Crumple Zones

One of the most effective inventions for auto safety is the design of the crumple zone. Crumple zones are areas of a vehicle designed to crumple in a collision and to absorb energy of the impact, preventing it from affecting the occupants. The design of the crumple zone is dependant on the size and weight of the vehicle and the designers must balance between too much impact resistance and too little impact resistance. Crumple zone designs include frame segments built to bend in certain areas or to collapses in on themselves. However, there are more advanced designs that make use of a variety of metals and materials that are engineered to absorb as much kinetic energy as possible.

Crumple Zones and Newtons Laws

Newtons first law states that an object in motion will remain in motion with the same speed and in the same direction unless acted upon by an unbalanced force. As a result of Newtons first law, if a car was travelling at a speed of 60kmph, the occupants inside are as well. Therefore if a vehicle were to make contact with a solid wall and come to an immediate stop, the occupants inside the vehicle will continue to travel in the same direction at 60kmph.

Newtons second law states that when an unbalanced force is applied to an object, it will accelerate according to force = mass x acceleration. Therefore the time taken for a vehicle to become stationary or change direction is increased, the force experienced by the vehicle and the passengers is decreased. As a result if the time taken to stop is shorter, the force is greater however, crumple zones add time to the crash by absorbing energy.

How They Work

Intense kinetic forces are in use whenever a vehicle is involved in a crash. The two safety goals crumple zones aim to accomplish is to reduce the initial force of the crash and to redistribute the force before it reaches the vehicle’s occupants. Crumple zones create buffer zones around the perimeter of the car where certain parts of the vehicle are rigid and resistant to deforming with an example being the passenger compartment and the engine. If these rigid parts were to hit something, they will automatically decelerate very quickly creating a lot of force.When crumple zones surround these parts, the less rigid materials will absorb the initial impact. As soon as the crumple zones begin crumpling, the vehicle will begin to decelerate, which will result in an extended deceleration over a few extra tenths of a second.

Structure

As a result of the passenger compartment of the car resisting being penetrated by outside objects and with the limitation that the entire car can’t become a crumple zone, only in the front of and rear of a car are designed with a rigid, strong frame to enclose the occupants. Force redistribution and reduction is achieved inside the passenger compartment through the airbags.

Building crumple zones into a large vehicle is much easier than a smaller car as a result of the large car containing plenty of room to crumple before the passenger compartment is impacted. An example of a small efficient vehicle is the smart fortwo. In this particular vehicle, the driver and passenger are enclosed in the trodden safety cell, which is composed of a steel framework with great rigidity for its size. It is designed to distribute impacts across the entire frame and located at the from and rear of the vehicle are crash boxes, which are small steel frameworks that collapse and crumple to absorb impacts.