Measure of a material's resistance to localized plastic deformation Most hardness tests involve indentation, but hardness may be reported as resistance to scratching (file test), or rebound of a projectile bounced off the material (scleroscope hardness) Some common measures of indentation hardness are Brinell Hardness Number, Rockwell Hardness Number, ASTM Hardness Number, Diamond Pyramid Impact Test Hardness Number, Durometer Hardness, Knoop Hardness, and Pfund Hardness A table relating various types of hardness values of metals is given in ASTM E-140 Hardness often is a good indication of tensile and wear properties of a material
a characteristic of water, imparted by salts of calcium, magnesium, and iron, such as bicarbonates, carbonates, sulfates, chlorides, and nitrates that cause curdling of soap, deposition of scale in boilers, damage in some industrial process, and sometimes objectionable taste It may be determined by a standard laboratory procedure or computed from the amounts of calcium and magnesium as well as iron, aluminum, manganese, barium, strontium, and zinc; expressed as equivalent parts per million of calcium carbonate
Resistance of a mineral to scratching, described relative to a standard scale of 10 minerals known as the Mohs hardness scale. Hardness is an important diagnostic property in mineral identification. There is a general link between hardness and chemical composition (via crystal structure); thus, most hydrous minerals, halides, carbonates, sulfates, and phosphates are relatively soft; most sulfides are relatively soft (two exceptions being marcasite and pyrite); and most anhydrous oxides and silicates are hard. See also hardening
the measure of some materials' resistance to deformation by surface indentation or by abrasion
(1) A measure of the amount of calcium, magnesium, and iron dissolved in water; (2) a property of water that is roughly proportional to the ion concentration Water from a calcareous aquifer is often hard due to calcium carbonate content Such waters are very resistent to fluctuations in pH (Lee unpublished)
In mineralogy "hardness" is a measure of the ability of a mineral to resist a mechanical force such as scratching or abrasion This contrasts with the definition of the metallurgist who is more concerned with the ability of one material to dent or penetrate another Hardness is a distinguishing characteristic of minerals that can be useful in identifying unknown specimens See hardness scale [glossary]
excessive sternness; "severity of character"; "the harshness of his punishment was inhuman"; "the rigors of boot camp"
1 mineralogy The measure of the resistance of a mineral to scratching or abrasion 2 water A property of water resulting from the presence of calcium carbonate and magnesium carbonate in solution
A common measurement of water mineral levels in the water supply, expressed as parts-per-million Temporary hardness is determined by the concentration of carbonate and bicarbonate The hardness that carbonate and bicarbonate ions contribute is temporary because carbonate and bicarbonote are precipitated when water is boiled Permanent hardness is determined by the amount of calcium and magnesium ions present in the water
Degree to which a metal will resist cutting, abrasion, penetration, bending and stretching The indicated hardness of metals will differ somewhat with the specific apparatus and technique of measuring For details concerning the various types of apparatus used in measuring hardness, See Brinell Hardness, Rockwell Hardness, Vickers Hardness, Scleroscope Hardness Tensile Strength also is an indication of hardness Brinell Hardness: Brinell hardness of aluminum alloys is obtained by measuring the permanent impression in the material made by a ball indenter 10 millimetres in diameter after loading with a 500 kilogram force for 15 seconds and dividing the applied load by the area of the impression
The amount of dissolved calcium salts and/or magnesium present in water Hardness is measured in units of parts per million (ppm) or grains per gallon (gpg) [gpg x 17 1 = ppm] Poor water treatment can result in excessive scale that provides excessive resistance to heat transfer and thus inefficiency and higher costs Optimum Utility Systems can direct you to effective water treatment systems
Is a measure of the amount of calcium and magnesium salts in water More calcium and magnesium lead to greater hardness The term "hardness" comes from the fact that it is hard to get soap suds from soap or detergents in hard water This happens because calcium and magnesium react strongly with negatively-charged chemicals like soap to form insoluble compounds
the property of being rigid and resistant to pressure; not easily scratched; measured on Mohs scale
The degree of resistance of a given mineral to scratching, indicating the strength of the bonds that hold the mineral's atoms together The hardness of a mineral is measured by rubbing it with substances of known hardness
the measure of a material's resistance to deformation by surface indentation or by abrasion
Hardness is the resistance of a material to deformation, indentation, or scratching Hardness is measured on various scales, such as Mohs, Brinell, Knoop, Rockwell, and Vickers
The resistance to surface indentation usually measured by the depth of penetration of a blunt point under a given load using a particular instrument according to a prescribed procedure Rockwell hardness is a test for the harder plastics in which the hardness number is derived from the dent, or permanent deformation, caused by a steel ball The Rockwell hardness may correlate with resistance to surface marring in end-use, but not usually with abrasion or wear resistance (ASTM D785)
A property of water which causes an increase in the amount of soap that is needed to produce foam or lather and that also produces scale in hot water pipes, heaters, boilers and other units in which the temperature of water is increased materially Hardness is produced almost completely by the presence of calcium and magnesium salts in solution The following scale may assist in appraising water hardness, measured by weight of dissolved salts (in milligrams) per unit (in liters) of water
Resistance of metal to plastic deformation, usually by indentation However, the term may also refer to stiffness or temper, or to resistance to scratching, abrasion or cutting Indentation hardness tests, such as Brinell, Rockwell and Vickers