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Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Overview of High Temperature and Thermo-mechanical
Fatigue (TMF)
Overview of High Temperature and Thermo-mechanical
Fatigue (TMF)
Huseyin SehitogluMechanical and Industrial Engineering,University of Illinois, Urbana, Il. 61801
Tel : 217 333 4112 Fax: 217 244 6534e-mail: [email protected]
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Talk OutlineTalk Outline
• Examples of High Temperature Problems• Basic Terminology at High Temperatures• Introduction to Constraint : Plasticity and ratchetting,
Out of Phase and In phase TMF• Experimental Techniques at High Temperatures• Fatigue Lives of Selected Materials under IF and TMF• Mechanics- Stress-strain Models• Life Models-Fatigue-Oxidation and Fatigue-Creep
Modeling• Future Directions
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Railroad Wheels undergoing Friction Braking• Brake Rotors • Pistons, Valves and Cylinder Heads of Spark-
ignition and Diesel Engines• Turbine Blades and Turbine Disks• Pressure Vessel and Piping
Examples of Components Experiencing High
Temperatures
Examples of Components Experiencing High
Temperatures
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Mechanical Strain
-2x10 -3 -3 -3-10 10
.
.
.
..
.
.
..
...
...
.
..
.. ....
.
2x10 -3-3x10 -3
-100
-200
-300St
ress
(MPa
)
100
200
60 min, 615 C°°
°°
°°°
50 min, 589 C
55 min, 603 C45 min, 572 C
40 min, 552 C35 min, 527 C
°° °
°°
°
°°°
°°
30 min, 497 C25 min, 459 C
20 min, 438 C 15 min, 362 C
10 min, 295 C
5 min, 210 C
65 min, 462 C
70 min, 401 C75 min, 354 C80 min, 314 C
85 min, 279 C°°
°
°°
°
90 min, 249 C95 min, 223 C
100 min, 200 C110 min, 162 C
120 min, 133 C
122.5 min, 78 C125 min, 24 C
Railroad Wheels under Friction Braking
Railroad Wheels under Friction Braking
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Schematic of a Railroad Wheel,Strain-Temperature-Stress Changes on the B1 location under brake shoe heating (laboratory simulation based
on strain temperature measurements on wheels)
-400
-200
0
200
400
Stre
ss (M
Pa),
Tem
pera
ture
(°C
)
6005004003002001000
Time (minutes)
Laboratory Simulation of Stress at B1 Location in Railroad Wheel
Stress
Temperature
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
cold
hot-200
-100
0
100
200
stre
ss (M
Pa)
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3mechanical strain (%)
cycle 1 cycle 20 cycle 36
Cast IronOP TMFMinimum Temperature = 150 °CMaximum Temperature = 500 °CCycle Time = 4 mintues∆εm = 0.6%Nf = 37 cycles
Brake Rotor Cracking
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Design-Manufacturing-Life Prediction Methodology for Cylinder Heads and BlocksDesign-Manufacturing-Life Prediction Methodology for Cylinder Heads and Blocks
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Percentage of Vehicles with Aluminum 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
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Cylinder Heads (FEM and Fatigue Life Contours)
Inlet Valve
Exhaust Valve
Spark Plug
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Turbine Blades
TF
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Turbine Blades( Thermo-mechanical fatigue failure)Turbine Blades( Thermo-mechanical fatigue failure)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Turbine Blades (strain-temperature variation)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Basic Terminology at High Temperatures
• What is a high temperature problem? Deformation under Constant or Variable Stress at homologous temperatures above 0.35 ( T/Tm >0.35 where Tmis melting temperature).
• Stress Relaxation: Decrease in Stress at Constant Strain
• Creep: Increase in Strain at Constant Stress
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
High temperaturefatigue testing or modeling
TMFexternal stresses
TFinternal stresses
HCF∆εin ≈ 0
LCF∆εin > 0
Isothermal fatigue Non-isothermal fatigue
Isothermal vs. Thermo-mechanical fatigue
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Disk Specimen under TF loading (Simovich)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Limitations in our Understanding of High
Temperature Material Behavior
Limitations in our Understanding of High
Temperature Material Behavior
•Experiments on TMF are missing (difficult, expensive).•Microstructural damage mechanisms are not well understood.
•Stress-strain (constitutive) models havenot been established
•Proposed failure models have severe drawbacks.
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
ControlTower
LABWIEV
MACINTOSH IICi
LOAD CELL
Loading History
High TemperatureExtensometer Induction
Coil
TemperatureController
ACTUATOR
GPIB
InductionHeater
RF
C/L
THERMOCOUPLEC/L
Strain, load,position control
Test Frame
Experimental Techniques at High Temperatures
Experimental Techniques at High Temperatures
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Total Constraint Total Constraint
T
Tot BD A
O
C
E
α (T-To)
σο
σο−
Mechanical Strain
Stre
ss
T
ε net = 0
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
The compatibility equation
εnet = εth+εmech = α (T-To) + εmech
When the net strain is zero and all of the thermal strain is converted to
mechanical strain. Then,
εmech = - α (T-To)
Total Constraint (ctd.)
