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M.S Ramaiah School of Advanced StudiesPostgraduate Engineering and Management Programme (PEMP)
M.S.Ramaiah School of Advanced Studies
Postgraduate Engineering and Management Programmes (PEMP)#470-P Peenya Industrial Area, 4th Phase, Bengaluru-560 058
ASSIGNMENTModule Code AME 510
Module Name Structures, Safety and Impact.
Course M.Sc [Engg] in Automotive Engineering
Department Automotive and Aeronautical Engg.
Name of the Student Keerthiraj Shetty
Reg. No BBB0911019
Batch Full-Time - 2011
Module Leader Dr. Vinod K. Banthia
PO
STGRADUATEENG
INEERING
ANDMA
NAGEMENTPROG
RAMME
PEMP
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M.S Ramaiah School of Advanced StudiesPostgraduate Engineering and Management Programme (PEMP)
Structures, Safety and Impact.ii
Tel; 080 4906 5555, website: www.msrsas.org
Declaration Sheet
DelegatesName KEERTHIRAJ SHETTY
Reg No BBB0911019
CourseM.Sc.[ENGG] in Automotive
EngineeringBatch Full time 2011
Module Code AME 510
Module Title Structures, Safety and Impact.
Module Start Date 09-07-2012 Submission Date 04-08-2012
Module Leader Dr. Vinod K. BanthiaSubmission ArrangementsThis assignment must be submitted to Academic Records Office (ARO) by the submission date before 1730 hours
for both Full-Time and Part-Time students.
Extension requests
Extensions can only be granted by the Head of the Department / Course Manager. Extensions granted by any other
person will not be accepted and hence the assignment will incur a penalty. A copy of the extension approval must beattached to the assignment submitted.
Late submission Penalties
Unless you have submitted proof of Mitigating Circumstances or have been granted an extension, the penalties for a
late submission of an assignment shall be as follows: Up to one week late: Penalty of one grade (5 marks) One-Two weeks late: Penalty of two grades (10 marks) More than Two weeks late: Fail - 0% recorded (F2)All late assignments must be submitted to Academic Records Office (ARO). It is your responsibility to ensure that
the receipt of a late assignment is recorded in the ARO. If an extension was agreed, the authorization should be
submitted to ARO during the submission of assignment.
To ensure assignments are written concisely, the length should be restricted a limit indicated in the assignment
questions. Each participant is required to retain a copy of the assignment in his or her record in case of any loss.
Declaration
The assignment submitted herewith is a result of my own investigations and that I have conformed to the guidelines
against plagiarism as laid out in the PEMP Student Handbook. All sections of the text and results, which have been
obtained from other sources, are fully referenced. I understand that cheating and plagiarism constitute a breach of
University regulations and will be dealt with accordingly.
Signature of the
DelegateDate
Date stamp from
ARO
Signature of
ARO Staff
Signature of
Module Leader
Signature of
Course Manager
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Structures, Safety and Impact.iii
Attendance Details Theory Laboratory Fine Paid
(if any for shortage ofattendance)
Remarks
AssignmentMarks-Sheet (Assessor to Fill)
Part a b c d e f Total Remarks
A
B
C
Marks Scored for 100 Marks Scored out of 50
Result PASS FAIL
Written ExaminationMarksSheet (Assessor to Fill)
Q. No a b c d Total Remarks
1
2
3
4
5
6
Marks Scored for 100 Marks Scored out of 50
Result PASS FAIL
PMAR- form completed for student feedback (Assessor has to mark) Yes No
Overall Result
Components Assessor Reviewer
Assignment (Max 50) Pass Fail
Written Examination (Max 50) Pass Fail
Total Marks (Max 100) (Before Late Penalty) Grade
Total Marks (Max 100) (After Late Penalty) Grade
A+ A A- B+ B B- C+ C FAIL
100-
74-
69-
64-
59-
54-
49-
44-
Less than 40
IMPORTANT1. The assignment and examination marks have to be rounded off to the nearest integer and entered in the respective
fields
2. A minimum of 40% required for a pass in both assignment and written test individually3. A student cannot fail on application of late penalty (i.e. on application of late penalty if the marks are below 40,
cap at 40 marks)
Signature of Reviewer with date Signature of Module Leader with date
M. S. Ramaiah School of Advanced Studies
Postgraduate Engineering and Management Programme- Coventry University (UK)
Assessment Sheet
Department Automotive & Aeronautical Engineering
Course M.Sc.[ENGG] in Automotive Engineering Batch Full-Time 2011
Module Code AME 510 Module Title Structures, Safety and Impact
Module Leader Dr. Vinod K. BanthiaModule CompletionDate
04-08-2012
Student Name KEERTHIRAJ SHETTY ID Number BBB0911019
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Structures, Safety and Impact.iv
ABSTRACT____________________________________________________________________
The assignment deals with study of vehicle dynamics which is the study of vehicles
response to the force acting on the contact patch on tire and road. Different type of
moments and the lateral forces acting on the vehicle and the vehicles response to those
moments and forces while maneuvering is explained.
