Analisis Finitos Analisis Biela Motor

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International Journal of Applied Engineering Research

ISSN 0973-4562 Volume 4 Number 7 (2009) pp. 12771285

Research India Publications

http://www.ripublication.com/ijaer.htm

Modeling & Analysis of Connecting Rod of Four

Stroke Single Cylinder Engine for Optimization of

Cost & Material

1S B Jaju and

2P G Charkha

1Professor, 2Student [M Tech (CAD-CAM)]1,2

Department of Mechanical Engineering, G H Raisoni College of Engineering

Nagpur, C R P F Gate No-3, Digdoh Hills, Hingna Road, Nagpur,

Maharashtra, India-440016

Email:[email protected],

[email protected]

Abstract

The main objective of this study was to explore weight reduction opportunities

for a production forged steel connecting rod. This has entailed performing a

detailed load analysis. Therefore, this study has dealt with two subjects, first,

static load stress analysis of the connecting rod, and second, optimization for

weight.

In this project, finite element analysis of single cylinder four stroke petrol

engine is taken as a case study. Structural systems of connecting rod can be

easily analyzed using Finite Element techniques. So firstly a proper Finite

Element Model is developed using Cad software Pro/E Wildfire 3.0. Then the

Finite element analysis is done to determine the Von Mises stresses in the

existing connecting rod for the given loading conditions using Finite Element

Analysis software ANSYS WORKBENCH 9.0. In the first part of the study,

the static loads acting on the connecting rod, after that the work is carried outfor safe design. Based on the observations of the static Finite Element

Analysis (FEA) and the load analysis results, the load for the optimization

study was selected. The results were also used to determine degree of stress

multiaxiality, and the fatigue model to be used for analyzing the fatigue

strength. Outputs include fatigue life, damage, factor of safety, stress

biaxiality, fatigue sensitivity. The component was optimized for weight

subject to fatigue life and space constraints and manufacturability.

Key Words: Connecting Rod, Modeling, Finite Element Analysis,

Optimization


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1278 S B Jaju and P G Charkha

Introduction

The main aim of the project is to determine the Von Misses stresses, Shear stresses,

Maximum Principle stress, Equivalent Alternating stress, Total Deformation, Fatigue

Analysis and Optimization in the existing Connecting rod. If the existing design

shows the failure, then suggest the minimum design changes in the existing

Connecting rod. A lot has been done and still a lot has to be done in this field. In this

Project, only the static FEA of the connecting rod has been performed by the use of

the software. This work can be extended to study the effect of loads on the connecting

rod under dynamic conditions. Experimental stress analysis (ESA) can also be used to

calculate the stresses which will provide more reasons to compare the different values

obtained. Now a day a lot is being said about vibration study of mechanical

component important role in its failure. So the study can be extended to the vibration

analysis of the connecting rod. The study identified fatigue strength as the mostsignificant design factor in the optimization process. Then the combination of finite

element technique with the aspects of weight reduction is to be made to obtain the

required design of connecting rod.[1]

Results & Discussion

Outputs include fatigue life, damage, factor of safety, stress biaxiality, fatigue

sensitivity as shown in Figures.

(1)A contour plot of available life over the model. This result can be over thewhole model or scoped to a given part or surface. This result contour plot

shows the available life for the given fatigue analysis. If loading is of constantamplitude, this represents the number of cycles until the part will fail due to

fatigue. If loading is non-constant, this represents the number of loading

blocks until failure. Thus if the given load history represents one month of

loading and the life was found to be 120, the expected model life would be

120 months.

(2)A contour plot of the fatigue damage at a given design life. Fatigue damage isdefined as the design life divided by the available life. This result may be

scoped. The default design life may be set through the Control Panel (Table

2.1)

(3)A contour plot of the factor of safety with respect to a fatigue failure at a givendesign life. The maximum FS reported is 15. Like damage and life, this result

may be scoped. This calculation is iterative for nonconstant amplitude loading

and may substantially increase solve time (Table 2.1).