Total Constraint (ctd.)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Two-Bar Model(ctd.)Two-Bar Model(ctd.)
A , l 1 1
A , l 22
P
∆T
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Simple RelationsSimple Relations
• Equilibrium : A1 σ1 + A2 σ2 = P• Compatability : l1 ε1 = l2 ε2
• Strain : ε1 = ε1 e + ε1 in + ε 1 th
ε2 = ε2 e
ε 1 th = α ( T- T0 )
ε1 in = inelastic (plastic) strain
ε1 e = elastic strain
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
The Concepts of Total, Partial, Over and Notch Constraint
The Concepts of Total, Partial, Over and Notch Constraint
ε1=-σ1E2C , C = A2.l1
A1.l2C→∞ ; Total Constraint
C→ finite ; Partial Constraint
A , l 1 1
A , l 22
P
∆T
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
The Stress-strain Response under Total and Partial Constraint
The Stress-strain Response under Total and Partial Constraint
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
The Stress-strain Response under Total and Partial Constraint (ctd.)
The Stress-strain Response under Total and Partial Constraint (ctd.)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Out-of-Phase TMF Response
Mechanical Strain
Tmax
Str
ess
Tmin
In-Phase TMF Response
Mechanical Strain
Str
ess
T
minT
max
Stress-strain Behavior under Out-of-Phase versus In-Phase Stress-strain Behavior under Out-of-Phase versus In-Phase
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Mechanical StrainTmax
Stre
ss
Tmin
∆σ
σmin
σmax
∆εm
AB
C
Some DefinitionsSome Definitions
Inelastic Strain range:
∆εin ≅ ∆εm - σBEB
+ σCEC
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Comparison of TMF IP and TMF OP Tests on 1010 Steel (Jaske’s Data)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMF experiments of Coffin
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Thermal Block Histories on Steels under Total Constraint
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Metallurgical Studies : (a) Damage Mechanisms (Crack nucleation from slip bands, precipitates, porosities, surface and internal oxidation, grain boundary cavitation)(b) Alloy Development
• Mechanistic Studies : (a) Constitutive Modeling ( phenomenological:non-unified and unified models for stress-strain prediction)(b) Life Prediction Modeling (Crack nucleation (stress, strain, time), Crack Growth (Mean stress, crack length)
Classification of IF and TMF StudiesClassification of IF and TMF Studies
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Engineering Application : (a) Material Selection(b) Early Design(c) Residual Life Assesment
Classification of IF and TMF Studies (ctd.)Classification of IF and TMF Studies (ctd.)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
1015
1010
105
100
10-5
εin/A
0.012 3 4 5 6 7
0.12 3 4 5 6 7
12 3 4 5 6 7
10σ/Κο
Al319- Solutionized Small SDAS
Power Law Creep
Plasticityn2=7.96
n1=3.12
Constitutive Modeling-Experimentally Determined Flow Rule
Constitutive Modeling-Experimentally Determined Flow Rule
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
TMF OP 100-300°C 1.0%
100°C
300°C
200°C
-200
-100
0
100
200
Stre
ss (M
Pa)
-6x10-3
-4 -2 0 2 4 6Strain
STRESS1-2fea Stress1-2 STRESS300fea Stress300
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Hysteresis loops for the tests performed at 5x10-3 s-1
-240
-180
-120
-60
0
60
120
180
240
Stre
ss (M
Pa)
-6x10-3
-4 -3 -2 -1 0 1 2 3 4 5 6Strain
experimental TNET
20oC
250oC
130oC
300oC
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Drag stress recoveryHyteresis loops at 20°C for the material pre-exposed at 300°C
-300
-200
-100
0
100
200
300
Stre
ss (M
Pa)
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6Strain (%)
0 h
1 h10 h
100 h
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Coarsening of the PrecipitatesCoarsening of the Precipitates
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
300
200
100
0
-100
-200
Stre
ss (M
Pa)
-0.4 -0.2 0.0 0.2 0.4Mechanical strain, (%)
TMF OP ∆T=100-300°C, ∆ε=0.6%, 5x10-5s-1
Al 319-T7B Small SDAS
Experiment Simulation
Cycle 1
Cycle 350
TMF OP Stress-Strain PredictionTMF OP Stress-Strain Prediction
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Constitutive Modeling:
Mechanistic Studies
Requirements for a good model:• Incorporate strain rate, temperature and mean
stress effect on stress-strain response• Incorporate temperature-strain induced
changes on material’s stress-strain response
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Constitutive Modeling:• Non-unified Plasticity (stress-strain) Models:
Plastic strains (time-independent) and creep strains are added.
