Comparison of Performance of Two Leaf Spring Steels Used For ...

R E S E A R C H A R T II C L E
____________________________
Available ONLINE www.vsrdjournals.com
VSRD-MAP, Vol. 2 (1), 2012, 9-16
Comparison of Performance of Two Leaf Spring
Steels Used For Light Passenger Vehicle
ABSTRACT
1 Dakshraj Kothari*, 2 Rajendra Prasad Sahu and 3 Rajesh Satankar
This paper describes static and fatigue life analysis of to conventional leaf springs made of respectively SUP 9
& EN 45. These springs are comparing for maximum stress, deflection and stiffness as well as fatigue life. The
CAD models are prepared in CATIA and analyzed by using ANSYS 12.1. Computer algorithm using C++
language has been used in calculating maximum stress, deflection and stiffness. Calculated results are
comparing with FEA result. SUP 9 springs has lower value of maximum stress, deflection and stiffness in
compare to EN45 spring. Predicted fatigue life of SUP 9 spring is higher than EN45 spring. Although, market
price is much lower than Sup 9 spring.
Keywords: Fatigue Life, C++ Language, leaf Spring, Static Analysis.
1. INTRODUCTION
In order to conserve natural resources and economic, energy, weight reduction has been the main focus of
automobile manufactures. In the present scenario weight reduction can be achieved primarily by the introduction
on better material. Design specialization and better manufacturing process. [1]
Leaf spring should absorb vertical vibration and impacts due to load irregularities by means of variation in the
spring deflection show that potential energy is stored in spring as strain energy and then release slowly so,
increasing energy stored capability of a leaf spring insure a more complaint suspension system. [2]
The large vehicle needs a good suspension system that can be delivered a good ride and handling. At the same
[3, 4]
time that component need to be light weight and had an excellent of fatigue life.
Most of researches focused on improving fatigue resistance by shoot penning process, making the nucleation
1,2 Research Scholar, 3 Assistant Professor, 1,2,3 Department of Mechanical Engineering, Jabalpur Engineering College,
Jabalpur, Madhya Pradesh, INDIA. *Correspondence : dask.kothari6@gmail.com

Dakshraj Kothari et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (1), 2012
and propagation of fatigue cracks difficult. Few publication, which are listed in references attempted predictions
of fatigue life from stress approach model. [5]
The fatigue durability testing of the mechanical structure is performed extensively in all industries as one of the
part in design process. In the real application, the fatigue loading services such as stresses on a car wheel,
bending moment on stub axle of a car, stresses on rear axle passenger car etc. [6]
2. MATERIALS
Flowchart of computer algorithm for design of leaf spring
Start
Input c1, c2, P, L, T, W, E, n
σa =[σmax]/(Factor of safty)
σ=[(6PL)/(nWT 2 )
σa >= σ
δmax =(C2PL 3 )/ (EWT 3 )
δ=PL 3 /(3EI)
δmax >= δ
K=P/ δ
Stop
The materials SUP 9 steel (equal grade5160 steel) behavior characteristics related to spring performance are first
determined. The effect of component processing on these characteristics is then documented followed by a
demonstration of the application of these concepts to component fatigue life. Of particulars concern in fatigue
problems is the tendency for material properties to change as a result of cyclic deformation. These
circumstances require the determinations cyclic stress –strain relation for fatigue analysis. [7]
Many industries are manufactured steel leaf spring by EN 45 material; these materials are widely used for
production of parabolic leaf spring and conventional multi leaf spring. Leaf spring absorbed the vertical
vibrations, shocks and bumps loads (induced due to road irregularities) by means of spring deflection, so that the
potential energy stored in the leaf spring and then relieved slowly [8] . Ability to store and absorb more amount of
strain energy insures the comfortable suspension system.
Page 10 of 16

