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Jurnal Mekanikal
December 2010, No. 31, 46 - 61
46
STRUCTURAL PERFORMANCE ANALYSIS OF FORMULA SAE CAR
Ravinder Pal Singh1
Department of Mechanical Engineering,
Chitkara Institute of Engineering and Technology,
Rajpura, Patiala, Punjab, India
ABSTRACT
Formula SAE competitions take place every year and challenge teams of engineering
students to design and build a small single-seater racing car. Among many other key
components, chassis is an indispensable structural backbone of an automobile especially
in a racing car. Good designs allow a light, stiff and extremely safe chassis to be
produced at a reasonable manufacturing cost. The work shown in this research paper
was taken from second international participation by Chitkara FSAE team. This paper
introduces several concepts of frame’s load distributions and consequent deformation
modes. Design model was prepared using anthropometric parameters of tallest driver
(95th
percentile male), SAE rules book and previous design knowledge. Static and
dynamic load distributions were calculated analytically followed by extensive study of
various boundary conditions to be applied during diverse FEA tests. Stress distributions,
lateral displacements during static, dynamic and frequency modes were analyzed and
found considerable factor of safety as required. Torsional rigidity was calculated to be
615.98 Nm/deg which was 2.46 times the torsional rigidity of older design (250 Nm/deg).
Weight of the chassis was measured to be approximately 32 kg which was 1.125 times
less than the previous chassis (36 kg). In nutshell, ratio of percentage increase in
torsional rigidity to percentage decrease in weight was calculated to be 13.15:1.
Keyword: Chassis, FEA, Stress, Displacement, Torsional rigidity.
1.0 INTRODUCTION
Formula SAE®
Series competitions challenge teams of university undergraduate and
graduate students to conceive, design, fabricate and compete with small, formula style,
autocross vehicles [1].The basis of the competition is that a fictitious company has
contracted a group of engineers to build a small formula car which can sell in the market.
Cars are expected to perform very high in acceleration, braking, handling, aesthetics,
ergonomics, manufacturing and maintenance etc. within minimum manufacturing cost
with no compromise on driver safety. Vehicle must accommodate drivers having statures
ranging from 5th
percentile female to 95th
percentile male. The car must also satisfy safety
requirements such as side impact protection and impact attenuator [1]. Finally the cars are
judged on the basis of performances during static and dynamic events including technical
inspection, business presentation, cost, design, endurance tests etc. This research paper is
casted from the work done for second international participation in FSAE competition by
Chitkara, India team which took place in USA in June 2010. Team had already
represented country in Australia in November 2008 and also adjudged as 2nd
overall
best team in SAE Chennai, India in December 2009. So on the basis of past experience
*
Corresponding author : ravinderpal.singh@chitkara.edu.in
Jurnal Mekanikal, December 2010
47
and knowledge, whole of the car was re-modeled and re-fabricated for international
participation in USA as per the SAE rules. This time reduction of chassis weight
minimally by 10% using new materials and efficient design was decided as one of the
main objective of car development. New materials were deemed to use to widen the
structure’s strength and re-modeled the design to inculcate more driver comfort, safety,
structure triangulation and reduced inertial properties etc. The work started from the
review of technical reports of several winning universities. Their main points regarding
materials, design and load estimations were noted and discussed. Along with it,
orthographic drawings, finite element analysis (FEA) reports of existing car’s chassis
were also brainstormed and reasons of high stresses and displacements were tried to
discover. Modes of load distribution and their deformation concepts were taken care of
from various reference books. Some of the concepts are also enunciated in this paper to
help other universities while preparing the design of their car.
2.0 CHASSIS LOADING
Frame is defined as a fabricated structural assembly that supports all functional vehicle
systems. This assembly may be a single welded structure, multiple welded structures or a
combination of composite and welded structures [1]. Depending upon application of loads
and their direction, chassis is deformed in respective manner briefed as follows [2]:
i. Longitudinal Torsion
ii. Vertical Bending
iii. Lateral Bending
iv. Horizontal Lozenging
2.1) Longitudinal Torsion
Figure 1: Longitudinal Torsion [3]
Application of equal and opposite forces act at a certain distance from an axis tends to
rotate the body about the same axis. Automobiles also experience torsion while moving
on road subjected to forces of different magnitudes acting on one or two oppositely
opposed corners of the cars as shown in Figure 1. The frame can be thought as a torsion
spring connecting the two ends where suspension loads act [2]. Torsional loading and
resultant momentary elastic or permanent plastic deformation and subsequent unwanted
deflections of suspension springs can affect the handling as well as performance of car.
The resistance to torsional deformation is called as stiffness and it is expressed in
Nm/degree in SI units. Torsional rigidity is a foremost and primary determinant of frame
performance of cars.
Jurnal Mekanikal, December 2010
48
2.2 Vertical Bending
Figure 2: Vertical Bending [3]
Weight of driver, engine, drive-train, radiator and shell etc. under an effect of
gravity produce sag in the frame as shown in Figure 2. Frame is assumed to act as simply
supported beam and four wheels as supports tend to produce reactions vertically upward
at the axles. Vertical dynamic forces due to acceleration/deceleration further increase the
vertical deflections, hence stresses in chassis.
2.3 Lateral Bending
Lateral bending deformation occurs mainly due to the centrifugal forces caused during
cornering and wind forces to some extent. Lateral forces act along the length of chassis
and is resisted by axles, tires and frame members viz. hoops, side impact members and
diagonal hoops etc as shown in Figure 3.
Figure 3: Lateral Bending [3]
2.4 Horizontal Lozenging
This deformation is caused by forward and backward forces applied at opposite wheels
[3]. These forces may be caused by vertical variations in the pavement or the reaction
from the road driving the car forward. These forces tend to distort the frame into a
parallelogram shape as shown in the Figure 4. The magnitude of these loads changes with
the operating mode of the car.
Jurnal Mekanikal, December 2010
49
Figure 4: Horizontal Lozenging [3]
It is generally thought that if torsional and vertical bending stiffness is
satisfactory, then the chassis structure is expected to perform well. But torsional stiffness
is given more weight-age as the total cornering traction is the function of lateral weight
transfers [2].
3.0 LOAD ESTIMATION
After literature review, it was brought in view that normally FSAE car parts are designed
to withstand 3.5 g bump, 1.5 g braking and 1.5 g lateral forces [4]. These loads have to be
considered individually and combined. Determination of magnitudes, types and center of
gravity (cg) of loads is obligatory for optimum frame structure which is likewise a
repetitive task. An understanding of different loads in respective directions is shown in
Figure 5 in reference to Formula cars.
