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To further increase the elastic modulus of the steel sword blade, the Japanese masters would
fold the steel 15 times to obtain 30,000 layers in the blade
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The samurai sword is made by folding the steel blade during fabrication resulting in approximately how many internal layers:
30,000
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If you would pick an elastic modulus for the Samurai Sword, it would be nearest which of the following:
piano wire (because the samurai sword is mild steel)
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The Roman Empire and later the Venetians were masters of, and greatly advanced, which of the following materials listed on the plot?
Glass
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Which of the following materials has the lowest Young's modulus?
Glass (because its slope is the lowest)
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Examine the elastic behavior for glass. The yield point (fracture point in this case) for glass is very low considering it is dominated by covalent bonds. Why is this so?
because the surfaces are full of small cracks (scratches)
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Which of the following has a body centered cubic atomic structure: bronze, ferrite, austenite, cementite?
ferrite
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Ferrite is
alpha-iron, or pure iron, with a body-centered cubic crystal structure. It is this crystalline structure which gives steel and cast iron their magnetic properties
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The development of glass technology had to wait for
the development of iron to make a blowpipe that could withstand the high temperatures
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All the glass surfaces contain small cracks, which can lead to easy fracture. This is despite the intrinsic strength of glass due to __ bonds.
Covalent
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The windscreen in your automobile overcomes this problem of small surface cracks by placing the windscreen surfaces in a state of ___
compression
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Most silica glasses that you come in contact with have this atomic structure: __ with __ range order
Amorphous with short range order
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The glass transition, T sub g, is:
the temperature below which a glass is considered to be a solid
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The reason to anneal the glass is __
to remove stresses within the object caused by uneven cooling from the working range.
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A perpetual motion machine that produces more energy than it takes to run its is a violation of primarily which law of thermodynamics? Conservation of energy--can't produce more energy than it goes into the machine.
First law
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Energy dissipation is described by which law of Thermodynamics
Second law
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The direction a process will go when it occurs with no human intervention is an example of which law of thermodynamics?
Second law
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The composition of the Japanese sword is near 99% iron -- 1% carbon (written: Fe-1.0%C). When heated to 1400 degrees Celsius the phase present are:
austenite + liquid
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At 600 degree Celsius the alloy Fe-1.0%C contains what amount of cementite?
15%
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The ideal Samurai sword contains only which two final microstructures?
bainite + martensite
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"Scythes are quenched cherry red" This color ensures the tool is cooled from what phase(s)?
austenite
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Which phases in piano wire allow dislocations to move?
Austenite, ferrite, bainite, pearlite
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Why would material scientists want to manipulate the microstructure of a material?
By manipulating the micro structural features, one can make materials with new, more wanted properties, or combinations of desired properties.
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What are 'crystal gains'?
Volume elements of uniform lattice orientation that are joined to similar volume elements but with different lattice orientations
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Why are x-rays, rather than visible light, used in determining the structure of crystals such as iron or copper?
To investigate the atomic structure, the wavelength of the radiation must be about the same or less than what you're examining
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Materials are frequently classified as either as crystalline or non-crystalline. The characteristic which determines whether a material is crystalline or not is the presence or absence of
- 1. Electrons that are not bound to atoms
- 2. Long-range periodicty
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What is the Rayleigh's Law for resolution?
The minimum spacing that we can see (resolve) d is given by: d = 0.61 lambda, where lambda is the wavelength of the radiation used during observation.
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Hardness
resistance to plastic deformation (e.g., a local dent or scratch). Thus, it is a measure of plastic deformation, as is the tensile strength, so they are well correlated. Historically, it was measured on an empirically scale, determined by the ability of a material to scratch another, diamond being the hardest and talc the softer.
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Yield point
If the stress is too large, the strain deviates from being proportional to the stress. The point at which this happens is the yield point because there the material yields, deforming permanently (plastically).
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Yield stress
Hooke's law is not valid beyond the yield point. The stress at the yield point is called yield stress, and is an important measure of the mechanical properties of materials. In practice, the yield stress is chosen as that causing a permanent strain of 0.002
The yield stress measures the resistance to plastic deformation
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Tensile strength
When stress continues in the plastic regime, the stress-strain passes through a maximum, called the tensile strength (sTS) , and then falls as the material starts to develop a neck and it finally breaks at the fracture point.
