review article enhancing fatigue life of component by ... iii/ijaers vol iii... · engineering...

Bachkar et al., International Journal of Advanced Engineering Research and Studies E-ISSN2249–8974

Int. J. Adv. Engg. Res. Studies/III/I/Oct.-Dec.,2013/80-82

Review Article

ENHANCING FATIGUE LIFE OF COMPONENT BY USING

SHOT PEENING 1S.K.Bachkar,

2Prof.V.D.Wakchaure,

3Swapnil S. Kulkarni

Address for Correspondence 1H.S.B.P.V.T.’s College of Engineering, Kashti, Ahmednagar.

2Amruitvahini College of Engineering, Sangamner, Ahmednagar

3Advent ToolTech Pvt. Ltd., Pune, On behalf of Sponsoring Company University of Pune.

ABSTRACT: In critically loaded component like piston, large coil springs, torsion bars and leaf spring fatigue is a main source of

damages. Although, traditionally, piston damages are attributed to wear and lubrication sources, fatigue is responsible for a

significant number of piston damages. Fatigue exists when cyclic stresses/deformations occur in an area on a component.

The cyclic stresses/ deformations have mainly two origins: load and temperature. High temperature fatigue (which includes

creep) is also present in some damaged pistons. Also thermal mechanical fatigue is present in other damaged pistons. Shot

peening is one of the process to enhance fatigue life of components & there is scope in study effect of shot peening on

fatigue life of piston.

KEYWORDS: Shot-peening, Multiple Impacts, Residual Stress, Design of Experiment, Finite Element Method.

1. INTRODUCTION

Shot is a cold work process, in which the metal part

is struck by a stream of small hard spheres (shot)

creating numerous overlapped dimples on the part

surface. The surface material resists to stretching

induced by the shots impacts resulting in a

formation of a compression stressed skin of about

0.01” (0.25 mm) thickness. Glass, steel or ceramic

balls of a diameter from the range 0.007-0.14”

(0.18-0.36 mm) are used as shot media. The

residual compression stresses inhibits both crack

initiation and propagation. Therefore shot peening is

used mainly for increasing fatigue strength. Dimples

formed on a part surface as a result of shot peening

may serve as lubricant “pockets”, which provide

continuous lubrication of the part preventing galling

steels, nodular (ductile) cast irons, Aluminum

alloys, Nickel alloys and Titanium alloys may be

treated by shot peening.

2. THEORY

2.1 Fatigue:-

In materials science, fatigue is the progressive and

localized structural damage that occurs when a

material is subjected to cyclic loading. The nominal

maximum stress values are less than the ultimate

tensile stress limit, and may be below the yield

stress limit of the material. Fatigue occurs when a

material is subjected to repeat loading and

unloading. If the loads are above a certain threshold,

microscopic cracks will begin to form at the stress

concentrators such as the surface, persistent slip

bands (PSBs), and grain interfaces. Eventually a

crack will reach a critical size, and the structure will

suddenly fracture. The shape of the structure will

significantly affect the fatigue life; square holes or

sharp corners will lead to elevated local stresses

where fatigue cracks can initiate. Round holes and

smooth transitions or fillets are therefore important

to increase the fatigue strength of the structure.

2.2 Methods to Improve Fatigue Life:-

i) Low Plasticity Burnishing (LPB) Process:-

LPB is a new method of surface enhancement that

provides deep stable surface compressive residual

stresses with little cold work for improved fatigue,

fretting fatigue, and stress corrosion performance

even at elevated temperatures where compression

from shot peening relaxes. LPB surface treatment is

applied using conventional multi-axis CNC machine

tools for unprecedented control of the residual stress

distribution developed through modification of the

pressure, feed, and tool characteristics. The resulting

deep layer of compressive residual stress has been

shown to improve high cycle fatigue (HCF) and low

cycle fatigue (LCF) performance and foreign object

damage (FOD) tolerance.

ii) Heat Treatment Processes:-

The purpose of Heat treatment is to increase Fatigue

life of a product by increasing its strength or

hardness, or prepare the material for improved

manufacturability. The microstructures of materials

are modified. The resulting phase transformation

influences mechanical properties like strength,

ductility, toughness, hardness and wear resistance.

• Hardening

• Annealing

• Normalizing

• Tempering

• Surface Hardening

iii) Shot Peening:-

Shot peening is a cold work process, in which the

metal part is struck by a stream of small hard

spheres (shot) creating numerous overlapped

dimples on the part surface. The surface material

resists to stretching induced by the shots impacts

resulting in a formation of a compression stressed

skin of about 0.01” (0.25 mm) thickness. Glass,

steel or ceramic balls of a diameter from the range

0.007-0.14” (0.18-0.36 mm) are used as shot media.