Figure 5: Forces acting on a formula one car [7]
To estimate an individual and total load of various components and car as a
whole, a block diagram showing estimated position of components was created as shown
in Figure 6. This schematic diagram simplified the understanding of different loads and
their respective positions.
Jurnal Mekanikal, December 2010
50
Figure 6: Car side view with all parts
Table 1: Approximate masses of main components
To consider mass of other components also, estimated mass of 250 kg was
considered instead of 215 kg. This includes mass of wishbones (front and rear), petrol
tank as well as radiator etc. Different forces viz. cornering, acceleration forces were
computed from masses using Newton’s second law of motion.
4.0 MATERIAL SELECTION
After load approximation, next step was the selection of material to construct a chassis.
Availability is one of the factors which dominate the material selection process. Working
on this single aspect, list of different desirable and available materials was prepared. Steel
and aluminum alloys are always the choice of most of the teams. After reviewing
mechanical properties, availability, cost and other significant factors, following material
was selected.
Table 2: Mechanical Properties of Chassis Material
C.G Components Mass (kg)
1 Driver 80
2 Engine 70
3 Drive-train 20
4 Steering 10
5 Battery 03
6 Chassis
32 (Later calculated from
mass properties)
Total 215
STEEL GRADE: IS 3074
S.No. Properties Values
1 Young’s modulus 2e+011 N/m2
2 Poisson ratio 0.266
3 Density 7860 kg/m3
4 Yield Strength 3.73e+008 N/m2
Jurnal Mekanikal, December 2010
51
5.0 SOLID MODELLING
After load approximation and material selection, preparing CAD model of chassis was a
next step. Based on past design knowledge, anthropometric data of tallest driver was
taken and previous 3-D chassis model was modified. CATIA V5 software tool was used
for designing as well as Finite Element analyses (FEA). SAE rules were taken care of
while designing. Mankin was created in same software on the basis of anthropometric
data and checked it under different realistic conditions to suit chassis design. It was a two
way process as firstly creating model and checking clashes with mankin and vice versa
was a repetitive task. After much iteration, CAD model was proposed as shown in Figure
7.
Figure 7: 3D Chassis Structure
Whole of the chassis model was made up of round hollow cross section tubes of
IS 3074 steel throughout chassis. Tubes of two different sizes were used in the design.
Whole of the structure comprises of tube 1” (outer diameter) and 1.6 mm wall thickness
except main hoop and front hoop. Both (front and main) hoops are made up of 1” (Outer
diameter) and 2.5 mm wall thickness as shown in red color in Figure 7. Mass properties
showed the mass of chassis was to be 32 kg.
6.0 FINITE ELEMENT ANALYSIS (FEA)
Structure designing was followed by its testing and consequent validity. To determine the
stiffness of a proposed frame design before construction, finite element analysis could
serve the purpose. While the process of solving Finite Element problems is a science,
creating the models is quite an art [2].
Conventionally in FEA, the frame is subdivided into elements. Nodes are placed
where tubes of frame join. There are many types of elements possible for a structure and
every choice the analyst makes can affect the results. The number, orientation and size of
elements as well as loads and boundary conditions are all critical to obtain meaningful
values of chassis stiffness [2]. Beam elements are normally used to represent tubes. The
assumption made in using beam elements is that the welded tubes have stiffness in
bending and torsion [2]. If a truss or link elements were used, the assumption being made
would be that the connections do not offer substantial resistance to bending or torsion [2].
Another aspect of beam elements is the possibility of including transverse shearing
effects.
Jurnal Mekanikal, December 2010
52
While modeling the stiffness contribution from each part of the frame, method to
apply the loads and constrain the frame plays significant role for an accurate analysis.
Accurate analysis means to predict the stiffness of frame close to actual stiffness as the
frame operates in real conditions. The problem here has normally been how to constrain
and load a frame, so to receive multiple load inputs from a suspension, while it has been
separated from that suspension and many other such problems. For practical reasons, it is
recommended that the load on the chassis frame, including its own weight should be
applied at the joints (nodes) of structural members. These point loads were statistically
equivalent to the actual distributed load carried by the vehicle [5].
Another thing to consider while modeling the frame is how to represent an
engine. For the engine, the first step is to locate a node at each position where there is an
engine mount. These mounts then need to be connected to the frame by an element.
Engine was assumed to be very stiff relative to the car frame. Thus assuming an engine to
be infinitely rigid, it can be modeled by connecting each engine mount node to every
other engine mount node by a beam element of high stiffness.
One of the few things that could be done to reduce the number of elements was to
replace the engine model with a solid block of aluminum connected to the frame by the
engine mounts. As most of the parts of an engine are made up of aluminum alloy, so it
was assumed that an engine as a whole will behave in the similar manner as can be
behaved by a solid block of same material. This greatly reduced the complexity of the
meshed model and produced satisfactory results. Various elements used in the present
paper to mesh the different parts of chassis are shown in Table 3.
Table 3: Elements used for meshing
Applying static loads on model is comparatively easier than ascertaining a frequency
range at which frame needs to be tested. In idle conditions, the speed range of Honda
VFR engine which was used in this project is 12 to 14 revolutions per second. This
translates into excitation frequency range of 13-15 Hz. The excitation from transmission
is about 0-100 Hz. [6]. The main excitation is at low speeds, when the vehicle is in the
first gear. At higher gear or speed, the excitation to the chassis is much less [5]. The
natural frequency of the vehicle chassis should not coincide with the frequency range of
the axles because this can cause resonance which may give rise to high deflection and
stresses and poor ride comfort. Excitation from the road is the main disturbance to the
chassis when the vehicle travels along the road. In practice, the road excitation has typical
values varying from 0 to 100 Hz [5]. At high cruising speed, the excitation is about 9000
rpm or 150 Hz. Various boundary conditions and force/moments applied during various
FEA tests are enunciated in the Table 4
S. No. Element Purpose
1 Linear Tetrahedral Round hollow tubes of frame,
2 Linear Tetrahedral Engine and suspension mounts
Jurnal Mekanikal, December 2010
53
Table 4: Boundary conditions used during various tests
7.0) RESULTS AND DISCUSSION
7.1 Static Shear
In static shear, it is assumed that frame acts like a cantilever beam and its one end is made
fixed and other end is subjected to vertical downward force as shown in Figure 8. Shear
force and bending moment diagrams were drawn and maximum bending moment was
calculated analytically at the fixed end of frame. Blue color shows clamping and yellow
color shows vertically downward forces acting at the front bulkhead as shown in figure 8.