In Part-A of the assignment a technical essay is given which includes introduction to
vehicle handling and also the understeer, oversteer characteristic of the vehicle. How the
understeer, neutral steer and oversteer characteristic is achieved by varying the lateral
load on front and rear part of the vehicle is explained. The effect of understeer gradientson vehicle turning radius is explained. The specific behavior required to maneuver in the
narrow lanes and also the latest electronic systems involved in vehicle stability is
explained.
Part-B of the assignment deals with the analytical calculation done to find out the
understeer gradient K value. The calculations are done by assuming standard equation
and also by cars technical and suspension data. After getting the understeer gradient
value, the cars behavior is analyzed at different maneuvering conditions.
In Part-C of the assignment, the car simulation is done by full vehicle analysis on
constant-radius cornering test to find out the K value, using ADAMS/Car software. The
K value obtained is compared with that of Part-B K value and commented on the
result comparison.
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Structures, Safety and Impact.v
TABLE OF CONTENTS_____________________________________________________________________
DECLARATION SHEET ................................................................................................. iiiABSTRACT .......................................................................................................................ivTABLE OF CONTENTS .................................................................................................... vLIST OF FIGURES ......................................................................................................... viiLIST OF TABLES .......................................................................................................... viii
NOMENCLATURE ..........................................................................................................ixPART-A .............................................................................................................................. 1CHAPTER 1 ....................................................................................................................... 1
1.1 Introduction to Vehicle Handling ...........................Error! Bookmark not defined.1.2 Understeer Vs Oversteered vehicle characteristics .Error! Bookmark not defined.1.3 Understeer Gradient and its significance ................Error! Bookmark not defined.1.4 Understeer gradient and turning radius ...................Error! Bookmark not defined.1.5 Manoeuvring in narrow lanes .................................Error! Bookmark not defined.1.6 Oversteer vehicle and stability control ...................Error! Bookmark not defined.
PART-B .............................................................................................................................. 4CHAPTER 2 ....................................................................................................................... 4
2.1 Introduction .............................................................Error! Bookmark not defined.2.2 Car specifications ....................................................Error! Bookmark not defined.2.3 Analytical equations to find Ku value...................Error! Bookmark not defined.2.4 Calculations.............................................................Error! Bookmark not defined.
2.4.1 Finding c and b values ................................Error! Bookmark not defined.2.4.2 Tire cornering stiffness Cf and Cr. ..............Error! Bookmark not defined.2.4.3 Tire cornering stiffness (Ktcs) ........................Error! Bookmark not defined.2.4.4 Wheel rate of front and rear wheels .................Error! Bookmark not defined.
2.4.5 Front and Rear suspension roll stiffness (Kf, Kr) ............Error! Bookmark not
defined.2.4.6 Load on front and rear wheels (Fzf, Fzr) ...........Error! Bookmark not defined.2.4.7 Second coefficient of cornering stiffness bf and br ...Error! Bookmark not
defined.2.4.8 Lateral load transfer stiffness (Kllt)................Error! Bookmark not defined.2.4.9 Tire patch length (p) ......................................Error! Bookmark not defined.2.5.1 Aligning torque stiffness (Kat).......................Error! Bookmark not defined.2.5.2 Steering system stiffness (Kst) .......................Error! Bookmark not defined.
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Structures, Safety and Impact.vi
2.5.3 Roll steer gradient (Krs) .................................Error! Bookmark not defined.2.5.4 Camber thrust gradient (Kct)..........................Error! Bookmark not defined.2.5.5 Lateral force compliance steer gradient (Klfcs) .............Error! Bookmark not
defined.
