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Ndt Measurement > physical & mechanical properties CHP 3 > Flashcards

physical & mechanical properties CHP 3 Flashcards

1
Q

what is strength?

A

The ability to resist change in shape or size when external force or stress is applied.

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2
Q

what are the four stresses?

A
  1. tensile
  2. compressive
  3. shear
  4. torsion
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3
Q

what type of strenght does steel has equal?

A
  1. compresssive
  2. tensile
  • but cast iron
    1. has low tensile! and high compressive!
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4
Q

define tensile

A
  • is used to obtain info about the mechanical properties of a material.
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5
Q

what are the tensile test?

A
  1. ductility
  2. tensile strenght
  3. proportional limit
  4. elastic limit
  5. modulus of elasticity(E)
  6. resilience
  7. yield point
  8. ultimate strenght
  9. ultm strenght
  10. breaking point
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6
Q

what is the formula for tensile strenght (psi)?

and

unit strenght?

A

tensile streght(psi) =

   (psi) =   maximum load (lb) /  org area (in)

unit stress = Load / area

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7
Q

what does it do to a metal that is compress & tension?

whats the new name when the metal deforms?

A
  1. when the metal is compress the metal will shorten.
  2. when the metal is in tension the metal will stretched longer.
  • the name is (strain) express as inch.
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8
Q

what hapens to (strains) when the stress increases?

what happens when the load is removed? what is this known for?

what happens when a load is applied above the elastic-limit?

A
  • strain increases by the proportion with in the elastic range.
  • when the load is removed the material returns to it orig shape. ► known as the hooke’s law.
  • the metal permantly deforms.
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9
Q

what is tensile strenght ?

A

Material ability to withstand stress in tension or pulling apart.

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10
Q

what is compressive strenght?

A

material ability to withstand a “pressing” or” squeezing together” type of stress.

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11
Q

what are the four factor that must be presented?

A
  1. stress concentrarion must be subceptible to brittle fraccture
  2. stress concentrarion must be present
  3. tensile stress must be present
  4. temp. must be relatively low
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12
Q

whath are some catastrophiic failure in tensile stress?

A
  • a part or structure can be completly free of an external or applied load, and fail suddenly and catastrophically while sitting on a bench or a floor.

welded, torch-cut or heat-threated steels are particularly susceptible to this.

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13
Q

where is tensile testing performed?

A

is performed on a tensile tester.

tools used extensometer (0.0505in)

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14
Q

what is shear strenght?

A

force that causes two contiguous parts of the same bode to slide relative to each other in a direction parallel to the plane of contact.

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15
Q

how are shear used?

what type of testing do they use?

what is the formula of the shear?

A
  • are used in the strength of the shank for load maintenance.
  • tested in a fixture configured. fixture in copresion
  1. Load / Area = shear (psi)
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16
Q

what is torsion?

A
  • torsion strenght is the materials ability to resist shear stress in rotation.

1.

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17
Q

how is torsion useful?

A
  1. it tests parts such as:
  • shafts
  • azles
  • sockets
  • and rotations tools

stress-grain curves may be ploted from torsion data.

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18
Q

what is faigue streght (endurance streght)

A
  • ability of a materia to resist reaped loading. vibrations is an exmple
  • deals with reapeated loading and unloading..
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19
Q

what are some effects of faigue stress?

why is fatigue failures serious?

A
  • slight cracks in the surface
  • it propagates across a piece of metal when it lacks good fatigue streght.
  1. becouse the can happen without warning.
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20
Q

what is elasticity?

what is the elastic limit?

A
  • the ability of a material to strain under load and then return to its original size and shape when unloaded.
  • is the greatest load a material can withstand and still be back to it original shape.
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21
Q

what is plasticity ?

A
  • is melleability. meaning that has th eability to permanently change shape, and retain that shape, from a compresive load.
    *
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22
Q

process of plasticity?

A
  1. plastic deformors materials and it becomes harder
    * yield point shift upwards

for forging, drawing, extruding, and forming

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23
Q
  • what happens to elastic deformation when strain increases ?
  • does the ratio remain the same?
    *
A

strain increases in direct proportion to the increase in stress.

  • ratio remains constant for low levels of stress.

and stresses below the proportional limit,

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24
Q

what will a stress-strain diagram help you determine?

A
  1. modolus of elasticity
  2. elastic deformation
  3. yield strenght
  4. proportional limit
  5. proof stress
  6. uninform elongation
  7. total elongation
  8. tield point elongation

sress-straincurves are used to calculate hystereis. if it absorbed or lost energy that occurs during any cycle of loading or unloading.

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25
Q

what is the formula for strain?

and how does a proportionality grahp shows?

A
26
Q

how does a graph look showing full-pull stress-strain?

A
27
Q

what is proportional limit?

A
  1. proportional limit is when both stress and strain increases at a constant rate.
  • the diagram line is linear
  • beyond that point increases fater
  • E no longer appliesis now a hook’s law
28
Q

what is it called when the material is stressed slighly beyond the proportional limit?

A
  1. is known as the elastic limits
29
Q

what is modulus or (stiffness)?

what is the formula for modolus of elasticity?

A
  • if the strain is devided by the corresponding strainat any given point, the result will be modolus of elastic for that material. ►psi = stress / strain or E = s / e or s = Ee
30
Q

what is yield strenth

A

is the info needed here cocerns the lowest stress at whch measureble permanent deformation occurs.