The rear suspension mounts were clamped in this case. Force of 1440 N was applied at
the bulkhead which is the sum of weight of impact attenuator, driver legs and steering
weight etc. Maximum bending moment of 2081 Nm calculated to act about the Y-axis.
Figure 8: Boundary conditions during static shear
S.
No.
Test Boundary condition Force Moments
1
Static Shear
Clamp- rear
suspension mounts Downward force at front
bulkhead
2
Static overall
bending
Clamp- front and rear
suspension mounts
Uniformly distributed
loading
3
Static
torsional
loading
Clamp- rear
suspension mounts
Clockwise Moment at
bulkhead side
4
Acceleration
Analysis
Clamp- front and rear
suspension mounts
Force applied towards
rear
5
Frequency
analysis
Clamp- front and rear
suspension mounts
Frequency range- 69.12
Hz to 204.79 Hz
Point Load
Clamp
Jurnal Mekanikal, December 2010
54
Figure 9: Von Misses stresses during static shearing
Results showed that maximum Von Misses stress was to be 1.17x108
N/m2
.
Maximum strain energy (Proof resilience) capability of 4.345 Joules was observed from
this analysis. Elements in red color show the maximum stress areas and corresponding
maximum stress is shown in red color in stress tree in the left of Figure 9.
7.2 Static Vertical Bending
Figure 10: Boundary conditions during static vertical bending
Both front and rear suspension mounts were clamped and vertically downward
point forces of 1550 N were applied equally in driver cabin, engine bay and drive-train
section as shown in Figure 10. Frame is assumed to be a fixed beam with both ends
clamped and subjected to point shear forces acting downward. Bending moment and
shear force diagrams were drawn and values were calculated analytically. Blue color
shows the clamping restraint and yellow color shows the point forces acting downward.
Clamp
Point Load
Jurnal Mekanikal, December 2010
55
Figure 11: Von Misses stresses during static vertical bending
Maximum bending moment of 4.482 Nm about Y-axis with maximum vertical
downward displacement of 0.369 mm was noted. Maximum Von Misses stress of
2.77x107
N/m2
was observed at one or two places shown in red color in Figure 11. Most
of the areas throughout chassis were observed to be subjected to minimum value of stress
as shown in stress distribution tree in Figure 11. Maximum deflection was observed in the
center of driver cabin floor and noted down its position to strengthen it. Strain energy of
0.087 J was noted.
7.3 Lateral Bending
Figure 12: Application of lateral forces acting on roll hoop in driver cabin
Clamping restraint was applied at both front and rear suspension mounts as in
previous cases. Lateral cornering point forces of 2325 N (Sum of engine and driver
forces) was applied on side impact bracings of driver cabin, engine mounts and drive-
train side braces. Yellow color arrows are depicted application of forces acting outwards.
Figure 13: Von Mises stresses during lateral bending
Jurnal Mekanikal, December 2010
56
Maximum principal stress of 1.48x107
N/m2
(Figure 13) was observed with
maximum translational displacement of 0.142 mm after post processing which are within
the permissible limit of stresses. Strain energy of 0.015 J was observed.
7.4 Static Torsional Loading
Figure 14: Boundary conditions during torsion test
Torsional rigidity test is one of the most important tests which validates/rejects
the chassis structure. In this case, chassis is assumed to act as a cantilever with one end
fixed and other end free and subjected to torque about its longitudinal axis as shown in
Figure 14. A chassis should be able to resist angular deformation and resultant shear
stresses. Again clamping is shown by the blue color and clockwise torque is shown in
yellow color. Clockwise moment 316 Nm about longitudinal X-axis was applied.
Figure 15: Von Misses stresses during torsion
Uniform stress of 5.02x107
N/m2
(Figure 15) was observed with maximum stress
of 01x108
N/m2
at few points as shown in red color. Maximum translational displacement
of 2.24 mm was noted in front bulkhead supports and lowers side impact members.
Almost all other areas were found to be safe with approximately no stress and
displacement. Strain energy of 2.303 J was observed from the results.
Clamp Torque
Jurnal Mekanikal, December 2010
57
7.5 Accelaration Test
Figure 16: Boundary conditions during acceleration test
Due to inertia effect, acceleration forces tend to act in opposite direction to the
motion of body. Forces due to acceleration were calculated considering masses of driver
(80 kg) and engine (70 kg) respectively. Engine acceleration of 6.61 m/s2
was taken from
the manual of Honda VFR engine to be used in this vehicle and calculated an acceleration
force using Newton second law of motion (F=m*a). Total acceleration force of 992.2 N
was applied on the structure in backward direction shown in thick yellow color arrows in
Figure 16. Load of 1550 N was applied throughout in driver cabin, engine bay and drive-
train section as to simulate realistic conditions.
Figure 17: Von Misses stresses during acceleration
Chassis experienced maximum bending moment of 171.4 Nm about Y-axis
(anticlockwise) at cross-sections shown in red color. Whole of the chassis was found to
be within permissible stress limit with maximum stress was observed to be 2.67x107
N/m2
as shown in red color in Figure 17. Strain energy of 0.102 J was given by the FEA results.
7.6 Frequency Test
Engine is a source of vibrations in any vehicle. Chassis as with any structure has an
infinite number of resonant frequencies [8]. A resonant frequency, also known as natural
frequency, is a preferred frequency of vibration and results when the inertial and stiffness
forces cancel. For each of the infinite natural frequencies of vibrations which exist, a
different shape that the chassis deform during vibration also exists [8]. The deformed
shape that chassis will vibrate is also known as modes of vibration [8]. So, frequency
Acceleration
Forces
Clamp
Point Load
Jurnal Mekanikal, December 2010
58
analysis is mandatory to check structural behavior during a set range of
frequencies. Indirect actuated suspension system was used at front and rear of the vehicle.
A component called as rocker used to transmit the forces and motion from the tires
through tie rods to springs of shock absorbers. The rocker was clamped and hinged with
the chassis. Hence chassis was clamped at both front and rear due to suspension
construction with no external load applied. Only structural mass was taken into account
for analysis as shown in Figure 18.
Figure 18: Boundary conditions during frequency test
Figure 19: Von Misses stresses and modal analysis during frequency test
Software checked the structure from 69 Hz to 205 Hz automatically. No stresses
were observed below 156.86 Hz and chassis was found to be safe (high factor of safety).
At frequency of 156.86 Hz, 5.53x1010
N/m2
(elements shown in red color in figure 19)
was observed to be more than the permissible stress of material (3.73e+008 N/m2
).