Note that it is called strength, not stress, but the units are the same, MPa
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Toughness
Ability to absorb energy up to fracture. The energy per unit volume is the total area under the strain-stress curve. It is measured by an impact test
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Crystalline alloys
Atoms arranged in a periodic pattern which repeats over millions or trillions of atoms
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How do materials deform?
Rows of atoms slide over another just liek the cards in a deck when you push them from aside
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What prevents atoms in an alloy from sliding?
Grain boundaries in discontinuities that prevent the planes of atoms from sliding, which strengthen the alloy
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Diffraction only occurs when
condition for constructive interference is satisfied
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Braggs Law
nλ = 2dsinθ
d is the distance between atomic layers in a crystal
λ is the wavelength of the incident X-ray beam
n is an integer
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Piano (Music) Wire
Piano wire has rightly been called the "specialty of specialties". It represents the highest attainment in the art of wire manufacture. In addition to the mechanical properties required, piano wire must possess acoustic properties. It is the strongest engineering material available in commercialquantities. Drawn pearlite steel wire is made to a carbon content between 0.80 and 1.00 w/o.
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Steelmaking
Pig iron consists of the element iron combined with numerous other chemical elements, the most common of which are carbon, manganese, phosphorus, sulphur, and silicon. In refining pig iron to convert it into steel, all five of these elements must be either removed almost entirely or at least reduced drastically in amount.Pneumatic Steelmaking (developed by Kelly & Bessemer)The fundamental principle is that the oxidation of the major impurities in liquid blast-furnace iron (Si, Mn, C) would be preferentially oxidized before the major oxidation or iron (Fig. 7).The Basic Oxygen Steelmaking Process (or BOP), (the furnace in which the process is carried out is referred to as the BOF) uses oxygen of high purity which is blown at high velocity onto the surface of the bath.
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Blast Furnace and Pig Iron
Pig iron is the term applied generally to the metallic product of the blast furnace when it contains over 90 percent iron. Most pig iron is transferred to the steel-making shops and used in the liquid state; in this form it is referred to as hot metal. The term "pig iron" arose from the old-fashioned method of casting iron into beds of molds form in sand, so arranged that they could be fed from a common runner. Since the group of molds resembled a litter of suckling pigs, the individual pieces of iron were referred to as "pigs" and the runner as a "sow".In the blast-furnace process, iron-bearing materials, such as iron ore, sinter, pellets, along with fuel (coke), and flux (limestone) are charged into the top of the furnace (Fig. 6). Heated air (blast) and, in some instances, fuel (gas, oil or powdered coal) are blown in at the bottom. The blast air burns part of the fuel to produce heat for the chemical reactions involved and for melting the iron, while the balance of the fuel and part of the gas from the combustion remove the oxygen combined with the metal.
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Fluxes in Iron and Steelmaking
Any metallurgical operation in which metal is separated by fusion from the impurities with which it may be chemically combined or physically mixed (as in ores) is called smelting. Since in iron smelting both these conditions with respect to impurities are always present, the production of crude iron involves two processes: (1) the reduction of the metal from its compounds and(2) its separation from the mechanical mixture.Many of the impurities associated with iron ores are of a highly refractory nature; that is, they are difficult to melt. The purpose of the flux then is to (1) render such substances more easily fusible and (2) to furnish a substance with which these impurities may combine in preference to the metal. The chief natural flux is limestone (CaCO3).
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the sluggishness of the atoms and molecules in rearranging to the state with the greatest long range order is related to the macroscopic property known as
viscosity. honey is more viscous than oil and then in turn more viscous than water
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complex molecules or impurities are included and either a high viscosity or a rapid cooling rate are conditions for __ instead of crystal formation
glass
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a ceramic is a partially __, partially ___ combination of metallic and non-metallic elements. The covalent forces tend to establish chains and networks in space, and the ionic forces provide structural alternatives, which make it easy to incorporate other ions and to decrease the long range-order, thus making the formation of a glass more probable.
ionic, covalent
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Glass usually fails in tension rather than ___ for the reason that a little accidental crack locally magnifies the tensile stress and since glass does not work harden, tension causes brittle fracture
compression
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