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Article by : Duane Bong

Introduction To Crumple Zones

Since crumple zones were first introduced by Volvo in 1966, they have become an indispensable safety feature in modern cars. By absorbing part of the impact from a car crash, crumple zones have been credited with saving thousands of lives each year. Nearly all cars sold today have front and rear crumple zones.

How Do Crumple Zones Work?

Crumple zones are deliberate weak spots that engineers have placed in the structure of a car. While this might appear contrary to passenger safety, there are sound principles behind this approach.

By placing the weak spots in strategic locations, the metal work of a car can be made to collapse in a controlled manner. This creates 2 mechanisms by which the energy from an impact can be managed:

1. in deforming the metal work of the car, energy from the impact gets "used up" or converted into heat. This reduces the amount of energy left to damage the passenger area.

2. since the collapse is controlled, energy from the impact can be directed away from the passenger area. In most designs, force from the impact is channelled to areas such as the floor, bulkhead, sills, roof and bonnet.

Force On The Passenger

To understand how crumple zones affect passengers, consider a car crashing head-on into a stationary concrete wall. Before the crash, the car and its passengers move together at the same speed. If the car has a rigid body, an impact will cause both the car and passengers to come to a stop in a split second.

It is this rapid deceleration that causes injuries and fatalities in a car crash. The force acting on the passengers is given by Newton's 2nd law:

  

As the stopping time is only a split second, the force on the passengers is very high.

Cars with crumple zones, however, do not have a rigid body. One can think of them as springs being compressed against a wall. Although the front bumper of the car immediately becomes stationary, it takes some time for the metal work to collapse. This allows the middle and rear of the car to continue in motion for a short time.

Since the stopping time is increased, the force acting on the passengers is greatly reduced.

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Antilock Brake System [ABS]





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