Maximum translational displacement of 562 mm was noted down at this frequency. Of
the infinite modes of vibration that exist on the frame structure, only the lowest
frequencies are of interest [8]. The lower modes of vibration maximize the kinetic energy
and maximize the strain energy, while the high modes act in an opposite manner [8]. This
means that the soft and stiff parts of chassis will be apparent in the low and high modes of
vibrations respectively. Therefore it is worth to note that at lower frequencies (below
156.86 Hz), no considerable stress was found and chassis was assumed to be safe with
considerable factor of safety. The most affected region was the main hoop and main hoop
bracings with maximum stress and displacement.
Clamp
Jurnal Mekanikal, December 2010
59
Table 5: Von Misses stresses and Factor of Safety
S. No.
Test Von Misses Stress (N/m2
)
FOS
1
Static Shear 1.17*108 3.18
2
Static overall bending 2.27*107 16.41
3
Lateral Bending 1.48*107 25.25
4
Static torsional loading 1*108 3.73
5
Acceleration test 2.67x107 13.97
6
Frequency analysis 5.53*1010
(156.86 Hz) 00
By dividing yield stress (3.73e+008 N/m2
) of chassis material with maximum
Von Misses stresses induced in frame, factor of safety was calculated as shown in table 5.
Considerable factor of safety was observed in all static (shear, bending and torsional test)
boundary conditions. Chassis was found to exhibit high factor of safety during dynamic
viz. acceleration test. Frame behavior was analyzed in frequency range of 69.12 to
204.793 Hz and observed maximum deformation (stress and deflection), more than the
yield stress of frame material at a frequency of 156.86 Hz. Below 156.86 Hz, chassis was
observed to be safe and experienced stress very small than the strength of material.
So, 156.86 Hz can be considered as threshold value for proposed chassis. Chassis was
found to have highest factor of safety in lateral bending (25.25) followed by static
bending (16.41) and dynamic acceleration test (13.97) respectively.
Factor of safety was noted to be 3.73 in torsional loading mode which represents
the stiff nature of frame. An ideal chassis is one that has high stiffness; with low weight
and cost. If there is considerable twisting, the chassis vibrates, complicating the system of
the vehicle and sacrificing the handling performance [8]. The chassis that flexes is more
susceptible to fatigue and subsequent failure, and “suspension compliance may be
increased or decreased by bending or twisting of the chassis [9]. Also if a chassis is well
designed to handle torsional loads, bending should not be an issue [9]. The torsional
rigidity can be calculated by finding the torque applied to the frame and dividing by the
angular deflection. The actual calculation is done as follows, with the figure 20 showing a
view looking from the front of the suspension bay.
K=R/Ө (1)
K= (F*L)/tan-1[(Δy1+Δy2)/2L] (2)
where K = Torsional Stiffness
T = Torque
Ө = Angular deformation
F = Shear Force
y1, y2= Translational displacement
Jurnal Mekanikal, December 2010
60
Figure 20: Front suspension bay testing loads
Force applied (F) = 1264 Nm
y1= y2 = 2.24 mm = 0.00224m
L= 0.250 m
K= (1264*0.250)/tan-1
[(0.00224+0.00224)/2*0.250] = 615.98 Nm/deg
Torsional rigidity of previous design was calculated to be 250 Nm/deg [11] which
was an indicator of moderate stiffness and hence needed to be improved following
changes in design and material. The torsional stiffness of present design was calculated to
be 615.98 Nm/deg as calculated above which shows significant increase in stiffness in
present model by 2.46 times than the older design. Deakin et al concluded that a Formula
SAE racer, which has a total suspension roll stiffness of 500–1500 Nm/degree, requires
chassis stiffness between 300 and 1000 Nm/degree to enable the handling to be tuned
[10]. Torsional rigidity of University of Southern Queensland (USQ) 2004 SAE car
experienced torsional rigidity of 214 Nm/degree and appeared to drive reasonably well,
apart from the under-steer and other minor construction matters [10]. Increase in chassis
stiffness in present work owes to good structural design having more triangulation and of
course higher yield strength of IS 3074.
8.0 CONCLUSIONS
The dominant characteristic of structural behavior viz. torsional rigidity increased by 2.46
times with an average value of 615.98 Nm/deg without compromising on weight. Weight
of chassis was observed to decrease by 11.11% with approximate value of 32 kg as
compared to weight of older chassis frame. Stress distributions were found to be even and
less than the yield strength of material (3.73e+008 N/m2
). Chassis was found to be safe
significantly in static (bending) and dynamic (acceleration) modes with stress values
noticeably less than the yield strength. Critical value of stress was found to be 5.53x1010
N/m2
at a frequency of 156.86 Hz. Although below this frequency, chassis was found to
be safe and exhibited almost no stress. Dynamometer testing of previous car at
approximate 9000 rpm with speed of 90 km/h, the maximum vibration frequency was
noted to be not more than 100 Hz. So, it was expected that vibration range under same
conditions will either remain same or decrease for the present design model. Hence
chassis was expected to perform well in motion also.
Jurnal Mekanikal, December 2010
61
REFERENCES
1. 2010 Formula SAE® Rules, SAE International, USA.
2. Riley, W.B., George, A.R., 2002. Design, Analysis and Testing of Formula SAE
Race Car Chassis, SAE paper 2002-01-3300, Motorsports Engineering
Conference and proceedings.
3. Horizontal Lozenging, Retrieved from http://rileydynamics.com/m-
eng%20web/sec2.htm. on 17 June, 2010 1:10:37 GMT.
4. Milliken, William F., Milliken, Douglas L., 1997. Race Car Vehicle Dynamics,
Society of Automotive Engineers.
5. Fui, T.H., Rahman, R.A., 2007. Statics and Dynamics Structural Analysis of a 4.5
Ton Structural Analysis, Jurnal Mekanikal, 24, 56-67.
6. Johansson, I., Edlund, S., 1993. Optimization of Vehicle Dynamics in Trucks by
Use of Full Vehicle FE-Models, Göteborg, Sweden, Department of Vehicle
Dynamics & Chassis Technology, Volvo Truck Corporation.
7. O’Neill, A.M., 2005. Chassis Design for SAE Racer, University of Southern
Queensland.
8. Ryan, A. 2008. Formula SAE Race Car Analysis: Simulation and Testing of the
Engine as a structural member, Retrieved from
http://www.fisita.com/students/congress/sc08papers/f2008sc005.pdf on 06 June,
2010 03:40:37 GMT.
9. William F., Miliken and Douglas L. 1995. Race Car Vehicle Dynamics, Society
of Automotive Engineers Inc., 673-667.
10. Deakin, A., Crolla, D., Ramirez, JP, and Hanley, R. 2004. The Effect of Chassis
Stiffening on Race Car Handling Balance, Racing Chassis and Suspension
Design, Society of Automotive Engineers, Warrendale, PA.
