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MAT E 202 > Chapter 2: Mechanical Properties > Flashcards

Chapter 2: Mechanical Properties Flashcards

1
Q

Mechanical properties

A

Standardized interpretations of a material’s response to stress that compare their response during plastic and elastic deformation.

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2
Q

Stress

A

Measure of what a material feels from externally applied forces.

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3
Q

Types of Stress (3)

A

Tension, compression, shear

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4
Q

Stress Formula

A

σ = P/A

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5
Q

Strain

A

Deformation of a material from stress.

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6
Q

Strain formula

A

ε = ΔL/L

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7
Q

Shear Strain Formula

A

γ = b/h = tanθ = θ for small angles

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8
Q

Hooke’s law formulae

A

σ = Eε
τ = γG

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9
Q

Poisson’s ratio

A

v = - Lateral Strain / Longitudinal (axial) Strain

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10
Q

Anisotropic
materials

A

Mechanical properties depend on the orientation of the material’s body, unsymmetrical crystalline structures.

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11
Q

Isotropic materials

A

Identical material properties in all directions at every given point

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12
Q

Poisson’s ratio range

A

0 - 0.5

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13
Q

v = 0.5

A

Perfectly incompressible isotropic material

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14
Q

Elastic deformation

A

Bonds stretch and shorten as stress is applied, deformations recover quickly.

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15
Q

Plastic deformation

A

Bonds are stretched and/or broken, deformations are permanent.

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16
Q

Metallic deformation behavior below the yield point

A

Elastic

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17
Q

Metallic deformation behavior above the yield point

A

Elastic and plastic

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18
Q

Tension testing

A

Constant rate of elongation applied to a dog bone specimen so that plastic deformation occurs only in the gauge section.

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19
Q

Young’s modulus (E)

A

Slope of the elastic portion of a stress-strain curve

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20
Q

Resilience modulus (U)

A

Measure of material stiffness, area under a stress-strain curve

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21
Q

Yield strength, proportional/elastic limit (σy)

A

Stress on a stress-strain curve that is the limit of elastic behavior and the beginning of plastic behavior.

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22
Q

Offset yield strength

A

When the yield point is difficult to define, stress is measured from ε = 0.002

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23
Q

Ultimate yield strength

A

Highest stress on a stress-strain curve, where a material begins to deform (have a local instability).

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24
Q

Reduction in area and length

A

Measures of ductility

25
Q

Ductility

A

The measure of plastic strain to fracture, the quality of being flexible.

26
Q

Hardness

A

Material’s resistance to localized plastic deformation, the ability to withstand force without scratching, penetration or indentation.

27
Q

Toughness

A

Amount of energy a material can absorb before fracturing

28
Q

Reduction in area formula

A

RA = (Ao - Af)/Ao

29
Q

Brittle fracture

A

Breakage of a material via rapid crack propagation with low energy release and without significant plastic deformation. Less strain is needed.

30
Q

Ductile fracture

A

Breaking of a material after extensive plastic deformation. Uses a lot of time and energy and needs an increased load.

31
Q

True stress

A

Instantaneous stress

32
Q

True stress formula

A

σT = σ(1+ε)

33
Q

True strain

A

Instantaneous strain

34
Q

True strain formula

A

εT = ln(Li/Lo) = ln(1+ ε)

35
Q

Hardness Formula

A

H = F/A

36
Q

Safety Factor

A

Ratio of a material’s strength to an expected strain.

37
Q

Safety factor formula

A

FS = σy or uts / σdesign

38
Q

Thermal expansion

A

Tendency of a material to change its shape, area, volume, and density in response to a change in temperature

39
Q

Thermal expansion formula

A

ΔL = αLΔT

40
Q

Thermal stress

A

Stress created by any change in temperature of a material.

41
Q

Thermal stress formula

A

σt = -EαΔT

42
Q

Thermal stress/strain gradient

A

Thermal stress/strain between 2 points

43
Q

Thermal stress gradient formula

A

σ = -E(α1 - α2)ΔT

44
Q

Thermal conductivity

A

The rate at which heat passes through a material

45
Q

Thermal conductivity formula

A

q = -k(dT/dx)

46
Q

Thermal conductivity mechanisms (k)

A
  1. Lattice Vibrations/photons in non-metals (kl)
  2. Free electrons in metals (ke)
    k = kl + ke
47
Q

Thermal strain gradient formula

A

εt = (α1 - α2)ΔT

48
Q

Wiedemann-Franz law

A

Thermal and electrical properties are related and proportional

49
Q

Thermal shock resistance

A

The ability of a material to withstand sudden changes in temperature

50
Q

Thermal shock resistance formula

A

TSR = σk / Eα

51
Q

Heat capacity

A

Amount of heat energy required to raise the temperature of a material by 1C

52
Q

Heat capacity formula

A

C = dQ/dT, K/(mol*K)

53
Q

Bond stiffness

A

Inflection point on a bond-energy curve, above this point, a material will melt.

54
Q

Bond stiffness formula

A

F = αEΔr

55
Q

Ohm’s law

A

R = V/I

56
Q

Resistivity

A

Measure of the resisting power of a specified material to the flow of an electric current. Affected by temperature, impurities and deformation. p = RA/l

57
Q

Conductivity

A

The degree to which a specified material conducts electricity. σ = 1/p

58
Q

Bonding force formula

A

F = dU/dr

59
Q

Work hardening

A

Toughening (increase of hardness) of a metal, happens during plastic deformation

MAT E 202 (13 decks)

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