Hüseyin ŞehitoğluC.J.Gauthier Professor and Head

University of Illinois, Department of Mechanical Science and Engineering, Urbana, IL,USA Presentation at the International Railway Symposium, December 13-15, Istanbul/Ankara

Freight Railroads- Research from Atoms to StructuresYük Trenleri-Atomik Boyuttan Gerçek Yapılara Uzanan Bir Araştırma

Nomenclature- Terimlendirme

Tension- Çekme GerilimiCompression- Basma GerilimiThermal Stress- Isıl GerilmeStrain- GerinimFatigue Limit- Yorulma SınırıYield Stress- Akma GerilimiStress Concentration- Gerilim YoğunlaşmasıMicrostructure-İçyapıConstraint-KısıtTexture- DokuShear Stress- Makaslama GerilimiSlip-KaymaStick-YapışmaGrinding- Taşlama

Demiryolu Endüstrisinin Önemi

Talk Outline (Konuşma Taslağı)

•Fatigue/Deformation Preliminaries (Yorulma)

•Wheels- Thermo-mechanical Fatigue

(Tekerlekler,Termo-mekanik Yorulma)

•Rails- Ratcheting and Fatigue/Wear

(Raylar- Gerinme ve Aşınma)

•Materials Design- Diamond Crossing

•(Yeni Mazemelerin Atomik Boyutta Tasarımı-Makas Elması)

•Bearings- Cone Bore Growth

(Rulmanlı Yataklar)

•Conclusions (Sonuçlar)

William John Macquorn RankineBorn: 2 July 1820 in Edinburgh, ScotlandDied: 24 Dec 1872 in Glasgow, Scotland

Stress ConcentrationsStress Concentrations-- Railroad Axles, the Railroad Axles, the Versailles Accident (Versailles Accident (Gerilim Yoğunlaşması, Ray , Ray aksiaksi, , VersayVersay KazasKazasıı))

BauschingerBauschinger Effect and the Presentation Effect and the Presentation of the Fatigue Limit (of the Fatigue Limit (BauschingerBauschinger etkisietkisi veve

YorulmaYorulma SSıınnıırrıı))

Early ObservationsEarly Observations(A. Ewing, Humphreys, W. Rosenhain, 1899)- Eski İncelemeler

H. F. Moore’s Book, p.224

(Ray üzerindeİçyapı)

Talk Outline (Konuşma Taslağı)

•Fatigue/Deformation Preliminaries (Yorulma)

•Wheels- Thermo-mechanical Fatigue

(Tekerlekler,Termo-mekanik Yorulma)

•Rails- Ratcheting and Fatigue/Wear

(Raylar- Gerinme ve Aşınma)

•Materials Design- Diamond Crossing

•(Yeni Mazemelerin Atomik Boyutta Tasarımı-Makas Elması)

•Bearings- Cone Bore Growth

(Rulmanlı Yataklar)

•Conclusions (Sonuçlar)

Total Constraint (Tam Kısıtlama)

T

Tot BD A

O

C

E

α (T-To)

σο

σο−

Mechanical Strain

Stre

ss

T

ε net = 0

Sehitoglu, H., "Constraint Effect in Thermo-mechanical Fatigue," ASME Journal of Engineering Materials and Technology,107, 221-226, 1985. Sehitoglu, H., Thermal and Thermo-Mechanical Fatigue of Structural Alloys, Handbook on Fatigue and Fracture, ASM, 19, 527-554, 1996.

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 C35 min, 527 C

°° °

°°

°

°°°

°°

30 min, 497 C25 min, 459 C

20 min, 438 C 15 min, 362 C

10 min, 295 C5 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 (Tekerlekler ve fren pabuçları kullanımı)

The Stress-strain Response under Total Constraint (Tam kısıtlama)

Hysteresis and Stress-strain Response in Total Constraint

Thermal Block Histories on Steels under Total Constraint (Blok ısı değişmeleri - tam kısıtlama)

Talk Outline (Konuşma Taslağı)

•Fatigue/Deformation Preliminaries (Yorulma)

•Wheels- Thermo-mechanical Fatigue

(Tekerlekler,Termo-mekanik Yorulma)

•Rails- Ratcheting and Fatigue/Wear

(Raylar- Gerinme ve Aşınma)

•Materials Design- Diamond Crossing

•(Yeni Mazemelerin Atomik Boyutta Tasarımı-Makas Elması)

