See discussions, stats, and author profiles for this publication at: https://www.researchgate.

net/publication/265262521

A Comparative Study of CAE and Experimental Results of Leaf Springs in

Automotive Vehicles

Article in International Journal of Engineering Science and Technology · September 2011

CITATIONS READS

28 5,315

3 authors:

Vinkel Kumar Arora M. L. Aggarwal

National Institute of Food Technology Entrepreneurship and Management YMCAUST FARIDABAD
64 PUBLICATIONS 610 CITATIONS 32 PUBLICATIONS 476 CITATIONS

SEE PROFILE SEE PROFILE

Gian Bhushan
National Institute of Technology, Kurukshetra
63 PUBLICATIONS 555 CITATIONS

SEE PROFILE

All content following this page was uploaded by Vinkel Kumar Arora on 02 June 2015.

The user has requested enhancement of the downloaded file.

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

A Comparative Study of CAE and

Experimental Results of Leaf Springs in
Automotive Vehicles
VINKEL ARORA1
Department of Mechanical Engineering
ITM University, Sector-23A, Guragaon-122017, Haryana, India
vinkelarora@gmail.com

Dr. M.L AGGARWAL2

Professor & Dean, Department of Mechanical Engineering
YMCA University of Science &Technology, Faridabad, Haryana, India

Dr. GIAN BHUSHAN3

Associate Professor, Department of Mechanical Engineering
National Institute of Technology, Kurukshetra, Haryana, India
Abstract:
The work is carried out on the front end leaf spring of a commercial vehicle. The objective of this work is to
carry out computer aided design and analysis of a conventional leaf spring, with experimental design
considerations and loading conditions. This conventional leaf spring model consists of 37 parts. The material of
the leaf spring is 65Si7.The CAD model of the leaf spring is prepared in CATIA and analyzed using ANSYS.
The CAE analysis of the leaf spring is performed for the deflection and stresses under defined loading
conditions, using ANSYS. The experimental and CAE results are compared for validation. Using CAE tools the
ideal type of contact and meshing element is determined in leaf spring model.

Keywords: Computer Aided Engineering (CAE); Leaf Spring; 65Si7; Static loading.

1. Introduction

CAE tools are widely used in the automotive industries. In fact, their use has enabled the automakers to reduce
product development cost and time while improving the safety, comfort, and durability of the vehicles they
produce. The predictive capability of CAE tools has progressed to the point where much of the design
verification is now done using computer simulation rather than physical prototype testing. CAE dependability is
based upon all proper assumptions as inputs and must identify critical inputs. Even though there have been
many advances in CAE, and it is widely used in the engineering field, physical testing is still used as a final
confirmation for subsystems due to the fact that CAE cannot predict all variables in complex assemblies,
therefore the validation of CAE results is important.
Mouleeswaran et al [1] describes static and fatigue analysis of steel leaf spring and composite multi leaf spring
made up of glass fibre reinforced polymer using life data analysis. The dimensions of an existing conventional
steel leaf spring of a light commercial vehicle are taken and are verified by design calculations. Static analysis
of 2-D model of conventional leaf spring is also performed using ANSYS 7.1 and compared with experimental
results. Hawang W et al [2] Fatigue of Composites – Fatigue Modulus Concept and Life Prediction Journal of
Composite Materials.H. A. Al-Qureshi [3] has described a single leaf, variable thickness spring of glassfiber
reinforced plastic (GFRP) with similar mechanical and geometrical properties to the multileaf steel spring, was
designed, fabricated and tested. J.J.Fuentes et al [4] in this work, the origin of premature failure analysis
procedures, including examining the leaf spring history, visual inspection of fractured specimens,
characterization of various properties and simulation tests on real components, were used. Rajendran I, S.
Vijayarangan [5] A formulation and solution technique using genetic algorithms (GA) for design optimization
of composite leaf springs is presented here. Gulur Siddaramanna et al [6] explain the automobile industry has
shown increased interest in the replacement of steel spring with fiberglass composite leaf spring due to high
strength to weight ratio. Therefore; the aim of this paper is to present a low cost fabrication of complete mono
composite leaf spring and mono composite leaf spring with bonded end joints. J.P. Hou et al [7] explained the
design evolution process of a composite leaf spring for freight rail application. Peiyong et al [8] describes that
the Leaf spring design was mainly based on simplified equations and trial-and-error methods. The simplified
equation models were limited to the three-link mechanism assumption and linear beam theory. This work

