This is a general view to select the materials as well as suitable processing methods.

1. Connecting Rods for
Automobile
Nitesh Kumar Sharma
112116041
M.M.E

2. Connecting Rods
• A connecting rod is a rigid member which connects a piston to a
crank or crankshaft in a reciprocating engine. Together with the
crank, it forms a simple mechanism that converts reciprocating
motion into rotating motion.
• It consists of
1. A pin – end (Small End)
2. A shank section (Middle), and
3. An crank end (Big End)

3. Applications
• Connection rods are widely used in vehicles that are powered by
internal combustion engines.
• All cars and trucks that use this type of engine employ the use of
connecting rods.
• Farm equipment like tractors and combines.
• Even construction equipment like bulldozers use internal combustion
engines, thus requiring connecting rods.

4. PROPERTIES OF MATERIALS
▪ The fracture toughness needs to be above a certain minimum
value.
▪ The connecting rod should not buckle during operation.
▪ For bending, an I-section is better than a solid section of the same
cross-sectional area
▪ High strength
▪ High damping capacity
▪ Low thermal expansion
▪ Good thermal conductivity
▪ Proper torque specifications
▪ Minimum weight
▪ High rotational speed bearing capacity

5. CANDIDATES MATERIALS
• Low alloy steel(42CrMo4, 43CrMo4, 44csr4, C-70, EN-8D, SAE1141)
• Titanium alloy
• Aluminium alloy
• Epoxy matrix(isotropic)

6. TYPES OF CONNECTING ROD
1. STEEL CONNECTING RODS
➢ Moderate to high horsepower (Forged 900 max, Billet 1200 max)
➢ Moderate RPM (9500-10,000 max)
➢ Suitable for daily driving, endurance racing, and drag racing
➢ Excellent strength and durability
2. ALUMINIUM CONNECTING RODS
➢ High horsepower (1,200 max) and high RPM (14,000 max)
3. TITANIUM CONNECTING RODS
➢ For high speed Motorsports engines
➢Higher horsepower (1,400 max) than Al- alloy and high RPM (14,000 max)

7. MANUFACTURING PROPERTIES
• Machinability
• Formability (rolling, forging, extrusion etc)
• Weldability
• Castability
➢ Above mentioned manufacturing properties are required for con rod
➢ Low alloy steel possess most of the properties than Al-alloy and Ti-
alloy.

8. OTHERS PROPERTIES
✓ Low cost
✓ Working environment(temperature, vibration and chemical)
✓ High pressure withstand
✓ Ease of service and maintenance
✓ Durability
✓Shape of Connecting rods( I and H shape)
➢ Low alloy steel is lowest in cost/kg than Al-alloy and Ti-alloy.

9. Materials Selection
A= Area of cross-section, L= length, µ=density
F = Force, Endurance limit =σ
𝑚 = µAL……(1)
Constrain requires,
F/A≤σ……….(2)
From equation (1)
m≥FL(σ/µ)….(3)
In order that mass is minimized we need to maximize the materials
index, ’M’
M =σ/µ…… (4)

10. A number of
candidate materials
emerge. The
prominent one is low
alloy steel which is
extensively used as
the connecting rod
material for engines
running at high
rotational speeds.

11. Strength versus density materials selection chart
When P is high
(low dense
materials) the
mass is less.
P =10 intercept –
Steel, Al- alloy
are lying on this.

12. Modulus-Strength Graph
• Modulus is high
and strength is
low – It will
deform
plastically before
buckling
• when strength
is more and
modulus is low –
it will buckle
before yield
• Low alloy steel
satisfy the
required data.

13. Strength-Max service temperature
Low alloy steel can
bear service
temperature about
350-540 degree C.
At this temperature
strength is approx
500-1000(MPa)

14. Wear rate - Hardness
Wear rate inversely
proportional to
Hardness.
Intercepting
line(.0001) is going
through low alloys
steel corresponding
harness value varies
1100-6500 H(MPa)

15. FORGING CASTING
MANUFACTURINGPROCESS

16. ForgingVsCasting
Forging
➢ Totalprocessesapproximate
16
➢ Dimensionalconsistency
andaccuracy
➢ Reducemassby 10%
➢ Consumeless energy
➢ Provides longer tool life
➢ smoother runningin the
engine
➢ Lesscost for >20,000 pieces
➢ Highproduction rate
➢ Lesstime consumes
➢ Reducecost about 25%
➢ It performed at
low temperature
Casting
➢ Totalprocessesapproximate
36
➢ Lessaccuracy
➢ More timeconsuming
➢ Requiredhightemperaturefor
melting
➢ Lowproduction rate
➢ Defectssuchas pin
hole, shrinkage,porosity,
Roughsurface etc.
➢ highcost for >20,000pieces
➢ More wasteof materials
➢ More laborcost
➢ Machining process
➢ Low strength
5

17. Manufacturing processflowchart
MATERIAL
CUTTINGTOLENGTHOF MATERIAL
BILLETS HEATING
HOT FORGING

18. PLERCING
TRIMMING
SHOTBLASTING/SHOTPEENING
MACHINING

19. MACHINEFRACTURESPLITTING GROOVE
FRACTURESPLITTING
ASSEMBLYOFCONNECTING ROD
MACHINING

20. INSERTIONOFCRANKENDBEARING SHELLS
INSERTIONOFSMALLENDBEARING BUSH
INSPECTION

21. Economiclimitation

22. Conclusion
Selected material = Low alloy steel
Required Shape = “I” Shape
Selected manufacturing process = Forging

23. THANK YOU