Crankshaft Deffect

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AFA ILion DVD CHAPTER: Crankshafts

Crankshafts

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In This Presentation• Nomenclature• Function• Materials• Manufacturing• Operation• Normal Appearance• Failure Analysis

CHAPTER: Crankshafts

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NomenclatureCHAPTER: Crankshafts

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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

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Materials Forged High/Medium Carbon Steel

Natural metal flow lines

CHAPTER: Crankshafts

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Hardening Process Medium Carbon Steel

Furnace Heated and water quenched• Hardness Rockwell C 48• Deep 2.5mm

CHAPTER: Crankshafts

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Hardening Process High Carbon Steel

Induction Hardened and water quenchedShot peened fillet radius

CHAPTER: Crankshafts

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Hardening Process Medium Carbon Steel

Rockwell C 40Ground and Polished to final finish

CHAPTER: Crankshafts

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Crankshaft Forces

• Bending - Fillets

• Torsion - Journals

• Thrust - Sidewalls

CHAPTER: Crankshafts

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Bending Loads Combustion Stroke

High tensile stresses rod fillets Compressive stresses in main fillets

CHAPTER: Crankshafts

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Bending Loads End of Combustion Stroke

Low tensile stresses in main fillets compressive stresses in rod fillets

CHAPTER: Crankshafts

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Torsional LoadsCHAPTER: Crankshafts

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Thrust LoadCarried by one main journal

CHAPTER: Crankshafts

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1. State Problem Clearly & Concisely2. Organize Fact Gathering3. Observe & Record Facts4. Think Logically with the Facts5. Identify Most Probable Root Cause6. Communicate with Responsible Party7. Make Repair as Directed8. Follow-Up with Customer

Eight Steps of Applied Failure AnalysisCHAPTER: Crankshafts

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Inspect All Surfaces

• Inspect Bearings• Inspect Fillets• Inspect Fractures

CHAPTER: Crankshafts

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Crankshaft Failures

• Bending Fatigues - Main Fillets - Rod Fillet

• Torsional Fatigue - Main Journals - Rod Journals

CHAPTER: Crankshafts

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Bending FatigueCHAPTER: Crankshafts

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Bending FatigueCHAPTER: Crankshafts

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Bending Fatigue Reverse Bending

CHAPTER: Crankshafts

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Torsional FatigueCHAPTER: Crankshafts

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Torsional FatigueCHAPTER: Crankshafts

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Fracture Causes

• Material Flaws• Process Errors

CHAPTER: Crankshafts

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Material Flaws

• Inclusions• Seams• Pipe• Flake

CHAPTER: Crankshafts

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Material Flaws (Inclusion)

CHAPTER: Crankshafts

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Material Flaws (Inclusion)

CHAPTER: Crankshafts

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Material Flaws (Inclusion)

CHAPTER: Crankshafts

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Material Flaws (Inclusion)

CHAPTER: Crankshafts

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Material Flaws (Inclusion)

CHAPTER: Crankshafts

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Material Flaws (Hydrogen Flake)

CHAPTER: Crankshafts

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Processing Errors

• Forging• Heat Treating• Straightening• Grinding

CHAPTER: Crankshafts

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Processing Errors (Forging Burns)

Failed after 80 hours of service

CHAPTER: Crankshafts

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Processing Errors (Forging Burns)

Subsurface originating fatigue

CHAPTER: Crankshafts

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Processing Errors (Heat Treating)

Quench Crack

CHAPTER: Crankshafts

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Processing Errors (Heat Treating)

Straightening Crack

CHAPTER: Crankshafts

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Reconditioned CrankshaftsCHAPTER: Crankshafts

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What do you see ?Beach Marks, subsurface

CHAPTER: Crankshafts

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What do you see ?Straightening crack

CHAPTER: Crankshafts

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What do you see ?CHAPTER: Crankshafts

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What do you see ?CHAPTER: Crankshafts

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What do you see ?Re- welded Thrust face ?!!!!

CHAPTER: Crankshafts

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Grinder Burns