materials selection and design consideration
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Materials Selection and Design Considerations
By: Paul MaglunsodCarlo Manzano
Why study Materials Selection and Design Considerations? An important task for an engineer to perform
is that of materials selection with regard to component design
Inappropriate or improper decisions can be disastrous from both economic and safety perspectives.
An engineering student should be familiar with and versed in the procedures and protocols that are normally employed in the process.
ISSUES TO ADDRESS...
• Price and availability of materials.
1
• How do we select materials based on optimal performance?
• Applications: --shafts under torsion --bars under tension --plates under bending --materials for a magnetic coil.
2
• Current Prices on the web(a): --Short term trends: fluctuations due to supply/demand. --Long term trend: prices will increase as rich deposits are depleted.
• Materials require energy to process them:--Energy to produce materials (GJ/ton)
AlPETCusteelglasspaper
237 (17)(b)
103 (13)(c)
97 (20)(b)
20(d)
13(e)
9(f)
--Cost of energy used in processing materials ($/GJ)(g)
elect resistancepropanenatural gasoil
2511 9 8
a http://www.statcan.ca/english/pgdb/economy/primary/prim44.htma http://www.metalprices.comb http://www.automotive.copper.org/recyclability.htmc http://members.aol.com/profchm/escalant.htmld http://www.steel.org.facts/power/energy.htme http://eren.doe.gov/EE/industry_glass.htmlf http://www.aifq.qc.ca/english/industry/energy.html#1g http://www.wren.doe.gov/consumerinfo/rebriefs/cb5.html
Energy using recycledmaterial indicated in green.
PRICE AND AVAILABILITY
3
• Reference material: --Rolled A36 plain carbon steel.• Relative cost, $, fluctuates less over time than actual cost.
Graphite/ Ceramics/ Semicond
Metals/ Alloys
Composites/ fibersPolymers
Rela
tive C
ost
($)
pl. carbon
Au
Si wafer
PETEpoxy
Nylon 6,6
0.050.1
5
100000
1000020000
50000
5000
20001000
500
20010050
2010
21
0.5
Steel
high alloy
Al alloysCu alloys
Mg alloys
Ti alloys
Ag alloys
Pt
Tungsten
Al oxide
Concrete
Diamond
Glass-soda
Si carbide
Si nitride
PC
LDPE,HDPEPPPS
PVC
Aramid fibersCarbon fibers
E-glass fibers
AFRE prepreg
CFRE prepreg
GFRE prepreg
Wood
Based on data in AppendixC, Callister, 6e.AFRE, GFRE, & CFRE = Aramid,Glass, & Carbon fiber reinforced epoxy composites.
$
$/kg($/kg)ref material
RELATIVE COST, $, OF MATERIALS
4
• Bar must not lengthen by more than under force F; must have initial length L.
• Maximize the Performance Index:
F,
L
c c
-- Stiffness relation: -- Mass of bar:
F
c2E
L (= E) MLc2
• Eliminate the "free" design parameter, c:
M
FL2
E
P
E
specified by applicationminimize for small M
(stiff, light tension members)
STIFF & LIGHT TENSION MEMBERS
5
• Bar must carry a force F without failing; must have initial length L.
• Maximize the Performance Index:
F,
L
c c
-- Strength relation: -- Mass of bar:
MLc2
• Eliminate the "free" design parameter, c:
specified by applicationminimize for small M
P
f(strong, light tension members)
MFLN
f
fN
F
c2
STRONG & LIGHT TENSION MEMBERS
6
• Bar must carry a moment, Mt ; must have a length L.
• Maximize the Performance Index:
-- Strength relation: -- Mass of bar:
• Eliminate the "free" design parameter, R:
specified by application minimize for small M
(strong, light torsion members)
fN
2Mt
R3 MR2L
L
2R
Mt
M 2 NMt 2/3L
f2/3
P
f2/3
STRONG & LIGHT TORSION MEMBERS
Increasing P for strong tension members
Increasing P for strong torsion members
0.1 1 10 30
1
10
102
103
104
Density, (Mg/m3)
Strength, f (MPa)
slope = 1
0.1
Metal alloys
Steels
Ceramics
PMCs
Polymers
|| grain
grain wood
Cermets
slope =
3/2
7
Adapted from Fig. 6.22, Callister 6e. (Fig. 6.22 adapted from M.F. Ashby, Materials Selection in Mechanical Design, Butterworth-Heinemann Ltd., 1992.)
