The crumple zone concept was invented and patented by the Austrian-Hungarian Mercedes-Benz engineer Bela Barely originally in 1937 before he worked for Mercedes-Benz and in a more developed form in 1952. The Mercedes-Benz patent number 854157, granted in 1952, describes the decisive feature of passive safety.
Barely questioned the opinion prevailing 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 carboy developed using this patent was the 1959 Mercedes W111 “Tail Fin” Saloon. The safety cell and crumple zones were achieved primarily by the design of the longitudinal members: these were straight in the center of the vehicle and formed a rigid safety cage with the body panels, the front and rear supports were curved, so they deformed in the event of an accident, absorbing part of the collision energy.
A more recent development was for these curved longitudinal members is to be weakened by vertical and lateral ribs to form telescoping “crash can” or “crush tube” deformation structures. Activated rear crumple zone Cross-section to show the different strength of the metal in a Saab 9000.
The safety cell is in stronger metal (red) compared to the crumple zones (yellow).VW Vent / Jetty activated front crumple zone A Toyota Camry after a front impact with a tree. 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 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.
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. Seatbelts 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. 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 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. 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.
Another misconception about crumple zones that is sometimes voiced is that they absorb energy of a crash so that less energy is transferred to the occupants, when in fact the total force imparted upon an occupant is solely determined by their mass and their acceleration (or in the case of a crash, deceleration) because Force = mass x acceleration, and crumple zones, airbags, and any other safety features do nothing to change either the mass of an occupant, or the total change in velocity (acceleration/deceleration) of the occupants. Instead, the entire premise of these safety features is to spread the total force imparted on the occupants out over a longer period of time so that the peak force imparted is lower, reducing the likelihood of injuries.
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 zones.
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 front of the bumper is designed to withstand low speed collisions, e.g. As in parking bumps to prevent permanent damage to the vehicle.
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. 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.
VW POLO first successful frontal full car crash simulation (ESI 1986). Visualisation of how a car deforms in an asymmetrical crash using finite element analysis. EuroNCAP FRONTAL IMPACT (left-hand drive vehicles). Lotus Elora front crash test showing Aluminum chassis crush structure, the height of the rigid front chassis side beams and rigid front cross-beam. In the early 1980s, using technology developed for the aerospace and nuclear industries, German carmakers started complex computer crash simulation studies, using finite element methods simulating the crash behavior of individual car body components, component assemblies, and quarter and half cars at the body in white(BIW) stage. These experiments culminated in a joint project by the Forschungsgemeinschaft Automobil-Technik (FAT), a conglomeration of all seven German carmakers (Audi, BMW, Ford, Mercedes-Benz, Opel (GM), Porsche, and Volkswagen), which tested the applicability of two emerging commercial crash simulation codes.
These simulation codes recreated a frontal impact of a full passenger car structure (Hang 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 behavior of the analyzed car body structure.
The drive for improved crash worthiness in Europe has accelerated from the 1990s onwards, with the 1997 advent of Euro NCAP, with the involvement of Formula One motor racing safety expertise. The 2004 Pininfarina Dido Experimental Safety Vehicle locates crumple zones inside the survival cell.
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.
Combined with a front crumple zone and airbag, this system could greatly reduce the forces acting on the driver in a frontal impact. ^ “Physics in the Crumple Zone | Plastics Helps Save Lives”.
Of course, keeping people safe in auto accidents isn't as simple as making the whole vehicle crumple. We'll even take a look at crumple zones designed to absorb the massive impact of a train collision.
To find out the forces involved in a collision, and to learn how a well-designed crumple zone can minimize occupant injury, read the next page. The best way to reduce the initial force in a crash with a given amount of mass and speed is to slow down the deceleration.
The forces you experience in an emergency stop are much greater than when you gradually slow down for a stoplight. In a collision, slowing down the deceleration by even a few tenths of a second can create a drastic reduction in the force involved.
Certain parts of a car are inherently rigid and resistant to deforming, such as the passenger compartment and the engine. If those rigid parts hit something, they will decelerate very quickly, resulting in a lot of force.
Surrounding those parts with crumple zones allows the less rigid materials to take the initial impact. Bending parts of the frame, smashing body panels, shattering glass -- all of these actions require energy.
Parts of the car are built with special structures inside them that are designed to be damaged, crumpled, crushed and broken. We'll explain the structures themselves shortly, but the fundamental idea is that it takes force to damage them.
Absorbing and redirecting impact is great, but it isn't the only safety issue auto designers have to worry about. You can't make an entire car a crumple zone because you don't want the people inside it to crumple also.
That's why cars are designed with a rigid, strong frame enclosing the occupants, with crumple zones in the front and rear. Sometimes, cars have to be redesigned to move the engine farther back in the frame to accommodate a larger crumple zone.
Fuel tanks and battery packs, in electric or hybrid vehicles, also need to be protected from impact to prevent fires or exposure to toxic chemicals. For example, if a car is rear-ended, the frame bends up, lifting the gas tank out of the way and absorbing some impact.
Newer cars have systems that cut off fuel supply to the engine during a crash, and the Tesla Roadster, a high performance electric car, has a safety system that shuts off the battery packs and drains all electrical energy from the cables running throughout the car when it senses an emergency . The driver and passenger are enclosed in the tuition safety cell, a steel framework with excellent rigidity for its size.
The short wheelbase of the for two means almost any impact will involve the tires, wheels and suspension. These components have been designed to deform, break away or rebound, helping absorb even more kinetic energy during an impact .
Next, we'll see how crumple zones are helping to keep your favorite race car driver alive. There have also been rare occasions when a race car has struck a solid object at high speed, such as NASCAR driver Michael Walt rip's crash at Bristol in 1990.
He hit the blunt end of a concrete wall at racing speeds, and the car stopped very suddenly. Clearly, the incident went well beyond the abilities of any crumple zone, and in fact it was simply a matter of luck that nothing intruded into the driver's compartment to injure Walt rip.
From the 1980s to the early 2000s, there were numerous racing fatalities due to overly stiff chassis. The crash didn't initially appear to be severe, and the car didn't seem to suffer extensive damage; however, that was exactly the problem.
A great deal of the force of impact was transferred directly to the driver, causing immediate and severe injuries. This injury is the cause of death in many auto racing accidents, and it occurs when the head snaps forward on impact while the body remains restrained by safety belts.
While head and neck restraint devices have lowered the incidence of basilar skull fractures, reducing impact forces on the driver have played a major role as well. The reason behind the increase in fatal crashes was simply the pursuit of higher performance.
Car designers and crews sought better handling by creating a more rigid chassis. Sure, they made the chassis more rigid, but when these inflexible cars hit a wall, there was no give.
Even before Earnhardt's death in 2001, racetracks were trying to find solutions to this problem. Tracks in the northeastern United States experimented with giant blocks of industrial Styrofoam lining the walls, a similar concept to the soft wall technology used on many super speedways today.
Thinner-gauge steel tubing is now used on certain portions of the chassis, and frame rails are given a bend or notch, so they deform somewhat predictably on impact. NASCAR's Car of Tomorrow, used in Sprint Cup racing, has foam and other impact absorbing material inserted into critical areas of the frame.
Although auto racing will always be a dangerous sport, the use of less rigid chassis construction, soft wall technology and head and neck restraint systems have greatly reduced crash impact forces on drivers. For more information about automotive safety devices, racing and other related topics, follow the links on the next page.