Design And Analysis Of Connecting Rod Using Forged Steel

International Journal of Scientific & Engineering Research, Volume 4, Issue 6, June-2013ISSN 2229-55182081Design And Analysis of Connecting RodUsing Forged steelLeela Krishna Vegi1, Venu Gopal Vegi2Department of Mechanical EngineeringJawaharlal Nehru Technological University, Kakinada, AP, INDIAE-mail ID: krishna.leeven@gmail.com1, ----------------------------------------Abstract – The connecting rod is the intermediate member between the piston and the Crankshaft. Its primary function is totransmit the push and pull from the piston pin to the crank pin, thus converting the reciprocating motion of the piston into rotarymotion of the crank. This thesis describes designing and Analysis of connecting rod. Currently existing connecting rod ismanufactured by using Carbon steel. In this drawing is drafted from the calculations. A parametric model of Connecting rod ismodeled using CATIA V5 R19 software and to that model, analysis is carried out by using ANSYS 13.0 Software. Finite elementanalysis of connecting rod is done by considering the materials, viz. Forged steel. The best combination of parameters like Vonmisses Stress and strain, Deformation, Factor of safety and weight reduction for two wheeler piston were done in ANSYS software.Forged steel has more factor of safety, reduce the weight, increase the stiffness and reduce the stress and stiffer than other materiallike carbon steel. With Fatigue analysis we can determine the lifetime of the connecting rod.IJSERKeywords: connecting Rod, Analysis of connecting rod, four stroke engine connecting rod, forged steel connecting rod, design andanalysis of connecting ------------------NomenclatureA cross sectional area of the connecting rod.L length of the connecting rod.C compressive yield stress.Wcr crippling or buckling load.Ixx moment of inertia of the section about x-axisIyy moment of inertia of the section about y-axisrespectively.Kxx radius of gyration of the section about x-axisKyy radius of gyration of the section about y- axisrespectively.D Diameter of pistonr Radius of crank1. INTRODUCTIONIn a reciprocating piston engine, the connecting rodconnects the piston to the crank or crankshaft. Inmodern automotive internal combustion engines, theconnecting rods are most usually made of steel forproduction engines, but can be made of aluminum (forlightness and the ability to absorb high impact at theexpense of durability) or titanium (for a combination ofstrength and lightness at the expense of affordability)for high performance engines, or of cast iron forapplications such as motor scooters. The small endattaches to the piston pin, gudgeon pin (the usualBritish term) or wrist pin, which is currently most oftenpress fit into the con rod but can swivel in the piston, a"floating wrist pin" design. The connecting rod is undertremendous stress from the reciprocating loadrepresented by the piston, actually stretching and beingcompressed with every rotation, and the load increasesto the third power with increasing engine speed.Failure of a connecting rod, usually called "throwing arod" is one of the most common causes of catastrophicengine failure in cars, frequently putting the broken rodthrough the side of the crankcase and therebyrendering the engine irreparable; it can result fromfatigue near a physical defect in the rod, lubricationfailure in a bearing due to faulty maintenance or fromfailure of the rod bolts from a defect, impropertightening, or re-use of already used (stressed) boltswhere not recommended. Despite their frequentoccurrence on televised competitive automobile events,such failures are quite rare on production cars duringnormal daily driving. This is because production autoparts have a much larger factor of safety, and oftenIJSER 2013http://www.ijser.org

