Design optimization of connecting rod in heavy commercial vehiclesBySathish.R(79510144048)Vivek.P(79510144059)Sriram.M(79510144512)Rajesh.R(79510144044)Department of Mechanical Engineering.Internal GuideMr. R.Sathish Kumar, M.TechAssistant Professor,TRPEC,Trichy.External GuideDr. M.Sathya Prasad, Phd.,Section Head, Adv Engg, Ashok Leyland Technical Centre, Chennai.1 April 2014TRPECREVIEW OF PROJECT1 The objective of this project is to optimize and to reduce the weight ofan automotive connecting rod.Austempered Ductile Iron (ADI) is chosen in the place of currently used forged steel, as ADI is cheaper and lighter when compared to forged steel. Forces acting on the connecting rod were computed using analytical method and ADAMS software and then compared. Static and Fatigue life estimation was done and compared with existing forged steel and proposed ADI material on existing connecting rod design. The design is then optimized using OPTISTRUCT solver for several iterations until achieving the convergence. The optimized designs were compared with existing connecting rod and the better design is chosen based on stress, displacement.OBJECTIVE1 April 2014TRPECREVIEW OF PROJECT2LOADS ACTING ON CONNECTING RODLITERATURE REVIEW Pravardhan Shenoy [1], a study was done to explore weight and cost reduction opportunities for a production forged steel connecting rod. Here the tensile load acting on surface area is taken as distributed over 180 degrees and compression force over 120 degrees.

Tensile load acting over 1800Compressive load acting over 1200120180HINO BS 3 EngineEngine type 6 cylinder Inline enginePeak pressure - 120barMaximum speed 3250rpmWeight of connecting rod 1.721 kgCylinder bore 104 mmEngine Specification - 1 April 2014TRPECREVIEW OF PROJECTLITERATURE REVIEW

Constrain the crank pin end for all degrees of freedom of the connecting rod and applying compressive force distributed over 120 in piston pin.Constrain the piston pin end for all degrees of freedom of the connecting rod and applying load at crank pin end over 120. Constrain the piston pin end for all degrees of freedom and applying tensile load at 180 at crank pin end. Bolt pretension force applied on beam element to equalize the bolt tightening torque and the bush pressure is given in small end of connecting rod.Three load cases were observed Vijayaraja [2] for FEA analysis of connecting rod.

Loads on Connecting Rod 1 April 2014TRPECREVIEW OF PROJECTLITERATURE REVIEWOPTIMIZATION The basic principle of optimization is to find the best possible solution under given circumstances. Structural optimization is one application of optimization. Anton Olason[3] has done an extensive work in optimization techniques. The type of optimization is basically branched into three types - Size optimization, Shape optimization, Topology optimization. Optimization process traditionally consists of the following steps.A design is suggested.The requirements of the design are evaluated with help of finite element analysis.If the requirements are satisfied, then the optimization process is over. Otherwise, steps 1 and 2 are repeated where modifications are made and a new improved design is proposed.

1 April 2014TRPECREVIEW OF PROJECTSizing optimization - The shape of the structure is known and the objective is to optimize the structure by adjusting sizes of the components.

Shape optimization - In shape optimization the design variables can be thickness distribution along structural members, diameter of holes, radii of fillets or any other measure

Topology optimization - In topology optimization the density is the variable and it takes a value between 0 and 1

LITERATURE REVIEWOPTIMIZATIONSizing optimization- Structure of truss being optimized

Shape optimization

Topology optimization1 April 2014TRPECREVIEW OF PROJECTHEAT TREATMENT OF ADIADI is produced by an isothermal heat treatment known as Austempering. First step is heating the casting to austenitizing temperature in the range of 815-927 C.Then holding the part at austenitizing temperature to get the entire part to temperature and to saturate the austenite with carbon.Quenching the part rapidly enough to avoid formation of pearlite. Austempering the part at the desired temperature to produce a matrix of ausferriteLITERATURE REVIEW1 April 2014TRPECREVIEW OF PROJECT

Heat Treatment of ADI1 April 2014TRPECREVIEW OF PROJECTThis table shows a picture of mechanical properties of ADI and compared to forged steel[4].MECHANICAL PROPERTIES OF ADILITERATURE REVIEWMechanical PropertyMATERIALForged steelPearlitic Ductile ironGrade 150/100/7 ADIYield Strength, Mpa600480830Tensile Strength, Mpa7906901100Elongation, %10310Hardness, BHN262262286Impact strength, joules 17555165

Comparison of yield strength of ADI and steelMechanical properties of ADI and forged steel1 April 2014TRPECREVIEW OF PROJECT

