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

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2 Freight Railroads- Research from Atoms to Structures Yük Trenleri-Atomik Boyuttan Gerçek Yapılara Uzanan Bir Araştırma Hüseyin Şehitoğlu C.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

3 Nomenclature- Terimlendirme Tension- Çekme Gerilimi Compression- Basma Gerilimi Thermal Stress- Isıl Gerilme Strain- Gerinim Fatigue Limit- Yorulma Sınırı Yield Stress- Akma Gerilimi Stress Concentration- Gerilim Yoğunlaşması Microstructure-İçyapı Constraint-Kısıt Texture- Doku Shear Stress- Makaslama Gerilimi Slip-Kayma Stick-Yapışma Grinding- Taşlama

4 Demiryolu Endüstrisinin Önemi

5 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)

6 Stress Concentrations- Railroad Axles, the Versailles Accident (Gerilim( Yoğunlaşması,, Ray aksi, Versay Kazası) William John Macquorn Rankine Born: 2 July 1820 in Edinburgh, Scotland Died: 24 Dec 1872 in Glasgow, Scotland

7 Bauschinger Effect and the Presentation of the Fatigue Limit (Bauschinger( etkisi ve Yorulma Sınırı)

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

9 H. F. Moore s Book, p.224 (Ray üzerinde İçyapı)

11 Total Constraint (Tam Kısıtlama) T E σ ο ε net = 0 C Stress O T Mechanical Strain T o t D B A σ ο α (T-To) Sehitoglu, H., "Constraint Effect in Thermo-mechanical Fatigue," ASME Journal of Engineering Materials and Technology,107, , Sehitoglu, H., Thermal and Thermo-Mechanical Fatigue of Structural Alloys, Handbook on Fatigue and Fracture, ASM, 19, , 1996.

12 Railroad Wheels under Friction Braking (Tekerlekler ve fren pabuçları kullanımı) 110 min, 162 C 100 min, 200 C 95 min, 223 C 90 min, 249 C 85 min, 279 C 80 min, 314 C 75 min, 354 C 70 min, 401 C 65 min, 462 C min, 133 C min, 78 C 125 min, 24 C 100-3x x x10-3 Mechanical Strain -100 Stress (MPa) 55 min, 603 C min, 572 C 35 min, 527 C 60 min, 615 C 50 min, 589 C 40 min, 552 C 5 min, 210 C 30 min, 497 C 25 min, 459 C 10 min, 295 C 20 min, 438 C 15 min, 362 C

13 The Stress-strain Response under Total Constraint (Tam kısıtlama) Hysteresis and Stress-strain Response in Total Constraint

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

16 Significant Texture ( Orientation) Develops in the Material Under 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, A Model for Rolling Contact Failure,Wear, Vol.224, No1., pp 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 Jiang, Y. and Sehitoglu, H., 1996, Rolling Contact Stress Analysis with the Application of a New Plasticity Model, Wear, Vol.191, pp.35-44

17 DEFINITION OF RATCHETTING : INCREMENT OF STRAIN PER CYCLE DUE NONCLOSURE OF THE HYSTERESIS LOOP Steel cycle cycle 256 Axial Stress, MPa A B RATCHETTING STRAIN 0PER CYCLE Axial Plastic Strain Axial Plastic Strain Jiang, R. and H. Sehitoglu, "Cyclic Ratchetting of 1070 Steel Under Multiaxial Stress States, " International Journal of Plasticity, 10:5, , Jiang, R. and H. Sehitoglu, "Multiaxial Cyclic Ratchetting Under Multiple Step L di

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

19 EXPERIMENTAL RATCHETTING FOR A NOPROPORTIONAL AXIAL-TORSIONAL LOADING PATH Jiang, Y. and H. Sehitoglu, ASME JAM, 63, , Jiang, Y. and H. Sehitoglu, ASME JAM, 63, , Axial Stress, MPa Stress-Controlled Loading Path Δσ/2= 225MPa σ m =-225MPa Δτ /2= 215MPa τ m = Shear Stress, MPa Axial Strain Steel cycle Shear Strain

20 SURFACE RATCHETTING IN CONTACT Rolling Direction x p0 a a x z Α σ z τ xz σ x y σ y z Q/P= Surface Ratchetting G/ka Steel p 0 /k= Number of Cycles

21 Residual Stress Profiles in Rolling Contact Jiang, Sehitoglu, ASME J.Tribology, 116:3, z/a G=79.6GPa μ=0.3 H=25.7G p 0 /k=4.124 Q/P=f=-0.2 z/a G=79.6GPa μ=0.3 H=25.7G p 0 /k=4.124 Q/P= FEM, Kumar et al. Proposed Method Merwin & Johnson's ( σ x ) r FEM, Kumar et al. Proposed Method Merwin & Johnson's ( σ y ) r (a) Case I: p 0 /k=4.124 Q/P= z/a G=79.6GPa μ=0.3 H=25.7G p 0 /k=4.5 Q/P=f=-0.2 z/a G=79.6GPa μ=0.3 H=25.7G p 0 /k=4.5 Q/P=f= FEM, Kumar et al. Proposed Method Merwin & Johnson's 2.0 FEM, Kumar et al. Proposed Method Merwin & Johnson's ( σ x ) r ( σ y ) r (b) Case II: p 0 /k=4.5 Q/P=-0.2