•Bearings- Cone Bore Growth

(Rulmanlı Yataklar)

•Conclusions (Sonuçlar)

Significant Texture ( Orientation) Develops in the MaterialUnder Contact

•Ratcheting strain is accumulated residual shear strain in the direction of motion of rolling instance. For definitions see:•Jiang, Y. and Sehitoglu, H., 1999, AModel for Rolling Contact Failure,Wear, Vol.224, No1., pp.38-49•Sehitoglu, H. and Jiang, Y., 1993, "Residual Stress Analysis in Rolling Contact," Rail Quality and Maintenance for Modern Railway Operation, Kalker et al., Eds., Kluwer Academic Publishers, pp.349-358•Jiang, Y. and Sehitoglu, H., 1996, Rolling Contact Stress Analysis with the Application of a New Plasticity Model,Wear, Vol.191, pp.35-44

DEFINITION OF RATCHETTING : INCREMENT OF STRAIN PER CYCLE DUE NONCLOSURE OF

THE HYSTERESIS LOOP

600

400

200

0

0.0350.0340.0330.0320.031

Axial Plastic Strain

cycle 256600

400

200

0

Axi

al S

tress

, MP

a

0.0200.0190.0180.0170.016Axial Plastic Strain

cycle 3

A B

1070 Steel

RATCHETTING STRAIN PER CYCLE

Jiang, R. and H. Sehitoglu, "Cyclic Ratchetting of 1070 Steel Under Multiaxial Stress States," International Journal of Plasticity,10:5, 579-608, 1994.

Jiang, R. and H. Sehitoglu, "MultiaxialCyclic Ratchetting Under Multiple Step L di

Contact Stress History in wheel -rail contact(Johnson, 1985)

-600

-400

-200

0A

xial

Stre

ss, M

Pa

-400 -200 0 200 400Shear Stress, MPa

Stress-ControlledLoading Path

Δσ /2= 225MPa σm=-225MPaΔτ /2= 215MPa τ m=0

-0.04

-0.03

-0.02

-0.01

0.00

Axi

al S

train

0.0200.0150.0100.0050.000-0.005-0.010Shear Strain

cycle1-28

32

128256

512

1024

2048

EXPERIMENTAL RATCHETTING FOR A NOPROPORTIONAL AXIAL-TORSIONAL LOADING PATH

Jiang, Y. and H. Sehitoglu, ASME JAM, 63, 726-733, 1996.Jiang, Y. and H. Sehitoglu, ASME JAM, 63, 720-725, 1996.

1070 Steel

SURFACE RATCHETTING IN CONTACT

-4

-2

0

2

4

Sur

face

Rat

chet

ting

G/k

a

12 3 4 5 6

102 3 4 5 6

1002 3 4 5

Number of Cycles

-0.2Q/P=-0.1

0

0.1

0.2

1070 Steelp0 /k=9.0

z

x

z

y

a a

Rolling Direction

x

Ασx

σz

σy

τxzp0

2.5

2.0

1.5

1.0

0.5

0.0

z/a

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15( σx) r

G=79.6GPa μ=0.3H=25.7Gp0/k=4.124 Q/P=f=-0.2

FEM, Kumar et al. Proposed Method Merwin & Johnson's

2.5

2.0

1.5

1.0

0.5

0.0

z/a

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15( σy) r

G=79.6GPa μ=0.3H=25.7Gp0/k=4.124 Q/P=-0.2

FEM, Kumar et al. Proposed Method Merwin & Johnson's

2.0

1.5

1.0

0.5

0.0

z/a

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15( σx) r

G=79.6GPa μ=0.3H=25.7Gp0/k=4.5 Q/P=f=-0.2

FEM, Kumar et al. Proposed Method Merwin & Johnson's

2.0

1.5

1.0

0.5

0.0

z/a

-0.15 -0.10 -0.05 0.00 0.05 0.10 0.15( σy) r

G=79.6GPa μ=0.3H=25.7Gp0/k=4.5 Q/P=f=-0.2

FEM, Kumar et al. Proposed Method Merwin & Johnson's

(a) Case I: p 0/k=4.124 Q/P=-0.2

(b) Case II: p 0/k=4.5 Q/P=-0.2

Residual Stress Profiles in Rolling ContactJiang, Sehitoglu, ASME J.Tribology, 116:3, 1994

