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DESIGN AND FATIGUE ANALYSIS OF METAL MATRIX COMPOSITE CONNECTING ROD USING
FEA
Submitted by
NITHIL.G, SARAVANAN.C
III-Year Mechanical DeptMother Teresa Collage of Engg and Tech, Pudukottai
Abstract
Composite materials are now a day widely used in engineering field
The objective of the project is to design and fatigue analysis of the metal
matrix composites (MMC) connecting rod
The connecting rods are commonly used in the internal combustion engines
and are subjected to millions of varying stress cycles loading to fatigue failure
In that project both the standard steel and composite connecting rods are
modeled and analyzed using solid works 2010 and cosmos software
IntroductionConnecting Rod
Connecting rod is an intermediate member between the piston and the
crankshaft
Its primary function is to transmit the push and pull from the piston pin to
the crank pin and thus converts the reciprocating motion of the piston into
the rotary motion of the crank
It consists of a long shank a small end and a big end. The cross section of
the shank may be rectangular, circular, tubular “ I section and H section”.
Generally circular sections are used for low speed engines where I section
is preferred for high-speed engines.
Forces Acting On Connecting Rod
Force on the piston due to gas pressure and inertia of the reciprocating
parts
Force due to inertia of the connecting rod or inertia bending forces
Force due to friction of the piston rings and of the piston
Forces due to friction of the piston pin bearing and crank pin bearings.
The Development Objectives For Light Metal Composite Materials
Increase in yield strength and tensile strength at room temperature and
above
While maintaining the minimum ductility or rather toughness,
Increase in creep resistance at higher temperatures compared to that of
conventional alloys,
Increase in fatigue strength especially at higher temperature,
Improvement of corrosion resistance,
Increase in young’s modulus,
Reduction of thermal elongation
Improvement of thermal shock resistance,
Mechanism Of Fatigue
A fatigue fracture always starts as a small crack which, under repeating
loading of stress grows in size.
As a crack expands, the load carrying cross-section of the metal component
is reduced, as a stress rises
The events that lead to fatigue include
1.crack nucleation
2.crack growth, and
3. fracture
STEPS INVOLVED IN FEA
PREPROCESSING
ANALYSIS
POSTPROCESSING
PREPROCESSING
..
Calculation
Specifications :
B.H.P = 7.6
Bore = 49 mm
Stroke = 56 mm
Crank Radius = 56/2 28 mm
Piston Diameter = 48.5 mm
Piston Weight = 65g (0.065 Kg)
After calculation load acting on the connecting rod
WB = 13020 N
Material Properties For Conventional Connecting Rod
Material name : Alloy steel
Elastic modulus : 210000 N/mm^2
Poisson's Ratio : 0.28
Density : 7700 Kg/m^3
Ultimate Tensile Strength : 723.83 N/mm^2
Thermal expansion : 1.3e-005 /k
specific heat : 460 j/kg k
Material Properties For Composite Connecting Rod
Material name : Alloy steel
Elastic modulus : 210000 N/mm^2
Poisson's Ratio : 0.28
Density : 7700 Kg/m^3
Ultimate Tensile Strength : 723.83 N/mm^2
Thermal expansion : 1.3e-005 /k
specific heat : 460 j/kg k
ANALYSIS
Software Used
Solid work for modeling and meshing,
Cosmos for analysis
Meshing In Solid Works
Displacement (mm) 0.05506
Maximum stress (vonmisses stress in Mpa) 0.624
Weight in grams 115.48
Result Output (Tension)
Tensile Analysis For Conventional Connecting Rod
Boundary condition :
Engine mounted vertically
Bottom end (Big end) – Fixed
Top end (small end) – application of load
Displacement (mm) 0.0373
Maximum stress (vonmisses stress in Mpa) 0.423
Weight in grams 72.17
Result Output (Tension)
Tensile Analysis For Composite Connecting Rod
Boundary condition :
Engine mounted vertically
Bottom end (Big end) – Fixed
Top end (small end) – application of load
21/07/11
Stress Conventional connecting rod
Composite connecting rod
Tensile stress (Mpa) 0.624 0.423
Life (Days) 76.71 302.69
Strength to weight ratio
Comparatively lesser Comparatively greater
Mass 115.48 grams 72.17 grams
Fatigue Analysis Comparison
RESULTS
STRESS ANALYSIS FOR CONVENTIONAL CONNECTING ROD
DISPLACEMENT – CONVENTIONAL CONNECTING ROD
STRESS ANALYSIS REPORT FOR COMPOSITE CONNECTING ROD
DISPLACEMENT RESULTS FOR COMPOSITE CONNECTING ROD
Conclusion
The conventional connecting rod used in the engines was replaced with a composite connecting rod
Stress induced in the composite connecting rod is found to be lower
then that of the conventional connecting rod
Number of working days for composite connecting rod is high
Composite connecting rod material is replaced for good fatigue
strength