I'm studying material science on tooling material and come across a term HRA as a representation of hardness of steel.  I want to know the significance of such units.
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There are several alternative definitions of indentation hardness, the most common of which are:\n\nBrinell hardness test (HB) \nJanka Wood Hardness Rating \nKnoop hardness test (HK) or microhardness test, for measurement over small areas \nMeyer hardness test \nRockwell hardness test (HR), principally used in the USA \nShore durometer hardness, used for polymers \nVickers hardness test (HV), has one of the widest scales \n\nHowever i must say that in industry the only one i have used is Rockwell in the C Scale (Metals, steel mostly).  But I've heard Brinell is also very usefull.  \n\nIn your case HRA means Rockwell hardness in Scale A.  This A, B, C in Rockwell are just scales ok? Because some materials are not too hard so in a Rockwell C scale the result would be a very small number in comparison with a steel with superficial teatment that comes to around 60 Rockwell C (just an example)\n\ncheck this link for more information on hardness.
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If 'T' is the greek 'Tau' then it is the symbol for shear stress, shear stress = Shear Force / Cross-section area, so for your example it is 2400 / 4 = 600 psi (pounds per square inch) which is a reallly really low stress... aluminum for example can sustain stresses of at least 20000psi and steel is 3x stronger.
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Hi\nthere are two options:\n\nMule (if you mean something that is made of steel, iron, etc.)\n\nThe diminutive of "Macho" related with a man.\n\nby
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Diamond is the hardest known naturally occurring material, scoring 10 on the relative Mohs scale of mineral hardness and having an absolute hardness value of between 167 and 231 gigapascals in various tests. Diamond's hardness has been known since antiquity, and is the source of its name. However, aggregated diamond nanorods, an allotrope of carbon first synthesized in 2005, are now believed to be even harder than diamond.
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There are literally thousands of grades of steel out there. Each one having different properties including tensile strength, carbon content, etc.  If you are wanting to know about a certain application, its best to consult an engineer. If you are just wanting to learn a little about it, just get a book about engineering materials.
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In the gem business:\n\nCarat (mass) is a unit of mass for gems. In the United States, carat almost exclusively means the unit of mass. \nCarat (purity) or karat is a unit of purity for gold. In the United States, karat almost exclusively means the unit of purity.
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It refers to the height...  Check out wiki...\nhttp://en.wikipedia.org/wiki/Hands_%28horses%29
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Looking at your very specific question, I'm assuming you have a reasonable handle on the engineering basics of what happens when you apply a force or load to something. \n\nLet's start by defining 'Strain'. If you take a metal rod, for example, and pull it by applying a large load at a prescribed rate, then the 'Strain', at any given point of time in the rod's elongation, is the ratio of the original length of the rod to the rod's current length. So 'Strain' is simply a measure of how much something has changed from its original shape, 'length' in this case. This is also called 'Engineering Strain'. \n\nWhen you keep pulling the rod, at a certain load it starts to yield at a point along its length where it forms a 'neck' before failure (assuming a 'ductile' or reasonably soft material). If you measure the cross-sectional area at the neck you can see that it reduces as the rod elongates. The 'Engineering Stress' is the ratio of the applied Load to the ORIGINAL cross-sectional area of the rod.\n\nThe point at which the metal rod starts 'yielding' is considered to be beyond its 'elastic' limit - its capability to 'recover' or get back to the original length. The strain beyond this 'yield' point is called 'Plastic Strain'.\n\nIn contrast with 'Engineering Strain', 'True Strain' is the natural log of the ratio of the original cross-sectional area to the current cross-sectional area at the neck. Correspondingly, the 'True Stress' is the ratio of the Load to the current cross-sectional Area. \n\n'Effective Plastic Strain' or 'EPS' is simply the Total True strain minus the Recoverable strain. So, it is the Residual True Strains after unloading elastically, or, in other words, its the unrecoverable portion of the true strain beyond the yield limit. \n\nUsually EPS is just called Plastic Strain, but when you are dealing with True Strains input in specific engineering applications or 'solver' software they like to define it as 'Effective' Plastic Strain. In that case, where you are defining a stress vs. effective plastic strain curve, the first (plastic) strain value would be zero and the first stress value would be the initial yield stress.\n\nSee below link for more details.
