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This: Hard Hardness refers to various properties of matter in the solid phase that give it high resistance to various kinds of shape change when force is applied. Hard matter is contrasted with soft matter.

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Wikipedia About Hardness

This: Hard Hardness refers to various properties of matter in the solid phase that give it high resistance to various kinds of shape change when force is applied. Hard matter is contrasted with soft matter.

Macroscopic hardness is generally characterized by strong intermolecular bonds. However, the behavior of solid materials under force is complex, resulting in several different scientific definitions of what might be called "hardness" in everyday usage.

In materials science, there are three principal operational definitions of hardness:

  • Scratch hardness: Resistance to fracture or plastic (permanent) deformation due to friction from a sharp object
  • Indentation hardness: Resistance to plastic (permanent) deformation due to a constant load from a sharp object
  • Rebound hardness: Height of the bounce of an object dropped on the material, related to elasticity.

In physics, hardness encompasses:

  • Elasticity, plasticity, viscosity, and viscoelasticity
  • Strength and strain
  • Brittleness/ductility and toughness

The equation based definition of hardness is the pressure applied over the projected contact area between the indenter and the material being tested. As a result hardness values are typically reported in units of pressure, although this is only a "true" pressure if the indenter and surface interface is perfectly flat.

Materials science

Vickers-tester.png

Hardness is a characteristic of a solid material expressing its resistance to permanent deformation. Hardness can be measured on the Mohs scale or various other scales. Some of the other scales used for indentation hardness in engineering—Rockwell, Vickers, and Brinell—can be compared using practical conversion tables.

Hardness increases with decreasing particle size. This is known as the Hall-Petch relationship. However, below a critical grain-size, hardness decreases with decreasing grain size. This is known as the inverse Hall-Petch effect.

It is important to note that hardness of a material to deformation is dependent on its microdurability or small-scale shear modulus in any direction, not to any rigidity or stiffness properties such as its bulk modulus or Young's modulus. Scientists and journalists often confuse stiffness for hardness, and spuriously report materials that are not actually harder than diamond because the anisotropy of their solid cells compromise hardness in other dimensions, resulting in a material prone to spalling and flaking in squamose or acicular habits in that dimension (e.g., osmium is stiffer than diamond but only as hard as quartz). In other words, a claimed hard material should have similar hardness characteristics at any location on its surface.

Scratch hardness

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News about Hardness

Carbon that cracks diamond

NatureA new ultra-hard form of carbon may exist between graphite and diamond.http://www.nature.com/news/2009/090512/full/news.2009.446.ht...

$1.5M Artificial Turf Field Gets Go-Ahead In EL

New London DayEast Lyme - Funding an artificial turf field triggered some debate at Monday's town meeting, but residents voted overwhelmingly to approve the project, alonghttp://www.theday.com/re.aspx?re=e21d85e9-d8c3-4c6f-9fe7-b5b...

Extension Launches Well-Owner Education Program

Rockbridge WeeklyVirginians who get their drinking water from privately owned systems such as wells, springs, or cisterns can get help evaluating their water's quality and learn more about maintaining their water systems from Virginia Cooperative Extension.http://www.rockbridgeweekly.com/rw_article.php?ndx=14099

Palestinians argue over Abbas' aim of forming new gov't

People's DailyOfficial Palestinian circles on Monday expressed concerns about forming a large government, within coming24 hours, which is likely to undermine the inter-Palestinian dialogue and close the doors for reaching a reconciliation agreement. The concerns mounted after President Mahmoud Abbas announced earlier that he intends to enlarge the government in the West Bank before the factions, including ...http://english.people.com.cn/90001/90777/90854/6655708.html

VIP Modular Wheels Makes ISG an Authorized Reseller of Their Luxury Wheels

PRWebVIP Modular has authorized In Sixth Gear (ISG) to resell its stylish and sophisticated wheels on their online aftermarket performance auto parts site. VIP Modular does not just let anyone resell their wheels, which makes this a huge honor for ISG. (PRWeb May 12, 2009) Read the full story at http://www.prweb.com/releases/2009/05/prweb2402364.htmhttp://www.prweb.com/releases/2009/05/prweb2402364.htm

News about Hardness

Sag Harbor

Salon ... percentage of "Sag Harbor" is a frequently hilarious, sad and profane chronicle about these uneasy teenage boys, caught between a disapproving older generation, the unforgivable crime of "acting white" and the sudden shift toward criminal hardness in ... http://www.salon.com/books/must_read/2009/05/11/colson_white...