International Journal of Scientific & Engineering Research, Volume 4, Issue 6, June-2013ISSN 2229-5518more systematic quality control. When building a highperformance engine, great attention is paid to theconnecting rods, eliminating stress risers by suchtechniques as grinding the edges of the rod to a smoothradius, shot peening to induce compressive surfacestresses (to prevent crack initiation), balancing allconnecting rod/piston assemblies to the same weightand Magnafluxings to reveal otherwise invisible smallcracks which would cause the rod to fail under stress.In addition, great care is taken to torque the con rodbolts to the exact value specified; often these bolts mustbe replaced rather than reused. The big end of the rodis fabricated as a unit and cut or cracked in two toestablish precision fit around the big end bearing shell.Recent engines such as the Ford 4.6 liter engine and theChrysler 2.0 liter engine have connecting rods madeusing powder metallurgy, which allows more precisecontrol of size and weight with less machining and lessexcess mass to be machined off for balancing. The cap isthen separated from the rod by a fracturing process,which results in an uneven mating surface due to thegrain of the powdered metal. This ensures that uponreassembly, the cap will be perfectly positioned withrespect to the rod, compared to the minormisalignments which can occur if the mating surfacesare both flat. A major source of engine wear is thesideways force exerted on the piston through the conrod by the crankshaft, which typically wears thecylinder into an oval cross-section rather than circular,making it impossible for piston rings to correctly sealagainst the cylinder walls. Geometrically, it can be seenthat longer connectin rods will reduce the amount ofthis sideways force, and therefore lead to longer enginelife. However, for a given engine block, the sum of thelength of the con rod plus the piston stroke is a fixednumber, determined by the fixed distance between thecrankshaft axis and the top of the cylinder block wherethe cylinder head fastens; thus, for a given cylinderblock longer stroke, giving greater engine displacementand power, requires a shorter connecting rod (or apiston with smaller compression height), resulting inaccelerated cylinder wear.2082analysis. After analysis a comparison is made betweenexisting steel connecting rod viz., Forged steel in termsof weight, factor of safety, stiffens, deformation andstress.Fig 2.1 Schematic Diagram of Connecting Rod3. DESIGN OF CONNECTING RODA connecting rod is a machine member which issubjected to alternating direct compressive andtensile forces. Since the compressive forces are muchhigher than the tensile force, therefore the crosssection of the connecting rod is designed as a strutand the rankine formula is used. A connecting rodsubjected to an axial load W may buckle with x-axisas neutral axis in the plane of motion of theconnecting rod,{or} y-axis is a neutral axis. Theconnecting rod is considered like both ends hingedfor buckling about x-axis and both ends fixed forbuckling about y-axis. A connecting rod should beequally strong in buckling about either axis.IJSER2. SPECIFICATION OF THE PROBLEMThe objective of the present work is to design andanalyses