(4)A stress biaxiality contour plot over the model. As mentioned previously,material properties are uniaxial but stress results are usually multiaxial. This

result gives the user some idea of the stress state over the model and how to

interpret the results. Biaxiality indication is defined as the principal stress

smaller in magnitude divided by the larger principal stress with the principal

stress nearest zero ignored. A biaxiality of zero corresponds to uniaxial stress,

a value of 1 corresponds to pure shear, and a value of 0.97 corresponds to a

pure biaxial state (Table 1). From the sample biaxiality plot shown below,


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Modeling & Analysis of Connecting Rod of Four 1279

most of the model is under a pure shear or uniaxial stress. This is expected

since a simple torque has been applied at the top of the model. When using the

biaxiality plot along with the safety factor plot above, it can be seen that the

most damaged point occurs at a point of nearly pure shear. Thus it would be

desirable to use S-N data collected through torsional loading if available. Of

course collecting experimental data under different loading conditions is cost

prohibitive and not often done.

(5)A fatigue sensitivity plot. This plot shows how the fatigue results change as afunction of the loading at the critical location on the model. This result may be

scoped to parts or surfaces. Sensitivity may be found for life, damage, or

factory of safety. The user may set the number of fill points as well as the load

variation limits.

Table 2.1: Fatigue Results.

Name Figure Scope TypeDesign

LifeMin Max

Alert

Criteria

Life None Model Life 1,000,000.0 1,000,000.0 None

Damage None Model Damage 1.0109

1,000.0 1,000.0 None

Safety

Factor1 Model

Safety

Factor1.0109 1.13 15.0 None

Biaxiality

Indication2 Model

Biaxiality

Indication-1.0 0.97 None

Equivalent

Alternating

Stress

3 ModelEquivalent

Reversed

Stress

0.01 Mpa 76.22 Mpa None

Figure 2.1: Safety Factor. Figure 2.2: Biaxiality Indication


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Figure 2.3: -Equivalent Alternating

Stress.

Figure 2.4: Fatigue Sensitivity.

Figure 2.5: Safety Factor. Figure 2.6: Biaxiality Indication.

Figure 2.7: Equivalent Alternating

Stress.

Figure 2.8: Fatigue Sensitivity.


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Table 2.2: Fatigue Results.

Name Figure Scope TypeDesign

LifeMin Max

Alert

Criteria

Life None Model Life 3,138.61 1,000,000.0 None

Damage None Model Damage 1.0109 1,000.0 318,612.73 None

Safety

Factor5 Model

Safety

Factor1.010

90.23 15.0 None

Biaxiality

Indication6 Model

Biaxiality

Indication-1.0 0.97 None

Equivalent

Alternating

Stress

7 Model

Equivalent

Reversed

Stress

5.6710-

2MPa

381.17 MPa None

Optimization StatementObjective of the optimization task was to minimize the mass of the connecting rod

under the effect of a load range comprising the two extreme loads, the peak

compressive gas load, such that the maximum, minimum, and the equivalent stress

amplitude are within the limits of the allowable stresses. The production cost of the

connecting rod was also to be minimized. Furthermore, the buckling load factor under

the peak gas load has to be permissible.[1]

Mathematically stated, the optimization statement would appear as follows:

Objective: Minimize Mass and Cost

Subject to:

Compressive load = peak compressive gas load. Maximum stress < Allowable stress. Side constraints (Component dimensions). Manufacturing constraints. Buckling load > Factor of safety x the maximum gas load (Recommended

FOS, 3 to 6).

Loads Applied

The load range under which the connecting rod was optimized is comprised of the

compressive load of 4319 N. The compressive load of 4319 N is independent of the

geometry of the connecting rod. The tensile load is, however, dependent upon the

specific geometry, as it is a function of the mass, moment of inertia, and location of

C.G.