Relative cost of ADI per unit yield strengthRelative weight per unit yield strengthLITERATURE REVIEWGraphs shows that the relative cost and relative weight per unit yield strength is low when compared to forged steel. 1 April 2014TRPECREVIEW OF PROJECTElementProportionEffectCarbon3 to 4 %Increases the tensile strength and helps in defect free Casting.Silicon2.4 to 2.8%It promotes graphite formation and decreases the solubility of carbon in austenite. Silicon increases the impact strength of ADI and lowers the ductile-brittle transition temperatureCopper0.8%Copper increases hardenability in ADI when added up to 0.8%. Copper has no significant effect on tensile properties but increases ductility at austempering temperatures below 350oC.Nickel2% Nickel can be added to ADI up to 2% to increase the hardenability. For austempering temperatures below 350oC nickel reduces tensile strength slightly but increases ductility and fracture toughness.Molybdenum0.3%Molybdenum is a hardenability agent in ADI, and may be required in heavy section castings to prevent the formation of pearliteALLOYING ELEMENTS OF ADILITERATURE REVIEW1 April 2014TRPECREVIEW OF PROJECT11

I Beam (Shank)Rod Small EndRod CapRod Bushing Rod BoltPARTS OF CONNECTING ROD1 April 2014TRPECREVIEW OF PROJECTDYNAMIC LOAD ANALYSISINERTIA FORCES ACTING ON CONNECTING ROD

Acceleration of connecting rod is aA = Force acting on connecting rod crank end FA = -mAaA FA = mA r 2 (cos t + sin t ) Force acting on connecting rod at piston end FB = -mBaB FB = mB r 2 (cos t + cos 2t)

- r 2 (cos t + cos 2t) and aB= 1 April 2014TRPECREVIEW OF PROJECT

Multi body Simulation Model built using ADAMS

DYNAMIC LOAD ANALYSISPosition of crank at 0 degPosition of crank at 90 degPosition of crank at 180 degConnecting rod was connected with the piston using rotational joint. Crank was connected with the connecting rod with the help of rotational joint and then separately connected with the ground with another rotational joint. Translational joint was applied between piston and ground for sliding motion. 1 April 2014TRPECREVIEW OF PROJECTCrank angle(deg)Acceleration at B(m/sec2)FB (manual calc)(N)Acceleration at A (m/sec2)FA (manual calc)(N)FB (ADAMS)(N)FA (ADAMS)(N)08581.6814811.095-6544.43-18253.1533314959.21-18435.68306686.2711539.81-8939.87-24934.2711655.21-25183.6190-2037.25-3516.08-6544.44-18253.15-3551.24-18435.68143-4665.08-8051.441288.083592.59-8131.953628.52180-4507.19-7778.946544.4418253.15-7856.7318435.68225-4627.62-7986.789255.2325813.86-8066.6526072.00270-2037.25-3516.086544.4418253.15-3551.2418435.683608581.6914811.10-6544.44-18253.1514959.21-18435.68585-4627.61-7986.789255.2325813.85-8066.6526071.997007710.3813307.32-3911.43-10909.4113440.39-11018.50Comparison of results with ADAMSGas force, FG = p*(/4*d2) = 12000000*(/4*0.104) = 101938.39 NCompressive load at Big End, Fmin BE = -FA + FG = -22970.078+101938.39 = 78968.31 NCompressive load at Small end, Fmin SE = FB - FG = 9868.94-101938.39 = -92069.45 N1 April 2014TRPECREVIEW OF PROJECT

Maximum Tensile force At piston end = 14631.7 NAt crank end = 25830 NMaximum compressive forceAt piston = 92069.45NAt crank end = 78968.31 N

Bush pressure = 8.7 MpaBolt pretension = 25000 N Graph shows the inertia forces at Crank end (FA) and at Piston end (FB) computed by both analytical method and Multi body systems (ADAMS). Crank angle Vs gas force is shown in the other graph which shows the gas pressure on connecting rod at every crank angle.DYNAMIC LOAD ANALYSIS1 April 2014TRPECREVIEW OF PROJECT The element length was taken as 2 mm by considering the minimum thickness of profile.Creating 2-D tria mesh Checking quality of elementsConverting 1st order elements into 2nd order Conversion of 2-D to 3-D elementsConnecting rod bolt is modeled using beam element and rigid element RBE2 The nodes and elements of connecting rod cap and body is connected using rigid elements

FINITE ELEMENT MODEL OF CONNECTING ROD BOLT

FINITE ELEMENT ANALYSIS1 April 2014TRPECREVIEW OF PROJECTQuality criteriaIdeal valueAcceptable valueWarping0< 5Aspect ratio1< 5Skew0< 60Jacobian1 >.7Distortion1.7Chord deviation0.1Minimum angle60>20Maximum angle60