Page 1
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering1
University of Illinois at Urbana-Champaign
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]
Page 2
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering2
University of Illinois at Urbana-Champaign
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
Page 3
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering3
University of Illinois at Urbana-Champaign
• 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
Page 4
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering4
University of Illinois at Urbana-Champaign
Mechanical Strain
-2x10 -3 -3 -3-10 10
.
.
.
..
.
.
..
......
.
..
.. ....
.
2x10 -3-3x10 -3
-100
-200
-300
Stre
ss (M
Pa)
100
200
60 min, 615 C°°
°°
°°°
50 min, 589 C
55 min, 603 C45 min, 572 C
40 min, 552 C 35 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
Page 5
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering5
University of Illinois at Urbana-Champaign
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 (
MPa
), T
empe
ratu
re (
°C)
6005004003002001000
Time (minutes)
Laboratory Simulation of Stress at B1 Location in Railroad Wheel
Stress
Temperature
Page 6
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering6
University of Illinois at Urbana-Champaign
cold
hot-200
-100
0
100
200
stre
ss (
MP
a)
-0.3 -0.2 -0.1 0.0 0.1 0.2 0.3
mechanical 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
Page 7
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering7
University of Illinois at Urbana-Champaign
Design-Manufacturing-Life Prediction Methodology for Cylinder Heads and BlocksDesign-Manufacturing-Life Prediction Methodology for Cylinder Heads and Blocks
Page 8
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering8
University of Illinois at Urbana-Champaign
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
Page 9
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering9
University of Illinois at Urbana-Champaign
Cylinder Heads (FEM and Fatigue Life Contours)
Inlet Valve
Exhaust Valve
Spark Plug
Page 10
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering10
University of Illinois at Urbana-Champaign
Turbine Blades
TF
Page 11
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering11
University of Illinois at Urbana-Champaign
Turbine Blades( Thermo-mechanical fatigue failure)Turbine Blades( Thermo-mechanical fatigue failure)
Page 12
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering12
University of Illinois at Urbana-Champaign
Turbine Blades (strain-temperature variation)
Page 13
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering13
University of Illinois at Urbana-Champaign
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
Page 14
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering14
University of Illinois at Urbana-Champaign
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
Page 15
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering15
University of Illinois at Urbana-Champaign
Disk Specimen under TF loading (Simovich)
Page 16
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering16
University of Illinois at Urbana-Champaign
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.
Page 17
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering17
University of Illinois at Urbana-Champaign
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
Page 18
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering18
University of Illinois at Urbana-Champaign
Total Constraint Total Constraint
T
Tot BD A
O
C
E
α (T-To)
σο
σο−
Mechanical Strain
Stre
ss
T
ε net = 0
Page 19
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering19
University of Illinois at Urbana-Champaign
The compatibility equation
εnet = εth+εmech = α (T-T o ) + εmech
When the net strain is zero and all of the thermal strain is converted to
mechanical strain. Then,
εmech = - α (T-T o )
Total Constraint (ctd.)
Total Constraint (ctd.)
Page 20
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering20
University of Illinois at Urbana-Champaign
Two-Bar Model(ctd.)Two-Bar Model(ctd.)
A , l 1 1
A , l 22
P
∆T
Page 21
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering21
University of Illinois at Urbana-Champaign
Simple RelationsSimple Relations
• Equilibrium : A1 σ1 + A2 σ2 = P• Compatability : l1 ε1 = l2 ε2
• Strain : ε1 = ε1 e + ε 1 in + ε1 th
ε2 = ε2 e
ε 1 th = α ( T- T0 )
ε 1 in = inelastic (plastic) strain
ε1 e = elastic strain
Page 22
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering22
University of Illinois at Urbana-Champaign
The Concepts of Total, Partial, Over and Notch Constraint
The Concepts of Total, Partial, Over and Notch Constraint
ε1=-σ1E2C
, C = A2.l1A1.l2
C→∞ ; Total ConstraintC→ finite ; Partial Constraint
A , l 1 1
A , l 22
P
∆T
Page 23
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering23
University of Illinois at Urbana-Champaign
The Stress-strain Response under Total and Partial Constraint
The Stress-strain Response under Total and Partial Constraint
Page 24
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering24
University of Illinois at Urbana-Champaign
The Stress-strain Response under Total and Partial Constraint (ctd.)
The Stress-strain Response under Total and Partial Constraint (ctd.)
Page 25
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering25
University of Illinois at Urbana-Champaign
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
Page 26
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering26
University of Illinois at Urbana-Champaign
Mechanical StrainTmax
Stre
ss
Tmin
∆σ
σmin
σmax
∆εm
AB
C
Some DefinitionsSome Definitions
Inelastic St rain range:
∆εin ≅ ∆εm - σBEB
+ σCEC
Page 27
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering27
University of Illinois at Urbana-Champaign
Comparison of TMF IP and TMF OP Tests on 1010 Steel (Jaske’s Data)
Page 28
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering28
University of Illinois at Urbana-Champaign
TMF experiments of Coffin
Page 29
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering29
University of Illinois at Urbana-Champaign
Thermal Block Histories on Steels under Total Constraint
Page 30
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering30
University of Illinois at Urbana-Champaign
• 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
Page 31
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering31
University of Illinois at Urbana-Champaign
• 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.)