MineCore Chairman Issues Comprehensive Annual Update to Shareholders

MSN MoneyCentralRelative to silicon, sapphire's resistance to radiation, chemical stability, physical hardness, higher melting point and lower leakage make it a superior high end material for technology applications. Green Energy Grant Applications The new ... http://news.moneycentral.msn.com/provider/providerarticle.as...

Willie John McBride and Gareth Edwards on the Lions chances in South ...

Daily TelegraphThey have a hardness. I'm not sure whether that comes from farming, or from their communities, or from the spirit of the Voortrekkers. But it seems to be in their genes. McBride: They never talk about losing. They're much harder mentally ... http://www.telegraph.co.uk/sport/rugbyunion/international/br...

Treatment plant means softer water

Times DailyThat brings the hardness of Tuscumbia's water to 180 parts per million, as opposed to 60 ppm in river water, he said. The new plant will bring Tuscumbia's water softness in line with neighboring cities by using a filter system called membrane ... http://www.timesdaily.com/article/20090510/ARTICLES/90510504...

PACS Instrument To Launch With Herschel

Space DailyFrom the spectral lines, the astrophysicists can infer the temperature, density and nature of the radiation source, the intensity and hardness of the radiation, and the velocity distribution. The goal of the SHINING project is to study star formation ... http://www.spacedaily.com/reports/PACS_Instrument_To_Launch_...

Search results for Hardness

hardness definition of hardness in the Free Online Encyclopedia.

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 ... http://encyclopedia2.thefreedictionary.com/hardness

Mineral Resources: Hardness

Information on the mineral property of hardness. A service of The Mineral and Gemstone Kingdom.http://www.minerals.net/resource/property/hardness.htm

hardness: Definition, Synonyms from Answers.com

hardness n. The quality or condition of being hard. The relative resistance of a mineral to scratching, as measured by the Mohs scalehttp://www.answers.com/topic/hardness

Mineral Hardness

Hardness of minerals ... Definition . Hardness is measured by the resistance which a smooth surface offers to abrasion.http://webmineral.com/help/Hardness.shtml

Hardness Testers in Rockwell, Brinell, Microhardness, and Macro ...

Hardness testers product and technical reference information: For common and unusual scales and for all tester configurations.http://hardnesstesters.com

Wikipedia results for Hardness

Hardness - Wikipedia, the free encyclopedia

Hardness refers to various properties of matter in the solid phase that give it high resistance to various kinds of shape change when force is applied.http://en.wikipedia.org/wiki/Hardness

Mohs scale of mineral hardness - Wikipedia, the free encyclopedia

Not to be confused with mhos, a unit of electric conductance.http://en.wikipedia.org/wiki/Mohs_scale_of_mineral_hardness

Hard water - Wikipedia, the free encyclopedia

The simplest way to determine the hardness of water is the lather/froth test: soap or toothpaste, when agitated, lathers easily in soft water but not in hard water.http://en.wikipedia.org/wiki/Hard_water

Rockwell scale - Wikipedia, the free encyclopedia

The Rockwell scale is a hardness scale based on the indentation hardness of a material. The Rockwell test determines the hardness by measuring the depth of penetration of an ... http://en.wikipedia.org/wiki/Rockwell_scale

Vickers hardness test - Wikipedia, the free encyclopedia

The Vickers hardness test was developed in 1924 by Smith and Sandland at Vickers Ltd as an alternative to the Brinell method to measure the hardness of materials. [1]http://en.wikipedia.org/wiki/Vickers_hardness
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Engine bearingThe video source is howautowork.com.it is about engine bearing function,materails like tin,lead and copper also design consideration .with focus on split sleeves type,with...Flash - Video

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Answers for Hardness

mikeHardness.......?mikeIf you use RO water, you shouldn't have any hardness at all. If you mix it with tap water, just lessen the amount of tap water you use. Reverse osmosis forces all the impurities (many of which const...sordafishWhat is the difference between hardness and brittleness?sordafishworldboy90How do you Lower Water Hardness In a fish tank?worldboy90Unless you have species that absolutely require soft water (like discus) or low pH, I wouldn't worry about changing either - and it's probably the hardness that's causing a higher pH. Most fish are a...halitleventWhat is the relation between hardness and resistance of a material?halitleventbitbotWhat is the relationship between salinity and water hardness?bitbotSalinity deals with the concentration of NaCl or salt as you pointed out.....thats basically it...... maybe a few other trace elements but nothing that would change things significantly.The more salin...
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