11. Singh, R.P. and Kaur, T., 2009. Designing and fabrication of formula SAE
vehicle (Chassis), National Conference on Innovative developments in
engineering applications, Bhai Gurdas Institute of Engineering and Technology,
Sangrur, Punjab, India, 265-271.

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5)structural performance analysis of formula sae car

  • 1. Jurnal Mekanikal December 2010, No. 31, 46 - 61 46 STRUCTURAL PERFORMANCE ANALYSIS OF FORMULA SAE CAR Ravinder Pal Singh1 Department of Mechanical Engineering, Chitkara Institute of Engineering and Technology, Rajpura, Patiala, Punjab, India ABSTRACT Formula SAE competitions take place every year and challenge teams of engineering students to design and build a small single-seater racing car. Among many other key components, chassis is an indispensable structural backbone of an automobile especially in a racing car. Good designs allow a light, stiff and extremely safe chassis to be produced at a reasonable manufacturing cost. The work shown in this research paper was taken from second international participation by Chitkara FSAE team. This paper introduces several concepts of frame’s load distributions and consequent deformation modes. Design model was prepared using anthropometric parameters of tallest driver (95th percentile male), SAE rules book and previous design knowledge. Static and dynamic load distributions were calculated analytically followed by extensive study of various boundary conditions to be applied during diverse FEA tests. Stress distributions, lateral displacements during static, dynamic and frequency modes were analyzed and found considerable factor of safety as required. Torsional rigidity was calculated to be 615.98 Nm/deg which was 2.46 times the torsional rigidity of older design (250 Nm/deg). Weight of the chassis was measured to be approximately 32 kg which was 1.125 times less than the previous chassis (36 kg). In nutshell, ratio of percentage increase in torsional rigidity to percentage decrease in weight was calculated to be 13.15:1. Keyword: Chassis, FEA, Stress, Displacement, Torsional rigidity. 1.0 INTRODUCTION Formula SAE® Series competitions challenge teams of university undergraduate and graduate students to conceive, design, fabricate and compete with small, formula style, autocross vehicles [1].The basis of the competition is that a fictitious company has contracted a group of engineers to build a small formula car which can sell in the market. Cars are expected to perform very high in acceleration, braking, handling, aesthetics, ergonomics, manufacturing and maintenance etc. within minimum manufacturing cost with no compromise on driver safety. Vehicle must accommodate drivers having statures ranging from 5th percentile female to 95th percentile male. The car must also satisfy safety requirements such as side impact protection and impact attenuator [1]. Finally the cars are judged on the basis of performances during static and dynamic events including technical inspection, business presentation, cost, design, endurance tests etc. This research paper is casted from the work done for second international participation in FSAE competition by Chitkara, India team which took place in USA in June 2010. Team had already represented country in Australia in November 2008 and also adjudged as 2nd overall best team in SAE Chennai, India in December 2009. So on the basis of past experience * Corresponding author : ravinderpal.singh@chitkara.edu.in
  • 2. Jurnal Mekanikal, December 2010 47 and knowledge, whole of the car was re-modeled and re-fabricated for international participation in USA as per the SAE rules. This time reduction of chassis weight minimally by 10% using new materials and efficient design was decided as one of the main objective of car development. New materials were deemed to use to widen the structure’s strength and re-modeled the design to inculcate more driver comfort, safety, structure triangulation and reduced inertial properties etc. The work started from the review of technical reports of several winning universities. Their main points regarding materials, design and load estimations were noted and discussed. Along with it, orthographic drawings, finite element analysis (FEA) reports of existing car’s chassis were also brainstormed and reasons of high stresses and displacements were tried to discover. Modes of load distribution and their deformation concepts were taken care of from various reference books. Some of the concepts are also enunciated in this paper to help other universities while preparing the design of their car. 2.0 CHASSIS LOADING Frame is defined as a fabricated structural assembly that supports all functional vehicle systems. This assembly may be a single welded structure, multiple welded structures or a combination of composite and welded structures [1]. Depending upon application of loads and their direction, chassis is deformed in respective manner briefed as follows [2]: i. Longitudinal Torsion ii. Vertical Bending iii. Lateral Bending iv. Horizontal Lozenging 2.1) Longitudinal Torsion Figure 1: Longitudinal Torsion [3] Application of equal and opposite forces act at a certain distance from an axis tends to rotate the body about the same axis. Automobiles also experience torsion while moving on road subjected to forces of different magnitudes acting on one or two oppositely opposed corners of the cars as shown in Figure 1. The frame can be thought as a torsion spring connecting the two ends where suspension loads act [2]. Torsional loading and resultant momentary elastic or permanent plastic deformation and subsequent unwanted deflections of suspension springs can affect the handling as well as performance of car. The resistance to torsional deformation is called as stiffness and it is expressed in Nm/degree in SI units. Torsional rigidity is a foremost and primary determinant of frame performance of cars.
  • 3. Jurnal Mekanikal, December 2010 48 2.2 Vertical Bending Figure 2: Vertical Bending [3] Weight of driver, engine, drive-train, radiator and shell etc. under an effect of gravity produce sag in the frame as shown in Figure 2. Frame is assumed to act as simply supported beam and four wheels as supports tend to produce reactions vertically upward at the axles. Vertical dynamic forces due to acceleration/deceleration further increase the vertical deflections, hence stresses in chassis. 2.3 Lateral Bending Lateral bending deformation occurs mainly due to the centrifugal forces caused during cornering and wind forces to some extent. Lateral forces act along the length of chassis and is resisted by axles, tires and frame members viz. hoops, side impact members and diagonal hoops etc as shown in Figure 3. Figure 3: Lateral Bending [3] 2.4 Horizontal Lozenging This deformation is caused by forward and backward forces applied at opposite wheels [3]. These forces may be caused by vertical variations in the pavement or the reaction from the road driving the car forward. These forces tend to distort the frame into a parallelogram shape as shown in the Figure 4. The magnitude of these loads changes with the operating mode of the car.
  • 4. Jurnal Mekanikal, December 2010 49 Figure 4: Horizontal Lozenging [3] It is generally thought that if torsional and vertical bending stiffness is satisfactory, then the chassis structure is expected to perform well. But torsional stiffness is given more weight-age as the total cornering traction is the function of lateral weight transfers [2]. 3.0 LOAD ESTIMATION After literature review, it was brought in view that normally FSAE car parts are designed to withstand 3.5 g bump, 1.5 g braking and 1.5 g lateral forces [4]. These loads have to be considered individually and combined. Determination of magnitudes, types and center of gravity (cg) of loads is obligatory for optimum frame structure which is likewise a repetitive task. An understanding of different loads in respective directions is shown in Figure 5 in reference to Formula cars. Figure 5: Forces acting on a formula one car [7] To estimate an individual and total load of various components and car as a whole, a block diagram showing estimated position of components was created as shown in Figure 6. This schematic diagram simplified the understanding of different loads and their respective positions.
