Fatique on Piston Ring

Proceedings of the National Conference on Emerging Trends In Mechanical Engineering 2k13

164 NCETIME 2k13

FATIGUE ANALYSIS OF A DIESEL PISTON RING BY USING FEA

1Mr.K.Kadambanathan,

2E.Selvan

1 Assistant Professor

, 2PG Students

Department Of Mechanical Engineering,

Mailam Engineering College, Mailam

E-Mail: [email protected],

2 [email protected]

ABSTRACT

Elastic finite element models were used to calculate the stresses in a diesel piston ring, for centrifugal forces,

gas pressure, piston-to-cylinder contact and thermo-mechanical loading. A fatigue analysis superimposed the four

loading conditions and calculated the fatigue life at each node on the model, adjusting the materials fatigue

properties for the effects of nodal temperature. The identification of fatigue-critical locations, and the calculated

fatigue lives, showed good agreement with test results

This work is concerned only with the analysis of fatigue-damaged pistons ring. Pistons from petrol and diesel

engines, from automobiles, motorcycles and trains will be analyzed. Damages initiated at the crown, ring grooves,

pin hole sand skirt are assessed. A compendium of case studies of fatigue-damaged pistons is presented. An analysis

of both thermal fatigue and mechanical fatigue damages is presented and analyzed in this work

1. INTRODUCTION.

Piston ring materials and designs have evolved

over the years and will continue to do so until fuel

cells, exotic batteries or something else makes the

internal combustion engines obsolete. The main

reason of this continuous effort of evolution is based

on the fact that the piston may be considered the

_heart_ of an engine .The piston is one of the most

stressed components of an entire vehicle Pistons must

also be light enough to keep inertial loads on related

parts to a minimum. The piston also aids in sealing

the cylinder to prevent the escape of combustion

gases. It also transmits heat to the cooling oil and

some of the heat through the piston rings to the

cylinder wall. As one of the main components in an

engine, pistons technological evolution is expected to

continue and they are expected to be more and

stronger, lighter, thinner and durable. The main

reason is because the mechanical efficiency of an

engine is still low and only about 25% of the original

energy is used in brake power. Not with standing this

technological evolution there are still a significant

number of damaged pistons Damages may have

different origins: mechanical stresses; thermal


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stresses; wear mechanisms; temperature degradation,

oxidation mechanisms; etc. In this work only

mechanical damages and in particular fatigue

damages will be assessed.

The cyclic stresses/deformations have mainly two

origins: load and temperature. Traditional mechanical

fatigue may be the main damaging mechanism in

different parts of a piston depending on different

factors. High temperature fatigue (which includes

creep) is also present in some damaged pistons ring.

Thermal fatigue and thermalmechanical fatigue are

also present in other damaged pistons. In this work,

different pistons, from different kinds of engines:

train engines; motorcycle engines; and automotive

engines will be presented

II. Experimental work

The fatigue-damaged piston rings assessed on

this work may be divided into two categories: the

mechanical and high temperature mechanical

damaged pistons and the thermal and thermal

mechanical damaged pistons rings.

The mechanical and high temperature

mechanical damaged pistons may be divided

according to the damaged area: piston head; piston

pin holes; piston compression ring grooves; and

piston skirt. The analysis, in this work, will be made

according to this classification.

And analyzed in this work

III.ANALYSIS OF COMPRESSION RING

Fig:1 Dimension of piston ring

Fig:2 Dimension of piston

Fig:3 Engine Piston With Damaged Grooves

IV. THE FINITE ELEMENT METHOD

Finite element method is a numerical

analysis technique for obtaining approximate

solutions to a wide variety of engineering problems.

Although originally developed and applied to the

broad field of continuum mechanics. Because of its

diversity and flexibility as analysis tool, it is


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receiving much attention in engineering schools and

industry.

