Presentation on crankshaft

By:

1. Sachin kumar(2010JE0751)

2. Vipin Sharma(2010JE0857)

3. Shashi Ranjan(2010JE0772)

PRESENTATION ON CRANKSHAFT

INTRODUCTION TO CRANKSHAFT

CRANKSHAFT is a part of the engine that translates reciprocating linear piston motion into rotation

• Has crank pins which is attached to big end of theconnecting rod

• Typically connects to a flywheel to reduce the pulsation characteristic of the 4-S cycle• Sometimes torsional or vibrational damper are connected to the other end to reduce the torsional vibrations• Counterweights to improve engine balance

PARTS OF A CRANKSHAFT

PISTON MOTION BASICS

COMPONENTS OF ACCELERATION

FORCES IMPOSED ON A CRANKSHAFT• If the gas pressure is assumed to be 200bar and piston diameter of 10cm, the force on

crankshaft will be of the order of 16,000kgf.

• This level of force produces substantial bending and torsional moments and the resulting tensile, compressive and shear stresses.

• The combined weight of the piston, ring package, wristpin, retainers, small end of connecting rod and a small amount of oil are continuously accelerated from rest to very high velocity and back to rest twice each crankshaft revolution.

• Combustion forces and piston acceleration are also the main source of external vibration produced by an engine.

• Rotating mass associated with each crankpin, weight of the big end of connecting rod , connecting rod bearing(s), some amount of oil, and the mass of the crankshaft structure comprising the crankpin and cheeks.

• These rotating forces are counteracted by counterweight masses located in appropriate angular locations opposing the rod journals

TORSIONAL VIBRATION AND MATERIALS USED IN CRANKSHAFT MANUFACTURING

By- Shashi Ranjan 2010JE0772

TORSIONAL VIBRATIONS• Crankshaft has its own torsional resonant frequency as it has mass and its own torsional

stiffness

• Torsional resonant frequency of the crankshaft system is a function of:

• Crankshaft length

• Crankshaft torsional stiffness

• Crankshaft stroke

• Balance masses

• Moments of inertia of rotating items attached to or driven by the engine

• Crankshaft has very little inherent damping as it is made of lump of high-strength steel. Therefore, vibration attenuating device is provided at the free end of engine crankshaft.

CRANKSHAFT TORSIONAL ABSORBERS• Difference between damper and absorber

• Damper dissipates energy, mainly in the form of heat

• Absorber is a device which is designed to oscillate in direct opposition to a vibration at either a specific frequency or a specific order, depending on the design.

• Types of absorber

• Elastomer absorber

• Pendulum absorber

PENDULUM-STYLE ORDER-ABSORBERS

MATERIALS USED IN MANUFACTURE OF CRANKSHAFTS• Crankshaft are subjected to shock and fatigue loads. Therefore material should be tough

and fatigue resistant.

• The crankshafts are generally made of carbon steel, special steel or special cast iron.

• Medium-carbon steel alloys are composed of predominantly the element iron, and contain a small percentage of carbon (0.25% to 0.45%)

• Several alloying mix are carefully mixed carefully in order to produce specific qualities in target alloy.

• These qualities are hardenability, nitridability, surface and core hardness, ultimate tensile strength, yield strength, endurance limit (fatigue strength), ductility, impact resistance, and corrosion resistance.

• Alloying elements typically used are manganese, chromium, molybdenum, nickel, silicon, cobalt, vanadium, and sometimes aluminium and titanium.

• In industrial engines, the crankshafts are generally made from carbon steel such as 40C8, 55C8 and 68C4

• In transport engines- managanese steel such as 20-Mn-2, 27-Mn-2 and 37-Mn-2

• In aero engines- Nickel Chromium steel such as 35-Ni-1-Cr-60 and 40-Ni-2-Cr-1-Mo-28

MANUFACTURING OF CRANK SHAFT

By: Sachin kumar 2010JE0751

MANUFACTURING OPERATIONS• Forging

• Crank web milling, Journal milling, Crank pin milling

• Drilling of flywheel flange, Drilling of crankpin, Drilling of crossed oil hole

• Grinding

• Crack Detection

• Nitriding

• Dynamic Balancing

• Lapping and Super finish

• Journal Grading and Bearing Selection

Raw forging

Billet Crankshaft machining

Drilling of crankpin Drilling of flywheel flange Drilling of crossed oil hole

Milling cutter used for journal and crankpin milling

• Grinding- Surface grinding is done for main journal and crank pin. Grinding of sidewalls is a critical step

• Crack detection- For a forged material there is possibility of internal flaws. Hence before sending materials for further operations, cracks are detected by magnaflux method.

• Nitriding- Higher surface hardness is obtained, extremely resistant to abrasion and high fatigue strength

• Lapping and Superfinishing- Crankshaft is super-finished so as to avoid cyclic fatigue failure

• Journal Grading and bearing selection

Fully counterweighted V8 crank

Bolt on counterweights

Thank you