  • 5. Jurnal Mekanikal, December 2010 50 Figure 6: Car side view with all parts Table 1: Approximate masses of main components To consider mass of other components also, estimated mass of 250 kg was considered instead of 215 kg. This includes mass of wishbones (front and rear), petrol tank as well as radiator etc. Different forces viz. cornering, acceleration forces were computed from masses using Newton’s second law of motion. 4.0 MATERIAL SELECTION After load approximation, next step was the selection of material to construct a chassis. Availability is one of the factors which dominate the material selection process. Working on this single aspect, list of different desirable and available materials was prepared. Steel and aluminum alloys are always the choice of most of the teams. After reviewing mechanical properties, availability, cost and other significant factors, following material was selected. Table 2: Mechanical Properties of Chassis Material C.G Components Mass (kg) 1 Driver 80 2 Engine 70 3 Drive-train 20 4 Steering 10 5 Battery 03 6 Chassis 32 (Later calculated from mass properties) Total 215 STEEL GRADE: IS 3074 S.No. Properties Values 1 Young’s modulus 2e+011 N/m2 2 Poisson ratio 0.266 3 Density 7860 kg/m3 4 Yield Strength 3.73e+008 N/m2
  • 6. Jurnal Mekanikal, December 2010 51 5.0 SOLID MODELLING After load approximation and material selection, preparing CAD model of chassis was a next step. Based on past design knowledge, anthropometric data of tallest driver was taken and previous 3-D chassis model was modified. CATIA V5 software tool was used for designing as well as Finite Element analyses (FEA). SAE rules were taken care of while designing. Mankin was created in same software on the basis of anthropometric data and checked it under different realistic conditions to suit chassis design. It was a two way process as firstly creating model and checking clashes with mankin and vice versa was a repetitive task. After much iteration, CAD model was proposed as shown in Figure 7. Figure 7: 3D Chassis Structure Whole of the chassis model was made up of round hollow cross section tubes of IS 3074 steel throughout chassis. Tubes of two different sizes were used in the design. Whole of the structure comprises of tube 1” (outer diameter) and 1.6 mm wall thickness except main hoop and front hoop. Both (front and main) hoops are made up of 1” (Outer diameter) and 2.5 mm wall thickness as shown in red color in Figure 7. Mass properties showed the mass of chassis was to be 32 kg. 6.0 FINITE ELEMENT ANALYSIS (FEA) Structure designing was followed by its testing and consequent validity. To determine the stiffness of a proposed frame design before construction, finite element analysis could serve the purpose. While the process of solving Finite Element problems is a science, creating the models is quite an art [2]. Conventionally in FEA, the frame is subdivided into elements. Nodes are placed where tubes of frame join. There are many types of elements possible for a structure and every choice the analyst makes can affect the results. The number, orientation and size of elements as well as loads and boundary conditions are all critical to obtain meaningful values of chassis stiffness [2]. Beam elements are normally used to represent tubes. The assumption made in using beam elements is that the welded tubes have stiffness in bending and torsion [2]. If a truss or link elements were used, the assumption being made would be that the connections do not offer substantial resistance to bending or torsion [2]. Another aspect of beam elements is the possibility of including transverse shearing effects.
  • 7. Jurnal Mekanikal, December 2010 52 While modeling the stiffness contribution from each part of the frame, method to apply the loads and constrain the frame plays significant role for an accurate analysis. Accurate analysis means to predict the stiffness of frame close to actual stiffness as the frame operates in real conditions. The problem here has normally been how to constrain and load a frame, so to receive multiple load inputs from a suspension, while it has been separated from that suspension and many other such problems. For practical reasons, it is recommended that the load on the chassis frame, including its own weight should be applied at the joints (nodes) of structural members. These point loads were statistically equivalent to the actual distributed load carried by the vehicle [5]. Another thing to consider while modeling the frame is how to represent an engine. For the engine, the first step is to locate a node at each position where there is an engine mount. These mounts then need to be connected to the frame by an element. Engine was assumed to be very stiff relative to the car frame. Thus assuming an engine to be infinitely rigid, it can be modeled by connecting each engine mount node to every other engine mount node by a beam element of high stiffness. One of the few things that could be done to reduce the number of elements was to replace the engine model with a solid block of aluminum connected to the frame by the engine mounts. As most of the parts of an engine are made up of aluminum alloy, so it was assumed that an engine as a whole will behave in the similar manner as can be behaved by a solid block of same material. This greatly reduced the complexity of the meshed model and produced satisfactory results. Various elements used in the present paper to mesh the different parts of chassis are shown in Table 3. Table 3: Elements used for meshing Applying static loads on model is comparatively easier than ascertaining a frequency range at which frame needs to be tested. In idle conditions, the speed range of Honda VFR engine which was used in this project is 12 to 14 revolutions per second. This translates into excitation frequency range of 13-15 Hz. The excitation from transmission is about 0-100 Hz. [6]. The main excitation is at low speeds, when the vehicle is in the first gear. At higher gear or speed, the excitation to the chassis is much less [5]. The natural frequency of the vehicle chassis should not coincide with the frequency range of the axles because this can cause resonance which may give rise to high deflection and stresses and poor ride comfort. Excitation from the road is the main disturbance to the chassis when the vehicle travels along the road. In practice, the road excitation has typical values varying from 0 to 100 Hz [5]. At high cruising speed, the excitation is about 9000 rpm or 150 Hz. Various boundary conditions and force/moments applied during various FEA tests are enunciated in the Table 4 S. No. Element Purpose 1 Linear Tetrahedral Round hollow tubes of frame, 2 Linear Tetrahedral Engine and suspension mounts