Dakshraj Kothari et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (1), 2012
3. CHEMICAL COMPOSITION (11)
SUP 9 Materials
%C %Si % Mn %S&P %Cr
0.50/0.60 0.15/0.35 0.65/0.95 0.035 0.65/0.95
EN 45 Materials
%C %Si %Mn %S %P
0.50/0.60 1.50/2.00 0.70/1.00 0.050 0.050
Design Parameter Of Steel Leaf Spring : Two leaf steel spring use in this work includes : total length (eye to
eye) ,990 mm; arc height of axle seat (camber), 127 mm; width of leaves, 50.8mm (SUP9 material) & 50mm
(EN 45 material); thickness of leaves 10mm, full bump loading 3250 N. even though the leaf spring is simply
supported at the end.
4. CAD MODELING
Stress Analysis Of Steel Leaf Spring Using Analytical and FEA
Analytical FEA
Parameters SUP 9 EN 45 SUP 9 EN 45
Load, N 3250 3250 3250 3250
Maximum stress (Mpa) 950 960 915 1004
Maximum deflection, (mm) 116.53 116.49 121 127.01
Maximum stiffness, (N/mm) 27.88 27.90 26.85 25.58
CAD Modeling any project is one of the most time consuming process. This model drawing can not shoot
directly from the sketch finite element model. Finite element software will consider shape, whatever is made in
CAD model the model of multi leaf spring structures also includes many complicated parts, which are difficult
to make by any of other CAD modeling as well as finite element software. The complete leaf spring structure
performed by using CATIA V5R16 model of leaf spring consists of total three parts which are assembled
together in an assembly design to make a complete spring model.
Load(N)
3250
3000
2750
2500
2250
2000
1750
1500
1250
1000
750
500
250
Sup9 material
En45 material
(analytical method)
0 10 20 30 40 50 60 70 80 90 100 110 120
Deflection(mm)
Fig. 1 : Load Deflection Curve for SUP 9 Materials and EN 45 Materials (Analytically Method)
Page 11 of 16

Dakshraj Kothari et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (1), 2012
Stress MPa
950
855
760
665
570
475
380
285
190
95
Sup9 material
En45 material
0 50 100 150 200 250 300 350 400 450 500
Spring Length(mm)
(analytical method)
Fig. 2 : Variation of Stress of SUPS 9 Material And EN 45 Material (Analytical Method)
Stress MPa
1045
950
855
760
665
570
475
380
285
190
Stress MPa
95
En45 material
FEM
En45 material
Anlytical
0 50 100 150 200 250 300 350 400 450 500
Spring Length(mm)
Fig. 3 : EN 45 Material Comparison of Two Methods (FEA & Analytical)
950
855
760
665
570
475
380
285
190
95
Sup9 material
Analytical
Sup9 material
FEA
0 50 100 150 200 250 300 350 400 450 500
Spring Length(mm)
Fig. 4 : SUP9 Material Comparisons of Two Methods (FEA & Analytical)
Page 12 of 16

Dakshraj Kothari et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (1), 2012
5. FATIGUE LIFE
The Material Properties of SUP 9 steel
Properties
Ultimate tensile strength, Su (Mpa) 1537
Modulus of elasticity, E (Gpa) 207
Fatigue strength coefficient, σf (Mpa) 2063
Fatigue strength exponent, b -0.08
Fatigue ductility coeffient ,ϵ’f 9.56
Fatigue ductility exponent,c -1.05
The Material Properties of EN 45 steel
Properties
Ultimate tensile strength, Su (Mpa) 621
Modulus of elasticity, E (Gpa) 204
Fatigue strength coefficient, σf (Mpa) 948
Fatigue strength exponent, b -0.092
Fatigue ductility coeffient ,ϵ’f
0.26
Fatigue ductility exponent,c -0.445
The main factors that contribute fatigue failure include number of load cycles analytically, range of stress and
mean stress experiments in each load cycle and presence of local stress concentration. Testing of leaf spring
using the regular procedure consumes a lot of time. Hence SAE [9] suggests a procedure for accelerated which
give quick result, particularly for steel leaf spring. The result of the accelerated tests can be extra plotted to get
the actual fatigue life under normal fatigue life conditions. Following the procedure out lined by the references
[9, 10] .
6. ANALYSIS USING ANSYS
The CAD model of leaf spring now imported into ANSYS 12.1 the boundary conditions and material properties
are specified as for the standards used in the practical application. The material used for the leaf spring for
analysis is structure steel, which have approximately similar isotropic behavior and properties as compared to
SUP 9 and EN 45.
7. BOUNDARY CONDITION
Model of parabolic spring was partition into small region for easier mashing process method is used patch
conforming method the boundary condition was set according to rear static load which is the front eye was
allowing on a rotational at y axis and rear eye was constrained in y and z translation and x and z rotations
alloying free x translation and y rotation. Contact from main to helper leaf also been defined helper leaf was
constant 2 nd degree of freedom to represent the clip that holds that to spring together. Finally vertical load was
applied at the center of the leaf spring.
Page 13 of 16

