Crankshafts

1. 1
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Crankshafts

2. 2
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In This Presentation
• Nomenclature
• Function
• Materials
• Manufacturing
• Operation
• Normal Appearance
• Failure Analysis
CHAPTER: Crankshafts

3. 3
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Nomenclature
CHAPTER: Crankshafts

4. 4
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Crankshaft Functions
• Convert Reciprocating to Rotary Motion
• Carry Heavy Bending, Torsional & Thrust Loads
• Deliver Pressurized Oil to Main & Rod Bearings
• Provide Bearing with Hard Wear Resistant Surface
• Deliver Power to Gears & Flywheel
• Provide Sealing Surface for Oil Seals
CHAPTER: Crankshafts

5. 5
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Materials Forged High/Medium Carbon Steel
Natural metal flow lines
CHAPTER: Crankshafts

6. 6
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Hardening Process Medium Carbon Steel
Furnace Heated and water quenched
• Hardness Rockwell C 48
• Deep 2.5mm
CHAPTER: Crankshafts

7. 7
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Hardening Process High Carbon Steel
Induction Hardened and water quenched
Shot peened fillet radius
CHAPTER: Crankshafts

8. 8
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Hardening Process Medium Carbon Steel
Rockwell C 40
Ground and Polished to final finish
CHAPTER: Crankshafts

9. 9
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Crankshaft Forces
• Bending - Fillets
• Torsion - Journals
• Thrust - Sidewalls
CHAPTER: Crankshafts

10. 10
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Bending Loads Combustion Stroke
High tensile stresses rod fillets
Compressive stresses in main fillets
CHAPTER: Crankshafts

11. 11
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Bending Loads End of Combustion Stroke
Low tensile stresses in main fillets
compressive stresses in rod fillets
CHAPTER: Crankshafts

12. 12
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Torsional Loads
CHAPTER: Crankshafts

13. 13
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Thrust Load
Carried by one main journal
CHAPTER: Crankshafts

14. 14
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1. State Problem Clearly & Concisely
2. Organize Fact Gathering
3. Observe & Record Facts
4. Think Logically with the Facts
5. Identify Most Probable Root Cause
6. Communicate with Responsible Party
7. Make Repair as Directed
8. Follow-Up with Customer
Eight Steps of Applied Failure Analysis
CHAPTER: Crankshafts

15. 15
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Inspect All Surfaces
• Inspect Bearings
• Inspect Fillets
• Inspect Fractures
CHAPTER: Crankshafts

16. 16
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Crankshaft Failures
• Bending Fatigues
- Main Fillets
- Rod Fillet
• Torsional Fatigue
- Main Journals
- Rod Journals
CHAPTER: Crankshafts

17. 17
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Bending Fatigue
CHAPTER: Crankshafts

18. 18
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Bending Fatigue
CHAPTER: Crankshafts

19. 19
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Bending Fatigue Reverse Bending
CHAPTER: Crankshafts

20. 20
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Torsional Fatigue
CHAPTER: Crankshafts

21. 21
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Torsional Fatigue
CHAPTER: Crankshafts

22. 22
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Fracture Causes
• Material Flaws
• Process Errors
CHAPTER: Crankshafts

23. 23
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Material Flaws
• Inclusions
• Seams
• Pipe
• Flake
CHAPTER: Crankshafts

24. 24
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Material Flaws (Inclusion)
CHAPTER: Crankshafts

25. 25
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Material Flaws (Inclusion)
CHAPTER: Crankshafts

26. 26
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Material Flaws (Inclusion)
CHAPTER: Crankshafts

27. 27
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Material Flaws (Inclusion)
CHAPTER: Crankshafts

28. 28
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Material Flaws (Inclusion)
CHAPTER: Crankshafts

29. 29
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Material Flaws (Hydrogen Flake)
CHAPTER: Crankshafts

30. 30
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Processing Errors
• Forging
• Heat Treating
• Straightening
• Grinding
CHAPTER: Crankshafts

31. 31
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Processing Errors (Forging Burns)
Failed after 80 hours of service
CHAPTER: Crankshafts

32. 32
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Processing Errors (Forging Burns)
Subsurface originating fatigue
CHAPTER: Crankshafts

33. 33
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Processing Errors (Heat Treating)
Quench Crack
CHAPTER: Crankshafts

34. 34
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Processing Errors (Heat Treating)
Straightening Crack
CHAPTER: Crankshafts

35. 35
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Reconditioned Crankshafts
CHAPTER: Crankshafts

36. 36
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What do you see ?
Beach Marks, subsurface
CHAPTER: Crankshafts

37. 37
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What do you see ?
Straightening crack
CHAPTER: Crankshafts

38. 38
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What do you see ?
CHAPTER: Crankshafts

39. 39
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What do you see ?
CHAPTER: Crankshafts

40. 40
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What do you see ?
Re- welded Thrust face ?!!!!
CHAPTER: Crankshafts

41. 41
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Grinder Burns