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Crumple zones, crush zones,
[ or crash zones are a structural safety feature used in vehicles, mainly in automobiles, to increase the time over which a change in ]velocity
Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...
(and consequently momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
) occurs from the impact during a collision by a controlled deformation
Deformation can refer to:
* Deformation (engineering), changes in an object's shape or form due to the application of a force or forces.
** Deformation (physics), such changes considered and analyzed as displacements of continuum bodies.
* Defor ...
; in recent years, it is also incorporated into trains and railcars.
Crumple zones are designed to increase the time over which the total force from the change in momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
is applied to an occupant, as the average force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
applied to the occupants is inversely related to the time over which it is applied. The physics involved can be expressed by the equation:
:
where is the force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
, is the time, is the mass, and is the velocity of the body. In SI units, force
In physics, a force is an influence that can change the motion of an object. A force can cause an object with mass to change its velocity (e.g. moving from a state of rest), i.e., to accelerate. Force can also be described intuitively as a p ...
is measured in Newtons, time in seconds, mass in kilogram
The kilogram (also kilogramme) is the unit of mass in the International System of Units (SI), having the unit symbol kg. It is a widely used measure in science, engineering and commerce worldwide, and is often simply called a kilo colloquially ...
s, velocity in metres per second
The metre per second is the unit of both speed (a scalar quantity) and velocity (a vector quantity, which has direction and magnitude) in the International System of Units (SI), equal to the speed of a body covering a distance of one metre in ...
, and the resulting impulse
Impulse or Impulsive may refer to:
Science
* Impulse (physics), in mechanics, the change of momentum of an object; the integral of a force with respect to time
* Impulse noise (disambiguation)
* Specific impulse, the change in momentum per uni ...
is measured in newton second
The newton-second (also newton second; symbol: N⋅s or N s) is the unit of impulse in the International System of Units (SI). It is dimensionally equivalent to the momentum unit kilogram-metre per second (kg⋅m/s). One newton-secon ...
s (N⋅s).
Typically, crumple zones are located in the front part of the vehicle, to absorb the impact of a head-on collision
A head-on collision is a traffic collision where the front ends of two vehicles such as cars, trains, ships or planes hit each other when travelling in opposite directions, as opposed to a side collision or rear-end collision.
Rail transport ...
, but they may be found on other parts of the vehicle as well. According to a British Motor Insurance Repair Research Centre study of where on the vehicle impact damage occurs, 65% were front impacts, 25% rear impacts, 5% left-side, and 5% right-side. Some racing cars use aluminium, composite/carbon fibre honeycomb, or energy absorbing foam to form an impact attenuator
An impact attenuator, also known as a crash cushion, crash attenuator, or cowboy cushion, is a device intended to reduce the damage to structures, vehicles, and motorists resulting from a motor vehicle collision. Impact attenuators are designed to ...
that dissipates crash energy using a much smaller volume and lower weight than road car crumple zones. Impact attenuators have also been introduced on highway maintenance vehicles in some countries.
On September 10, 2009, the ABC News
ABC News is the news division of the American broadcast network ABC. Its flagship program is the daily evening newscast ''ABC World News Tonight, ABC World News Tonight with David Muir''; other programs include Breakfast television, morning ...
programs ''Good Morning America
''Good Morning America'' (often abbreviated as ''GMA'') is an American morning television program that is broadcast on ABC. It debuted on November 3, 1975, and first expanded to weekends with the debut of a Sunday edition on January 3, 1993. Th ...
'' and ''World News
World news or international news or even foreign coverage is the news media jargon for news from abroad, about a country or a global subject. For journalism, it is a branch that deals with news either sent by foreign correspondents or news agenc ...
