crashing testing of cars
TRANSCRIPT
“Crash Testing Of Cars” – By Sumukh.T.Deshpande & Harshvardhan.P.Patil
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Crash Testing Of Cars-a race of technology against fatality….
Authors
Sumukh T Deshpande & Harshvardhan P Patil205, Aekdanth Apartments, c/o K.P.Harlapur,
Nehru Road, Rajaram Marg, 4th Cross,Near Lele Ground, Tilakwadi, Chidambar-Nagar,Belgaum. Belgaum.Ph: - 09886574634 Ph: - 09448634898
Email Id - [email protected] Email Id: [email protected]
4th Semester
Department of Mechanical Engineering
Gogte Institute of Technology
Udyambag, BELGAUM -590008.
Abstract
“Crash Testing Of Cars” – By Sumukh.T.Deshpande & Harshvardhan.P.Patil
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Driving a car is a high in itself, but safety is important too. Choosing a safer car is very important to help
prevent crashes and accidents. While cars are becoming safer each year and fatality rates are falling, car
crashes continue to be one of the primary causes of death and injury. Thus, a thorough crash-testing program is
critical for the carmakers, (each year, many vehicles are crashed by Carmakers themselves!) and contributes
significantly to the rapidly improving safety of cars. Finding out whether newly improved safety features will
perform efficiently in an accident is the responsibility of the crash-testing facility. The idea is to use every part
of the vehicle in some way to save the occupant rather than the vehicle. One would be amazed at how much
thought and preparation goes into making sure that safe cars are on the roads! In this paper we try to present
all about automotive crash testing – types, ratings, infrastructure required for conducting tests, dummies and
recent safety improvements.
Keywords: - Crash Test Dummies, Frontal Crash Test, Offset Crash Test, Side Impact Test, Crash
Energy, and Crash Testing Centres.
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INDEX
1. Introduction 4
2. Infrastructure 4
3. Crash Test Dummies 5
4. Types Of Crash Tests
1. Frontal Crash Test 7
2. Side Impact Test 8
3. Offset Crash Testing 9
5. Safety Features 10
6. Absorption Mechanism Of Crash Energy 11
7. Crash Test Ratings Of Cars 13
8. Crash Testing Centers 14
9. Scope… 14
10.Conclusion 15
References
Abstract Word Count: - 187
Paper Word Count: - 2705
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1. Introduction
Every year, over 80,000 people die on Indian roads; in every five-road accident there
is at least one casualty reported. Yet, it's just a statistic, which hardly changes our apathy
towards road safety. Yes, road safeties are an unpleasant, boring subject, but remember, it
affects us all.
In recent years, cars have got much safer. One reason is that safety is now a selling
point in new cars. Frontal collisions, offset collisions, cars hitting another vehicle or object in
the traffic environment they are all tested using cars of different sizes. Each vehicle's overall
evaluation is based on three aspects of performance — measurements of intrusion into the
occupant compartment, injury measures from a dummy positioned in the driver seat, and
analysis of slow-motion film to assess how well the restraint system controlled dummy
movement during the test.
The different aspects of the crash testing are discussed below: -
2. Infrastructure
Crash testing needs infrastructure that could best simulate the real road
conditions, and capture the details required for crash analysis. The basic infrastructure, any
crash testing facility would need are:
A crash laboratory with an advanced high-tech crash barrier.
An outdoor test track that accommodates research for different weather conditions.
Highly advanced crash simulator
Lighting system, which can provide up to 750,000 watts of illumination without
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glare to film tests in slow motion. The resulting pictures must be
clear and dramatic.
Equipment for advanced component testing [6].
Supercomputers that crash tests non-existing cars.
A system that propels vehicles to impact, accelerating full-size pickups up to 80 kph.
3. Crash Test Dummies
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The dummy's job is to simulate a human being during a crash, while collecting data
that would not be possible to collect from a human occupant. The dummies come in
different sizes and they are referred to by percentile and gender. A dummy is built from
materials that mimic the physiology of the human body. For example, it has a spine made
from alternating layers of metal discs and rubber pads [4].
