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Mokashi Imrankhan Sherkhan Guided by: M S Bobji

Seminar on. Mokashi Imrankhan Sherkhan Guided by: M S Bobji. Importance of Fracture Mechanics in Tribology. Wear Erosion Surface Formation. Fracture Mechanics approach. Energy Based : Energy release rate(G) and J integral

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Mokashi Imrankhan Sherkhan Guided by: M S Bobji

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  1. Seminar on Mokashi Imrankhan Sherkhan Guided by: M S Bobji

  2. Importance of Fracture Mechanics in Tribology • Wear • Erosion • Surface Formation

  3. Fracture Mechanics approach • Energy Based : Energy release rate(G) and J integral • Stress Based : Stress intensity factor (K) • Displacement Based : Crack tip opening displacement (CTOD)

  4. Modes of Crack Propagation

  5. Energy Approach

  6. Griffith’s Energy balance approach • First documented paper on fracture (1920) Considered as father of Fracture Mechanics

  7. Energy Approach Cont… • Surface energy Es = 2(2a B ᵞ) • ᵞ -Surface energy per unit area • B-Thickness of plate

  8. Energy Approach Cont.. • Total PE of Body with crack • U = UE – Uwork + US • Strain Energy • System always try to minimize its PE

  9. Thick plate is more resistant to fracture or thin?

  10. J Integral • J Integral over a closed loop = 0 • Path independent

  11. Displacement Approach

  12. Displacement Approach From Hooke’s law, displacement field can be obtained as

  13. Stress Approach

  14. Stress Intensity Factor for infinite plate for other geometry  can be obtained from : 1. handbook solution 2. approximate method 3. numerical method

  15. Stress near crack tip Plastic zone size

  16. Plastic Zone Shapes plane strain plane stress

  17. = 1 = 1 Mixed Loading where KIc, KIIc, KIIIc, ni (i = 1, 2, 3) – parameters that characterize material near the concentrator, determined experimentally

  18. Cont… (1) Diagrams of the deformed body limiting-equilibrium state the conditions of mixed (I+II), (I+III) fracture mechanisms Curve 1 – according to formula (1) when KIII = 0 and ni = 4, curve 2 according formula (1) when KIII = 0 and ni= 2 Curves 1 and 2 are plotted according to formula (1) when ni = 4 and ni=2 correspondingly

  19. FATIGUE FRACTURE

  20. Every Coin has two sides… • Useful Fracture • Metal cutting • Rock cutting in Mining • “Biting” of candies • Unwanted Fracture • Fracture of Liberty ships in World war II • Fracture of wheels, axles and rails

  21. Fracture Avoidance with Proper Use of Material • Pyramid of Egypt Schematic Roman Bridge Design • The primary construction material prior to 19th were timber, brick and mortar • Arch shape producing compressive stress  stone have high compressive strength

  22. Fracture Avoidance with Proper Use of Material (cont’) • Roof spans and windows were arched to maintain compressive loading

  23. REFERENCES A book on “Fracture Mechanics” by Prashant Kumar “Introduction to Fracture Mechanics” book by C. H. Wang

  24. Thank you for your attention

  25. Finite Element Analysis • Stress analysis near crack • Quarter point element • J- integral

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