In more and more engineering situation

today, it is necessary to obtain numerical solutions to

problem rather than exact closed from solutions. The

resourcefulness of the analyst usually comes to the

rescue and provides several alternatives to overcome

this dilemma. One possibility is to make simplifying

assumption to ignore the difficulties and reduce the

problem to one that can be handled sometimes this

procedure works but more often than not it leads to

series inaccurate or wrong answers.

Now that computers are widely available, a

more viable alternative is to retain the complexities

of the problem and to find an approximate numerical

solution.

A finite element model of a problem gives a

piecewise approximation to the governing equations.

The basic premise of the finite element method is that

a solution region can be analytically modeled or

approximated by replacing it with an assemblage of

discrete elements since these can be put together in a

variety of ways, they can be put together in a variety

of ways, and they can be used to represent

exceedingly complex shape.

Compression Rings

The compression rings provide sealing above

the piston and prevents the gas leakage from the

combustion side. The compression rings are located

in the top most grooves of the piston. However, this

may differ according the design of the engine. The

main function of these rings is to seal the combustion

gases and transfer heat from the piston to piston

walls.

Application: Piston ring with high break resistance

Chemical composition (%):

C: 3.0 - 3.7 Si: 1.5 - 2.3 Mn: 0.5 - 1.0

P: max 0.4 S: max 0.15 Cr: 0.2 - 0.7

Mo: max 0.5 Cu: max 0.5

Other elements may be present as impurities.

Microstructure:

Graphite: predominantly lamellar and uniformly

distributed

Matrix: pearlite, ferrite not exceeding 5 %

Phosphates eutectic: predominantly non-continuous

network

Mechanical properties:

Hardness: 200 - 280 HB

Bending strength: min 420 MPa

Modulus of elasticity: 90000 - 120000 MPa

Material: LP 8Alloyed lamellar cast iron

Application: Wear resistant piston rings with high

break resistance Above 200 mm nominal diameter

Chemical composition (%): C: 2.9 -

3.4 Si: 1.2 - 1.6 Mn: 0.6 - 0.9

P: 0.1 - 0.2 S: max 0.05 Cr: 0.1 - 0.3

V: 0.1 - 0.3 Mo: 0.4 - 0.7 Cu: 0.4 - 0.8

Other elements may be present as impurities.

Microstructure: Graphite: preferably A-graphite,

size: 4 - 6 Matrix: perlite with special carbides, max

5 % ferrite Phosphate eutektikum: point-reticular

shaped

Mechanical properties:

Hardness: 220 - 280 HB 2.5/187.5

Tensile strength: min 340 MPa

Bending strength: min 700 MPa

Modulus of elasticity: 110000-140000 MPa


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V.APPLIED LOADS

The in-piston ring compressive load has

been determined from an actual engine running

critical load cases on ring at various conditions such

etc. and is applied on piston ring outer side. The

compressive load is found to be 420Mba.

