Structural Analysis of Bush Bearingfor Small End Connecting Rodusing PRO-MECHANICA

INTERNATIONAL JOURNAL OF INFORMATION, KNOWLEDGE AND RESEARCH INMECHANICAL ENGINEERING

Structural Analysis of Bush Bearingfor small end connecting rodUSING “PRO-MECHANICA”

1K.M BHUPTANI , 2 DR. J. M. PRAJAPATI

1 PhD Scholar, Mech. Engg, J.J.T. University, Jhunjhunu, Rajasthan

2 Associate Prof., Mech. Engg.Dept., M.S.U., BARODA, GUJARAT

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ABSTRACT: It is well known fact that connecting rod is the important 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, thus converting the reciprocating motion of the piston into rotary motion of the crank. Existing Bearing of connecting rod is manufactured by using non ferrous materials like Gunmetal, Phosphor Bronze etc.. This paper describes modeling and analysis of connecting rod bearing for small end using ProE Wildfire 4.0.A two dimensional drawing is drafted from the calculations. A parametric model of bearing is modeled using PRO-E 4.0 software. Analysis is carried out by using Pro-mechanica software. Static structural analysis of Bearing for small end of connecting rod is done by considering three different materials. The best combination of parameters like Von misses stress , Maximum shear stress and weight reduction for Four stroke diesel engine were studied in ProE software.

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1INTRODUCTION:

Hydrodynamic journal bearings are commonly used in various rotating machines such as Engines, pumps, compressors, fans, turbines and generators are widely used in industries. A journal bearing is the most common hydrodynamic bearing in which, a circular shaft, called the journal, is made to rotate in a fixed sleeve is called the bearing. The bearing and the journal operates with a small radial clearance of the order of 1/1000th of the journal radius. The clearance space between the journal and the bearing is assumed to be full of the lubricant. The radial load squeezes out the oil from the journal and bearing face and metal-to-metal contact is established. When the journal begins to rotate inside the bearing, it will climb the bearing surface and as journal speed is further increased; it will force the fluid into the wedge-shaped region. Since more and more fluid is forced into the

Wedge-shaped clearance space, which begins to exert pressure with increasing journal speed. At a particular speed, the pressure becomes enough to support the load and the closest approach between journal and bearing where the oil film thickness is the minimum. A condition of perfect lubrication will exit when minimum oil film thickness is greater than the quantity dependent on the nature of the irregularities of the contacting surfaces. The value of minimum oil film thickness, the angle between the line of center with the vertical is called the attitude angle and the location of the maximum film pressure is important considerations in journal bearing lubrication [1]. In this type of bearing, it is not necessary to supply thelubricant under pressure and the only requirement is sufficient and continuous supply of the lubricant [2].

In the past few years, wood, iron and skin have been used as journal bearing materials. Later, brass, bronze and white metal have also found some applications. Currently, in addition to these bearing materials, aluminum and zinc based materials are used as journal bearing materials. With technological improvements, self-lubricated sintered bearings and plastic materials are used where continuous lubricating is impossible. Therefore, it is essential that the bearing material be chosen depending upon area of application. Wear resistance is one of the most important properties that journal bearings should possess. Copper based materials are widely used as bearing materials because they have high thermal and electrical conductivity, self-lubrication property, good corrosion and wear resistance [3].The effect of tin on wear in copper based materials is important. Copper based tin bronzes are used as bearing materials to have a high wear resistance [4]. Friction and wear properties of these materials can be improved by adding tin [5] Tin bronze (90% Cu and 10% Sn) is the most suitable bearing material under corrosive conditions, at high temperatures and high loads.

Lead and tin based white metal alloys are used due to their antifriction property as bearing materials. These alloys are produced by casting and spray deposition method. These casting alloys contain intermetallic phase. The process variables during spray forming of Babbitt bearing metal alloy strongly influence the microstructure and porosity of the spray deposits. The wear rate of the spray-formed alloy is lower than that of the as-cast alloy. Wear properties of the spray-formed alloy are attributed to the decreased intermetallic phases and modification inthe microstructure of the eutectic phases [6]. SnPbCuSb (white metal) alloys are important due to non-seizure and good wear resistance as journal bearing material [7].Journal bearing materials are expected to have several properties such as low friction coefficient, high load capacity, high heat conductivity, compatibility, high wear and corrosion resistance. These properties directly affect the fatigue and wear life. White metal (Babbitt), cast iron, bronze, aluminum, and zinc–aluminum-based materials have been widely used as journal bearings due to their superior wear properties [8][9]. Some metal bearings provide these properties. Journal samples were determined by wearing, AlCuMg2 duralumin, and SnPbCuSb white metal for Cu, Zn, Al, and Sn–Pb based alloys. These alloys are especially used in automotive and machine element applications as journal bearing materials [7].

2OBJECTIVES:

The main objective of this work is to offer better option with respect to existing bearing of small end connecting rod with desired strength. In this paper, only the static FEA of the bearing for small end of connecting rod was performed. The aim of the project is to determine the Von Misses stresses, Shear stresses, and Equivalent Alternating stress, Total Deformation, Fatigue Analysis and Optimization in the existing Connecting rod’s small end bearing. If the existing design shows the failure, then suggest the minimum design changes in the existing bearing. The results were determined under the same weight and loading condition as for the existing connecting rod small end bearing. The case are analyzed one with load applied at the piston end and restrained at the crank end. An Bearing pressure Load is applied on the connecting rod at the small end, and cylindrical support is given at the crank end.

3 PROBLEMFORMULATIONS:

Due to the development of high strength materials and to meet the industries requirements people are trying to replace better and economical component giving better quality with respect to existing product. For this purpose the Oil Engine Bearing for the connecting rod small end is considered here for stress analysis. The SOLID BUSHING full journal bearing structure is considered for the stress analysis and Pro- Mechanica used for the Analysis purpose.