All crash tests are conducted using the same type of dummy. (Nowadays the most
commonly used is the Hybrid III)
With the help of a number of specially built rigs, studies are being conducted to
discover what happens when parts of the human body collide with parts of the interior or
exterior of a car.
Crash test dummies are carefully calibrated and then positioned in vehicles to mimic
the movement of humans and record crash forces during the tests. Each complex dummy
includes 25 to 40 sensors to record the forces on various parts of the body.
The dummies contain following three types of instrumentation: -
1. Accelerometers: - measure the acceleration in a particular direction. This data can be
used to determine the probability of injury. Inside the dummy's head, there is an
accelerometer that measures the acceleration in all three directions (fore-aft, up-down,
left-right). There are also accelerometers in the other parts of the body.
2. Load Sensors: - Inside the dummy are load sensors that measure the amount of force
on different body parts during a crash. The maximum load in the bone can be used to
determine the probability of it breaking.
3. Movement Sensors: - These sensors are used in the dummy's chest. They measure how
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much the chest deflects during a crash.
Before the crash-test dummies are placed in the vehicle, researchers apply different
colors of paint to the parts of the dummies' bodies most likely to hit during a crash. The paint
marks in the car will indicate what part of the body hit what part of the vehicle inside the
cabin. This information helps researchers develop improvements to prevent that type of injury
in future crashes.
4. Types Of Crash Tests
Simulating every accident type is impossible, which is why there are number of
standardized crash tests (which may resemble most of the crashes that may take place) based
on international classifications and industry practices are used in the development of the
vehicle. This defines a repeatable way of conducting crashes, so that improvements can be
quantified and modifications made. The three standard crash tests conducted are:
1. Frontal Crash Test 2. Side Impact Test 3. Offset Crash Testing
4.1 Frontal Crash Testing
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At 55 kph the car runs straight into a solid concrete barrier. This is equivalent to a car
moving at 55 kph hitting another car of comparable weight moving at 55 kph. The kinetic
energy involved in the frontal crash test depends on the speed and weight of the test vehicle
[5]. Crashing the full width of a vehicle into a rigid barrier maximizes energy absorption so
that the integrity of the occupant compartment, or safety cage, can be maintained well in all
but not in very high-speed crashes. Full-width rigid-barrier tests produce high occupant
compartment decelerations, so they're especially demanding of restraint systems (Figure.2)
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4.2 Frontal Offset Crash Testing
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In offset tests, only one side of a vehicle's front end, not the full width, hits the barrier
so that a smaller area of the structure, about 40% of the width of the front of the vehicle on
the driver's side must manage the crash energy. This means the front end on the struck side
crushes more than in a full-width test, and intrusion into the occupant compartment is more
likely [1].
In the offset crash test the vehicle is travels at 64kph and collides with a crushable
aluminum barrier, which makes the forces in the test similar to those involved in a frontal
offset crash between two vehicles of the same weight. The resulting crash forces place severe
demands on the structure of the vehicle, particularly on the driver's side. This test is also
conducted by using two vehicles of same weight, at 65kph. (Figure.3)
The test results can be compared only among vehicles of similar weight. The vehicle
structure affects the outcome of an offset frontal crash in two main ways: -absorption and
dissipation of crash energy and integrity of the passenger compartment. The bottom line is
that full-width tests are especially demanding of restraints but less demanding of structure,
while the reverse is true in offsets [3].
4.3 Side Crash Test
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In the side test a sled (of about 1,368-kg) with a deformable "bumper" runs into the
side of the test vehicle at around 50kph. The test simulates a car that is crossing an
intersection being sides wiped by a car running a red light. Side impacts can be of two
types: - perpendicular impact and angled impact (as shown in figure above) [4].
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The
protection of occupants in side impacts is more important as the space between the car’s
body and the occupant is much less than with the front and rear. Side impact crash test
ratings can be compared across vehicle type and weight categories, while frontal crash test
ratings cannot. This is because the kinetic energy involved in the side impact test depends
on the weight and speed of the moving barrier, which are the same in every test.
(Figure.4)
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5. Safety Features
1. Anti-lock Brake Systems: - Prevent a car's wheels from locking during 'panic' braking
and allow the driver to maintain steering control as the car slows down. It keeps the car
going straight, even after applying brakes on a slippery surface [6].