'' showed a U.S. Insurance Institute for Highway Safety
The Insurance Institute for Highway Safety (IIHS) is a U.S. nonprofit organization funded by auto insurance companies, established in 1959 and headquartered in Arlington, Virginia. It works to reduce the number of motor vehicle traffic collision ...
crash test
A crash test is a form of destructive testing usually performed in order to ensure safe design standards in crashworthiness and crash compatibility for various modes of transportation (see automobile safety) or related systems and componen ...
of a 2009 Chevrolet Malibu
The Chevrolet Malibu is a mid-size car manufactured and marketed by Chevrolet from 1964 to 1983 and again since 1997. The Malibu began as a trim-level of the Chevrolet Chevelle, becoming its own model line in 1978. Originally a rear-wheel-drive ...
in an offset head-on collision with a 1959 Chevrolet Bel Air
The Chevrolet Bel Air is a full-size car produced by Chevrolet for the 1950–1975 model years. Initially, only the two-door hardtops in the Chevrolet model range were designated with the Bel Air name from 1950 to 1952. With the 1953 model year, ...
sedan. It dramatically demonstrated the effectiveness of modern car safety design over 1950s design, particularly of rigid passenger safety cells and crumple zones.
Early development history
The crumple zone concept was originally invented and patented by the Hungarian Mercedes-Benz
Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
engineer Béla Barényi
Béla Barényi (1 March 1907, Hirtenberg, Austro-Hungarian Monarchy – 30 May 1997, Böblingen, Germany) was an ethnic Hungarian engineer from Austria-Hungary, who was a prolific inventor, sometimes even compared to Thomas Edison. Barényi ma ...
in 1937 before he worked for Mercedes-Benz and in a more developed form in 1952.[The crumple zone man – AutoSpeed]
/ref> The 1953 Mercedes-Benz ''"Ponton"'' was a partial implementation of his ideas, by having a strong deep platform to form a partial safety cell, patented in 1941.
The Mercedes-Benz patent number 854157, granted in 1952, describes the decisive feature of passive safety. Barényi questioned the opinion that had prevailed until then that a safe car had to be rigid. He divided the car body into three sections: the rigid non-deforming passenger compartment and the crumple zones in the front and the rear.
The first Mercedes-Benz carbody developed using the patent was the 1959 Mercedes W111
: ''See Mercedes-Benz S-Class for a complete overview of all S-Class models.''
The Mercedes-Benz W111 was a chassis code given to a range of Mercedes-Benz vehicles produced between 1959 and 1971, including four-door saloons (1959-1968) and two- ...
“Tail Fin” Saloon. The safety cell and crumple zones were achieved primarily by the design of the longitudinal members: these were straight in the centre of the vehicle and formed a rigid safety cage with the body panels, the front and rear supports were curved so that they deformed in the event of an accident, absorbing part of the collision energy.
A more recent development for these curved longitudinal members is to be weakened by vertical and lateral ribs to form telescoping "crash can" or "crush tube" deformation structures.
Function
Crumple zones work by managing crash energy and increasing the time over which the deceleration of the occupants of the vehicle occurs, while also preventing intrusion into or deformation of the passenger cabin. This better protects car occupants against injury. This is achieved by controlled weakening of sacrificial outer parts of the car, while strengthening and increasing the rigidity of the inner part of the body of the car, making the passenger cabin into a "safety cell", by using more reinforcing beams and higher strength steels. Impact energy that does reach the "safety cell" is spread over as wide an area as possible to reduce its deformation. Volvo introduced the side crumple zone with the introduction of the SIPS (Side Impact Protection System
Side Impact Protection System (SIPS) is a passive safety system in an automobile to protect against injury in a side collision, developed by Volvo Cars.
History
SIPS was first introduced in 1991 for the Volvo 700, 900 and 850 series cars of mod ...
) in the early 1990s.
When a vehicle and all its contents, including passengers and luggage are travelling at speed, they have inertia
Inertia is the idea that an object will continue its current motion until some force causes its speed or direction to change. The term is properly understood as shorthand for "the principle of inertia" as described by Newton in his first law ...
/ momentum
In Newtonian mechanics, momentum (more specifically linear momentum or translational momentum) is the product of the mass and velocity of an object. It is a vector quantity, possessing a magnitude and a direction. If is an object's mass an ...