10-6

10-5

10-4

10-3

Axi

al R

atch

ettin

g R

ate,

1/c

ycle

1 10 100 1000 10000Number of Cycles

1070 Steel

Δσ /2=225MPa σm=-225MPaΔτ /2=215MPa τm=0

Experiment New Model

-0.010

-0.005

0.000

0.005

0.010

She

ar R

atch

ettin

g S

train

1 10 100 1000 10000Number of Cycles

Experiment New Model

CAPABILITY OF PROPOSED MODEL IN NONPROPORTIONAL LOADING

τσ

Failure Mechanism Map

University of Illinois at Urbana-Champaign

A: Crack initiation A-B:As crack length increases, the crack propagation rate decreasesB-C: At longer crack lengths the crack growth rates increase again

High wear (and crack mouth truncation) rate: Crack will be worn away.Low wear (and crack mouth truncation) rate: ZERO NET crack growth rate possible.

Crack Propagation

x'

e/a, Normalized Distanceto Load Center

x

z

a a

p0

Q/P>0

Rolling Direction

45°

UI

UII

UI,UPPER

UII,UPPER

UII,LOWER

UI,LOWER

Initial Locationof Nodes

ΔUII

ΔUI

Variation of Sliding and Opening Displacements as a Function of Crack Length

Crack Propagation( ) ( ) 21

21m

IIm

I UCUCdNda

Δ+Δ=

C1

C2

da/dN

m1

m2

ΔUI

ΔUII

ΔUI , ΔUII

Data for da/dN in slidingis not available: Normalization by C1

10-72

4

10-62

4

10-52

4

10-4

(da/

dN)/C

1 [m

m/c

ycle

]

1210864Crack Length [mm]

C2/C1=m1=m2=2

0.001

0.01

0.1

2200 MPa 2000 MPa

Wear

Fatigue

Talk Outline (Konusma Taslağı)

•Fatigue/Deformation Preliminaries (Yorulma)

•Wheels- Thermo-mechanical Fatigue

(Tekerlekler,Termo-mekanik Yorulma)

•Rails- Ratcheting and Fatigue/Wear

(Raylar- Gerinme ve Aşınma)

•Materials Design- Diamond Crossing

•(Yeni Mazemelerin Atomik Boyutta Tasarımı-Makas Elması)

•Bearings- Cone Bore Growth

(Rulmanlı Yataklar)

•Conclusions (Sonuçlar)

Grinding Operations after Weld Metal deposition

FeMnN-Theory vs. Experiment - [111] Orientation

2000

1500

1000

500

0

True

Stre

ss (M

Pa)

0.200.150.100.050.00True Inelastic Strain

Hadfield Steel [111] Orientationunder Compression, T=293 K

Experiment Simulation

HNHS (1.06 wt.% N)

HSw/oN (0 wt.% N)

Pressure Vessel

Compressor

Vacuum Pump

Kanthal FurnaceGraphite FurnacePressure Vessel

Compressor

Vacuum Pump

Kanthal FurnaceGraphite FurnacePressure Vessel

Compressor

Vacuum Pump

Kanthal FurnaceGraphite Furnace

ASEA HIP30,000 PSI(2,069 Bar)

HIP EquipmentTensile TestingEquipment

Mechanical Testing

1. Strength increases with increased HIP treatment temperature

2. Some ductility can be regained by a subsequent 980C-30min treatment

3. Vickers hardness reflects strength trends4. Introducing nitrogen by welding can

increase strength

340

320

300

280

260

240

220

200

Vic

kers

Har

dnes

s (H

v)

110010501000950900

HIP Temperature (°C)

Virgin frog = 230 Hv

Average of nine measurementsper sample

Multilevel Microstructureas envisioned by Reamur in 1722

Hierarchical Materials-Mechanics Design

Structural Design( )αn( )αs

( )0αs

( )0αn

*RF

F p( )0αs

( )0αn

Quantum Mechanics (Design)

0.1nm

Micro-Mechanics (Design) Structural Mechanics (Design)

0.1mm 0.1m

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Nano- Mechanics (Design)

5 nm

Physics - Materials Science - Mechanical Sciences and Eng. (Mech./Aero/Civil)