The residual compression stresses inhibits both

crack initiation and propagation. Therefore shot

peening is used mainly for increasing strength.

Dimples formed on a part surface as a result of shot

peening may serve as lubricant “pockets”, which

provide continuous lubrication of the part

preventing galling. Steels, nodular (ductile) cast

irons, Aluminum alloys, Nickel alloys and Titanium

alloys may be treated by shot peening. Shot peening

allows metal parts to accept higher loads or to

endure a longer fatigue life in service without

failure. In usual applications shot peening can be

done without changing the part design or its

material.

2.3 SHOT PEENING For longer fatigue life:

Shot Peening allows metal parts to accept higher

loads or to endure a longer fatigue life in service

without failure. In usual applications shot peening

can be done without changing the part design or its

Bachkar et al., International Journal of Advanced

Int. J. Adv. Engg. Res. Studies/III/I/Oct.-Dec.,2013/

material. If you strike a part surface with a rounded

object at a velocity, sufficient to leave an impression

and continue until you completely cover (cold work)

the entire surface then you will have peened that

part. In modern usage peening is applied by

throwing tiny cast steel balls or “shot” at high

velocity hence the term “shot peening”. Actually the

effect of peening was discovered centuries ago by

sword smiths and black smiths who found the

peening the surface of a sword or wagon spring

would greatly increase its resistance to breaking

when bent or loaded repeatedly. The reasons for this

improvement were not then understood. The round

knob of the “ball peen” hammer was the smith’s tool

for applying this process to cold (not hot) parts.

Material failures are mostly caused from fractures,

or cracks, which start at the surface of the material.

These fractures are caused from over stressing or

bending past the materials yield strength, fatigue

from continuous or repeated stresses, or from

corrosion weakening the surface. When forces are

applied to any material, tension stress and

compressive stress regions form. Fractures only

occur in tension stress regions, never in compression

stress regions.

2.4 Shot Peening prevents Fatigue Life

peening material, internal compressive stress areas

are formed which oppose these tension stress

regions and aid to prevent fractures in the material.

The compressive stress areas in a shot peened

surface are a residual effect and can profoundly

increase the Fatigue life of the material.

3. SOFTWARE ANALYSIS OF VARIOUS

PARAMETERS

The material selected for target is aluminum & for

shot is steel. The target material is circular in shape

having its radius is 4mm & height is 8 mm. The

Poisson ratio is 0.35. The density of the material is

2070kg/m3.The material selected for shot is steel.

The density of material is 7200 kg/m

shot material is 1mm. In case of conventional peen

forming, the component is kept straight during shot

peening, while in stress peen forming, the

component is elastically pre-bent before shot

peening and kept bending during shot peening. With

this 3D random model, LS-DYNA Explicit

sequence solution is used to study the influence of

pre-bending on the peen forming results. An explic

simulation with shots impacting at the pre

component allowed determination of the average

combined stress com in the representative volume of

the component.

3.1 Iteration by Varying Shot Velocity

The shot velocity is 10,15,20,25,35,45,55. The

size & Impact angle is constant.

International Journal of Advanced Engineering Research and Studies E-ISSN

Dec.,2013/80-82

material. If you strike a part surface with a rounded

a velocity, sufficient to leave an impression

and continue until you completely cover (cold work)

the entire surface then you will have peened that

part. In modern usage peening is applied by

throwing tiny cast steel balls or “shot” at high

the term “shot peening”. Actually the

effect of peening was discovered centuries ago by

sword smiths and black smiths who found the

peening the surface of a sword or wagon spring

would greatly increase its resistance to breaking

edly. The reasons for this

improvement were not then understood. The round

knob of the “ball peen” hammer was the smith’s tool

for applying this process to cold (not hot) parts.


the surface of the material.





n stress and



Fatigue Life: By shot

material, internal compressive stress areas

are formed which oppose these tension stress

regions and aid to prevent fractures in the material.

The compressive stress areas in a shot peened

can profoundly

life of the material.

SOFTWARE ANALYSIS OF VARIOUS

The material selected for target is aluminum & for

shot is steel. The target material is circular in shape

having its radius is 4mm & height is 8 mm. The

density of the material is

.The material selected for shot is steel.

The density of material is 7200 kg/m3.The size of

In case of conventional peen

forming, the component is kept straight during shot

peen forming, the

bent before shot

peening and kept bending during shot peening. With

DYNA Explicit

sequence solution is used to study the influence of

bending on the peen forming results. An explicit

simulation with shots impacting at the pre-stressed

component allowed determination of the average

the representative volume of

Iteration by Varying Shot Velocity

The shot velocity is 10,15,20,25,35,45,55. The shot

3.2 Iteration by Varying Shot Angle

The Shot angle 10, 20, 30,40,50,60,70,80,90 Deg.

and other parameters keep constant.