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6856

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

presents detailed finite element modeling and analysis of a two-stage multi-leaf spring, a leaf spring assembly,
and a Hotchkiss suspension using ABAQUS. Muhammad Ashiqur et al [9] describes that the tapered cantilever
beams, traditionally termed as leaf springs, undergo much larger deflections in comparison to a beam of
constant cross-section that takes their study in the domain of geometric nonlinearity. This paper studies response
of a leaf spring of parabolic shape, assumed to be made of highly elastic steel. Leaf springs industries working
with 65Si7 spring steel ,are using a very low factor of safety for weight reduction .To achieve this, experimental
testing is done to predict the spring rate, bending stress and deflection. Aggarwal M.L et al [10] evaluated the
axial fatigue strength of EN45A spring steel specimen experimentally as a function of shot peening in the
conditions used for full-scale leaf springs testing in industries. S/N curves of the specimens are correlated with
leaf springs curve in vehicles. The process is time consuming and costly. In the present work, a CAE system
predicts all variables in complex assemblies of leaf springs and the results are compared with experimental
testing.

2. Experimental Setup

The leaf spring involves two full length leaves and seven graduated leaves, four packing which are made of
65Si7 material. This conventional leaf spring model consists of 37 parts which, includes two full length leave,
seven graduated leaves. The remaining part involves four rebound clips of MS, four shim pipes of
C.D.S.T/ERW, centre nut & bolt and bush of bronze. [10]The experimental setup consists of a full scale testing
machine for leaf spring, jigs and fixture. The system consists of a hydraulic power pack to give a hydraulic
pressure of 20.6 MPa with a flow rate of 210 lpm, which is sent to a hydraulic actuator to operate at a frequency
of 0.3 Hz with the displacement specified by the alternating load. This involves applying the axial load on the
leaf spring and measure the deflection and bending stress. Supavut,Chantranuwathana, et al [11] have simulated
a leaf spring model. An experimental leaf spring model was verified by using a leaf spring test rig that can
measure vertical static deflection of leaf spring under static loading condition.

Figure 1 Full scale testing machine for leaf spring

2.1 Material

The basic requirements of a leaf spring steel is that the selected grade of steel must have sufficient harden ability
for the size involved to ensure a full martenstic structure throughout the entire leaf section. In general terms
higher alloy content is mandatory to ensure adequate harden ability when the thick leaf sections are used. The
material used for the experimental work is 65Si7 .The chemical composition of the material is shown below in
Table -1:-

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6857

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

Table 1 Chemical composition of 65Si7

GRADE C% Si% Mn % P% S% Cr%

65Si7
0.51-0.62 0.15-0.35 0.65-0.95 .035 max .035 max 0.65-0.95

2.2 Design Parameters

The design parameters are shown below in Table-2

Table 2 Design Parameters

Parameter Value
Material selected- steel 65Si7
Young’s Modulus, E 2.1* 105 N/mm2
Poisson’s Ratio 0.266

BHN 455-461

Tensile strength Ultimate 460 MPa

Tensile strength Yield 250 MPa
Leaf span 1450mm
Spring stiffness 220 N/mm
No Load Camber Angle 153°
Density 0.00000785 Kg/mm3

2.3Loading conditions

The static Loading condition of the multi leaf spring involves the fixation of one of the revolute joint and
applying displacement support at the other end of leaf spring. Loading conditions involves applying a load at the
centre of the main leaf. As per specifications the spring is drawn at flat condition, therefore the load is applied in
downward direction to achieve initial no load condition. As no load assembly camber is 153°. The loading
conditions are shown below in the Fig-2

Figure 2 Static Loading Condition

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6858

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

2.4 Experimental Load-Deflection Curve

A static load of 35KN (Full Load) and 17.5KN (Half load) is applied by a universal testing machine and the
corresponding deflection and stress values are observed. A graph between load –deflection is plotted. The plot
shown below in Fig 3 depicts a linear relationship between load and deflection for full as well as for half load.

Experimental Load-Deflection curve

40

30
35KN;158m
126kgf/m
LOAD (KN)

20

17.5KN;79mm;
48kgf/mm2
10

0
0 20 40 60 80 100 120 140 160

Figure 3 Load-deflection curve

3.0 2D- drawing of Leaf spring.

For performing the CAE of leaf spring the 2D drawing of a leaf spring is converted into a part model using
CATIA.

