Stress:
=
F Chapter6MechanicalPropertiesofMetals
Typesofstresses:Tensile,Compressive,Shear,BiaxialTensionCompression,Hydrostatic. A0
,Strain:
=
l l0
Shearstress: = F ,Shearstrain: = l = tan A0 l0
= E
Stressandstrainareproportionaltoeachotherusing
W=
F (EYoungsModulus)or = G (GShearModulus).Physicsofelasticity: E= :: r
E = 2 G 1+
2U ,Energystored: r 2
2V0 1 ,Poissonsratio: V0 = 2 2E
=
x z
(bottomofratiostrainindirectionofappliedforce)
(
)
.
Deformation:Metallicmaterialsdeformelastically(reversible)untilstrainsofabout.005.Afterthat,plastic(irreversible)deformationoccurs.*Note:Elasticdoesntconservevolume, plasticdoes.* Workhardening:Aftertheyyield,metalsgethardertodeform.TensileStrength=Fmax/A0 Ductility:%elongation=](lfl0)/l0]*100,%areareduction=[(A0Af)/A0]*100 Hardnesstests: H : Pindent (pressurevs.area) Chapter18ElectricalPropertiesofSolids Aindent Brinell:
HB =
D D D 2 d 2
(
2P
)
(Pload,Ddiameterofsteelball:10mm,dindentdiameter),Resilience:
UR =
2 y
2E
OhmsLaw: V = IR J = (electricalconductivity, or theareaperpendiculartothedirectionofthecurrent.
p: e
Eg kT
= / 1
, electricfieldintensity, = V / l ),Resistivity:
RA =
/l
,wherelisthedistancewherevoltageismeasured,Ais
(pprobability,#ofelectronsexcited(holescreated)),ifEg>2eV,thenp0insulator.Forsemiconductors,asT,Ne .
e
Metals:ElectronDriftVelocity
T n,but dominant(morecollisionsimpede =ne v = e d Conductivity: (n#freee s,echargeofe electronmobility) movement).Resistivity(MatthiessensRule): = TR thermal + impurity + dislocations . E g 2 kT Extrinsic(doped):ntype: Semiconductors:Intrinsic(pure): (n=p),Temp.dependence: (excesse,n>>p,n=#ofvalencee#dopantatoms, = n e (e + h ) n = n0 e n e e E g kT Eg 2 kT addgroupVP);ptype: (excessholes,p>>n,p=#ofholesinvalence#dopantatoms,addgroupIIIAltogroupIVSi).Temp.dep.: p e h n = n0 e =e e e . .
Chapter19ThermalPropertiesofSolids
Forsemiconductors,T .Forwardbias:
Reversebias:
Q V Capacitancechargedensity: A = h / + h / Typicalconductivityrangesmetals: 11 2 2
107,semiconductors:104.Orbitals:sshell:Nstates;pshell:3Nstates;dshell:5Nstates(2e/state) dQ ,forT< D,C=AT3;forT> D,C=3R( DDebyetemperature,Rgasconstant) HeatCapacity: C= dt Thermalflux: dT q = k dx ThermalStress:inducedbyconstraints,diff.matls.bonded,Tgradients: Coolingrate:
k f E
Constants&Conversions
giga mega kilo centi
23
G M k c
109 10 10
6
milli micro nano pico
5
m n p
103 106 109 1012
= thermal = E T E
thermal
L = = T room T Lroom
(
)
,
103
2
,
Q R = k T =
TSR
. L =
k elecT
k=1.3810 J/atom K=8.6210 eV/atom K R=8.314J/mol KNA=6.0231023atoms/mol e=1.6021019Cme=9.111031kg
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