2. 1. Rigid members that connects a piston to the crankshaft in a recipro
cating engine.
2. Converts reciprocating motion into rotating motion ( or vice versa)
3. Imparts both pushing and pulling
4. Also finds uses in steam engines and sawmill machines
5. Consists of six parts: Bushing, rod, bearing, cap and b
olts
Connecting Rods
3.
4.
5. Two main class of materials used are : alloys and composite
s
Common materals used are for making connecting rod
s are:
1. Steel
2. Titanium
3. Aluminium
4. Cast Iron
5. Eglass
6. Epoxy
Manufactured using mainly three methods:
1. Casting
2. Forging
3. Powder Metallurgy
6.
7. Size and Shape
Dimensions of connecting rods mainly depend upon the type of ap
plication- viz: high speed, heavy duty, etc.
Cross section of the rod can be of the following types:
1. I- Section
2. H- Section
3. Rectangular
4. Circular
• I- Section connecting rods are the most common ones because
of the ability to resist buckling
8. Materials chosen for
Connecting Rods
Should
1. Possess high strength
2. Absorbs impact force
3. Be able to operate at high temperatures
4. Be light
5. Cost effective
6. Durable
7. Last long
8. Oxidation resistive
9.
10. Ways to increase the strength of materials
1. Grain Boundary Strengthening: By changing the average gr
ain size.
As grain boundary increases,
• Resistance to slip increases
• Difficulty arises for dislocation to migrate and hen
ce strength of materials increases
2. Heat Treatment: alters the physical and chemical properties. Ma
jor heat treatment techniques include: Annealing, which involves he
ating the material to a certain limit holding it there for some time an
d then cooling it back,; normalising, etc.
11. 3.Strain Hardening: Involves plastic deformation, which helps in m
ovement of dislocation and also generates new dislocations there
by increasing strength materials.
4. Alloying: Process in which two ore more metals are combined to
gether to form a new material with specific composition and propert
ies
5. Quenching: Involves rapid cooling of materials in cold water, oil
or air to achive increased strength,.
• It is to be said that the manufacturing process as well as th
e density of material also affects the strength of the materi
al
12.
13. Impact Absorption
1. Each time the fuel in the piston chamber explodes, it exerts a very
high impact force on the connecting rods.
2. This impact force continues to be exerted as along as the engine i
s running and hence causes failure
3. Materials with high impact absorbing properties are used to comb
at this problem. Amajor indicator of impact absorbing property is h
ence the ductility of the material.
4. Aluminium alloys such as T6-2024 Aluminium are best suited for i
mpact absorption.
14. Weight of Materials
1. Usually manufacturers try to keep the weight of each of the co
mponents as low as possible to increase the performance of t
he vehicle .
2. Most high performance vehicles contain connecting rods mad
e of titanium or aluminium or an alloy of any of these as they a
re very much lighter when compared to other materials like ste
el, cast iron, etc.
Cost of materials
1. In bulk produced vehicles, cost of materials should be kept
minimum without compromising safety, and material qualitie
s.
2. In this regard aluminium alloys and steels are great candida
te materials.
16. Ti6-Al4-V
• It is an alpha-beta alloy with high strength to weight ratio and excell
ent corrosion resistance.
• The microstructures of Ti6Al4V are complex and strongly affect its
mechanical properties and fatigue behavior.
• Ti6Al4V alloy is widely used for its many desirable properties, inclu
ding its;
• strength to weight ratio
• corrosion resistance
• biocompatibility
• processability.
17. • The microstructures of titanium alloys are generally described by t
he size and arrangement of their α and β phases.
• The two extreme cases of phase arrangements are;
• lamellar microstructure (with a greater α/β surface area a
nd more oriented colonies), which is generated upon cooli
ng from the β phase field
• equiaxed microstructure (a uniform structure composed of
α grains and grain boundaries of β), which results from a r
ecrystallization and globularization process .
18. Microstructures of Ti alloys
Microstructure of
pure titanium
Lamellar microstructure
of titanium alloy
Equiaxed microstructure
19. Previous research has indicated that lamellar microstructure exhibits:
• lower strength,
• lower ductility, and
• better fatigue propagation resistance compared with equiaxed micr
ostructure.
20. 4340 Steel
• AISI 4340 steel is a medium carbon, low alloy steel known for its tou
ghness and strength in relatively large sections .
• It contains 0.4% of carbon.
• AISI 4340 alloy steel is a heat treatable alloy steel containing Cr,Ni a
nd Mo.
• Generally supplied hardened and tempered in the tensile range of 9
30 – 1080 Mpa. Can be further surface hardened by flame or inducti
on hardening and by nitriding.
21. Properties of 4340 Steel;
•It has high toughness and strength in the heat treated conditio
n.
•has good shock and impact resistance as well as wear and ab
rasion resistance in the hardened condition.
