MSE 2001

Material constant / Material Property

a property of a material that doesn’t dep on size or shape
often in adjectives ending in “ivity”

loading and unloading a metal past its yield point but below its Ult tens strength will…

increase the yield strength due to work hardening

adding impurities to metal will make it….

less ductile

Two metal alloys are nearly identical, except Alloy A has 2% impurity content and Alloy B has 8% impurity content. Assuming lattice resistance is nearly zero for both alloys, what do you predict the difference in yield strength (sigma)_y to be for these two materials?

Alloy B will have a 2x higher yield strength than Alloy A.

increases # of cyc to failure

flame polishing, shot peening

Adding precipitates to a metal alloy will

incr yield strength but decrease its fracture toughness.

fracture toughness

critical stress

hi density glass = __ Refractice ind

hi

Molar vol is ____ proportional to density

Inversely

fast cooling leads to

hi molar vol

tetragonal shape

orthorhombic shape

Rhombohedral

Monoclinic

Triclinic

hexagonal

a = b = c, α = β = γ = 90

cubic

a = b ≠ c, α = 120, β = γ = 90

Hexagonal

a = b ≠ c, α = β = γ = 90

Tetragonal

a ≠ b ≠ c, α = β = γ = 90

Orthorhombic

a = b = c, α = β = γ ≠ 90

Rhombohedral

a ≠ b ≠ c, α ≠ 90, β = γ = 90

Monoclinic

a ≠ b ≠ c, α ≠ β ≠ γ ≠ 90

Triclinic

HCP stacking

ABA

HCP # of atoms

6

HCP packing factor

74%

HCP coord #

12

FCC stacking

ABCA

FCC # of atoms

4

FCC packing factor

74%

FCC coord #

12

BCC coord #

8

BCC # atoms

2

BCC packing factor

68%

Band Gap Theory

describes the behavior of how electrons move between groups of atoms depending on the size of the band gap (Eg) (measured in around 10-19 Joules) btw atoms

band gap behavior

e^- move from valence band (filled with e^-) to conduction band (empty of e^-)

speed of energy

J/s (Watt)

when a mat elastic mod is too low, that means its …

not stiff

Modulus of Resilience (Ur)

• Amt of elastic energy returned to mat after load is removed

• Area under elastic portion of stress strain curve

Coef or restitution

Ductility (ε_f)

• Max strain experienced at point of failure

plastic deformation

Atoms are permanently displaced

Elastic deformation

Atoms are uniformly separated but can return to previous possition

Yield Stress

• The stress required to permanently deform mat

• (σ_y)

porous

containing small holes that water and air can enter
ex: pumus

Auxetic mat

Material with a negative poisson’s ratio (elongation in one dir causes elongation in another dir

Ohms law

R = v / i
R = resistance (ohms)
v = voltage
i = current (amps)

Resistance eq

p (Rho): Resistance

l: length

A: cross-sectional area

Performance parameter

a property of a mat that is det by

1. mat

2. shape

3. size

often in adjectives ending in “ance”

emissivity

Material’s ability to reflect it’s thermal energy in the form of light (think of thermal cams)
Ranges from 0 (completely reflective of light energy, ie. polished metal) to 1 (completely absorbs light energy ie. mat that absorbs heat quickly and is painted black)

Shear modulus eq

(F/A) / tan(theta)

Bulk modulus eq

(F/A) / (delta V / V)

Precious metals

Metals rare on earth

Rare earth metals

Metals with ~57-70 atoms that are sparse when found (but not necessarily rare)

Elastic Modulus (Stiffness)

force needed to stretch, bend, flex mat 

Yield Strength (Strength)

Force needed to deform mat

toughness

energy needed to break mat

*stress

aka pressure

σ (sigma)

strain

• Δ load / load

• ε (epsilon)

Hooke’s law

F= -kΔx (spring Kin En)

*Deformation has a __ relationship to strain in the elastic portion of the stress strain curve

linear

Young’s Modulus

slope of the elastic curve (E)

in Pa

stretches the atoms of mat while

Poisson’s ratio

• the neg of rat btw lateral (transverse) strain and longitudinal (axial) strain in longitudinal tensile loading

• Usually .3

Acoustic Impedance

(Z)
used to det sound absorption and reflection as it travels btw dif mat

Low Z diff =

most sound is passed through

High Z diff =

most sound is reflected

stress equation

σ = E * ε

Young’s Modulus equation (in Pa)

E = σ / ε

= (F/A) / ( delta L/ L)

Shear modulus

(G)

Bulk Modulus

(K)

Ex: Hydrostatic pressure

Flexural Modulus

(E_f)

thermal Diffusivity

rate at which a mat will reach a certain temp from const pwr heat source

Thermal Conductivity (Λ)

The rate of heat flow through a mat at steady state

heat flux (Q)

flow of energy from one mat to another

Thermal Diffusivity (D_^th)

ratio btw thermal cond and heat cap

material type with the highest diffusivity

polymers

Cathodic protection

use of a sacrificial anode to protect the cathod

reduction (gain e^-) occ at the

cathode

oxidation (lose e^-) occ at the

anode

part being sacrificed in galvanization is

the anode

metals lower on the Reduction potential table make for better

Anodes to metals above them

Capacitance

the ability of a mat to store electric charge

permittivity (ε)

how easy it is to polarize a mat

Dielectric const (K)

how much charge a dielectric mat can store

Band Gap Theory

Remanent magnetization

remaining magnetization when external mag field is removed

Saturation magnetization

max magnetization achievable in mat

Coercive field

external magnetization (energy) required to “switch” the magnetization

Hard magnet

• “Permanent” magnet 

• High coercive field

• Can stick to hard or soft magnets

Soft magnet

• Loses magnetization very easily

• Low coercive field

Diamagnets

• Very weak mat response to external mag field

• No mag dipoles until there is an external field

• ex: wood, glass, water, gold, super conductors, N2

Paramagnets

• Weak mag response to external mag field

•  random dir mag dipoles

• ex: O2,