DATA: STRONG & LIGHT TENSION/TORSION MEMBERS
0.1 1 10 30 0.1
1
10
102
103
104 Cermets
Steels
Density, (Mg/m3)
Str
en
gth
,
f (M
Pa)
slop
e = 2
Increasing P for strong bending members
Metal alloys
Ceramics
PMCs
Polymers
|| grain
grain wood
8
• Maximize the Performance Index:
P
1/2
Adapted from Fig. 6.22, Callister 6e. (Fig. 6.22 adapted from M.F. Ashby, Materials Selection in Mechanical Design, Butterworth-Heinemann Ltd., 1992.)
DATA: STRONG & LIGHTBENDING MEMBERS
9
• Other factors: --require f > 300MPa. --Rule out ceramics and glasses: KIc too small.
• Maximize the Performance Index: P
f2/3
• Numerical Data:
• Lightest: Carbon fiber reinf. epoxy (CFRE) member.
material
CFRE (vf=0.65)
GFRE (vf=0.65)Al alloy (2024-T6)Ti alloy (Ti-6Al-4V)4340 steel (oil quench & temper)
(Mg/m3)1.52.02.84.47.8
P (MPa)2/3m3/Mg)7352161511
Data from Table 6.6, Callister 6e.
f (MPa)11401060 300 525 780
DETAILED STUDY I: STRONG, LIGHT TORSION MEMBERS
10
• Minimize Cost: Cost Index ~ M$ ~ $/P (since M ~ 1/P)
• Numerical Data:
• Lowest cost: 4340 steel (oil quench & temper)
materialCFRE (vf=0.65)GFRE (vf=0.65)Al alloy (2024-T6)Ti alloy (Ti-6Al-4V)4340 steel (oil quench & temper)
$804015
1105
P (MPa)2/3m3/Mg)7352161511
($/P)x100112769374846
• Need to consider machining, joining costs also.
Data from Table 6.7, Callister 6e.
DETAILED STUDY I: STRONG, LOW COST TORSION MEMBERS
11
• Background(2): High magnetic fields permit study of: --electron energy levels, --conditions for superconductivity --conversion of insulators into conductors.• Largest Example: --short pulse of 800,000 gauss (Earth's magnetic field: ~ 0.5 Gauss)• Technical Challenges: --Intense resistive heating can melt the coil. --Lorentz stress can exceed the material strength.• Goal: Select an optimal coil material.
(1) Based on discussions with Greg Boebinger, Dwight Rickel, and James Sims, National High Magnetic Field Lab (NHMFL), Los Alamos National Labs, NM (April, 2002).(2) See G. Boebinger, Al Passner, and Joze Bevk, "Building World Record Magnets", Scientific American, pp. 58-66, June 1995, for more information.
Pulsedmagneticcapable of600,000 gaussfield during20ms period.
Fracturedmagnetcoil.(Photostaken at NHMFL,Los AlamosNational Labs,NM (Apr. 2002)by P.M. Anderson)
DETAILED STUDY II: OPTIMAL MAGNET COIL MATERIAL
12
• Applied magnetic field, H:
H = N I/L
• Lorentz "hoop" stress: • Resistive heating: (adiabatic)
R
I
A
IoHRA
( fN
)
temp increaseduring currentpulse of t
T I2e
A2cv
t ( Tmax)
Magneticfieldpointsout ofplane.