Dakshraj Kothari et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (1), 2012
8. CONCLUSION
SUP 9
SUP 9
FATIGUE LIFE
EN 45
EN 45
EN 45
These work involves and comparison of conventional SUP9 and EN45 material leaf spring under static loading
conditions the model is preferred of in CATIA and then analysis is perform through computer programming in
C ++ and ANSYS 12.1 from the result obtained it will be concluded that.
1. Variation of 3.82% is observed in maximum stress among analytical and FEA values for SUP9
material.
2. Variation of 4.38% is observed in maximum stress among analytical and FEA values for EN45
material.
Page 14 of 16

Dakshraj Kothari et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (1), 2012
3. Variation of 3.69% is observed in maximum deflection among analytical and FEA values for SUP9
material.
4. Variation of 8.28% is observed in maximum deflection among analytical and FEA values for EN45
material.
5. Similarly variation of 3.83% is observed in maximum stiffness among analytical and FEA values for
SUP9 material.
6. Similarly variation of 9.06% is observed in maximum stiffness among analytical and FEA values for
EN45 material.
7. It is found that value of maximum stress, maximum deflection, and stiffness are higher for EN45
material leaf spring comparison to SUP9 material leaf spring.
8. As for as compare to economically leaf spring EN45 material are better than SUP9 material.
9. FUTURE SCOPE
(a) Experimental work.
(b) Harmonic analysis with finding and compression of first five natural frequencies.
(c) Variable amplitude load.
10. REFERENCES
[1] Gulur Siddaramanna Shiva Shankar, Sambagam Vijayarangan “Mono Composite leaf spring for Light
Weight Vehicle –Design, End Joint Analysis and Testing” Journal-ISSN 1392-1320 MATERIAL
SCIENCE(MEDZIAGOTYRA) Vol12. NO 3 2006
[2] M Senthil Kumar And Vijayarangan “Static analysis and fatigue life prediction of steel and composite leaf
spring for light passenger vehicles” Journal of scientific and Industries Research vol 66,February 2007,pp
128-134
[3] F.N.Ahmad Refngah,S.Abdullah,and A Jalar ,L.B.,Chua “Life Assessment of a parabolic Spring Under
Cyclic Strain Loading” European Journal of Scientific Research ISSN 1450-216X Vol.28 No.3 (2009),
pp.351-363
[4] M Senthil Kumar ,S Vijayarangan “ Analytical and Experimental Studies on Fatigue Life Prediction of
Steel and Composite Multi-leaf Spring for Light Passenger Vehicles Using Life Data Analysis” Journal-
ISSN 1392-1320 MATERIALS SCIENCE (MEDZIAGOTYRA) Vol.13, No. 2.2007
[5] M.L Aggarwal V.P.Agrawal, R.A.Khan “ A stress approach model for predictions of fatigue life by shot
penning of EN45A spring steel” .International Journal of Fatigue 28 (2006) 1845–1853
[6] S.Abdullah,C.K.E.Niz Wan and M.Z.Nuaw “ A Study of Fatigue Data Editing using the Short-Time Fourier
Transform(STFT)” Journal-American Journal of applied Sciences 6(4):565-575,2009 ISSN 1546-9239
[7] R. W. Landgraf and R. C. Francis, “Material and Processing Effects on Fatigue Performance of Leaf
Springs”. Congress and Exposition Cobo Hall, Detroit February 26-March 2, 1979
Page 15 of 16

Dakshraj Kothari et al / VSRD International Journal of Mechanical, Auto. & Prod. Engg. Vol. 2 (1), 2012
[8] M. M. Patunkar1, D. R. Dolas2 “Modelling and Analysis of Composite Leaf Spring under the Static Load
Condition by using FEA” International Journal of Mechanical & Industrial Engineering, Volume 1 Issue 1-
2011
[9] Design and application of leaf spring, in Spring Design Manual, HS- 778, AE-11 (Society of Automotive
Engineer) 1990.
[10] ANSYS 7.1 (ANSYS Inc, New York) 1997.
[11] British & Japanese standard specifications steel hand book.
���
Page 16 of 16