  • 8. Jurnal Mekanikal, December 2010 53 Table 4: Boundary conditions used during various tests 7.0) RESULTS AND DISCUSSION 7.1 Static Shear In static shear, it is assumed that frame acts like a cantilever beam and its one end is made fixed and other end is subjected to vertical downward force as shown in Figure 8. Shear force and bending moment diagrams were drawn and maximum bending moment was calculated analytically at the fixed end of frame. Blue color shows clamping and yellow color shows vertically downward forces acting at the front bulkhead as shown in figure 8. The rear suspension mounts were clamped in this case. Force of 1440 N was applied at the bulkhead which is the sum of weight of impact attenuator, driver legs and steering weight etc. Maximum bending moment of 2081 Nm calculated to act about the Y-axis. Figure 8: Boundary conditions during static shear S. No. Test Boundary condition Force Moments 1 Static Shear Clamp- rear suspension mounts Downward force at front bulkhead 2 Static overall bending Clamp- front and rear suspension mounts Uniformly distributed loading 3 Static torsional loading Clamp- rear suspension mounts Clockwise Moment at bulkhead side 4 Acceleration Analysis Clamp- front and rear suspension mounts Force applied towards rear 5 Frequency analysis Clamp- front and rear suspension mounts Frequency range- 69.12 Hz to 204.79 Hz Point Load Clamp
  • 9. Jurnal Mekanikal, December 2010 54 Figure 9: Von Misses stresses during static shearing Results showed that maximum Von Misses stress was to be 1.17x108 N/m2 . Maximum strain energy (Proof resilience) capability of 4.345 Joules was observed from this analysis. Elements in red color show the maximum stress areas and corresponding maximum stress is shown in red color in stress tree in the left of Figure 9. 7.2 Static Vertical Bending Figure 10: Boundary conditions during static vertical bending Both front and rear suspension mounts were clamped and vertically downward point forces of 1550 N were applied equally in driver cabin, engine bay and drive-train section as shown in Figure 10. Frame is assumed to be a fixed beam with both ends clamped and subjected to point shear forces acting downward. Bending moment and shear force diagrams were drawn and values were calculated analytically. Blue color shows the clamping restraint and yellow color shows the point forces acting downward. Clamp Point Load
  • 10. Jurnal Mekanikal, December 2010 55 Figure 11: Von Misses stresses during static vertical bending Maximum bending moment of 4.482 Nm about Y-axis with maximum vertical downward displacement of 0.369 mm was noted. Maximum Von Misses stress of 2.77x107 N/m2 was observed at one or two places shown in red color in Figure 11. Most of the areas throughout chassis were observed to be subjected to minimum value of stress as shown in stress distribution tree in Figure 11. Maximum deflection was observed in the center of driver cabin floor and noted down its position to strengthen it. Strain energy of 0.087 J was noted. 7.3 Lateral Bending Figure 12: Application of lateral forces acting on roll hoop in driver cabin Clamping restraint was applied at both front and rear suspension mounts as in previous cases. Lateral cornering point forces of 2325 N (Sum of engine and driver forces) was applied on side impact bracings of driver cabin, engine mounts and drive- train side braces. Yellow color arrows are depicted application of forces acting outwards. Figure 13: Von Mises stresses during lateral bending
  • 11. Jurnal Mekanikal, December 2010 56 Maximum principal stress of 1.48x107 N/m2 (Figure 13) was observed with maximum translational displacement of 0.142 mm after post processing which are within the permissible limit of stresses. Strain energy of 0.015 J was observed. 7.4 Static Torsional Loading Figure 14: Boundary conditions during torsion test Torsional rigidity test is one of the most important tests which validates/rejects the chassis structure. In this case, chassis is assumed to act as a cantilever with one end fixed and other end free and subjected to torque about its longitudinal axis as shown in Figure 14. A chassis should be able to resist angular deformation and resultant shear stresses. Again clamping is shown by the blue color and clockwise torque is shown in yellow color. Clockwise moment 316 Nm about longitudinal X-axis was applied. Figure 15: Von Misses stresses during torsion Uniform stress of 5.02x107 N/m2 (Figure 15) was observed with maximum stress of 01x108 N/m2 at few points as shown in red color. Maximum translational displacement of 2.24 mm was noted in front bulkhead supports and lowers side impact members. Almost all other areas were found to be safe with approximately no stress and displacement. Strain energy of 2.303 J was observed from the results. Clamp Torque
  • 12. Jurnal Mekanikal, December 2010 57 7.5 Accelaration Test Figure 16: Boundary conditions during acceleration test Due to inertia effect, acceleration forces tend to act in opposite direction to the motion of body. Forces due to acceleration were calculated considering masses of driver (80 kg) and engine (70 kg) respectively. Engine acceleration of 6.61 m/s2 was taken from the manual of Honda VFR engine to be used in this vehicle and calculated an acceleration force using Newton second law of motion (F=m*a). Total acceleration force of 992.2 N was applied on the structure in backward direction shown in thick yellow color arrows in Figure 16. Load of 1550 N was applied throughout in driver cabin, engine bay and drive- train section as to simulate realistic conditions. Figure 17: Von Misses stresses during acceleration Chassis experienced maximum bending moment of 171.4 Nm about Y-axis (anticlockwise) at cross-sections shown in red color. Whole of the chassis was found to be within permissible stress limit with maximum stress was observed to be 2.67x107 N/m2 as shown in red color in Figure 17. Strain energy of 0.102 J was given by the FEA results. 7.6 Frequency Test Engine is a source of vibrations in any vehicle. Chassis as with any structure has an infinite number of resonant frequencies [8]. A resonant frequency, also known as natural frequency, is a preferred frequency of vibration and results when the inertial and stiffness forces cancel. For each of the infinite natural frequencies of vibrations which exist, a different shape that the chassis deform during vibration also exists [8]. The deformed shape that chassis will vibrate is also known as modes of vibration [8]. So, frequency Acceleration Forces Clamp Point Load
  • 13. Jurnal Mekanikal, December 2010 58 analysis is mandatory to check structural behavior during a set range of frequencies. Indirect actuated suspension system was used at front and rear of the vehicle. A component called as rocker used to transmit the forces and motion from the tires through tie rods to springs of shock absorbers. The rocker was clamped and hinged with the chassis. Hence chassis was clamped at both front and rear due to suspension construction with no external load applied. Only structural mass was taken into account for analysis as shown in Figure 18. Figure 18: Boundary conditions during frequency test Figure 19: Von Misses stresses and modal analysis during frequency test Software checked the structure from 69 Hz to 205 Hz automatically. No stresses were observed below 156.86 Hz and chassis was found to be safe (high factor of safety). At frequency of 156.86 Hz, 5.53x1010 N/m2 (elements shown in red color in figure 19) was observed to be more than the permissible stress of material (3.73e+008 N/m2 ). Maximum translational displacement of 562 mm was noted down at this frequency. Of the infinite modes of vibration that exist on the frame structure, only the lowest frequencies are of interest [8]. The lower modes of vibration maximize the kinetic energy and maximize the strain energy, while the high modes act in an opposite manner [8]. This means that the soft and stiff parts of chassis will be apparent in the low and high modes of vibrations respectively. Therefore it is worth to note that at lower frequencies (below 156.86 Hz), no considerable stress was found and chassis was assumed to be safe with considerable factor of safety. The most affected region was the main hoop and main hoop bracings with maximum stress and displacement. Clamp