2.6 Comments on assumptions .....................................Error! Bookmark not defined.2.7 Final calculation and assumption tabulation ...........Error! Bookmark not defined.2.8 Analyzing car behavior at different maneuver ........Error! Bookmark not defined.2.9 Conclusion ..............................................................Error! Bookmark not defined.
PART-C ....12
CHAPTER 3 ..................................................................................................................... 153.1 Introduction to ADAMS/Car ..................................Error! Bookmark not defined.3.2 Building the vehicle for constant-radius cornering test .........Error! Bookmark not
defined.3.2.1 Steering system hard point and C.G settings ...Error! Bookmark not defined.3.2.2 Camber and Toe settings ..................................Error! Bookmark not defined.3.2.3 Caster setting ....................................................Error! Bookmark not defined.
3.3 Post processing results ............................................Error! Bookmark not defined.3.3.1 Front and rear slip angle plot ...........................Error! Bookmark not defined.3.3.2 Lateral slip angle for front wheels ...................Error! Bookmark not defined.3.3.3 Lateral slip angle for rear wheels .....................Error! Bookmark not defined.3.3.4 Understeer gradient plot from post processing Error! Bookmark not defined.
3.4 Comparison of K value from calculation and simulation ...Error! Bookmark not
defined.3.4.1 Comments on results ........................................Error! Bookmark not defined.
3.5 Conclusion ..............................................................Error! Bookmark not defined.3.6 Module learning outcomes ...................................................................................... 17
REFERENCES ................................................................................................................. 18BIBLIOGRAPHY ............................................................................................................. 19
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LIST OF FIGURES_______________________________________________________________________
Figure 1. 1 Understeer and Oversteer vehicle characteristics [2]. ...Error! Bookmark not
defined.Figure 3. 1 Car suspension assembly [12]. .......................Error! Bookmark not defined.
Figure 3. 2 Suspension and wheel base positioning [12]. .Error! Bookmark not defined.Figure 3. 3 Hardpoint modification [12]. ..........................Error! Bookmark not defined.Figure 3. 4 C.G height and fore, aft positions [12]. ..........Error! Bookmark not defined.Figure 3. 5 Camber and toe value settings [12]. ...............Error! Bookmark not defined.Figure 3. 6 Caster angle hardpoints [12]. ..........................Error! Bookmark not defined.Figure 3. 7 Constant radius cornering parameter setup [12]. ...........Error! Bookmark not
defined.Figure 3. 8 Constant radius cornering animation [12]. .....Error! Bookmark not defined.Figure 3. 9 Front wheel lateral slip angle [12] ..................Error! Bookmark not defined.Figure 3. 10 Rear wheel lateral slip angle [12]. ................Error! Bookmark not defined.Figure 3. 11 Understeer post processing plot [12] ............Error! Bookmark not defined.Figure 3. 12 Understeer gradient plot [12]........................Error! Bookmark not defined.Figure 3. 13 Characteristic speed plot [12]. ......................Error! Bookmark not defined.
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Structures, Safety and Impact.viii
LIST OF TABLES_______________________________________________________________________
Table 2. 1 Technical specifications [6]. ............................Error! Bookmark not defined.Table 2.2 Assumption table [7] ........................................Error! Bookmark not defined.Table 2. 3 Tabulation of calculation results and assumptions .........Error! Bookmark not
defined.Table 3. 1 Result table of understeer gradient
values...Error! Bookmark not defined.
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Structures, Safety and Impact.ix
NOMENCLATURE_______________________________________________________________________
ABS Antilock Braking System
CATIA Computer Aided Three dimensional Interactive Application
C.G Centre of gravity
ECS Engine Control System
ESC Electronic Stability Control
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M.S Ramaiah School of Advanced StudiesPostgraduate Engineering and Management Programme (PEMP)PART-A
CHAPTER 1
1.1 Introduction to crash pulse
A basic characteristic of a vehicle structural response in crash testing and model simulation is theCrash signature, commonly referred to as the crash pulse [1]. This is the deceleration time history
at a point in the vehicle during impact. In a frontal impact, the crash pulse at a point on the rocker
panel at the B-pillar is presumed to identify the significant structural behaviour and the gross motion
of the vehicle in a frontal impact. Other locations, such as the radiator and the engine, are frequently
chosen to record the crash pulse for component dynamic analysis. The nature of the crash pulse
response depends on the mass, structural stiffness, damping at that location, and on external
interactions from neighbouring components. Impact severity in rear collisions that can cause soft
tissue neck injuries are most commonly specified in terms of change of velocity. However, it has
been shown from real-world collisions that mean acceleration influences the risk of these injuries.