, which means that they will continue forward with that direction and speed (Newton's first law of motion). In the event of a sudden deceleration of a rigid framed vehicle due to impact, unrestrained vehicle contents will continue forwards at their previous speed due to inertia, and impact the vehicle interior, with a force equivalent to many times their normal weight due to gravity. The purpose of crumple zones is to slow down the collision to increase the time over which the occupants decelerate so as to decrease the peak force imparted on the occupants over a given time.
Seatbelt
A seat belt (also known as a safety belt, or spelled seatbelt) is a vehicle safety device designed to secure the driver or a passenger of a vehicle against harmful movement that may result during a collision or a sudden stop. A seat belt red ...
s restrain the passengers so they don't fly through the windshield, and are in the correct position for the airbag and also increase the time over which the occupants decelerate. Seat belts also absorb passenger inertial energy by being designed to stretch during an impact, again to increase the time over which an occupant decelerates. In short: a passenger whose body is decelerated more slowly due to the crumple zone (and other devices) over a longer time survives much more often than a passenger whose body indirectly impacts a hard, undamaged metal car body which has come to a halt nearly instantaneously. It is like the difference between slamming someone into a wall headfirst (fracturing their skull) and shoulder-first (bruising their flesh slightly) is that the arm, being softer, has tens of times longer to slow its speed, yielding a little at a time, than the hard skull, which isn't in contact with the wall until it has to deal with extremely high pressures. The stretching of seatbelts while restraining occupants during an impact, means that it is necessary to replace them if a vehicle is repaired and put back on the road after a collision. They should also be replaced if their condition has deteriorated e.g. through fraying or mechanical or belt mounting faults. In New Zealand
New Zealand ( mi, Aotearoa ) is an island country in the southwestern Pacific Ocean. It consists of two main landmasses—the North Island () and the South Island ()—and over 700 smaller islands. It is the sixth-largest island count ...
it is officially mandatory to replace worn inertia reel type seatbelts only with "webbing grabber" type belts that have less play and are more effective on older cars. Newer cars have electronically fired pre-tension seatbelts that are timed to work with the airbag firing. Buying used seatbelts is not a good idea even in countries where it is legal to do so, because they may have already been stretched in an impact event and may not protect their new users as they should.
The final impact after a passenger's body hits the car interior, airbag or seat belts is that of the internal organs hitting the ribcage or skull due to their inertia. The force of this impact is the way by which many car crashes cause disabling or life-threatening injury. Other ways are skeletal damage and blood loss, because of torn blood vessels, or damage caused by sharp fractured bone to organs and/or blood vessels. The sequence of speed-reducing technologies—crumple zone — seat belt — airbags — padded/deformable interior—are designed to work together as a system to reduce the peak force of the impact on the outside of the passenger(s)'s body by lengthening the time over which this force is imparted. In a collision, slowing down the deceleration of the human body by even a few tenths of a second drastically reduces the peak force imparted.[
A misconception about crumple zones sometimes voiced is that they reduce safety for the ''occupants'' of the vehicle by allowing the body to collapse, therefore risking crushing the occupants. In fact, crumple zones are typically located in front of and behind the main body of the car (which forms a rigid "safety cell"), compacting within the space of the engine compartment or boot/trunk. Modern vehicles using what are commonly termed "crumple zones" provide far superior protection for their occupants in severe tests against other vehicles with crumple zones and solid static objects than older models or SUVs that use a separate chassis frame and have no crumple zones.
They do tend to come off worse when involved in accidents with SUVs without crumple zones because most of the energy of the impact is absorbed by the vehicle with the crumple zone—however, even for the occupants of the "worse off" car, this will still often be an improvement, as the result of two vehicles without crumple zones colliding will usually be more hazardous to both vehicles' occupants than a collision that is at least partly buffered.