3.3 Iteration by Varying Shot Distance

The Distance between Shot & Target is 70,

80,100,120,140,160,180,200,230 mm. and other

parameter keep constant.


The Shot size 1mm, 0.85 mm, 0.60mm and

parameter keep constant.

From above iteration value the typical parameter

selected for analysis is given below:

The Software is utilized for analysis is Ls Dyna.

finite element method will be used to conduct the

analysis for this project. The software used will be

LS-DYNA. LS-DYNA is an advanced general

purpose multi physics simulation software package

developed by the Livermore Software Technology

Corporation (LSTC). While the package continues

to contain more and more possibilities for the

calculation of many complex, real world

its origins and core-competency lie in highly

nonlinear transient dynamic finite element analysis

(FEA) using explicit time integration. LS

being used by the automobile

construction, military, manufacturing

bioengineering industries. The stress plot

below:

The displacement plot of the analysis is given

below:

The graph of Time vs Stress shows that as stress

goes on increasing at certain time interval & then

goes on decreasing.

ISSN2249–8974

Varying Shot Angle

10, 20, 30,40,50,60,70,80,90 Deg.

and other parameters keep constant.


The Distance between Shot & Target is 70,

80,100,120,140,160,180,200,230 mm. and other


0.60mm and other

From above iteration value the typical parameter

en below:

r analysis is Ls Dyna. The

finite element method will be used to conduct the

analysis for this project. The software used will be

is an advanced general-

purpose multi physics simulation software package

developed by the Livermore Software Technology

Corporation (LSTC). While the package continues

to contain more and more possibilities for the

calculation of many complex, real world problems,

competency lie in highly

finite element analysis

(FEA) using explicit time integration. LS-DYNA is

automobile, aerospace,

manufacturing, and

stress plot is given in

The displacement plot of the analysis is given

Stress shows that as stress

goes on increasing at certain time interval & then

Bachkar et al., International Journal of Advanced

Int. J. Adv. Engg. Res. Studies/III/I/Oct.-Dec.,2013/

Fig 3.1: Graph of Time (sec) vs Stress (MPa)

Fig 3.2: Graph of Depth (mm) vs Stress (MPa)

Fig: Graph of Time (sec) vs Depth (mm)

4. First DOE Study Set up:

Design of Experiments (DoE) is a structured,

organized design/run matrix creation method that

once run will be used to determine the relationships

between the different factors/variables (Xs)

affecting a process and the output of that process

(Y).

Design variable – impact velocity

From above DOE the analysis result will be

From above DOE result the residual compressive

stresses form inside material is 33.5859 MPa &

Permanent set form inside material is 0.004 mm.

Residual stresses can be defined as self

internal stresses existing in a free body which has no

external forces or constraints acting on its boundary.

These stresses arise from the elastic response of the

material to plastic deformation. Ther

peening which causes plastic deformation in the

surface layers of the material, causes residual

stresses in these layers.

5. RELATION BETWEEN SHOT PEENING &

FATIGUE LIFE:

Shot peening is a cold work process that induces a

protective layer of compressive residual stress at the

surface of components. The objective of that

compressive layer is to offset the applied stress,

International Journal of Advanced Engineering Research and Studies E-ISSN

Dec.,2013/80-82

Stress (MPa)

Stress (MPa)

Depth (mm)

is a structured,

organized design/run matrix creation method that

once run will be used to determine the relationships

between the different factors/variables (Xs)

affecting a process and the output of that process

impact velocity

e DOE the analysis result will be:

From above DOE result the residual compressive

stresses form inside material is 33.5859 MPa &

ent set form inside material is 0.004 mm.

Residual stresses can be defined as self-equilibrating

internal stresses existing in a free body which has no

external forces or constraints acting on its boundary.

These stresses arise from the elastic response of the

material to plastic deformation. Therefore, shot

peening which causes plastic deformation in the

surface layers of the material, causes residual

RELATION BETWEEN SHOT PEENING &

Shot peening is a cold work process that induces a

mpressive residual stress at the

surface of components. The objective of that

compressive layer is to offset the applied stress,

resulting in a benefit in terms of fatigue, corrosion

fatigue and fretting fatigue. In order to produce

plastic deformation, a stream of metal, glass or silica

particles (“shot”) is animated at high velocity and

projected against the surface of the metallic

component in a defined and controlled way. It is a

study of the increase in fatigue life that it is possible

to achieve with an appropriate use of shot peening.