For a given change of velocity, this means an increased risk for shorter duration of the crash pulse.
The results from the crash tests reveal that, the similar changes of velocity can be generated with
various durations of crash pulses for a given change of velocity in rear impacts. Hence it plays an
important role in the design of automotive structure.
1.2 Characterisation of crash pulse
To fulfil the full scale dynamic testing of vehicle crashworthiness, mathematical models and
laboratory tests like Hyge sled or a vehicle crash simulator are frequently employed. The objective
of these tests is the prediction of changes in overall safety performance as vehicle structural and
occupant restraint parameters are varied. To achieve this objective, it is frequently desirable to
characterize or simplify vehicle crash pulses such that parametric optimization of the crash
performance can be defined. Crash pulse characterization greatly simplifies the representation of
crash pulse time histories and yet maintains as many response parameters as possible. The response
parameters used to characterize the crash pulse are those describing the physical events occurring
during the crash such as (maximum) dynamic crush, velocity change, time of dynamic crush,
centroid time, static crush, and separation (rebound) velocity [2]. A number of crash pulse
approximations and techniques have been developed for the characterization. These are divided into
two major categories according to whether or not the initial deceleration is zero, as follows [2].
Pulse approximations with non-zero initial deceleration like, ASW, ESW and TESW. Pulse approximations with zero initial deceleration like, FEWSA, TWA and BSA.
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Structures, Safety and Impact.2
1.3 Structure design affecting the crash pulse
Some of the studies have shown that in some existing cars, the concept of increasing the mass is
coupled with stiffening the structural components, component design variation and also the
modification in wheelbase length, bumper height, track width and over hanging size indicating that,
size or geometry may affect at least as much as mass [3]. The study included full vehicle MADYMO
model on 1995 model Ford Explorer at 56kmph frontal barrier crash of vehicle, using a mid size
hybrid III dummy as driver [4].Five simulations were conducted, where the first had rear, side and
frame masses uniformly scaled so that it is 20 percent less massive than the baseline case, the second
with the mass values scaled down by 10 percent, the third being the baseline case, and the fourth and
fifth with masses scaled up by 10 and 20 percent, respectively [4]. The results obtained on plots are
as shown in figure 1.1
Figure 1.1 Simulation plots [4].
Simulation results [4]:
The acceleration pulses as measured on the driver side door sill and on the drivers thorax are shown
in figure 1.1 plot A and plot B respectively. In both plots, the curve with the highest peak represents
the lightest vehicle and the lowest curve represents the heaviest vehicle.
From figure 1.1 plot A, it is evident that the peak acceleration in the lighter two cases occurs near the
first peak at 45ms and the peak acceleration in the heavier cases occurs closer to 60ms. This peak
shifting may account for non-uniform behaviour when observing any peak acceleration criteria as it
changes over different vehicle designs.
A second behaviour is seen in figure 1.1 plot B, where the thoracic peak acceleration does not follow
a linear trend from the heaviest to the lightest vehicle, but there is an unexpected higher value on the
default case acceleration curve. It shows that although the vehicle is responding as expected, dummy
interactions with different body parts or vehicle components designs can cause significant changes in
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Structures, Safety and Impact.3
the model response. These nonlinearities in crash pulse data, demonstrate that dummy contact or
non-contact with a particular vehicle structure can produce sharp changes in dummy response as the
independent variables are manipulated.
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Structures, Safety and Impact.4
PART-B
CHAPTER 2
2.1 Introduction to rear impact (whiplash) of vehicles
Basically majority of the tests were conducted to investigate the effect and results, on vehicle and itsoccupant, which are caused due to frontal impact of the automobiles, due to its high severity in
collision and also due to frequent collision frequency. However, even slower speed rear end impacts
can also cause the occupant debilitating neck and back injuries, because of whiplash of the neck. To
prevent the extension of the neck during whiplash, head rests are provided in the back rest of the
seats. Euro NCAPs is the one to perform the first rear impact (whiplash) test, which showed nearly
80% of the seats tested need to be improved [5]. It performed the sled test on the dummy and found
the severity on the spine part damage, and gave ranking accordingly in which it found only 20% of
the seats had less whiplash. Whiplash is not uncommon in frontal and side impact accidents, but
more often occurs in low speed, rear end collisions in urban environments. Based on sled test rating
Volvo XC60, Alfa Romeo Mito, Volkswagen Golf VI, Audi A4 and Opel Insignia are the cars which
received Euro NCAPs best score with a good or green result [5]. Figure 2.1 shows the whiplash in
rear end collision of vehicles.