Another problem is "impact incompatibility" where the "hard points" of the ends of chassis rails of SUVs are higher than the "hard points" of cars, causing the SUV to "override" the engine compartment of the car.] In order to tackle this problem, more recent SUV/off-roaders incorporate structures below the front bumper designed to engage lower-height car crumple zone
Volvo XC70 low level front safety cross members shown here
Volvo's press release about this feature:
'' "Lower cross-member that helps protects lower cars: The front suspension subframe in the new Volvo XC60 is supplemented with a lower cross-member positioned at the height of the beam in a conventional car. The lower cross-member strikes the oncoming car's protective structure, activating its crumple zone as intended so the occupants can be given the maximum level of protection." ''
Low speed impact absorption
The front of the bumper is designed to withstand low speed collisions, e.g. as in parking bumps to prevent permanent damage to the vehicle. This is achieved by elastic elements, such as the front apron. In some vehicles, the bumper is filled with foam or similar elastic substances. This aspect of design has received more attention in recent years as NCAP crash assessment has added pedestrian impacts to its testing regime. The reduction of rigid support structures in pedestrian impact areas has also been made a design objective.
In the case of less severe collisions (up to approx. 20 km / h), the bumper and outer panel design should ensure that the crumple zone and the load-bearing structure of the vehicle is damaged as little as possible and repairs can be carried out as cheaply as possible. For this purpose, so-called crash tubes or crash boxes are used for mounting bumpers. Crashtubes consist of a hollow steel profile, which transforms the incident energy by rolling up the profile.
Computer modelled crash simulation
In the early 1980s, using technology developed for the aerospace
Aerospace is a term used to collectively refer to the atmosphere and outer space. Aerospace activity is very diverse, with a multitude of commercial, industrial and military applications. Aerospace engineering consists of aeronautics and astrona ...
and nuclear industries, German car makers started complex computer crash simulation
A crash simulation is a virtual recreation of a destructive crash test of a car or a highway guard rail system using a computer simulation in order to examine the level of safety of the car and its occupants. Crash simulations are used by autom ...
studies, using finite element method
The finite element method (FEM) is a popular method for numerically solving differential equations arising in engineering and mathematical modeling. Typical problem areas of interest include the traditional fields of structural analysis, heat ...
s simulating the crash behaviour of individual car body components, component assemblies, and quarter and half cars at the body in white
Body in white (BIW) is the stage in automobile manufacturing in which a car body's frame has been joined together, that is before painting and before the motor, chassis sub-assemblies, or trim (glass, door locks/handles, seats, upholstery, elect ...
(BIW) stage. These experiments culminated in a joint project by the Forschungsgemeinschaft Automobil-Technik (FAT), a conglomeration of all seven German car makers (Audi
Audi AG () is a German automotive manufacturer of luxury vehicles headquartered in Ingolstadt, Bavaria, Germany. As a subsidiary of its parent company, the Volkswagen Group, Audi produces vehicles in nine production facilities worldwide.
Th ...
, BMW, Ford
Ford commonly refers to:
* Ford Motor Company, an automobile manufacturer founded by Henry Ford
* Ford (crossing), a shallow crossing on a river
Ford may also refer to:
Ford Motor Company
* Henry Ford, founder of the Ford Motor Company
* Ford F ...
, Mercedes-Benz
Mercedes-Benz (), commonly referred to as Mercedes and sometimes as Benz, is a German luxury and commercial vehicle automotive brand established in 1926. Mercedes-Benz AG (a Mercedes-Benz Group subsidiary established in 2019) is headquartere ...
, Opel
Opel Automobile GmbH (), usually shortened to Opel, is a German automobile manufacturer which has been a subsidiary of Stellantis since 16 January 2021. It was owned by the American automaker General Motors from 1929 until 2017 and the PSA Grou ...
( GM), Porsche
Dr. Ing. h.c. F. Porsche AG, usually shortened to Porsche (; see #Pronunciation, below), is a German automobile manufacturer specializing in high-performance sports cars, SUVs and sedans, headquartered in Stuttgart, Baden-Württemberg, Germany ...
, and Volkswagen
Volkswagen (),English: , . abbreviated as VW (), is a German Automotive industry, motor vehicle manufacturer headquartered in Wolfsburg, Lower Saxony, Germany. Founded in 1937 by the German Labour Front under the Nazi Party and revived into a ...