The details of the compression ring

Outside diameter of the ring : 59.5mm

Inside diameter of the ring : 56mm

Width of the ring : 3mm

Load on the ring : 420Mp

VI.MODELING OF PISTON RING

FOR STATIC CONDTION

The finite element model is generated using solid

185 element type using sweep mesh the wheel and

the connecting links are meshed the platform model

generated as using mapped mesh platform solid

model is changed to FEA model

1

X

Y

Z

DEC 7 2012

15:02:38

VOLUMES

TYPE NUM

Fig;4 Modeling of compression ring

MESHING COMRESION RING

1

X

Y

Z

DEC 7 2012

15:05:51

ELEMENTS

Fig: 2.Meshing compression ring

DISPLACEMENT OF THE RING

1

X

Y

Z

DEC 7 2012

15:11:28

ELEMENTS

U

Fig:5 Displacement Of The Ring


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DISPLACEMENT ARESST

1

XY

Z

DEC 7 2012

15:19:52

ELEMENTS

U

F

Fig :6 Displacement Arrest

1

XY

Z

DEC 7 2012

15:18:44

ELEMENTS

U

F

Fig;7 Load applied on of the compression ring

VII.DEFORMED SHAPE OF RING

Different damage mechanisms where fatigue

prevails over other damaging mechanisms will be

assessed. For a better understanding of the damaging

mechanism different analytical tools, such as finite

element analysis, metallurgical analysis, etc., will be

used whenever they are necessary for a clear

understanding of the damaging mechanism. A finite

element linear static analysis

The cyclic stresses/deformations have mainly two

origins: load and temperature. Traditional mechanical

fatigue may be the main damaging mechanism in

different parts of a piston depending on different

factor

1

X

Y

Z

DEC 7 2012

15:24:18

DISPLACEMENT

STEP=1

SUB =1

TIME=1

DMX =10317

Fig;8 deformed Shape Of Ring

1

MNMXX

Y

Z

-1469

-1019-568.838

-118.894331.05

780.9941231

16812131

2581

DEC 7 2012

15:26:20

NODAL SOLUTION

STEP=1

SUB =1

TIME=1

UX (AVG)

RSYS=0

DMX =10317

SMN =-1469

SMX =2581

Fig9; Deformed shape shear stress of piston ring

VIII.BENDING STRENGTH OF PISTON

RING1

MNMX

X

Y

Z

-.217E+08

-.138E+08-.584E+07

.210E+07.100E+08

.180E+08.259E+08

.339E+08.418E+08

.497E+08

DEC 7 2012

15:27:06

NODAL SOLUTION

STEP=1

SUB =1

TIME=1

SXY (AVG)

RSYS=0

DMX =10317

SMN =-.217E+08

SMX =.497E+08

Fig; 10 Bending Strength Of Piston Ring

VIII.ANALYSIS AND RESULTS

The fatigue analysis used the ANSYS software

from Safe Technology. And FEA-SAFE


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accesses the results database of ANSYS, and writes

fatigue analysis results . The fatigue life results can

then be displayed as 3-dimensional contour plots

using the FEA graphics. In this analysis, FEA-SAFE

superimposed the four types of loading. The

centrifugal stresses were multiplied by a time history

of centrifugal force based on reciprocating mass and

engine speed. The gas pressure stresses were

multiplied by the pressure curve. These calculated

time histories of nodal stresses were The fatigue lives

at each node were calculated. FE-SAFE also

calculates fatigue strength factors at each node for a

specified design life. The analysis included the

effects of temperature on the fatigue properties of the

material.

The contour plot of fatigue lives is shown in Figure

The analysis has identified the most critical fatigue

crack initiation sites, and these agree well with test

results

FUTURE WORK

Work is continuing on algorithms to calculate

elastic-plastic stresses from the Elastic FEA, for the

general case of out-of-phase stresses with fluctuation

stress Amplitudes. Further work on the effects of

large compressive stresses and temperature fatigue is

also proceeding

CONCLUSION

The first main conclusion that could be drawn from

this work is that although fatigue is not the

responsible for biggest slice of damaged pistons, it

remains a problem on engine pistons and its solution

remains a goal for piston manufacturers. And it will

last a problem for long because efforts on fuel

consumption reduction and power increase will push

to the limit weight reduction that means thinner walls

and higher stresses. To satisfy all the requirements

with regard to successful application of pistons, in

particular mechanical and high temperature

mechanical fatigue and thermal/thermalmechanical

fatigue there are several concepts available that can

be used to improve its use, such as design, materials,

processing technologies,

REFERENCE

[1] Junker H, Issler W. Pistons for high loaded

direct injection diesel engines. MAHLETechnical

information

[2] Taylo CM. Automobile engine tribology

design considerations for efficiency and

durability. Wear 1998; 221:18.

[3] Kajiwara H, Fujioka Y, Suzuki T, Negishi H.

An analytical approach for prediction of piston

temperature distribution in dieselengines. JSAE Rev

2002;23(4):42934.

[4] Payri F, Benajes J, Margot X, Gil A. CFD

modeling of the in-cylinder flow in direct-

injection diesel engines. Computer

Fluids2004;33(8):9951021.

Fatique on Piston Ring

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