TECHNICAL DATA : Diesel engine following Technical details are used.(4 stroke) referring to Rajkot based engine manufacturer.(P.M. DIESELS LTD)

Description: Vertical, single cylinder, compression ignition, Water cooled, four stroke cycles, cold starting diesel engine.

4 PROBLEMSOLUTION:

Forces Acting on the Connecting Rod

The various forces acting on the connecting rod are as follows:

1. Force on the piston due to gas pressure and inertia

of the reciprocating parts,

2 . Force due to inertia of the connecting rod or inertia

bending forces,

3. Force due to friction of the piston rings and of the piston

4 . Force due to friction of the piston pin bearing and the

crankpin bearing.

It may be noted that the inertia force of reciprocating parts opposes the force on the piston when it moves during its downward stroke (i.e when the piston moves from the top dead centre to bottom dead centre). On the other hand, the inertia force of the reciprocating parts helps the force on the piston when it moves from the bottom dead centre to top dead centre.

Therefore,

Net force acting on the piston or piston pin

(or gudgeon pin or wrist pin),

FP = Force due to gas pressure ± Inertia force

= FG ± FI

The -ve sign is used when piston moves from TDC to BDC and +ve sign is used when piston moves from BDC to TDC.

When weight of the reciprocating parts (WR =MR . g) is to be taken into consideration, then

FP = FG ± FI ± WR

The force FP gives rise to a force FC in the connecting rod and a thrust FNon the sides of the blinder walls. From Fig. , we see that force in the connecting rod at any instant,

FC = =

The force in the connecting rod will be maximum when the crank and the connecting rod are perpendicular to each other (I.e. when Ө = 90°). But at this position, the gas pressure would be decreased considerably. Thus, for all practical purposes, the force in the connecting rod (FC) is taken equal to the maximum force on the piston due to pressure of gas (FG), neglecting piston inertia effects. I Force due to inertia of the connecting rod or inertia bending forces.Therefor, while doing analysis in ProE software it was opted to go for the static structural analysis.

Good bearing design involves three fundamental elements: understanding the service environment, designing for proper lubrication and selecting the best bearing material for the job. Accurately assessing expected service conditions cannot be overemphasized; it is the basis for all subsequent decisions. Creating or at least identifying the lubrication mode in which the bearing will operate is equally important. Sometimes the mode can be established through design; other times it is simply dictated by operating conditions.

Finally, the bearing material selected must suit both the service environment and the operating mode. The wide array of properties offered by the bearing bronzes simplifies material selection process and helps insure that the alloy chosen will provide optimum bearing performance

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.

Table: 1 Mechanical and Physical properties of Bearing Materials

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5 Modeling and ANALYSIS:

For preparing solid modeling ProE wild fire 4.o was used. Here the model was prepared from the existing model utilized in the actual practice. Its dimensions and other features like round radius, lubricating holes etc. were taken from the actual bushing used in the market.(OD 38.1 xID 31.9x 47.2 L with 7.9 oil hole – All dimension are in mm.)

Figure: 2 Bearing Model

Figure 3 Brass bushing Analysis

Figure 4 Bronze bushing Analysis

Figure: 5 Von Misses Stress ANALYSIS

Figure: 6 Shear Stress ANALYSIS

6 CONCLUSIONS:

We conclude that journal bearings manufactured from non ferrous alloying based materials may be effectively used in the industry due to better tribological and mechanical properties. In this study, Modeling with geometrical parameters and mechanical properties of journal bearing manufactured from different non ferrous metals were investigated.

.The following conclusions can be drawn:

(1) The Brass found better resistance material when it is subjected to maximum pressure of 25 MPa. The Von Misses stress induced in the bearing found 33.76 N/mm2 compare to Gun Metal 36.2 N/mm2 and 48.44 N/mm2respectively in Gunmetal and Bronze.

(2) The Brass found better material for shear stresses induced when it is subjected to maximum pressure of 25 MPa. The Maximum shear stress induced in the bearing found 18.87 N/mm2 compare to Gun Metal 21.41 N/mm2 and 27.96 N/mm2 respectively in Gunmetal and Bronze.

(3) The mechanical properties of Brass is better than Gun metal and Phosphorous Bronze. The reason for this is due to the Brass which containing Zinc.

The stress types, magnitudes and distributions in journal bearings are affected by the geometrical and physical properties of the bearing material. The load carrying capacity and misalignment moment decrease with an increase in the roughness for all values of the eccentricity ratio while attitude angle and end leakage flow increase with the roughness parameter

REFERENCES:

[1] S.K. Basu, S.N. Sengupta and B.B. Ahuja, Fundamental of Tribology, Prentice-Hall of India (2006).

[2] V.B. Bhandari, Design of machine elements, Tata Mcgraw Hill (2008).

[3] Paulo D 2000 J. Mater. Proc. Technol. 100 273 (2000)

[4] Prasad B. K. 1997 Metal Trans. 28 809 (1997)

[5] Backensto A B 1990 Effect of lubricants on the properties of copper-tin powder and compacts, Advances in P/M. Proc. Of PM conf.. N. Jersey, pp 303-314 (1990)

[6] Upadhyaya A N, Mishra S and Ojha S N 1997 J. Mater. Science 32 3227 (1997)

[7] Unlu B S 2004 Determination of usability of boronized ferrous based materials as bearing and tribological properties in journal bearings, PhD thesis, Celal Bayer University, Manisa, Turkey (2004)

[8] Cuvalc H and Bas H 2004 Tribol. Int, 37 433 (2004)

[9] Zeren A 2007 Mater. Des. 28 2344 (2004).

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