Page 32
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering32
University of Illinois at Urbana-Champaign
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
Page 33
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering33
University of Illinois at Urbana-Champaign
TMF OP 100-300°C 1.0%
100°C
300°C
200°C
-200
-100
0
100
200
Str
ess
(MP
a)
-6x10 -3 -4 -2 0 2 4 6Strain
STRESS1-2fea Stress1-2 STRESS300fea Stress300
Page 34
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering34
University of Illinois at Urbana-Champaign
Hysteresis loops for the tests performed at 5x10-3 s-1
-240
-180
-120
-60
0
60
120
180
240
Str
ess
(MP
a)
-6x10-3
-4 -3 -2 -1 0 1 2 3 4 5 6Strain
experimental TNET
20oC
250oC
130oC
300oC
Page 35
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering35
University of Illinois at Urbana-Champaign
Drag stress recoveryHyteresis loops at 20°C for the material pre-exposed at 300°C
-300
-200
-100
0
100
200
300
Str
ess
(MP
a)
-0.6 -0.4 -0.2 0.0 0.2 0.4 0.6Strain (%)
0 h
1 h10 h
100 h
Page 36
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering36
University of Illinois at Urbana-Champaign
Coarsening of the PrecipitatesCoarsening of the Precipitates
Page 37
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering37
University of Illinois at Urbana-Champaign
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
Page 38
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering38
University of Illinois at Urbana-Champaign
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
Page 39
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering39
University of Illinois at Urbana-Champaign
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
Page 40
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering40
University of Illinois at Urbana-Champaign
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
Page 41
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering41
University of Illinois at Urbana-Champaign
Coffin’s ApproachCoffin’s Approach
Page 42
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering42
University of Illinois at Urbana-Champaign
Coffin’s Approach (Frequency Modified Life)
Coffin’s Approach (Frequency Modified Life)
Page 43
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering43
University of Illinois at Urbana-Champaign
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
Page 44
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering44
University of Illinois at Urbana-Champaign
Strain Range Partitioning Method(SRP)
∆ε∆ε
∆ε
∆ε∆ε
∆ε
pp
cp
cppc
pc
cc
Page 45
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering45
University of Illinois at Urbana-Champaign
SRP Data on Two Class of Steels(Manson et al.)
Page 46
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering46
University of Illinois at Urbana-Champaign
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.
Page 47
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering47
University of Illinois at Urbana-Champaign
• 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.)
Page 48
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering48
University of Illinois at Urbana-Champaign
• 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
Page 49
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering49
University of Illinois at Urbana-Champaign
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
Page 50
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering50
University of Illinois at Urbana-Champaign
Combined Damage Model Predictions (1070 Steel)
Combined Damage Model Predictions (1070 Steel)
Page 51
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering51
University of Illinois at Urbana-Champaign
Combined Damage Model Predictions (1070 Steel)
Combined Damage Model Predictions (1070 Steel)
Page 52
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering52
University of Illinois at Urbana-Champaign
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.
Page 53
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering53
University of Illinois at Urbana-Champaign
• Modified Strain-Life Relation
- initial pore size– fatigue strength coefficient– fatigue strength exponent– fatigue ductility coefficient– fatigue ductility exponent
C'b
ε f'
c
Fatigue Damage Equation
a0
∆εmech
2= C'a0
2−b2b (2N f
fat )−1b +ε f
' (2N ffat )c
Page 54
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering54
University of Illinois at Urbana-Champaign
- empirical constants- activation energy
- universal gas constant- hydrostatic stress- effective stress
- initial pore size
Cc,mc
σσ H
H∆R
Creep Damage Equation
a0
Dcr = Cc(mc − 1)a0mc −1 σ H
σ H
σ n+1 exp −∆HRT
dt
0
tc
∫m c
Page 55
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering55
University of Illinois at Urbana-Champaign
TMF IP versus TMF OP Comparison- Al 319
2
3
4
5
6
7
8
90.01
2
3
4
5
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
Page 56
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering56
University of Illinois at Urbana-Champaign
Initial Voids and after TMF IP
Page 57
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering57
University of Illinois at Urbana-Champaign
Future DirectionsFuture Directions
• A simple model is developed to predict lifefor a given mechanical strain range, maximumtemperature, and material.
• Given a strain and temperature field in a component,the model can predict the most critical location wherecrack nucleation will occur.
Page 58
Huseyin Sehitoglu
Department of Mechanical and Industrial Engineering58
University of Illinois at Urbana-Champaign
• Given an elastic strain, temperature history from FEM, the model is 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 accounts for the initial defect size.
Future Directions (ctd.)Future Directions (ctd.)