university of illinois at urbana-champaign thermo
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University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
ThermoThermo--Mechanical Fatigue of CastMechanical Fatigue of Cast319 Aluminum Alloys319 Aluminum Alloys
Huseyin Sehitoglu, 1 Carlos C. Engler-Pinto Jr. 2,Hans J. Maier 3 ,Tracy J. Foglesong4
1 University of Illinois at Urbana- Champaign, USA,2 Ford Motor Company, Dearborn, 3 Universität-GH Paderborn, Germany, 4 Exxon , Houston
Research Supported by Ford Motor Company
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Use of Aluminum Alloys in engine blocks and cylinder
heads
• Thermo-Mechanical Fatigue Results
• Summary
• Modeling Studies (Precipitation hardened aluminum
alloys)
OutlineOutline
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Percentage of Vehicles with AluminumPercentage of Vehicles with AluminumEngine Blocks and Heads (*)Engine Blocks and Heads (*)
(*) Delphi VIII Study, 1996
20%10%5%Light trucks
50%30%13%Passenger cars
Blocks
60%40%20%Light trucks
95%85%78%Passenger cars
Heads
200520001994
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Advantages of cast aluminumAdvantages of cast aluminum
• Lightweight
– V-8 Engine Block: 150 lbs Cast Iron vs. 68 lbsAluminum
• Cast into complex shapes
• Increased thermal conductivity
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Cylinder Heads
Inlet Valve Exhaust Valve
Spark Plug
Practical ApplicationPractical Application
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Al319Al319--T7BT7B
• Nominal Composition in weight percentage
– (*) WAP319: max 0.4% Fe - EAP319: max 0.8% Fe
• Thermal treatment– solutionizing at 495°C for 8 hours followed by precipitating at
260°C for 4 hours)
*
Fe
0.05max
0.25max
0.25max
0.20-0.30
0.25-0.35
3.3-3.7
7.2-7.7
Bal.
CrTiZnMnMgCuSiAl
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
ThermoThermo--Mechanical Fatigue CyclesMechanical Fatigue Cycles
• Simultaneously changing strain andtemperature (T)
• In-Phase: max-strain at max-T
• Out-of-Phase: max-strain at min-T
300
200
100
T(¡
C)
-1
0
1
ε mec
h(%
)
6420time (min)
OP
IP
-1
0
1
ε mec
h(%
)
300200100T (¡C)
IP
OP
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Fatigue of materials subjected to simultaneously changingtemperature and strain.
• εtot = εth + εmech
• Terminology– in-phase
– out-of-phase
ThermoThermo--Mechanical FatigueMechanical Fatigue
Temp.
Mech. Strain
Tmax
Tmin
εmaxεmin
TMF IPTMF OP
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Micro-Computer
HydraulicTesting
Machine
FT εεεεT vs. t
TMF TestingTMF Testing
pyrometer
extensometerInductionHeating
load cell
εεεε vs. t
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Isothermal LCF
– 20°C, 150°C, 250°C and 300°C
– 2×10-1 s-1 , 4×10-3 s-1 and 5×10-5 s-1
• Thermo-Mechanical Fatigue
– 100–300°C — 5×10-5 s-1
Experimental ProceduresExperimental Procedures
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMF LoopsTMF Loops
-0.4 -0.2 0.0 0.2 0.4
Mechanical Strain (%)
100¡C 300¡C
1
200
In-Phase∆εm = 0.54%
Nf = 39020
-200
-100
0
100
200
Stre
ss(M
Pa)
-0.4 -0.2 0.0 0.2 0.4
Mechanical Strain (%)
100¡C
300¡C
Cycle 1
200
1220
Out-of-Phase∆εm = 0.6%
Nf = 2460
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMF OP 100TMF OP 100--300°C 1.0%300°C 1.0%
-200
-100
0
100
200
Str
ess
(MP
a)
-6x10-3
-4 -2 0 2 4 6Strain
STRESS1-2fea Stress1-2STRESS300fea Stress300
100°C
300°C
200°C
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Fatigue Life CriterionFatigue Life Criterion
LCF - 250°C - 0.3% - 0.5 hzWAP319-T7B
120
80
40
0
Max
imum
Stre
ss(M
Pa)
50000Number of Cycles
50% Load Drop
Nf
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
80
60
40
20
0
Yie
ldSt
reng
th(M
Pa)
120100806040200time (h)
PrecipitatePrecipitateCoarseningCoarsening
45000 cycles / ~25 hours(300°C, ∆εm = 0.2%).