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Ok, you have lots of concepts.  1st, alloys are mixtures of metals, not a metal.  Second, you listed a bunch of different kinds of strength.  Stainless steel is stronger than titanium alloys for some applications.  Titanium has a SLIGHTLY higher heat capacity.  Alluminum alloys are fairly strong as well, but it's strength by weight, not strength by volume, which is what engineers need.  Not only that, but alot of metal alloys are "strong" to the point of unusable because they're not able to be shaped.
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It's quite possible that you will end up with a diamond-shaped dimple in both the hammer and the anvil, because diamond is harder which means that the iron will deform first.  However, "hard" can also be "brittle", and the diamond might break into a few pieces.  The iron is most unlikely to do this, because "softer" can still be "tougher".
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Y2K was used as a catchy, quick reference to the year 2000, which, in metric parlance, could be written as 2K.\n\nYttrium and Potassium should not form any kind of stable alloy, nor would it be terribly explosive.
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It's an iron bearing oxide compound used as an abrasive.\n\nIt's only one of the abrasives in Emery Cloth.\n\nIt's also used as a powder in comercial applications, or in a colodial suspension for lapping compounds..
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1.  Diamond is the hardest known natural material and one of the two best known forms (or allotropes) of carbon, whose hardness and high dispersion of light make it useful for industrial applications and jewelry.\n\n2.  Covalent bonds.
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There is a HUGE amount of infomation on metallurgy out there, but if you want an interesting search, try searching out why the HUBBLE Space Telescope failed - there was some deformed metal and the reason the optics tests passed before launch is an interesting story about materials, optics and people.\n\nI'm a metallurgist, and of all the exotic materials it turns out steel has the greatest range of properties (from annealed iron all the way up to ball bearing steel and stainless).  Titanium is interesting stuff (good for corrosion and medium temps (500°F-1000°F), but aluminum can have the highest density-to-strength ratio.  Research on how tungsten filaments are made is interesting too.  \n\nMark Twain said that a metallurgy student would learn more making his own pocket knife by digging the ore out of the ground, refining it into steel, and fabricating the knife than he would by book learning - do you have a passion you're particularly interesting in?  Learning about something you're interested in is effortless.\n\nAnother optics subject of interest is what is currently going on in semiconductor photolithography - they are reaching the limits of what can be done with light and refractive materials (CaF lenses) and immersion lithography (see link below).
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Your question lacks clarity.  Is the question about an element on the periodic table? If it is - and once again, you don't specify - then a likely answer is "Thorium" named after Thor, the greek god of thunder.  I don't know, you didn't actually give any context with the question.  I suggest going to www.wikipedia.com for help with anything, though.   \n\nThe second question, about the order of the planets by rotation - do you have a science book?  That would help you more than the internet because the answers will all be there.  Open the book, go to the chapter(s) about planets, take out a piece of paper, and write down the name of the planet next to the length of the respective planet's day.  When you have all of the written down, you will be able to order it.  \n\nHere is some extra help for you for a question you did not ask but clearly need answered:\n\n"Your" is possessive - "Your eyes are like deep buckets of molasses" \n\n"You're" is an abbreviation of "You are".
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Part of the downfall of USX,(US Steel) was the little companies specialized in doing high quality, specialized steel and alloys. Bethlehem steel kept wanting to make more and the old fashion way. \nLow tech side. I have heard of steel studs for houses. They are put together like an erector set. Wood business wants to steel more wood and would not have thought of doing that. I worked with a group making new wires and diffusion barriers for semiconductors. Copper is conducts faster, but diffuses more for example. Gold is used on the outside since it doesn't corrode. \nPerhaps a solar, induction furnace to melt down old cars, cans? Non Pt, catalytic converter?\nFind a need, replace something for efficiency,
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Mohs' hardness scale is somewhat arbitrary.  Moh tried to find commonly available minerals that were about equally spaced in hardness.  Talc was arbitrarily assigned "1."\n\nAs one example of the inconsistency, diamond (Moh's 10) is about 10 times harder than corundum (Moh's 9).\n\nThere should be some minerals sites out there that allow you to list minerals in order of Moh's hardness.  There may also be some with Vicker's hardness for comparison.\n\nThe main advantage of Moh's hardness scale is its practicality for field use.\n\nA lot of the sheet silicates are very soft.  In the soft ones, the only forces holding the sheets together are van der Waal's forces, which are quite weak.\n\nClays are very soft.  The crystals are very small and only van der Waals forces act between them.  (They are also sheet silicates, but the sheets are held tightly together by cations.)