when the hair reacts with hard water, the cations; calcium and magnesium are absorbed from the water by the anion sites of hair and results in oxidation of hair (similar to oxidative damage in hair dyeing), is influenced by both water hardness and/or pH.16,20 Keeping in view the importance of both hair and hard water and their regular interaction with each other during bathing, washing etc., and the pH as calculated in Table-2 and its effect, we conducted this study to evaluate the effect of hard water on strength of hair in men and also create awareness among people about the effect of hard water on hair.
[12] showed that nanoindentation and microindentation hardness tests have similar load effect and their differences are between 10% and 30%.
Conclusion: It can be concluded from this study that micro hardness of imported plates is more than local plates so recommendations should be sent to manufacturers of local industry of Pakistan to improve the hardness of local plates so that they can meet international standards.
Here are a few metallurgical and casting process factors that will contribute to hardness:
So, the hardness of water may be one of the characteristics of processing water that should be monitored by poultry processors.
Moreover, as the load force weakens and enters the area of micro-hardness, the Vickers hardness is no more depending on the power of applied load (unlike in macro-hardness that is measured according to geometric similarity of individual dints).
Hardness was determined by loading 200 micronewton force.
in accordance with European standard EN 13262:2004 on cast wheels, hardness in the whole wear area at up to 35 mm depth from the nominal diameter must be over 255HB, however, in accordance with GOST 398-96 ([GAMMA]OCT 398-96) 2 cat., the hardness of rims used in old locomotives must be over 269HB at 40 mm depth and in the flange area--up to 321 HB at 16 mm depth);