Figure 4- 2D drawing of leaf spring

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6859

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

3.1 CAD Modeling

CAD Modeling of any project is one of the most time consuming process. One cannot shoot directly from the
form sketches to Finite Element Model. CAD Modeling is the base of any project. Finite Element software will
consider shapes, whatever is made in CAD model. Although most of the CAD Modeling software have
capabilities of analysis to some extent and most of Finite Element software have capabilities of generating a
CAD model directly for the purpose of analysis, but their off domain capabilities are not sufficient for large and
complicated models which include many typical shapes of the product. The model of the 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. CAD modeling of the complete multi Leaf Spring structure is performed by
using CATIA V5 R17 software. CAD model of leaf spring consist of total 37 different parts which are
assembled together in assembly design to make a complete multi leaf spring model, out of all 37 parts, some
parts are similar in shape & size. The CAD model of multi leaf spring used for analysis is shown in Fig-5
below:-

Figure-5 CAD model of a leaf spring

3.2 Analysis using ANSYS

The CAD model of leaf spring is now imported into ANSYS-11 as shown below in Fig-6. All the boundary
conditions and material properties are specified as per the standards used in the practical application. The
material used for the leaf spring for analysis is structural steel, which has approximately similar isotropic
behavior and properties as compared to 65Si7.

Figure -6 CAD model imported in ANSYS

The procedure for performing analysis in ANSYS involves:

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6860

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

3.2.1. Setting contact reign-Contact conditions are formed where bodies meet. When an assembly is imported
from a CAD system, contact between various parts is automatically detected. In addition you can also set up
contact regions manually. You can transfer structural loads and heat flows across the contact boundaries and
connect the various bodies. Depending on the type of contact, the analysis can be linear or nonlinear. The
differences in the contact settings determine how the contacting bodies can move relative to one another. This is
the most common setting and has the most impact on what other settings are available. Most of these types only
apply to contact regions made up of faces only. In this assembly the No separation contact is used for the
analysis. It only applies to regions of faces. Separation of faces in contact is not allowed, but small amounts of
frictionless sliding can occur along contact faces. In general CONTA 72 and TARGET 71 are used.

Figure- 7 No separation contact

3.2.2. Specifying joints: A joint is an idealized kinematics linkage that controls the relative movement between
two bodies. Joint types are characterized by their rotational and translational degrees of freedom as being fixed
or free. In this assembly two revolute joints are used between eye and pin. The joint rotation is 27˚
corresponding to no load camber angle of 153º.

Figure -8 Revolute joint between eye and pin

3.2.3. Meshing- Meshing is the process in which your geometry is spatially discretized into elements and nodes.
This mesh along with material properties is used to mathematically represent the stiffness and mass distribution

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6861

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

of your structure. The default element size is determined based on a number of factors including the overall
model size, the proximity of other topologies, body curvature, and the complexity of the feature. If necessary,
the fineness of the mesh is adjusted up to four times (eight times for an assembly) to achieve a successful mesh.
In this assembly SOLID92 element is used for the results

Figure -9 Meshed model of leaf spring

3.2.4. Setting analysis environment: A static structural analysis determines the displacements, stresses, strains,
and forces in structures or components caused by loads that do not induce significant inertia and damping
effects. Steady loading and response conditions are assumed; that is, the loads and the structure's response are
assumed to vary slowly with respect to time. Static structure analysis takes into consideration some parameters,
like material properties, loading conditions, support conditions, joints and contacts which are to be specified as
the input to the pre processing of the analysis

3.2.5. Setting boundary conditions-The boundary conditions are applied by taking into consideration the
experimental loading conditions.

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6862

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

Figure 10 Boundary condition

3.2.6 Solution

Figure 11 Deflection at 17.5KN (half load)

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6863

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

Figure 12 Deflection at 35KN (full load)

40

30 35K
156.15
141.5kg
LOAD (KN)

20
17.5KN;
78.07mm;
53.7kgf/mm2
10

0
0 20 40 60 80 100 120 140 160

Figure 13 CAE Load-deflection curve

4. Results and Discussions

CAE analysis of the leaf spring has been done and the results are compared with the experimental results as
follows:-

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6864

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

4.1 For Static Load 35 KN

Table- 3 Experimental and CAE results for 35KN

Parameters Exp. Results CAE Results Variation

Deflection 158 mm 156.15 mm 1.17%
2 2
Bending Stress 126 Kgf/mm 141.56 Kgf/mm 12.30%
Spring rate 221.5 N/mm 224.5N/mm 1.35%

From the above Table -3 it has been observed that for the same static loading conditions, deflection in
experimental & CAE results are 158mm and 156.15mm respectively. Bending stress for experimental results
and CAE results is126kgf/mm2 and 141kgf/mm2.the variation in deflection and bending stress is 1.17%
and12.30% respectively.