Figure 2. 1 whiplash in rear collision [5].
Similarly in this chapter, the neck injury criteria is studied from the results obtained by simulation of
standard dummy in rear impact car collision models using LS-Dyna and MADYMO softwares.
2.2 Modelling of rear end collisions
The idea of modelling rear end collision is carried out by placing two car models, one behind the
other with some assumed distance between them, so that there is considerable amount of impact on
neck region of occupant inside car during rear collision. In order to carry out crash analysis the given
standard car.key file of single car model is imported to LS-Dyna working environment, which is
duplicated and positioned one behind the other, so that the rear car will hit the front stationary car
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during rear collision analysis. The rear car is positioned at an assumed distance of 100mm from the
front car to get the quick rear impact effect when velocity is assigned for collision as shown in figure
2.2.
Figure 2. 2 car positioning for simulation [6].
Now by using this full car models, if the analysis is done then the computational time required to
get the results will be very high, hence the idea to reduce computational time is by reducing the size
of model by deleting some elemental mass from front and rear car models without affecting the
physics of problem.
2.2.1 Reducing car model size
Initially the given car model is made up of number of rigid, solid, shell and beam elements. Hence to
reduce the size, front portion of front car and rear portion of rear car is deleted.To carry out this, the car models are cropped in LS-Dyna work space accordingly by deleting the
elements and nodes. The figure 2.3 shows that the front portion, from windshield portion of front car is
deleted.
Figure 2. 3 front car front end deleted [6].
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After reducing size of front car, the rear car size is reduced by deleting the element and nodes in the
same way. The figure 2.4 shows the rear portion deleted from A- pillar portion of rear car.
Figure 2. 4 rear car rear end deleted [6].
After deleting some of the masses from front and rear portion of the car, the C.G of the vehicle is
varied hence to compensate that mass, an arbitrary mass should be added to front and rear car to
maintain their original C.G. This process of adding the mass is done in HYPERMESH software.
2.2.2 Location of C.G and mass
The method of adding the mass to properly locate the C.G is done in HYPERMESH. Following are
the data given, which is used to properly locate C.G and mass as shown in table 2.1.Table 2. 1 Table of C.G location and mass.
Velocity
(kmph)
Front
end mass
(kg)
Front end C.G Rear end
mass
(kg)
Rear end C.G
- - X(mm) Y(mm) Z(mm) - X(mm) Y(mm) Z(mm)
36.88 374.12 -784.39 0 -499.58 430.30 -2824.49 0 -521.05
Once the frontal and rear portions of the cars are deleted, it is then imported to hypermesh working
environment. Here the car models are checked for proper geometry clean-up to remove all the
unwanted free nodes and positioned properly to add mass.
To locate the C.G, a node is created at a certain distance from both front and rear portion of car cut
sections. These locating distances are calculated as follows,
Front car
Distance of front cars C.G = front car length + distance between carfront end C.G distance
= 3700mm +100mm784.39mm
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Distance of front cars C.G = 3015.61mm.
Therefore front car C.G coordinates are, x = 3015.61, y = 0, z = 499.92
Rear car
Distance of rear cars C.G = rear car length + distance between car= 2824.49mm +100mm
Distance of rear cars C.G = 2924.49mm.
Therefore rear car C.G coordinates are, x = 2924.49, y = 0, z = 521.05
The C.G coordinates obtained from calculation is used to locate C.G in HYPERMESH and to that
particular C.G node the given front end and rear end mass is allocated as mentioned in table 2.1.
the figure 2.5 shows the mass added to the C.G point and also the C.G location with respect to axis
coordinates.
Figure 2. 5 C.G location and mass added [7].
2.2.3 Rigid body creation
After locating the C.G and applying mass to that C.G point, the rigid body creation is done so that
whatever the elements have been removed will be compensated back by assigning the rigid body
connection to the front and rear portion of the both cars.
Figure 2.6 shows the rigid body allocation for the front car.
Figure 2. 6 front end rigid body creation [7].