of connecting rod made of Forged steel. Steelmaterials are used to design the connecting rod. In thisproject the material (carbon steel) of connecting rodreplaced with Forged steel .Connecting rod was createdin CATIAV5 R19. Model is imported in ANSYS 13.0 forAccording to rankine formulaeWcr about x-axis[𝜎𝑐 𝐴] 𝐿 2]𝐾𝑥𝑥1 𝑎[ [𝜎𝑐 𝐴]𝑙 2]𝐾𝑥𝑥1 𝑎[[ 𝑓𝑜𝑟 𝑏𝑜𝑡ℎ 𝑒𝑛𝑑𝑠 ℎ𝑖𝑛𝑔𝑒𝑑 𝐿 𝑙]Wcr about y-axis [𝜎𝑐 𝐴][𝜎𝑐 𝐴]𝐿 2𝑙] 1 𝑎[]2𝐾𝑦𝑦2𝐾𝑦𝑦1 𝑎[ [ 𝑓𝑜𝑟 𝑏𝑜𝑡ℎ 𝑒𝑛𝑑𝑠 𝑓𝑖𝑥𝑒𝑑 𝐿 𝑙/2]In order to have a connecting rod equally strong inbuckling about both the axis, the buckling loads mustbe equal. i.e. [𝜎𝑐 𝐴]𝑙 2]𝐾𝑥𝑥1 𝑎[IJSER 2013http://www.ijser.org [𝜎𝑐 𝐴]𝑙]22𝐾𝑦𝑦1 𝑎[[or]

International Journal of Scientific & Engineering Research, Volume 4, Issue 6, June-2013ISSN 2229-5518K2xx 4K2yy[𝑙𝐾𝑥𝑥]2 [𝑙2𝐾𝑦𝑦 288.855 o K]2[or] I xx 4Iyy[ 𝐼 𝐴 𝐾 2 ]This shows that the connecting rod is four times strongin buckling about y-axis than about-axis. If I xx 4Iyy,Then buckling will occur about y-axis and if I xx 4Iyy,then buckling will occur about x-axis .In Actual practiceI xx is kept slightly less than 4Iyy. It is usually takenbetween 3 and 3.5 and the Connecting rod is designedfor buckling about x-axis. The design will always besatisfactory for buckling about y-axis. The most suitablesection for the connecting rod is I-section with theproportions shown mfg.Mass Density Volume 737.22E-9 x149.5E3 0.11kgMolecular Weight of Petrol 114.228 g/moleFrom Gas Equation,PV Mrt RR Mxw 8.3143/114228Area of the cross section 2[4t x t] 3t x t 11t2 72.76Moment of inertia about x-axis 2[4txt] 3txt 11t2Moment of inertia about x-axisI xx 11241912[𝑡 4 ]I yy 12 t {4t} 112149.5𝐸3P 15.5 Mpa.3.2 Design Calculations for Existing Connecting RodAnd moment of inertia about y-axis3(0.11 72.786 288.85)P IJSER[4𝑡 {5𝑡}3 3𝑡 {3𝑡}3 ] 2 12083131{3t}t 3I xx/I yy [419/12]x[12/131] 3.212Thickness of flange & web of the section t4[t ]Width of section B 4tThe standard dimension of I - SECTION.Since the value of I xx/I yy lies between 3 and 3.5 mtherefore I-section chosen is quite satisfactory.3.1 Pressure Calculation for 150cc EngineSuzuki 150 cc SpecificationsEngine type air cooled 4-strokeBore x Stroke (mm) 57 58.6Displacement 149.5 CCMaximum Power 13.8 bhp @ 8500 rpmMaximum Torque 13.4 Nm @ 6000 rpmCompression Ratio 9.35/1Density of Petrol C8H18 737.22 kg/m3Fig 3.1 Standard Dimension of I – SectionHeight of section H 5tArea of section A 2(4t t) 3t tA 11t²M.O.I of section about x axis:I xx 737.22E-9 kg/mm3 Temperature 60 FoIJSER 2013http://www.ijser.org11241912[4𝑡 {5𝑡}3 3𝑡 {3𝑡}3 ][𝑡 4 ]

International Journal of Scientific & Engineering Research, Volume 4, Issue 6, June-2013ISSN 2229-5518 112.64mm2MI of section about y axis:Iyy 2 112 t {4t}3 131 Ixx12Iyy[t 4 ]112{3t}t 3Height at the big end (crank end) H2 1.1H to 1.25H 1.1 16 3.2Length of connecting rod (L) 2 times the strokeL 117.2 mmBuckling load WB maximum gas force F.O.SWB 2084(𝜎𝑐 𝐴)H2 17.6mmHeight at the small end (piston end) 0.9H to 0.75H 0.9 16H1 12mm(1 a (L/Kxx)2 37663N𝜎𝑐 compressive yield stress 415MPaK xx I xxIJSERAK xx 1.78ta 𝜎𝑐𝜋2𝐸a 0.0002By substituting 𝜎𝑐 , A, a, L, Kxx on WB then 4565t4-37663t2-81639.46 0Stroke length (l) 117.2mmt2 10.03Diameter of piston (D) 57mmFig 3.2 2D Drawing for Connecting Rodt 3.167mmP 15.5N/mm2t 3.2mmRadius of crank(r) stroke length/2Width of section B 4t 58.6/2 4 3.2 12.8mmHeight of section H 5t 29.3Maximum force on the piston due to pressureFl 5 3.2 π/4 x (57)2x15.469 16mmArea A 11t2π4xD2 xp 39473.16NMaximum angular speed Wmax [2πNmax] [2π 8500] 11 3.2 3.2IJSER 2013http://www.ijser.org6060𝐴 𝜋𝑟 2