31
Q
  • name the material that contain the highest modolus?
  • name the material that contain the lowest modolus?
A
  • steel has the highest with 30.0x 1000000psi
  • wood has th elowest with 1.5 -2.0x1000000psi
  • in elements:
  1. titunium 16.0
  2. aluminum 10.0
  3. magnesium 6.5
32
Q

which element is the most potent to notch toughness?

A

carbon.

when notch toughness is of concern, carbon content should be kept as low as possible

  • balance with strenght requires
33
Q

what are some of the application without force that can be measure physical properties?

  • density
  • electrical -conductivity
  • coef. of thermal expansion
  • magnetic permeability
A
34
Q

what conditions can cause metals to fail?

A
  1. rapture
  2. wear
  3. tempt.effect
  4. corrosion
35
Q

what is rapture?

A

overly applied mechanical forces that high tensile stresses

36
Q

what is plastic range?

A

this properties makes metal very useful. when force is applied by rollling, pressing hammered blows metal can form when hot or cold into useful shape.

37
Q

high carbon and alloying elements for hardneability and trenght.

increasing lead for machinability purposes.

A
  • generally are difficult to machine and weld.
  • it lower life fatigue stregnht and makes welding and cold forming difficult.
    *
38
Q

what is ductility?

A

is the ability of a material to:

  1. bend
  2. residual stretch
  3. distort
39
Q

when a metal is stretch, its lenght increases and is reffered to:

A
  1. elengation
  2. deformation
  3. change of lenght
  4. stretch
40
Q

term ductile and brittle are opposites.

whats the difference?

how does it look?

A
  • if a material stretches before it breaks, is consider ductile.
  • ductile material resists shock better and absorb more energy berfore failure.
    *
41
Q

what does toughness and impact measure?

A

the ability of a material to resist shock.

42
Q

what is creep?

A
  1. when a material is loaded to a spesific(constand) stress-strain leve and held there for a period of time.
  2. it can be acelerated by higher temp.
43
Q

what is impact strenght?

A

describe the resistance of a material to fracture from impacct loading.

  • altered by grain size
  • carbon content
  • temp
  • residual stress
44
Q

what is fracture toughness?

A

a term for measure of resistance to the extension of a crack.

  • charpy testing machine- measures absorbed energy in foot-pound.
    *
45
Q

which metals is the best thermal conductor?

A

silver is the best conductor

46
Q

what is hot rolling?

A

breaks down coarse grains and reform them back to an ‘equiaxed state’

  • the process is called recrystallization.

final grain size is influenced by th org grain size.

47
Q

what does hot rolled steel develops?

A
  • it developes shear planes due to severe plastic deformation and ‘grain flow’ without the benefit of heat.
48
Q

what is ingot?

after it has been storage there are new name for the ingot?

A
  • the form of the steel after it solidifies in the mold.
  • ► ingot is rectangular with rounded corner
  • become into slabs
  • bloom
  • or billet
49
Q

why is an ingot heated in a soaking pit before its rolled?

A
  • is heated in a soaking pit because the ingot is coarse and columnar-making it weak.
    *
50
Q

what happens when a metal aloy solidifues?

A
  • the atoms (nucleate) develop and forms dentrities crystal.

the process continue until the grain are formed.

the crystal grows in all directions until it makes contact with one another .

51
Q

what is equiaxed crystal?

A

are crystals that have axes of the same lenght.

  • has more planes on which to slip and thus can have higher ductility and toughness.
  • grain can be an indication for recrystallization
52
Q

what is microstructure?

A

is the formation of grain, which are usually unique to a given metal called ‘ microstructure’

53
Q

what is the process of work herdening?

slip plane yielding?

A
  • plastic deformation is the sliding of crystal planes.
  • grains elongation occurs in direction of deformation.
  1. becomes resistant to further slippage upon the offset of:
  • imperfections
  • alloying element
  • inclusion
54
Q

what is permanent distortion?

A
  • the ability of metals to flow in a plastic anner without fracture is the fundamental basis for all metal forming process
  • exp: rolling or hammering ingots to form bloom, billet, bars, plate,.etc…
55
Q

what is work hardening?

A
  • an increase in harness and strenght caused by deformation at temp below the recrystalization range. called: strain hardening,
  • raiseds the ratio of yield strenght to tensile and lower ductility
    *
56
Q

what are some productions of rolling mills?

A

produce a viriety of shapes from low carbon steel( mild steel)

57
Q

what is forging?

A

the process of working metal to a desire shape by impact or pressure.

  • hammers, forging, machines, presses or rolls
58
Q

how much percent does plain carbon steel has?

A

from 0.05 to 1.7 percent

59
Q

classify the carbon steel:

A
  • low carbon steel: known as mild steel. under 0.25% nolt and forged parts.
  • medium-carbon: 0.90 to 0.60 % carbon.
  1. better machining capabilities
  2. meduim strenght and wear resisntance surface are needed.
  3. exmp: shaft and gears.
60
Q

forging discontinuities?

A

forging laps(die mismatch-metal folded back and press into surface.

  • location: surface of forging( visually detected)

forging lasa( die design) flow of metal folds back on itself due to improper die design.

  • location: surface of forging at abrupt changes of section( visually detected)

forging burst: rapture of metals due to forging at improper temp.

  • location: may be internal or external
61
Q

what are the two typer of extrusion processes without using a lubricant?

A
  1. direct or foward
  2. inderect or backward
62
Q

extrusion foward?

extrusion backward?

A

the billet is extruded by the force of the ra, bein pushed against it.

  • this upsets the billet, then forces the metal to flow throu gh the die.

the die is pushed by the hollow stem & move relative to the container , but there is no relative displacement between the billet and the container.

Ndt Measurement (2 decks)

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