2. Side Impact Bars/Side Door beams: - Side impact bars are made from high strength
steel tubes and are fitted into the central portion of the door panels, thus increasing their
strength. Stronger doors protect passengers during a side impact.
3. Three - Stage Protective Bumpers: - It includes a unique plastic energy absorber and
reinforced steel Impact, energy absorber that crushes upon collision that prevents severe
damage to body and a reinforced Impact Beam and Bracket that perform a double shock
absorbing function.
4. Roll Control: - A Roll Control device in the front suspension imparts greater stability and
prevents the car from toppling over while negotiating sharp curves at high speeds.
5. Fuel Tank safety: - In some cars the fuel tank is designed to stay intact even in a big
accident allowing no leaks at all. The fuel tank is also centrally located for safety and
performance-keeping it out of way in the event of an accident.
6. Seat Belts: - They hold the person in an optimal position in the event of a car crash. They
also reduce the risk of collision with the steering wheel, dashboard or windshield.
1. Air Bags: Airbags are very useful in avoiding two types of accidents: rear-end and
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head-on collisions. They are very important in a crash because depending on the speed at
impact and the stiffness of the object struck, front air bags inflate to prevent your head
and face from striking your car's interior, especially the dashboard, steering wheel and
windshield. In a head-on crash, sensors take less than 1/20th of a second to alert the
inflators that fill the bag. (Figure 5.) Using air bags in conjunction with automatic safety
belts provides much more protection than using either one alone. Side air bags reduce the
risk of occupants hitting the door or object that crash through it. They provide additional
chest protection by inflating instantly during many side crashes; some, also provide
head protection [6].
8. Head Restraints: -Head restraints are extensions of the car's seats that limit head
movement during a rear-impact crash, thus, reducing the probability of neck injury.
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9. Collapsible Steering: -The steering wheel column in a collapsible steering works in two
stages to absorb impact in the event of an air crash. This protects the driver from being
trapped between the steering wheel and seat, during a collision.
10. Non-jamming Doors: -During a heavy collision the front doors are pushed over the outer
skin of the rear doors, leaving them free to open.
6. Absorption Mechanism Of Crash Energy
Obviously the ideal crash would be no crash at all. But, let's assume you are going to
crash, and that you want the best possible chances of survival. How can all of the safety
systems come together to give you the smoothest crash possible?
Surviving a crash is all about kinetic energy. When the body of occupant is moving
(say at 55 kph), it has a certain amount of kinetic energy. After the crash, when it comes to a
complete stop, it will have zero kinetic energy. To minimize risk of injury, removing the
kinetic energy as slowly and evenly as possible is done by some of the following safety
systems in the car: -
1. As soon as car hits the barrier the seatbelt can then absorb some of your energy before the
airbag deploys.
2. Milliseconds later as the driver moves forward towards the airbag, the force in the seatbelt
holding him back would start to hurt him, so the force limiters make sure that the force in
the seatbelts doesn't get too high.
3. Next, the airbag deploys and absorbs some more of your forward motion while protecting
you from hitting anything hard [3].
In a crash it is desirable that most of the crash energy is absorbed and dissipated in the
deformation of components of each vehicle. For this purpose: -
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Crumple Zones are vacant spaces in the front portion of the car that act as cushions, where
metal parts are supposed to deform and absorb all the kinetic energy of the vehicle.
The engine on most cars is mounted so that in a crash, it is forced backwards and
downward so that it won't come into the cabin and injure the occupant.
Increasing the use of engine/suspension cradles allows designers to better control this
deformation and to by-pass very rigid components such as engine blocks, which are not
effective energy absorbers.
To avoid load concentrations it is important that the crash forces are spread across the
face of the deformable barrier.
In a collision between two vehicles the occupants of the heavier vehicle would generally
be better off, due to the physics of the collision. In the case of four-wheel-drive vehicles
colliding with passenger cars, however, this advantage can be diminished by a stiff front
structure.
Integrity of the passenger compartment should be maintained in the crash test. The
steering column, dash, roof, roof pillars, pedals and floor panels should not be pushed
excessively inwards, where they are more likely to injure the occupants [3].