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Similarly the rigid body allocation to the rear end portion of the rear car is done from the rear end mass
nose as shown in figure 2.7.
Figure 2. 7 rear end rigid body creation [7].
The final modeling of both the cars with C.G location, mass defining and rigid body allocation are asshown in figure 2.9. Now this model is carried to LS-Dyna and carried out the simulation.
Figure 2. 8 final modeling of car models [7].
2.3 Boundary conditions applied
In order to simulate the rear collision following are the boundary conditions applied,
2.3.1 Defining Parts and applying material property
The car model is having many components out of which some are rigid, shell, solid and beams.
Some particular elements are chosen and given the Linear plastic characteristics so that they plastic
behavior in the collision. Some of the parts selected for plastic behavior from front and rear cars are
front, rear, rear left of window glass etc.
2.3.2 Set IDWhen the model containing two cars is imported from HYPERMESH it will be a single entity, hence
they are separated as two models naming as front and rear car by selecting all the nodes and
elements by picking the areas option in the software. The ID set given for cars as Set-ID 841 for rear
car and Set-ID 842 for front car. The part set given for rear car is Set-Part 849 and that of front car is
Set-Part 850.
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2.3.4 Defining contact
The contact between both cars had to be defined to let the program know which parts are going to hit
each other. The type of contact between the rear and front car is selected as, automatic Surface to
Surface contact because, Surface to Surface contact algorithm establishes contact, when the surfaceof one body penetrates the surface of another. Single surface contact is not chosen because we are
defining the slave and master for the cars. Also in single surface collision, impact will be
concentrated only at certain point and stress as well deformation will be minimal. Since rear
collision is having large surface area of contact, Surface to Surface contact is chosen.
Also while defining contacts, the master type and slave type in between the cars are selected. Front
car is selected as master and rear car as slave.
Figure 2. 9 contact type defining [6].
Figure 2.9 shows the contact type defined between two cars. The slave section type (SSTYP) and
master section type (MSTYP) are selected as 2 and also the master section ID (MSID), slave
section ID (SSID) are set 842 and 841.
2.3.5 Velocity generation
To simulate a rear-end collision, the striking car (rear) was given an initial velocity. The struck car
(front) is standing still during simulation. The initial velocity simulates that the striking car is driving
with a certain velocity before hitting the struck car. The velocity of magnitude 36.88kmph, as
mentioned in table 2.1 is given in terms of mm/s2 i.e. (10244.44 mm/s2) for the slave car which is
nothing but the rear car. The velocity data fed into the LS-Dyna in the positive x - direction is as
shown in figure 2.10
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Structures, Safety and Impact.10
Figure 2. 10 initial velocity data fed [6].
2.3.6 Simulation time length
The simulation time step is decided by the length of the collision time in a normal rear end collision.
The time set for simulation is basically given in terms of milliseconds. Lesser the time step lesser
will be the computational time. After study of some of the thesis, where they have conducted lot of
trials using time steps for simulation in milliseconds, for rear end collision, a standard value of 150
milliseconds is assumed as termination time for simulation [8]. The termination time data fed into
software is as shown in figure 2.11.
Figure 2. 11 simulation time steps [6].
2.4 Crash pulse plot
After assigning all the boundary conditions, the simulation is carried out and the crash pulse is
generated. The severity of crash in the rear end collision is as shown in the figure 2.12. The plot of
acceleration verses time is plotted where we can find the high acceleration in the drivers cabin.
Figure 2.13 shows the acceleration pattern obtained randomly with some peak acceleration and very
low acceleration. This peak value depends on the time period of collision and also the severity of
collision with high hitting velocity.
It is seen that the peak acceleration value obtained is around 100mm/s at a time period of 28 th
milliseconds of the simulation time.
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Structures, Safety and Impact.11
Figure 2. 12 rear end collision [7].
Figure 2. 13 crash pulse plot [6].
2.4.1 Energy plot
The plots of kinetic energy, internal energy and total energy are shown in the figure 2.14. As like the
physics behind crash phenomena, the total energy remains unchanged, and only the transformation
of energy takes place on this impact, as per the plots shown.
During collision the car comes and hit with given velocity, due to which the kinetic energy will be
decreased from high level to low level.
Same way before collision the system is not disturbed by any external excitations or forces hence the
internal energy will be zero and will increase gradually with the collision time. But total energy will
remain almost constant.
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Figure 2. 14 energy plot [6].