4.2 For Static Load 17.5 KN

Table 4 Experimental and CAE results for17.5KN

Parameters Exp. Results CAE Results Variation

Deflection 79 mm 78.07 mm 1.1%
Spring Rate 221.5 N/mm 224.5 N/mm 1.35%
Bending Stress 48 Kgf/ mm2 53.77 Kgf/ mm2 12.02%

From the above shown Table-4, it has been observed that for the same static loading conditions, deflection in
experimental results is 78 mm and deflection for CAE results is 78.07 mm. Bending stress for experimental
results and CAE results are is 48 kgf/mm2 and 53.77kgf/mm2.the variation in deflection and bending stress is
1.17% and12.02% respectively.

5. Conclusion

This work involves design and analysis of a conventional leaf spring under static loading conditions. The 3D
model is prepared in CATIA and then CAE analysis is performed using ANSYS-11. From the results obtained
from ANSYS, many discussions have been made and it will be concluded that:

1. When the leaf spring is fully /half loaded, a variation of 1.17% in deflection is observed among the
Experimental & CAE value, which proves the validation of our CAD model and analysis.

2. At the same time bending stress for fully loaded, is increased by 12.30 % in CAE analysis as compared with
experimental and for half loaded bending stress is increased by 12.02 %. This may be observed because the
actual material is 65Si7 but for CAE analysis Structural steel is used.

3. The maximum equivalent stress is 172.5 MPa & 86.29 MPa for fully and half loaded leaf spring respectively,
which is below the Yield Stress i.e. 250MPa.Therefore the design, is safe.

4. It is concluded that when CONTA72, TARGET71 type of contact and SOLID 92 mesh element is used for
CAE analysis the results are closer to the Experimental results. Therefore the CAD model can be used for
fatigue loading under defined boundary conditions.

References

[1] Mouleeswaran Senthil kumar;sabapathy vijayarangan; (2007) “Analytical and Experimental Studies on Fatigue Life Prediction of
Steel and Composite Multi-leaf Spring for Light Passenger Vehicles Using Life Data Analysis” Materials Science,Vol.-13,No.
2, p.p 141-146.
[2] Hawang, W., Han, K. S. (1986) Fatigue of Composites – “Fatigue Modulus Concept and Life Prediction” Journal of
Composite Materials, vol-20, p.p. 154 – 165.

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6865

 Vinkel Arora et al. / International Journal of Engineering Science and Technology (IJEST)

[3] H. A. Al-Qureshi (2001), “Automobile leaf springs from composite materials”, Journal of Material Processing Technology, vol-
118,p.p 58-61.
[4] J.J.Fuentes,H.J. Agulilar,J.A.Rodriguez,E.J. Herrera (2008) , “Premature fracture in automobile leaf springs”, Engineering
Failure Anlysis,vol-16,p.p 648-655.
[5] I. Rajendran, S. Vijayarangan, (2002) “Design and Analysis of a Composite Leaf Spring” Journal of Institute of Engineers India,
vol-82 pp. 180 – 187
[6] Gulur Siddaramanna Shiva shanker, Sambagam Vijayaragan (2006), “Mono Composite Leaf Spring for Light Weight Vehicle
Design, End Joint Analysis and Testing” Materials Science, vol-12, No-3,p.p 220-225.
[7] J.P. Hou; J.Y. Cherruault, I. Nairne, G. Jeronimidis, R.M. Mayer (2004), “Evolution of the eye-end design of a composite leaf
springs for heavy axle loads”, Composite Structures vol-28,p.p 351-358.
[8] Peiyong Qin, Glenn Dentel, and Mikhail Mesh (2002), “Multi-Leaf Spring and Hotchkiss Suspension”, ABAQUS Users’
Conference.
[9] Muhammad Ashiqur Rahman*, Muhammad Tareq Siddiqui and Muhammad Arefin Kowser (2002), “Design and Non-Linear
Analysis Of A Parabolic Leaf Spring”, Journal of Mechanical Engineering vol-ME 37,p.p 47-51.
[10] Aggarwal M.L; Agarwal V.P;Khan R.A (2006)”A stress approach model for predicting fatigue life of shot peened EN45A
springs steel”, International Journal of Fatigue,Elsevier publication,vol 28, p.p 1845-1853.
[11] Supavut Chantranuwathana,Kadekheaw Panichanun, Preedanood,Prempreeda Pimply Wichienprakarn, Parig Kruo-ongarjnukool
(2009) “Experimental Verification of Leaf Spring Model by Using a Leaf Spring Test Rig” at 23rd conference of Mechanical
Engineering Network of Thailand.

ISSN : 0975-5462 Vol. 3 No. 9 September 2011 6866

View publication stats