), which tested the applicability of two emerging commercial crash simulation codes. These simulation codes recreated a frontal impact of a full passenger car structure (Haug 1986) and they ran to completion on a computer overnight. Now that turn-around time between two consecutive job-submissions (computer runs) did not exceed one day, engineers were able to make efficient and progressive improvements of the crash behaviour of the analyzed car body structure. The drive for improved crashworthiness in Europe has accelerated from the 1990s onwards, with the 1997 advent of Euro NCAP
The European New Car Assessment Programme (Euro NCAP) is a European voluntary car safety performance assessment programme (i.e. a New Car Assessment Program) based in Leuven (Belgium) formed in 1996, with the first results released in February ...
, with the involvement of Formula One
Formula One (also known as Formula 1 or F1) is the highest class of international racing for open-wheel single-seater formula racing cars sanctioned by the Fédération Internationale de l'Automobile (FIA). The World Drivers' Championship, ...
motor racing safety expertise.
"Sleds" inside safety cells
The 2004 Pininfarina
Pininfarina S.p.A. (short for Carrozzeria Pininfarina) is an Italian car design firm and coachbuilder, with headquarters in Cambiano, Turin, Italy. The company was founded by Battista "Pinin" Farina in 1930.
On 14 December 2015, the Indian mu ...
'' Nido'' Experimental Safety Vehicle Experimental Safety Vehicle (ESV) is the designation for experimental concept cars which are used to test car safety ideas.
In 1973, the United States Department of Transportation, U.S. DOT announced its ESV project, the aim of which was to obtain ...
locates crumple zones ''inside'' the survival cell. Those interior crumple zones decelerate a sled-mounted survival cell.
Volvo has also been developing this idea for use in small cars. Their driver's seat is mounted to what is basically a "sled" on a rail, with shock absorbers in front of it. In an impact, the whole "sled" of driving seat and belted-in driver, slides forward up to 8 inches, and the shock absorbers dissipate the peak shock energy of the impact, lengthening the deceleration time for the driver. Simultaneously, the steering wheel and the driver's side dashboard slide forward to make room for the driver, as he is thrown forwards stretching the seatbelt. Combined with a front crumple zone and airbag, this system could greatly reduce the forces acting on the driver in a frontal impact.
See also
* Automobile safety
Automotive safety is the study and practice of design, construction, equipment and regulation to minimize the occurrence and consequences of traffic collisions involving motor vehicles. Road traffic safety more broadly includes roadway design.
...
* Guard rail#Automotive safety
* Traffic barrier
Traffic barriers (sometimes called Armco barriers,AK Steel (formerly Armco) genericized trademark also known in North America as guardrails or guard rails and in Britain as crash barriers) keep vehicles within their roadway and prevent them from ...
* Crash test
A crash test is a form of destructive testing usually performed in order to ensure safe design standards in crashworthiness and crash compatibility for various modes of transportation (see automobile safety) or related systems and componen ...
* New Car Assessment Program
A New Car Assessment Program (or Programme) is a government car safety program tasked with evaluating new automobile designs for performance against various safety threats.
History
The first NCAP was created in 1979, by the United States Nation ...
References
External links
Before and after crash between 1959 Bel Air and 2009 Malibu
Stuntbusters: Head-On Collision 1962 Cadillac vs. 2002 Cadillac
Crumple Zones(How Do Crumple Zones Work)
* ttp://auto.howstuffworks.com/car-driving-safety/accidents-hazardous-conditions/crash-test.htm How Crash Testing Works - Howstuffworks.combr>Why is it still necessary to crash test vehicles? - Howstuffworks.com
BBC News - How the dead have helped the living
British TV 'Fifth Gear' programme. How a badly repaired Ford Focus crumple zone fails to work in a crash test.
British TV 'Fifth Gear' programme. Renault Modus small car with 5 star NCAP rating vs 1990 Volvo 940GLE head on crash test.
Mythbusters - Car crash force
Béla Barényi – a history of safety - Mercedes-Benz original
The fundamental dynamics of violence in car crashes. The physics. The engineering. John Cadogan of autoexpert.com.au
Crash Engineering and Safety Design - engineeringclicks.com
{{Portal bar, Cars, Trains
Vehicle safety technologies
Hungarian inventions