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Table 3.1.1: Values for Shape Results.

Name Figure ScopeTarget

Reduction

Predicted

Reduction

"Shape

Finder"9 "Model" 20.0% 9.24% to 9.51%

Table 3.1.2: Total Weights.

Name Original OptimizedMarginal

(Discretionary)

"ShapeFinder"

0.13 kg 0.12 kg 3.4610-4 kg

Figure 3.1: Shape Finder.

Observations from the Optimization Exercise(1)The literature survey suggests that connecting rods are typically designed under

static loads. It appears that different regions are designed separately with different

static loads (i.e. such as in Sonsino and Esper, 1994). Doing so increases the

number of steps in the design process. In contrast, a connecting rod could very

well be designed under dynamic loads. Doing so would reduce the number ofsteps in the design process.

(2)The applied load distribution at the crank end and at the piston pin end were basedon experimental results (Webster et al., 1983). They were also used in other

studies in the literature by Folgar et al. (1987) and Athavale and Sajanpawar

(1991). Since the details were not discussed by Webster et al., the applicability of

the loading to this connecting rod could not be evaluated.

(3)With manual optimization under static axial loading, at least 9.24 % weightreduction could be achieved for the same fatigue performance as the existing

connecting rod as shown in fig. 5.33. This is in spite of the fact that C-70 steel has

18% lower yield strength and 20% lower endurance limit. Clearly, higher weight


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reduction may be achieved by automating the optimization and more accurate

knowledge of load distributions at the connecting rod ends. The axial stiffness is

about the same as the existing connecting rod and the buckling load factor is

higher than that for the existing connecting rod.

(4)C-40 has lower yield strength and endurance limit, As a result it was essential toincrease weight in the pin end region. New fracture cracking materials are being

developed (such as micro-alloyed steels) with better properties (Repgen, 1998).

Using these materials can help significantly reduce the weight of the connecting

rod in the pin end and crank end cap. However in the shank region, manufacturing

constraints such as minimum web and rib dimensions for forgeability of the

connecting rod present restrictions to the extent of weight reduction that can be

achieved.

(5)Considering static strength, buckling load factor, and fatigue strength, it wasfound that the fatigue strength of the connecting rod is the most significant and the

driving factor in the design and optimization of connecting rod.

Future ScopeA lot has been done and still a lot has to be done in this field. In this project, only the

static FEA of the connecting rod has been performed by the use of the software Pro/E

wildfire 3.0 for cad modeling and ANSYS WORKBENCH 9.0 for Finite Element

Analysis. This work can be extended to study the effect of loads on the connecting rod

under dynamic conditions. Experimental stress analysis (ESA) can also be used to

calculate the stresses which will provide more reasons to compare the different valuesobtained.

Now days a lot is being said about vibrational study of mechanical component

important role in its failure. So the study can be extended to the vibrational analysis of

the connecting rod. We can change the material of the connecting rod for better result.

Changing the geometry, but as it was the restriction from customer end, this is not

covered in this project. We can notice from the design that the factor of safety

considered for the design is too large which results in the wastage of the material and

also increases its cost. So the need of the hour is the optimization of the connecting

rod which will lead to a revolution in the manufacturing sectors of the automobile

industry.

ConclusionThis research project investigated weight and cost reduction opportunities that steel

forged connecting rods offer. This Project is concentrated on the calculation of the

stresses developed in the connecting rod and to find region more susceptible to

failure. The connecting rod chosen for the study is of 4 stroke single cylinder engine

in which failure of the connecting rod results in the replacement of the whole

connecting rod crankshaft assembly. FEA was performed using these results obtained

from load analysis to gain an insight of the structural behavior of connecting rod and

to determine design loads for further study. First the Cad Modeling of connecting rod


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with the help of Cad software Pro/E Wildfire 3.0 and then Load analysis was

performed with different cases consideration. The analysis was carried out with

computer aided simulation. The tool used for analysis is ANSYS WORKBENCH

9.0.The following conclusions can be drawn from this study:

(1) There is considerable difference in the structural behavior of the connectingrod between axial fatigue loading. The results obtained with the analysis tool

are quite comfortable and can be used to optimize the model.

