Structural Analysis of Small Aircraft Connecting Rod Made of Hybrid Composite Material

Structural Analysis of Small Aircraft Connecting Rod Made of Hybrid Composite Material

Hybride composite: Al-2024, Al2O3 and Graphite

Gurubasavaraju T M Department of Computer aided engineering VTU center for post graduation, Bangalore

Bangalore, India

Dr. Thirtha Prasad HP

Associate Professor Department of Computer aided engineering VTU center for post graduation, Bangalore

Bangalore, India

Abstract In IC engine, reciprocating motion of the piston is converted into rotary motion by using connecting rod (CR).It acts as the intermediate link between the piston and crank. Most of automobile connecting rods are made of steel, now a days connecting rod are made of aluminum composite materials are used in race cars. The gas pressure inside the combustion chamber creates axial stress and inertial force due to reciprocation creates tensile and compressive stress on the connecting rod. In the present work, an investigation on structural behavior of connecting which is made of aluminum hybrid composite at different loading conditions. The Analysis done by using ANSYS WORKBENCH 15.0 and model is created in Pro/E WF4.0.Finallys comparison of analytical and FEA results are done.

KeywordsConnecitng Rod; Piston force, Alumimum Hybride composites, Structural Analysis,FEA; ANSYS WORKBENCH 15.0, Pro/E

1. MATERIAL PROPERTIES

   Mechanical properties of Aluminum hybrid composite material are evaluated by experimental methods. The composition of composite are: Al-2024, 6 wt% of Al2O3 and 3 wt% Graphite. Al-2024 is the matrix and Al2O3, Gr are reinforcements. The reinforcements are distributed in random manner throughout the matrix, hence the material is considered as the isotropic.

   1. INTRODUCTION

      Main function of connecting rod is to transmit the thrust of the piston to the crankshaft, and which results in conversion of reciprocating motion of piston into rotational motion of crank

      i.e linear motion into rotary motion. Due to reciprocating action created due to gas pressure and inertia loads, rods are subjected to the alternating loads of order 108 to 109cycle. It consists of a long shank, a small end, a big end. The cross- section of the shank may be circular, rectangular, tubular, I- section or H-section.

      Sonsino and Esper (1994) have discussed the fatigue design of sintered connecting rods. They did not perform optimization of the connecting rod. They performed preliminary FEA followed by production of a prototype. Fatigue tests and experimental stress analysis were performed on this prototype based on the results of which they proposed a final shape. In order to verify that design was sufficient for fatigue, they computed the allowable stress amplitude at critical locations, taking the ratio, the stress concentrations and statistical safety factors into account and ensure that maximum stress amplitudes were below the allowable stress amplitude.

      Pathade et al. (2012) analyzed the two most critical areas of the connecting rod. Specified dimensioned connecting rod was modeled in PROE which was later imported to ANSYS. In their problem statement three different loads were applied at pin end whereas the crank end was fixed. When theoretical and FEA results were compared.

      Material Properties of Al-2024, Al2O3 and graphite
      Youngs modulus	83.795 Mpa
      Poisson Ratio	0.319
      Density	2.809 g/cc3
      Ultimate strength	275.92 N/mm2
      Yield Strength	250.55 N/mm2

      Table 1: Properties of Composite

2. ENGINE SPECIFICATION AND DIMENSIONS OF THE CONNECTING ROD

   Engine specification
   Displacement (cc)	7.49
   Bore (mm)	22.25
   Stroke (mm)	19.28
   Output (Kw/rpm)	1.30/17000
   Practical rpm	2000-17500
   Weight (g)	412

   Table 2: Engine specification

   Dimensions in mm
   Parameter	Value
   Length of the CR	43.5
   Big end outer diameter	9.8
   Small end outer diameter	8.2
   Big end inner diameter	6
   Small end inner diameter	5.4

   Table 3: Connecting rod dimensions

   Fig 1: Side view and Dimensions of connecting rod

   Fp = 0.5948 N

   1. COMPONENT MODELING AND FEA OF CONNECTING ROD

      Connecting rod is modeled as per the dimension shown in the fig 1 & 2, using Pro/E WF 4.0. Model is exported to desired folder in *IGES format. Model in *IGES format is imported to ANSYS WORKBENCH 15.0. Mechanical properties are specified to the model.

      1. Meshing

   Fig 3: Pro/E model of Connecting rod

   Fig 2: Top view and Dimensions of connecting rod

3. LOAD CALCULATION

Mechanical efficiency of the engine = 0.8 Output power BP= 1.30 kw

Indicated power IP= BP/ = (1.30/0.80) = 1.625 Kw Indicated power IP: (Pi LANnK)

60000

Descritization of the domain into small sub domain is done by meshing. The elements used for meshing here is tetrahedron. Total number of element is 19196 and nodes are 37921.

Where

Pi = Mean effective pressure L= Stroke length

D= Bore diameter K=no. Of cylinder

N= For 4 stroke engine N= Speed in RPM

N= N/2 = (17000/2) = 8500 rpm

A= (d^2)/4 = (( 22.25)^2)/4 = 388.82 mm2 Pi= (IP X 60000)/LAnK

Pi = (1.625 X 60000)/(19.28 X 388.82 X 8500 X 1)

= 0.001530 N/mm2

At the TDC of piston,

Force transmitted through connecting rod

Piston force = Cylinder bore are X Mean affective pressure

= 0.001530 X 388.82

Fig 4: Mashed Connecting Rod

1. Boundary conditions

   Loading condition	Tensile Load condition		Compressive Load condition
   Load application	Crank Pin End	Piston Pin End	Crank Pin End	Piston Pin End
   Fixed constrain	Piston Pin End	Crank Pin End	<>Piston Pin End	Crank Pin End

   Table 4: Boundary conditions applied to connecting rod

2. Analytical Stress calculation at different cross sections

Stress Along A-A

= = = 0.03913

Stress along B-B

= = = 0.02542

Stress along C-C

= = = 0.02754

Stress along D-D

= = = 0.02832

Fig 5: Sections of connecting rod

1. RESULTS AND DISCUSSION

   Results obtained in finite element analysis using ANSYS WORKBENCH are.

   Compressiv e Load condition	Crank Pin End	0.595	0.069547	1.53E-08
   	Piston Pin End	0.595	0.046012	1.35E-08

   Table 5: FEA results

   1. Tensile Load at Piston Pin End

      Fig 6: von mises stress and deformation for condition a

   2. Tensile Load at Crank Pin End

      Fig 7: von mises stress and deformation for condition b

   3. Compressive Load at Piston Pin End

      Fig 8: von mises stress and deformation for condition c

      	Load Applied at	Load-N	Max.Von Mises Stress- N/mm2	Total deformation- m
      Tensile Load condition	Crank Pin End	0.595	0.068409	1.55E-08
      	Piston Pin End	0.595	0.042069	1.35E-08

   4. Compressive Load at Crank Pin End

      Fig 9: von mises stress and deformation for conditions

      The following factors have been found in the finite element analysis.

      1. Maximum Von-mises stress occurred at the crank end and minimum at the piston end.

      2. Max Deformation occurred at the side, where the application of load.

      3. Stress induced is maximum at the circular ring section, so there is a chance of failure in that location.

2. REFERENCES

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