Some of these examples are: leafs spring

increase; helicoidal springs - 1300%; gears

These are some impressive examples how much life

improvement is possible with shot peening. The

main importance of shot peening is because it acts at

the surface of components reducing the effective

stress due to the compressive layer. This layer is

only of some hundreds of microns depth, but enough

to be quite effective. Some improvement is also

attributed to the strain hardening due to plastic work

at surface. However it is also necessary to account

for the increase of surface roughness which has a

negative contribute to the fatigue improvement.

Normally it is assumed that contribute due to strain

hardening is balanced by the increase in surface

roughness. The Surface characteristics, the

nucleation of fatigue crack generally occurs at

the surface because this is the layer experiencing

greatest stresses owing to presence of micro

notches, surface flaws, changed physical and

chemical properties etc.

6. CONCLUSION: Material failures are mostly caused from fractures,



bending past the materials yield



applied to any material, tension stress and


occur in tension stress regions, never in compressi

stress regions.

By shot peening material, internal compressive

stress areas are formed which oppose these tension

stress regions and aid to prevent fractures in the

material. The compressive stress areas in a shot

peened surface are a residual effect a

profoundly increase the fatigue life

REFERENCES: 1. De Los Rios, E. R., Walley, A., Milan, M. T. and

Hammersley, G., Int. J. of Fatigue

2. Cláudio, R.A., Branco, C.M., Byrne, J.,

Conference on Experimental Mechanics, ICEM13(2007) Greece.

3. Cláudio, R.A., Silva, J.M., Branco, C.M: Byrne,

J.,"Crack Propagation Behaviour of Shot PeenedComponents at Elevated Temperature", 10as Jornadas

de Fractura (2006) Univ. do Minho.

4. Zhao, L. G.Tong, J., Vermeulen, B. and ByJ.Mechanics of Materials 33 (2001) 593.

5. Zhan, Z., A study of creep-fatigue interaction in a new

nickel-based superalloy. PhD Thesis of Portsmouth.

6. Junker H, Issler W. Pistons for high loaded direct

injection diesel engines. MAHLE TecInformation.

7. Taylo CM. Automobile engine tribology

considerations for efficiency and durability. Wear 1998;221:18.

8. Kajiwara H, Fujioka Y, Suzuki T, Negishi H. An

analytical approach for prediction of piston temperature distribution in diesel engines. JSAE Rev

2002;23(4):429–34.

ISSN2249–8974

resulting in a benefit in terms of fatigue, corrosion-

fatigue and fretting fatigue. In order to produce

stream of metal, glass or silica

particles (“shot”) is animated at high velocity and

projected against the surface of the metallic

component in a defined and controlled way. It is a

study of the increase in fatigue life that it is possible

an appropriate use of shot peening.

Some of these examples are: leafs spring - 600%

1300%; gears - 1500%.

These are some impressive examples how much life

improvement is possible with shot peening. The

peening is because it acts at

the surface of components reducing the effective

stress due to the compressive layer. This layer is

only of some hundreds of microns depth, but enough

to be quite effective. Some improvement is also

ardening due to plastic work

at surface. However it is also necessary to account

for the increase of surface roughness which has a

negative contribute to the fatigue improvement.

Normally it is assumed that contribute due to strain

the increase in surface

roughness. The Surface characteristics, the

nucleation of fatigue crack generally occurs at

the surface because this is the layer experiencing

greatest stresses owing to presence of micro-

ed physical and







material, tension stress and



By shot peening material, internal compressive

stress areas are formed which oppose these tension

stress regions and aid to prevent fractures in the

material. The compressive stress areas in a shot

peened surface are a residual effect and can

of the material.

De Los Rios, E. R., Walley, A., Milan, M. T. and Int. J. of Fatigue 17 (1995) 493.

Cláudio, R.A., Branco, C.M., Byrne, J., International

Mechanics, ICEM13,

Cláudio, R.A., Silva, J.M., Branco, C.M: Byrne,

"Crack Propagation Behaviour of Shot Peened Components at Elevated Temperature", 10as Jornadas

(2006) Univ. do Minho.

Zhao, L. G.Tong, J., Vermeulen, B. and Byrne, (2001) 593.

fatigue interaction in a new

based superalloy. PhD Thesis (2004) University

Junker H, Issler W. Pistons for high loaded direct

injection diesel engines. MAHLE Technical

Taylo CM. Automobile engine tribology – design

considerations for efficiency and durability. Wear

Kajiwara H, Fujioka Y, Suzuki T, Negishi H. An

analytical approach for prediction of piston temperature l engines. JSAE Rev

review article enhancing fatigue life of component by ... iii/ijaers vol iii... · engineering...

Documents