2.5 High neck acceleration time
The simulation to get the neck acceleration of the driver in the driver compartment is done by
assuming a standard dummy from the library of MADYMO software. This is done by modifying the
dummy seat with a standard seat dimension of a selected car. Initially the crash pulse generated in
the drivers compartment due to rear collision from LS-Dyna simulation is imported to MADYMO
and the software is run for the partial run period of 149milliseconds. The figure 2.15 shows the
MADYMO simulation results showing the peak neck acceleration plot along with NIC plot.
Figure 2. 15 neck acceleration and NIC plot [6].
The plot shows that the x- axis is plotted for the time for simulation in milliseconds and y-axis as
NIC and linear acceleration of dummy during simulation. The graph shows the peak acceleration of
point, which means that the dummy head is experiencing so much acceleration during collision. The
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acceleration magnitude obtained as 1150m/s2, exactly at 104th milliseconds. The other plot also
shows the NIC value of the dummy neck at the same 104 th milliseconds of simulation. It is also seen
that the NIC value of 1100 is obtained during collision.
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PART-C
CHAPTER 3
3.2 Environment modeling on MADYMO
The simulation to find any sort of criterion or finding acceleration in MADYMO is done byimporting whatever the crash pulse generated in LS-Dyna simulation. This is done because whatever
the dummy we select on different sled test we require will have their own default crash pulse values,
hence in order to simulate the rear collision in MADYMO, the crash pulse generated from in LS-
Dyna from part-B is imported. The crash pulse data from LS-Dyna will be having the time of
simulation list and particular acceleration value to that particular instant of time of simulation. This
data is obtained for the acceleration in only x-direction which is in m/s2 hence the value is converted
to mm/s2, and then imported to MADYMO. It is also seen that the co-ordinates in LS-Dyna and
MADYMO are in opposite direction hence, whatever the direction of magnitude of crash pulse data
obtained from Dyna is reversed and then fed into MADYMO. The crash pulse data is fed into
MADYMO in LOAD.SYSTEM_ACC option, as shown in figure 3.1.
Figure 3. 1 X,Y data importing to MADYMO [9].
Once the crash pulse data is set, the proper seat dimension data is fed by selecting a car of choice.
The seat dimensions are selected from SUV class, Land Rover series as mentioned in table 3.1.
Table 3. 1 seat dimension table [10].
Head rest Seat back Seat cushion
Height(mm) Width(mm) Height(mm) Width(mm) Height(mm) Width(mm)
152.7 305.4 610 350 508 350
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The seat dimensions from the table 3.1 is fed into MADYMO in terms of meters. The dimensions
fed into the software are as shown in figure 3.2.
Figure 3. 2 seat dimension fed [9].
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3.6 Module learning outcomes
This module is intended to familiarize with the more complex aspects of vehicle dynamicsand their use and to develop skills in using simulation software to investigate and improve
performance of vehicle.
Use of bicycle model to investigate vehicle handling is well taught. Using theoretical knowledge and simulation, how to improve vehicle and driver performance
is understood.
The lab session instructions, on how to use simulation software, including validation ofresults is efficiently taught and well understood.
The module notes data helped in modelling an existing vehicle, run a simulation to validatethe model and then investigate various changes with the goal of optimizing the vehicles
performance.
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The module helped in gaining the knowledge of most important vehicle dynamics estimationand vehicle control problems. In particular, the main expected learning outcome is how the
control algorithms of longitudinal Anti-Lock Braking Systems, Traction Control Systems,
Cruise Control Systems, Yaw Control Systems, Roll-Over Prevention systems, and verticaldynamics Active and Semi-Active Suspensions systems, play an important role in controlling
vehicle stability.
The module also helped in estimating road friction, yaw rate and road grades, whichsimplified the calculations involved in calculating the understeer gradient values.
The module helped in understanding the concept of acceleration, braking and corneringperformance of the vehicle.
Difference between understeer and oversteer behavior of the vehicle is understood. The concept of center point and Ackermans steering is understood. Effect of variation in bump steer, roll steer, caster angle, camber angle and toe angles are
studied.
REFERENCES______________________________________________________________________________
[1] How do understeer and oversteer work? (The math and the
physics)http://www.physicsforums.com/showthread.php?t=505028
[2] Understeer_Oversteer: http://en.wikipedia.org/wiki/Understeer_and_oversteer.[3] Handling Characteristic of Road vehicles:
http://www.thecartech.com/subjects/auto_eng2/Handling_characteristics_of_road_vehicles.htm
[4] Thomas D. Gillespie, - Fundamentals of Vehicle Dynamics.