elect. resistivity
specific heat
current I
N turns total
L = length of each turn
Forcelength
IoH
LORENTZ STRESS & HEATING
13
• Mass of coil:
M = dAL
• Eliminate "free" design parameters A, I from the stress & heating equations (previous slide):
• Applied magnetic field:
H = N I/L
H2
M
1
2R2LoN
fd
--Stress requirement
specified by application
Performance Index P1:maximize for large H2/M
H tM
Tmax2 RL
1d
cve
specified by application
Performance Index P2:maximize for large Ht1/2/M
--Heating requirement
MAGNET COIL: PERFORMANCE INDEX
14
• Relative cost of coil:
$ = $ M
• Eliminate M from the stress & heating equations:
• Applied magnetic field:
H = N I/L
--Stress requirement
specified by application
Cost Index C1:maximize forlarge H2/$
specified by application
Cost Index C2:maximize forlarge Ht1/2/$
--Heating requirement
H t$
Tmax2 RL
1d$
cve
H2
$
1
2R2LoN
fd$
MAGNET COIL: COST INDEX
15
• Data from Appendices B and C, Callister 6e:Material1020 steel (an)1100 Al (an)7075 Al (T6)11000 Cu (an)17200 Be-Cu (st)71500 Cu-Ni (hr)PtAg (an)Ni 200units
f
395 90572220475380145170462MPa
d
7.852.712.808.898.258.9421.510.58.89g/cm3
$ 0.812.313.4 7.951.412.91.8e4271 31.4 --
cv
486904960385420380132235456J/kg-K
e
1.600.290.520.170.573.751.060.150.95-m3
P1
50 33204 25 58 43 7 16 52 f/d
P2
2 21 15 5 3 1 19 <1 2 (cv/e)0.5
d
C1
63 315 3 1 3<1<1 2P1/$
C2
2.5 1.7 1.1 0.6<0.1<0.1<0.1<0.1<0.1P2/$
Avg. values used. an = annealed; T6 = heat treated & aged;st = solution heat treated; hr = hot rolled
• Lightest for a given H: 7075 Al (T6)
• Lightest for a given H(t)0.5: 1100 Al (an)
• Lowest cost for a given H: 1020 steel (an)• Lowest cost for a given H(t)0.5: 1020 steel (an) C2
C1
P2
P1
INDICES FOR A COIL MATERIAL
16
• Application:Space Shuttle Orbiter
• Silica tiles (400-1260C):--large scale application --microstructure:
100m
~90% porosity!Si fibersbonded to oneanother duringheat treatment.
Fig. 23.0, Callister 5e. (Fig. 23.0 courtesy the National Aeronautics and Space Administration.
reinf C-C (1650°C)
Re-entry T Distribution
silica tiles (400-1260°C)
nylon felt, silicon rubber coating (400°C)
Fig. 19.2W, Callister 6e. (Fig. 19.2W adapted from L.J. Korb, C.A. Morant, R.M. Calland, and C.S. Thatcher, "The Shuttle Orbiter Thermal Protection System", Ceramic Bulletin, No. 11, Nov. 1981, p. 1189.)
Fig. 19.3W, Callister 5e. (Fig. 19.3W courtesy the National Aeronautics and Space Administration.
Fig. 19.4W, Callister 5e. (Fig. 219.4W courtesy Lockheed Aerospace CeramicsSystems, Sunnyvale, CA.)
THERMAL PROTECTION SYSTEM
• Space Shuttle Tiles: --Silica fiber insulation offers low heat conduction.
• Thermal Conductivity of Copper: --It decreases when you add zinc!
Composition (wt%Zinc)Therm
al C
onduct
ivit
y
(W/m
-K)
400
300
200
100
00 10 20 30 40
17
Fig. 19.0, Callister 6e.(Courtesy of LockheedMissiles and SpaceCompany, Inc.)
100m
Adapted fromFig. 19.4W, Callister 6e. (Courtesy of Lockheed Aerospace Ceramics Systems, Sunnyvale, CA)(Note: "W" denotes fig. is on CD-ROM.)
Adapted from Fig. 19.4, Callister 6e.(Fig. 19.4 is adapted from Metals Handbook: Properties and Selection: Nonferrous alloys and Pure Metals, Vol. 2, 9th ed., H. Baker, (Managing Editor), American Society for Metals, 1979, p. 315.)
THERMAL
18
• Material costs fluctuate but rise over the long term as: --rich deposits are depleted, --energy costs increase.• Recycled materials reduce energy use significantly.• Materials are selected based on: --performance or cost indices.• Examples: --design of minimum mass, maximum strength of: • shafts under torsion, • bars under tension, • plates under bending, --selection of materials to optimize more than one property: • material for a magnet coil. • analysis does not include cost of operating the magnet.
SUMMARY