• Unified Creep-Plasticity Models: Plastic strain and creep srain is combined as inelastic strain.
Mechanistic Studies
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Requirements for a good model:• Incorporate stress,strain, thermal expansion,
mean stress, stress state effect on life• Predict the effect of temperature, strain rate,
metallurgical changes on life.
Life Prediction ModelingLife Prediction Modeling
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Coffin’s ApproachCoffin’s Approach
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Coffin’s Approach (Frequency Modified Life)
Coffin’s Approach (Frequency Modified Life)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Coffin’s ApproachCoffin’s Approach
Advantages:
(1) Simple to use; accounts for frequency effects
Disadvantages;
(1) Not sensitive to location of hold time within the cycle (tension or compression).
(2) Does not account for creep damage effects
(3) TMF life prediction not explicitly handled.
(4) No stress-strain model
Advantages:
(1) Simple to use; accounts for frequency effects
Disadvantages;
(1) Not sensitive to location of hold time within the cycle (tension or compression).
(2) Does not account for creep damage effects
(3) TMF life prediction not explicitly handled.
(4) No stress-strain model
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Strain Range Partitioning Method(SRP)
∆ε∆ε
∆ε
∆ε∆ε
∆ε
pp
cp
cppc
pc
cc
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
SRP Data on Two Class of Steels(Manson et al.)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
SRP ApproachSRP Approach
Advantages:
(1) Accounts for location of hold time within a cycle
Disadvantages;
(1) Life curves are often too close, expensive to generate all these curves
(2) Does not account for oxidation/environment effects
(3) TMF Life prediction not explicitly handled.
Advantages:
(1) Accounts for location of hold time within a cycle
Disadvantages;
(1) Life curves are often too close, expensive to generate all these curves
(2) Does not account for oxidation/environment effects
(3) TMF Life prediction not explicitly handled.
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Damage per cycle is sum of the dominant mechanisms Dfat, Dox , Dcreep.
• The terms in the damage equations should be physically based, specifically, they should be linked to specific experiments, stress-strain behavior and microstructural observations.
Development of a Mechanism Based Failure Model (Sehitoglu et al.)
Development of a Mechanism Based Failure Model (Sehitoglu et al.)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Neu, Sehitoglu, Boismier, Kadioglu, 1987-
1Nf
ox = hcr δo
BΦox Kpeff
-1β 2 ∆εmech
ox 2β +1
ε (1-a '/β)
This equation accounts for the strain range at the oxide tip hence the oxide-metal properties the shapeof the oxide are included.
depends on the temperature strain history
and the temperature- time variation in the cycle.
Fatigue - Oxidation Models (ctd.)
Fatigue - Oxidation Models (ctd.)
Φ ox Kpeff
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Combined Damage Model Predictions
Combined Damage Model Predictions
10-4
10-3
10-2
10-1
Mec
hani
cal S
trai
n R
ange
101
102
103
104
105
106
107
108
Nf
WAP319-T7B Small SDAS All Fatigue Results
RT 40Hz 250¡C 0.5Hz
250¡C 5 x10-5s-1
300¡C 5 x10-5s-1
TMF OP 100-300¡C TMF IP 100-300¡C
300¡C Dox=0
300¡C Dox
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Combined Damage Model Predictions (1070 Steel)
Combined Damage Model Predictions (1070 Steel)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Combined Damage Model Predictions (1070 Steel)
Combined Damage Model Predictions (1070 Steel)
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Fatigue - Creep Modeling Fatigue - Creep Modeling
Dcreep= Φcreep
exp -∆HRT
α1σ+α2σhK
m
dt0
tc
where tcis cycle period, Φcreeptemperature strain phasing factor,
σ is the effective stress,σh is the hydrostatic stress,
and K is the drag stress
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Combined Damage ModelCombined Damage Model
Advantages:
(1) Accounts for TMF loading.
(2) Damage due to oxidation and creep are included.
Disadvantages:
(1) Requires some time to understand how it all works.
Advantages:
(1) Accounts for TMF loading.
(2) Damage due to oxidation and creep are included.
Disadvantages:
(1) Requires some time to understand how it all works.
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
Future DirectionsFuture Directions
• A simple model should be developed to predict lifefor a given mechanical strain range, maximumtemperature, and material.
• Given a strain and temperature field in a component,the model should predict the most critical location wherecrack nucleation will occur.
Huseyin Sehitoglu
University of Illinois at Urbana-Champaign
Department of Mechanical and Industrial Engineering
• Given an elastic strain, temperature history from FEM, the model should be able to predict the stresses and plastic strains assuming the mechanical strain is equal to the elastic strain from FEM. This is known as the ‘ strain invariance method’.
• To predict component behavior the model shouldcapture the crack growth rates as the crack grows ina varying stress, temperature field.
Future Directions (ctd.)Future Directions (ctd.)