[5] OVERSTEER -http://www.oversteer.org.uk/2012/07/vauxhall-adam-odd-name-interesting-
car.html
[6] Volkswagen Passat Alltrack 1.8TSIautomobile technical data :
http://www.carfolio.com/specifications/models/car/?car=266783
[7] Autobuildindia_handling_test.pdf (SECURED).
[8] Dr. S.R. Shankpal- FT-11 AME-508, Vehicle Dynamics, handling and Simulation-Module
Notes.
[9] Thomas D. Gillespie: CarSimData Manual, Version 5.
[10] Tire_dimension calculator: bndtechsource.ucoz.com/index/tire...calculator/0-20 - United States.
[11] Neha Ravi Dixit - Evaluation of Vehicle Understeer Gradient Definitions thesis.
http://www.physicsforums.com/showthread.php?t=505028http://www.physicsforums.com/showthread.php?t=505028http://www.physicsforums.com/showthread.php?t=505028http://www.oversteer.org.uk/2012/07/vauxhall-adam-odd-name-interesting-car.htmlhttp://www.oversteer.org.uk/2012/07/vauxhall-adam-odd-name-interesting-car.htmlhttp://www.oversteer.org.uk/2012/07/vauxhall-adam-odd-name-interesting-car.htmlhttp://www.oversteer.org.uk/2012/07/vauxhall-adam-odd-name-interesting-car.htmlhttp://www.carfolio.com/specifications/models/car/?car=266783http://www.carfolio.com/specifications/models/car/?car=266783http://www.carfolio.com/specifications/models/car/?car=266783http://www.oversteer.org.uk/2012/07/vauxhall-adam-odd-name-interesting-car.htmlhttp://www.oversteer.org.uk/2012/07/vauxhall-adam-odd-name-interesting-car.htmlhttp://www.physicsforums.com/showthread.php?t=505028 -
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[12] ADAMS/CarMultibody Dynamic Software tool.
[13] Bridgestone TyresWheel alignment centre, west of chord road Rajajinagar, Bengaluru.
BIBLIOGRAPHY______________________________________________________________________________
1.
Evaluation of Vehicle Understeer Gradient Definitions thesis, byNeha Ravi Dixit.2. FT-11 AME-508, Vehicle Dynamics, handling and Simulation-Module Notes, by Dr. S.R.
Shankpal.
3. Fundamentals of Vehicle Dynamics, SAE, Warren dale, PA, 1992by Gillespie T. D.4. CarSimData Manual, Version 5 by, Thomas D. Gillespie.5. http://www.rearwheeldrive.org/rwd/rwdlist.html, retrieved on 1-7-20126. http://www.ford-trucks.com/specs/2003/2003_expedition_1.html, retrieved on 2-7-20127. http://www.carfolio.com/specifications/models/car/?car=2667838. http://www.trackpedia.com/wiki/Oversteer9. http://www.motortrend.com/roadtests/exotic/1202_2013_ferrari_f12_berlinetta_first_look/10.http://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+nar
row+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.
0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQU
11.http://www.volkswagen.co.in/en/models/newpassat/gallery.html
http://www.carfolio.com/specifications/models/car/?car=266783http://www.carfolio.com/specifications/models/car/?car=266783http://www.trackpedia.com/wiki/Oversteerhttp://www.trackpedia.com/wiki/Oversteerhttp://www.motortrend.com/roadtests/exotic/1202_2013_ferrari_f12_berlinetta_first_look/http://www.motortrend.com/roadtests/exotic/1202_2013_ferrari_f12_berlinetta_first_look/http://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.google.co.in/search?hl=en&safe=active&q=oversteer+and+manoeuvring+on+narrow+lanes&oq=oversteer+and+manoeuvring+on+narrow+lanes&gs_l=serp.3...18084.23947.0.24558.14.14.0.0.0.0.627.2686.4j2j5j1j0j1.13.0...0.0...1c.4c62kKg-IQUhttp://www.motortrend.com/roadtests/exotic/1202_2013_ferrari_f12_berlinetta_first_look/http://www.trackpedia.com/wiki/Oversteerhttp://www.carfolio.com/specifications/models/car/?car=266783 -
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