Exposure at 300°C
Initial
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMF LoopsTMF Loops
200
100
0
-100
OP
Stre
ss(M
Pa)
-0.6 -0.4 -0.2 0.0 0.2 0.4
OP Inelastic Strain (%)
-200
-100
0
100
IPStress
(MPa)
0.6 0.4 0.2 0.0 -0.2 -0.4IP Inelastic Strain (%)
OPIP
100¡C
300¡C
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMFTMF –– Peak StressesPeak Stresses300
250
200
150
100
50
Stre
ss(M
Pa)
2 3 4 5 6 7 8 90.1
2 3 4 5 6 7 8 91
2
Inelastic Strain Range (%)
OP IPσmax-σmin 100¡C
300¡C
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMFTMF –– Stress Range EvolutionStress Range Evolution350
300
250
200
150
100
50
Stre
ssR
ange
(MPa
)
25002000150010005000Number of Cycles
TMF OPTMF IP
EAP319-T7B
Initial Behavior
IPN f /2
OPN f /2
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Cyclic StressCyclic Stress--Strain CurvesStrain Curves400
350
300
250
200
150
Stre
ssR
ange
(MPa
)
0.00012 3 4 5 6 7 8 9
0.0012 3 4 5 6 7 8 9
0.012
Inelastic Strain Range
WAP319TMF OPTMF IP
EAP319TMF OPTMF IP300¡C 0.5 hz
300¡C 5x10-5
s-1
WAP319
EAP319
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMF LifeTMF Life
0.001
2
3
4
56
0.01
2
3
4
5
Mec
hani
calS
trai
nR
ange
101
102
103
104
105
106
107
108
Cycles to Failure
150¡C 40 hz250¡C 40 hz250¡C 0.5 hz
250¡C 5x10-5
s-1
300¡C 5x10-5
s-1
300¡C 0.5 hzTMF OPTMF IP
RoomTemperature
EAP319-T7B
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMF LifeTMF Life400350300
250
200
150
100
50
Stre
ssR
ange
(MPa
)
101
102
103
104
105
106
107
108
Cycles to Failure
RoomTemperature
300¡C 5x10-5
s-1
TMF OP 5x10-5
s-1
TMF IP
5x10-5
s-1
300¡C 2x10-3
s-1
150¡C
2x10-1
s-1
250¡C
2x10-3
s-1
EAP319-T7B
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
0.0001
2
4
68
0.001
2
4
68
0.01
2
Inel
astic
Stra
inR
ange
101
102
103
104
105
Cycles to Failure
EAP319250¡C 0.5 hz
250¡C 5x10-5
s-1
300¡C 0.5 hz
300¡C 5x10-5
s-1
TMF OPTMF IP
OP + LCF
IP
WAP319TMF OPTMF IP
TMF LifeTMF Life
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
EAP319EAP319--T7BT7BTMFTMF--OPOP
100100––300°C300°C∆ε∆εmm=0.6%=0.6%NNff=2460 c.=2460 c.
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
EAP319EAP319--T7BT7BTMFTMF--IPIP
100100––300°C300°C∆ε∆εmm=0.54%=0.54%NNff=390 c.=390 c.
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
2
3
4
5
6
7
8
90.01
2
3
4
5
Meha
nica
l St
rain
Ran
ge
101
2 3 4 5 6 7 8 9
102
2 3 4 5 6 7 8 9
103
2 3 4 5 6 7 8 9
104
Nf
WAP EAP PredictionTMF-IPTMF-OP
a0 = 70 µm
300 µm
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
1. TMF stress-strain behavior is identical for both IP andOP loading conditions. TMF-IP lives are shorter thanTMF-OP (based on the mechanical or inelastic strainrange) lives.