Ratings for Side-Impact Tests
Result
5 5% or lower chance of serious injury
4 6% to 10% chance of serious injury
3 11% to 20% chance of serious injury
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2 21% to 25% chance of serious injury
1 26% or greater chance of serious injury
Ratings for Frontal-Impact Tests
Result
5 10% or lower chance of serious injury
4 11% to 20% chance of serious injury
3 21% to 35% chance of serious injury
2 36% to 45% chance of serious injury
1 46% or greater chance of serious injury
7. Crash Test Ratings Of Cars
In frontal crashes, the worst score in the following three criteria determines the star rating:
-Head Injury Criteria (HIC), Chest deceleration, and Femur load [5].
In side-impact crashes, there are three criteria: - Driver and passenger injury measures,
Head protection and Structural performance [5].
Tata Indigo has passed European standards of full frontal and offset frontal crash tests as
well as endurance safety tests. Tata has also recently tested Indica, Sierra and Safari
successfully [2].
Ford's Freestyle, a midsize SUV introduced for the 2005 model year, earned the highest
rating in a 65kph frontal test recently conducted by the Insurance Institute for Highway
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Safety.
8. Crash Testing Centers
Throughout the world there are many institutes who crash test vehicles, each
organization’s test results are generally for vehicles sold in its respective country or region.
1. Insurance Institute for Highway Safety (IIHS- U.S)
http://www.hwysafety.org/vehicle_ratings/ratings.htm
2. Euro New Car Assessment Programme: - established in 1997 and now backed by five
European Governments. www.euroncap.com
3. New Car Assessment Japan: - evaluates the safety of automobiles currently on the
Japanese market. http://www.nasva.go.jp/english
4. Australian NCAP (ANCAP): - Australian New Car Assessment Program (ANCAP), is
supported by Australian and New Zealand automobile clubs.
http://www.aaa.asn.au/ancap.htm
5. India has centres for crash testing at the Automotive Research Association of India
(ARAI) and Society of Indian Automobile Manufacturers (SIAM) in Bangalore [2].
Tata Motors is the only carmaker in India that has a crash-test facility located at huge
plant in Pune established in 1996 [2].
9. Scope…Computer Aided Engineering (CAE) packages like ANSYS and LS-Dyna are being
developed to simulate variety of crash situations by using finite element analysis.
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Volvo has developed a unique physical crash simulator in which real-life collisions can
be simulated without destroying the car body itself.
These developments give engineers a good preview of what’s going to happen in the
physical crash test.
10. Conclusion
The safety deficits of cars observed in accident statistics can be alleviated if the
structures of these cars are designed and optimized for the situation they will most likely
encounter in a real world situation.
One of the prime reasons for the alarming increase in deaths due to accidents in India
is that crash testing of vehicles is not mandatory. Every carmaker emphasizes that his make is
better. But the consumer has to change his approach and consider that car, which can best
avoid injuries to him in a crash. This will force the carmakers to crash test all the vehicles
they launch and provide all the necessary information to the consumer, and facilitate him in
buying a safe car.
Crash testing leads to improvement of the safety systems. These systems again have
to be tested for their workability during a crash. Hence crash testing plays a vital role in
continuous improvement of the safety systems. Design changes in vehicles like the crumple
zones and the location of engine block have been the results of evolution of crash testing.
Therefore in future, crash testing could suggest many more design changes, which could
further minimize the probability of injury during a crash. These observations stress that any
car model would not be complete without crash testing. Thus crash testing can be a major
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factor that will make driving a more secure and reliable experience.
References
[1] Michael Paine, Vehicle Design and Research Private Limited; Donald McGrane Crash
lab, NSW Roads and Traffic Authority; Jack Haley NRMA Limited, “Offset Crash
Tests – Observations about vehicle design and structural performance”
[2] http://www.tata.com/tata_motors/articles/index.htm
[3] http://www.nhtsa.dot.gov/cars/testing/ncap/
[4] www.howstuffworks.com
[5] http://www.iihs.org/ratings/rating.aspx
[6] http://www.driveandstayalive.com/info%20section/crash%20testing/aaa-index_crash-t
esting-index-and-intro.htm