•It offers good ductility in the annealed condition, allowing it to
be bent or formed.
• Fusion and resistance welding is also possible with our 4340
alloy steel
23. Grey Cast Iron
• Cast iron is made when pig iron is re-melted in small cupola furnace
s (similar to the blast furnace in design and operation) and poured in
to molds to make castings.
• Cast Iron is generally defined as an alloy of Iron with greater than 2
% Carbon, and usually with more than 0.1% Silicon.
• Gray Iron: Graphite flakes surrounded by a matrix of either Pearlite
or a-Ferrite. Exhibits gray fracture surface due to fracture occurring
along Graphite plates. The product of a stable solidification. Consid
erable strength, insignificant ductility.
24. • Gray Cast Irons contain silicon, in addition to carbon, as a primary al
loy. Amounts of manganese are also added to yield the desired mic
rostructure.
• Generally the graphite exists in the form of flakes, which are surroun
ded by an a-ferrite or Pearlite matrix.
• Most Gray Irons are hypoeutectic, meaning they have carbon equiv
alence (C.E.) of less than 4.3.
• Gray cast irons are comparatively weak and brittle in tension due to
its microstructure; the graphite flakes have tips which serve as point
s of stress concentration.
• Strength and ductility are much higher under compression loads.
Contd…….
25. • The chemical analysis of gray iron can be broken into three m
ain categories;
Carbon, Silicon, and Iron.
• Gray cast irons typically contain 3.0-3.5% carbon, with silicon
levels varying from 1.8-2.4%.
Grey cast iron magnified to show the flakes of
carbon( graphite)
26. Carbon Fibre
• Carbon fibers or graphite fibres are fibers about 5–10 micrometres
in diameter and composed mostly of carbon atoms.
• Advantages :
• High stiffness,high tensile strength, low weight, high chemical resi
stance, high temperature tolerance and low thermal expansion.
• These properties have made carbon fiber very popular in aerospa
ce, civil engineering, military, and motorsports, along with other co
mpetition sports.
• However they are relatively expensive when compared with simila
r fibers, such as glass fibers or plastic fibers.
27. • To produce a carbon fiber, the carbon atoms are bonded toget
her in crystals that are more or less aligned parallel to the long
axis of the fiber as the crystal alignment gives the fiber high str
ength-to-volume ratio (in other words, it is strong for its size).
Carbon fiber :microstructure
28. • Several thousand carbon fibers are bundled together to form a to
w, which may be used by itself or woven into a fabric.
• Carbon fibers are usually combined with other materials to form a
composite. When impregnated with a plastic resin and baked it for
ms carbon-fiber-reinforced polymer (often referred to as carbon fi
ber) which has a very high strength-to-weight ratio, and is extrem
ely rigid although somewhat brittle.
29. Contd……
•Carbon fibers are also composited with other materials,
such as graphite, to form reinforced carbon-carbon comp
osites, which have a very high heat tolerance.
•Carbon fiber is frequently supplied in the form of a conti
nuous tow wound onto a reel.
•The tow is a bundle of thousands of continuous individu
al carbon filaments held together and protected by an or
ganic coating, or size, such as polyethylene oxide (PEO)
or polyvinyl alcohol (PVA).
30. • The tow can be conveniently unwound from the reel for use.
• Each carbon filament in the tow is a continuous cylinder with a dia
meter of 5–10 micrometers and consists almost exclusively of carb
on.
• The earliest generation (e.g. T300, HTA and AS4) had diameters o
f 16–22 micrometers. Later fibers (e.g. IM6 or IM600) have diamet
ers that are approximately 5 micrometers.
31. • The atomic structure of carbon fiber is similar to that of graphit
e, consisting of sheets of carbon atoms arranged in a regular
hexagonal pattern (graphene sheets)
• the difference being in the way these sheets interlock.
• Graphite is a crystalline material in which the sheets are stack
ed parallel to one another in regular fashion.
• The intermolecular forces between the sheets are relatively w
eak Van der Waals forces, giving graphite its soft and brittle c
haracteristics.
Atomic structure
33. • Depending upon the precursor to make the fiber, carbon fiber may be;
• turbostratic carbon fiber
• Graphitic carbon fiber
• or have a hybrid structure with both graphitic and turbostratic par
ts present.
• In turbostratic carbon fiber, the sheets of carbon atoms are haphazar
dly folded, or crumpled, together.
• Carbon fibers derived from polyacrylonitrile (PAN) are turbostratic. wh
ereas carbon fibers derived from mesophase pitch are graphitic carbo
n fiber after heat treatment at temperatures exceeding 2200 °C.
• Turbostratic carbon fibers tend to have high tensile strength, whereas
Graphitic carbon fibers have high Young's modulus (i.e., high stiffness
or resistance to extension under load) and high thermal conductivity.
Types of carbon fiber