2. Creep damage dominates for TMF-IP loading and inthe high strain range regime.
3. The secondary alloy (EAP319) is softer than theprimary alloy (WAP319), but TMF lives are verysimilar.
SummarySummary
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
AluminumAluminum--Copper AlloysCopper Alloys• Precipitate-dislocation interactions
– Anisotropy on plastic flow behavior (Hosford & Zeisloft ‘72, Bate et al. ‘81, Barlat & Liu ‘98,Choi & Barlat ‘99)
– Bauschinger effect (Abel & Ham ‘66, Moan & Embury ‘79, Wilson ‘65)
• Coherent particles - GP zones and θ'' (Price and Kelly ‘64)
– Higher yield stress than Al shearing of particles
– Comparable work hardening rates and
deformation to Al
• Semi-coherent - θ' ( P & K ‘64, Russell & Ashby ‘70)
– High yield stress and high work hardening rates
• Incoherent particles - θ ( P & K ‘64, R & A ‘70)
– Low initial yield stress
– Highest rates of work hardening
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Precipitate DevelopmentPrecipitate Development
GP zones * Peak aged, θ'
Over aged, θ' & fine θVery over aged, coarse θ*Sato & Takahashi, 1983
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Limitations of current modelsLimitations of current models
• No implicit consideration of aging treatment.– Models were developed for one specific aging treatment
• Peak aged, θ'
• No inclusion of length scale– Volume fraction, precipitate size, mean free path etc. with aging treatment
• Empirical hardening models with a microstructural basis.
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Proposed Hardening LawProposed Hardening Law• Single crystal formulation - one precipitate type
• Polycrystal formulation– More than one type of precipitate– Incorporate grain size length scale
Ýτ = Koα 2µ 2b
2 τ −τ o( )d+θo
τ s −ττ s −τ o
Ýγ kk∑
Ýτ = µ2b
2 τ −τ o( )α1
2 ′ K1
d1
+α 2
2 ′ K2
d2
+α 3
2 ′ K3
d3
+ θo
τ s −ττ s −τ o3
Ýγ kk∑
d3
d1
d2
grain
θ'
θ
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Constitutive EquationsConstitutive Equations• Relate stress and strain rate at single crystal and
polycrystal level.
• Can be written in pseudo-linear form.
• Assume overall polycrystal response described by lawsimilar to that of single crystal.
Ýε iin = Ýγ o
mism j
s
τ cs
mks ′ σ kτ c
s
s =1
S
∑n−1
′ σ j wherei =1,5
Ýε iin = Mij
c (sec) ′ σ ( ) ′ σ j
ÝEiin = Mij
(sec) ( ′ Σ ) ′ Σ j
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Hardening with PrecipitatesHardening with Precipitates• Start with dislocation evolution equation
• Combine with the Bailey-Hirsch relationship for flow stress.
Ýρ = Ko
db+ k1 ρ − k2ρ
k∑ Ýγ k
Geometric storage term dueto boundaries / obstacles
Statistical storage of dislocations
Dynamic recoveryof dislocations
τ = τ o +αµb ρ
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
500
400
300
200
100
0
Stre
ss, (
MP
a)
20151050
Inelastic Strain, (%)
Solid line - Experiment
Dashed line - Simulation
Experiment and Simulation for Al - 4% Cu Single Crystals[123] Orientation - Different Aging Conditions
190C, 24 hrs
190C, 3 hrs
No Aging
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
SummarySummary
• The hardening law including the effects ofprecipitates on the deformation behavior of binaryAl - Cu alloys is physically based and accounts forprecipitate size, orientation, and mean free path.
• The model incorporates hardening law andpredicts single crystal behavior of pure Al and Al-Cu alloys, it also predicts polycrystallineexperiments from knowledge of single crystalbehavior.