22 CAPABILITY OF PROPOSED MODEL IN NONPROPORTIONAL LOADING Axial Ratchetting Rate, 1/cycle Steel Experiment New Model Δσ/2=225MPa σ m =-225MPa Δτ /2=215MPa τ m = Number of Cycles σ τ Shear Ratchetting Strain Experiment New Model Number of Cycles

23 Failure Mechanism Map

24 Crack Propagation A: Crack initiation A-B:As crack length increases, the crack propagation rate decreases B-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. University of Illinois at Urbana-Champaign

25 e/a, Normalized Distance to Load Center Q/P>0 p 0 x' 45 a a x z Rolling Direction

26 U II,UPPER U I,LOWER U I,UPPER U II,LOWER U I Initial Location of Nodes U II

27 ΔUII

28 ΔUI

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

30 Crack Propagation da/dn C 1 da dn m 2 = ΔU I m 1 C ΔU II 1 ( ) m ( ) m ΔU + C ΔU 2 I 1 2 ΔU I, ΔU II II Data for da/dn in sliding is not available: Normalization by C 1 C 2

31 (da/dn)/c 1 [mm/cycle] m 1 =m 2 = MPa 2000 MPa Fatigue Wear C 2 /C 1 = Crack Length [mm] 12

32 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)

33 Grinding Operations after Weld Metal deposition

34 FeMnN-Theory vs. Experiment - [111] Orientation 2000 Hadfield Steel [111] Orientation under Compression, T=293 K 1500 HNHS (1.06 wt.% N) True Stress (MPa) 1000 Experiment Simulation HSw/oN (0 wt.% N) True Inelastic Strain

35 HIP Equipment Tensile Testing Equipment Graphite Furnace Kanthal Furnace Graphite Kanthal Furnace Furnace Pressure Vessel Pressure Vessel Compressor Compressor ASEA HIP 30,000 PSI (2,069 Bar) Vacuum Pump Vacuum Pump

36 Mechanical Testing 340 Average of nine measurements per sample 320 Vickers Hardness (Hv) Virgin frog = 230 Hv HIP Temperature ( C) 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 trends 4. Introducing nitrogen by welding can increase strength

37 Hierarchical Materials-Mechanics Design Multilevel Microstructure as envisioned by Reamur in 1722 Physics - Materials Science - Mechanical Sciences and Eng. (Mech./Aero/Civil) Quantum Mechanics (Design) Nano- Mechanics (Design) Micro-Mechanics (Design) ( α) n ( α) s Structural Mechanics (Design) Structural Design QuickTime and a TIFF (LZW) decompressor are needed to see this picture. F n ( α) 0 n ( α) 0 * R s ( α) 0 F p ( α) s0 0.1nm 5 nm 0.1mm 0.1m

38 Addition of nitrogen to Fe-based materials Max at 1%N J. Reed, J.Metals, Rawers and Slavens (1995)

39 Background- Dislocations are line defects in materials Callister, Material Science and Engineering: An Introduction

40 Extended edge dislocation Y (111) b b 1 b X, d Z, 1 12 b = b 1 + b = Z direction is equivalent to <112> direction for GSFE X direction equivalent to <110> direction for GSFE

41 GSFE curve along <112> <112> a b u s Z, symmetry of γ surface m Z, 1 12 X, 110 c m b b HCP γ u u s γ SF γ max b FCC lattice FCC S. Kibey, J.B. Liu, M.J. Curtis, D.D. Johnson, H. Sehitoglu, "Stacking Fault Energy and Stacking Fault Widths in High γ -curve along <112> direction Nitrogen Steels," Acta Mater. 54, (2006).

42 Fourier fit for GSFE Fe-4 at.%n u z 1 <112> 6 u x 1 2 <110>

43 6 Effect of stable SFE (note finite separation for negative values) Increasing nitrogen 5 4 1% wt. goes to infinity Peierls d / b γ u = 514 mj/m 2 γ max = 1998 mj/m 2 Volterra γ SF (mj/m 2 )

45 Neu, R. and H. Sehitoglu, "Determination of Cone Bore Growth Due to Microstructural Changes," ASME Journal of Tribology, 112, , Neu, R. and H. Sehitoglu, "Transformation of Retained Austenite in Carburized 4320 Steel, Metallurgical Transactions, 22A, , 1990.

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

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

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52 Conclusions (Sonuçlar) (1) Mechanics of Materials plays a crucial role in understanding the integrity of the rails, wheels,crossings, bearings and other components. (Maddeler mekaniği ray, tekerlek,makas, ve yatay rulmanların güvenirliğini anlamak açısından önemli bir rol oynamaktadır.) (2) New tools are available for experiments and modeling in the mechanics and materials fields.(deneyler ve model yapmak için mühendislikte yeni gelişmeler ortaya çıkmaktadır.)