  • 14. Jurnal Mekanikal, December 2010 59 Table 5: Von Misses stresses and Factor of Safety S. No. Test Von Misses Stress (N/m2 ) FOS 1 Static Shear 1.17*108 3.18 2 Static overall bending 2.27*107 16.41 3 Lateral Bending 1.48*107 25.25 4 Static torsional loading 1*108 3.73 5 Acceleration test 2.67x107 13.97 6 Frequency analysis 5.53*1010 (156.86 Hz) 00 By dividing yield stress (3.73e+008 N/m2 ) of chassis material with maximum Von Misses stresses induced in frame, factor of safety was calculated as shown in table 5. Considerable factor of safety was observed in all static (shear, bending and torsional test) boundary conditions. Chassis was found to exhibit high factor of safety during dynamic viz. acceleration test. Frame behavior was analyzed in frequency range of 69.12 to 204.793 Hz and observed maximum deformation (stress and deflection), more than the yield stress of frame material at a frequency of 156.86 Hz. Below 156.86 Hz, chassis was observed to be safe and experienced stress very small than the strength of material. So, 156.86 Hz can be considered as threshold value for proposed chassis. Chassis was found to have highest factor of safety in lateral bending (25.25) followed by static bending (16.41) and dynamic acceleration test (13.97) respectively. Factor of safety was noted to be 3.73 in torsional loading mode which represents the stiff nature of frame. An ideal chassis is one that has high stiffness; with low weight and cost. If there is considerable twisting, the chassis vibrates, complicating the system of the vehicle and sacrificing the handling performance [8]. The chassis that flexes is more susceptible to fatigue and subsequent failure, and “suspension compliance may be increased or decreased by bending or twisting of the chassis [9]. Also if a chassis is well designed to handle torsional loads, bending should not be an issue [9]. The torsional rigidity can be calculated by finding the torque applied to the frame and dividing by the angular deflection. The actual calculation is done as follows, with the figure 20 showing a view looking from the front of the suspension bay. K=R/Ө (1) K= (F*L)/tan-1[(Δy1+Δy2)/2L] (2) where K = Torsional Stiffness T = Torque Ө = Angular deformation F = Shear Force y1, y2= Translational displacement
  • 15. Jurnal Mekanikal, December 2010 60 Figure 20: Front suspension bay testing loads Force applied (F) = 1264 Nm y1= y2 = 2.24 mm = 0.00224m L= 0.250 m K= (1264*0.250)/tan-1 [(0.00224+0.00224)/2*0.250] = 615.98 Nm/deg Torsional rigidity of previous design was calculated to be 250 Nm/deg [11] which was an indicator of moderate stiffness and hence needed to be improved following changes in design and material. The torsional stiffness of present design was calculated to be 615.98 Nm/deg as calculated above which shows significant increase in stiffness in present model by 2.46 times than the older design. Deakin et al concluded that a Formula SAE racer, which has a total suspension roll stiffness of 500–1500 Nm/degree, requires chassis stiffness between 300 and 1000 Nm/degree to enable the handling to be tuned [10]. Torsional rigidity of University of Southern Queensland (USQ) 2004 SAE car experienced torsional rigidity of 214 Nm/degree and appeared to drive reasonably well, apart from the under-steer and other minor construction matters [10]. Increase in chassis stiffness in present work owes to good structural design having more triangulation and of course higher yield strength of IS 3074. 8.0 CONCLUSIONS The dominant characteristic of structural behavior viz. torsional rigidity increased by 2.46 times with an average value of 615.98 Nm/deg without compromising on weight. Weight of chassis was observed to decrease by 11.11% with approximate value of 32 kg as compared to weight of older chassis frame. Stress distributions were found to be even and less than the yield strength of material (3.73e+008 N/m2 ). Chassis was found to be safe significantly in static (bending) and dynamic (acceleration) modes with stress values noticeably less than the yield strength. Critical value of stress was found to be 5.53x1010 N/m2 at a frequency of 156.86 Hz. Although below this frequency, chassis was found to be safe and exhibited almost no stress. Dynamometer testing of previous car at approximate 9000 rpm with speed of 90 km/h, the maximum vibration frequency was noted to be not more than 100 Hz. So, it was expected that vibration range under same conditions will either remain same or decrease for the present design model. Hence chassis was expected to perform well in motion also.
  • 16. Jurnal Mekanikal, December 2010 61 REFERENCES 1. 2010 Formula SAE® Rules, SAE International, USA. 2. Riley, W.B., George, A.R., 2002. Design, Analysis and Testing of Formula SAE Race Car Chassis, SAE paper 2002-01-3300, Motorsports Engineering Conference and proceedings. 3. Horizontal Lozenging, Retrieved from http://rileydynamics.com/m- eng%20web/sec2.htm. on 17 June, 2010 1:10:37 GMT. 4. Milliken, William F., Milliken, Douglas L., 1997. Race Car Vehicle Dynamics, Society of Automotive Engineers. 5. Fui, T.H., Rahman, R.A., 2007. Statics and Dynamics Structural Analysis of a 4.5 Ton Structural Analysis, Jurnal Mekanikal, 24, 56-67. 6. Johansson, I., Edlund, S., 1993. Optimization of Vehicle Dynamics in Trucks by Use of Full Vehicle FE-Models, Göteborg, Sweden, Department of Vehicle Dynamics & Chassis Technology, Volvo Truck Corporation. 7. O’Neill, A.M., 2005. Chassis Design for SAE Racer, University of Southern Queensland. 8. Ryan, A. 2008. Formula SAE Race Car Analysis: Simulation and Testing of the Engine as a structural member, Retrieved from http://www.fisita.com/students/congress/sc08papers/f2008sc005.pdf on 06 June, 2010 03:40:37 GMT. 9. William F., Miliken and Douglas L. 1995. Race Car Vehicle Dynamics, Society of Automotive Engineers Inc., 673-667. 10. Deakin, A., Crolla, D., Ramirez, JP, and Hanley, R. 2004. The Effect of Chassis Stiffening on Race Car Handling Balance, Racing Chassis and Suspension Design, Society of Automotive Engineers, Warrendale, PA. 11. Singh, R.P. and Kaur, T., 2009. Designing and fabrication of formula SAE vehicle (Chassis), National Conference on Innovative developments in engineering applications, Bhai Gurdas Institute of Engineering and Technology, Sangrur, Punjab, India, 265-271.