Addition of nitrogen to Fe-based materials

J. Reed, J.Metals, 1989. Rawers and Slavens (1995)

Max at 1%N

Background- Dislocations are line defects in materials

Callister, Material Science and Engineering: An Introduction

Extended edge dislocationY

(111)

b

d

1b

2b X, 1 10⎡ ⎤⎣ ⎦

Z, 112⎡ ⎤⎣ ⎦b = b1 + b2

12

110⎡⎣ ⎤⎦ =16

211⎡⎣ ⎤⎦ +16

121⎡⎣ ⎤⎦

Z direction is equivalent to <112> direction for GSFE

X direction equivalent to <110> direction for GSFE

GSFE curve along <112>

Z, 112⎡ ⎤⎣ ⎦

uγSFγ

maxγu

sb

m

b

c

u

s

m

b

b

a

FCC lattice

<112>

HCP

FCC

X, 110⎡ ⎤⎣ ⎦

060

030

1 2116

⎡ ⎤⎣ ⎦

1 1216

⎡ ⎤⎣ ⎦

1 1102

⎡ ⎤⎣ ⎦

Z, 1 12⎡ ⎤⎣ ⎦

γ -curve along <112> direction

600 symmetry of γ surface

S. Kibey, J.B. Liu, M.J. Curtis, D.D. Johnson, H. Sehitoglu,"Stacking Fault Energy and Stacking Fault Widths in High

Nitrogen Steels," Acta Mater. 54, 2991-3001 (2006).

Fourier fit for GSFE Fe-4 at.%N

ux

12

<110>

zu1 <112>6

ux

12

<110>

Effect of stable SFE (note finite separation for negative values)

6

5

4

3

2

1

0

d /

b

4002000-200-400

γSF (mJ/m2)

γu = 514 mJ/m2

γmax = 1998 mJ/m2

Volterra

Peierls

goes to infinityIncreasing nitrogen

1% wt.

Talk Outline (Konuşma Taslağı)

•Fatigue/Deformation Preliminaries (Yorulma)

•Wheels- Thermo-mechanical Fatigue

(Tekerlekler,Termo-mekanik Yorulma)

•Rails- Ratcheting and Fatigue/Wear

(Raylar- Gerinme ve Aşınma)

•Materials Design- Diamond Crossing

•(Yeni Mazemelerin Atomik Boyutta Tasarımı-Makas Elması)

•Bearings- Cone Bore Growth

(Rulmanlı Yataklar)

•Conclusions (Sonuçlar)

Neu, R. and H. Sehitoglu, "Determination of Cone Bore Growth Due to Microstructural Changes," ASME Journal of Tribology, 112, 433-441, 1990.

Neu, R. and H. Sehitoglu, "Transformation of Retained Austenite in

Carburized 4320 Steel,” Metallurgical Transactions, 22A, 1491-1500, 1990.

Neu, R. and H. Sehitoglu, "Low-Temperature Creep of a Carburized Steel,”Metallurgical Transactions, 23A, 2619-2624, 1992.

Neu, R. and H. Sehitoglu, "Thermal-Induced Transformations of Retained Austenite in the Simulated Case of a Carburized Steel," ASME Journal of Engineering Materials and

Neu, R. and H. Sehitoglu, "Simulation of Cone Bore Growth in Bearings with aThree-Ring Model," ASME Journal of Applied Mechanics, 61:3,589-595, 1994.

Talk Outline (Konuşma Taslağı)

•Fatigue/Deformation Preliminaries (Yorulma)

•Wheels- Thermo-mechanical Fatigue

(Tekerlekler,Termo-mekanik Yorulma)

•Rails- Ratcheting and Fatigue/Wear

(Raylar- Gerinme ve Aşınma)

•Materials Design- Diamond Crossing

•(Yeni Mazemelerin Atomik Boyutta Tasarımı-Makas Elması)

•Bearings- Cone Bore Growth

(Rulmanlı Yataklar)

•Conclusions (Sonuçlar)

Conclusions (Sonuçlar)

(1) ‘Mechanics of Materials’ plays a crucial role in understanding the integrity of the rails, wheels,crossings,bearings and other components. (Maddeler mekaniğiray, tekerlek,makas, ve yatay rulmanların güvenirliğinianlamak açısından önemli bir rol oynamaktadır.)

(2) New tools are available for experiments and modeling in the ‘mechanics and materials’ fields.(Deneylerve model yapmak için mühendislikte yeni gelişmelerortaya çıkmaktadır.)