(2) The Optimization carried out in analysis gives deep insight by consideringoptimum parameter for suggestion of modification in the existing connecting

rod.

(3) Optimization was performed to reduce weight. Weight can be reduced bychanging the material of the current forged steel connecting rod to crackable

forged steel (C-70).(4) Fatigue strength was the most significant factor (design driving factor) in theoptimization of this connecting rod.

(5) The parameter consideration for optimization are its 20 % reduction inweight of connecting rod, while reducing the weight, the static strength,

fatigue strength, and the buckling load factor were taken into account.

(6) The optimized geometry is 20% lighter than the current connecting rod. PMconnecting rods can be replaced by fracture splitable steel forged connecting

rods with an expected weight reduction of about higher than existing

connecting rod, with similar or better fatigue behavior.

(7) By using other facture crackable materials such as micro-alloyed steelshaving higher yield strength and endurance limit, the weight at the piston pinend and the crank end can be further reduced. Weight reduction in the shank

region is, however, limited by manufacturing constraints.

(8) The stresses developed in the four load cases of connecting rod are below theyield value.

(9) The stress multiaxiality is high, especially at the critical region of the crankend transition. Therefore, multiaxial fatigue analysis is needed to determine

fatigue strength. Due to proportional loading, equivalent stress approach

based on von Mises criterion can be used to compute the equivalent stress

amplitude. Outputs include fatigue life, damage, factor of safety, stress

biaxiality, fatigue sensitivity.

(10) The buckling occurs in the rod is basically maximum at the piston pin end.(11) The software gives a view of stress distribution in the whole connecting rod

which gives the information that which parts are to be hardened or given

attention during manufacturing stage.

(12) The software also reveals the importance of the varying I- cross sectionwhich is provided for uniform stress distribution over the entire web of the

connecting rod.


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References

[1] Pravardhan S Shenoy, Dynamic load analysis and optimization of connectingrod, 2004, Masters Thesis, University of Toledo

[2] James R Dale,Connecting Rod Evaluation, January 2005[3] R Vozenilek, C Scholz, P Brabec,FEM Analysis of Connecting Rod:,2004[4] Adila Afzal, Ali Fatemi, A Comparative study of Fatigue Behaviour and Life

Prediction of Forged Steel and PM Connecting Rods, University of Toledo.

[5] Pro/E Wildfire 3.0 Reference Manual[6] Hero Honda Splendor Company Manual[7] ANSYS WORKBENCH 9.0 Reference Manual.[8] Sonsino, C. M. and Esper, F. J., 1994, Fatigue Design for PM Components,

European Powder Metallurgy Association (EPMA).[9] Hippoliti, R., 1993, FEM method for design and optimization of connecting

rods for small two-stroke engines

[10] J. Sugita, T. Itoh, T. Abe, Honda R. & D. Engine Component Design SystemUsing Boundary Element Method, 905206.

[11] Afzal, A., 2004, Fatigue Behavior and Life prediction of Forged Steel andPM Connecting Rods, Masters Thesis, University of Toledo.

[12] R. C. Patel, Elements of Heat engine, vol-I, II.[13] Robert Cook, Concepts and Application of FEA[14] Athavale, S. and Sajanpawar, P. R., 1991, Studies on Some Modelling

Aspects in the Finite Element Analysis of Small Gasoline Engine

Components, Small Engine Technology Conference Proceedings, Society ofAutomotive Engineers of Japan, Tokyo, pp. 379-389.

[15] Rabb, R., 1996, Fatigue failure of a connecting rod, Engineering FailureAnalysis, Vol. 3, No. 1, pp. 13-28.


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