CONNECTING ROD

A connecting rod is a part of engine which transfers motion from piston to the

crankshaft and functions as a lever arm. With the crank, it forms a

mechanism that converts reciprocating motion into rotating motion.

Connecting rods are mostly used in internal combustion piston engines .

Fig. 1 : Connecting rod

Fig. 2 [1] : Types of Connecting rod

Fig. 3 : Connecting rods

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Fig. 4 : Connecting rods

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Fig. 5 : Powder Forging Process

Fig. 6 [4,Pg 411]

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Fig. 7 [7]: Electrolytic Fabrication

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Fig. 8[5] : Hoganas sponge iron

Fig. 9 [7] : Water Atomization

Fig. 10 : Gas Atomization

Fig. 11 [7] : Centrifugal Atomization

POWDER MIXING

In the manufacturing of sintered

parts, iron powders are always

used and mixed with a

small amount of lubricant in powder

form in order to minimize the friction

in the compacting tool. In many

cases, they are also blended with

alloying elements in powder

form, like graphite, copper, nickel,

molybdenum and others (in order to

achieve increased strength

properties).

Fig. 12 [6] : Powder Mixing

Fig. 13[3,Pg49]

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STRESS AND FAILURE

The rod suffers formidable stress due to its motion, being compressed and extended on each cycle . In the manufacture of connecting rods, stress risers are eliminated by grinding the edges of the rod to a smooth radius, shot peening is done to induce compressive surface stresses (to prevent crack initiation), all connecting rod/piston assemblies are balanced to the same weight. The larger end of the rod is fabricated as a unit and then cracked in two to establish a good fit around the big end bearing shell.

Connecting rods which are made using powder metallurgy, have greater precision over size and weight with less machining. The cap is then separated from the rod by a fracturing process, ensuring that upon reassembly, the cap will be perfectly positioned with respect to the rod.

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Fig. 14 [2,Pg 178,199] : Chemical Composition

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Fig. 15 [2,Pg 179,200] : Mechanical Properties

Fig. 16 [2,Pg 204,225] : Reversal to failure

Fig. 17 [2,Pg 219,234] : Fracture surface

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Fig. 18 [2,Pg 43]