Safety Airbags in Cars – Seminar pdf Report Download

ABSTRACT
The present topic is about safety airbags in cars. No safety device has consumed more attention and resources than the airbag. It is known with high confidence that when a crash occurs , the presence of airbag reduces fatality risk to drivers.
Airbags are subject of serious government and industry research. My seminar takes you to the history, development and working aspects of airbag.

INTRODUCTION

For years, the trusty seat belt provided the sole form of passive restraint in our cars. There were debated about their safety, especially relating to children. But over time, mush of the country adopted mandatory seat-belt laws. Statistics have shown that the use of seat belts has saved thousands of lives that might have been lost in collisions. Air Bags have been under development for many years. The attraction of a soft pillow to land against in a crash must be very strong – the first patent on an inflatable crash-landing device for airplanes was filed during World War II.

In the 1980’s the first commercial air bags appeared in automobiles .Since 1988, all new cars have been required to have air bags on both driver and passenger sides (Light Trucks came under the rule in 1999). Todate, Statistics show that air bags reduce the risk of dying in a direct frontal crash by 30 percent. Newer than steering Wheel mounted or Dashboard mounted bags, but not so widely used, are seat-mounted and door mounted side air-bags. Some experts say that within the next few years, our cars will go from having dual air bags top having six or even eight air bags. Having evoked some of the controversy that surrounded seat-belt use in its early years, air bags are the subject of serious government and industry research and tests.

THE BASICS OF AIR BAGS

Before looking at specifics, let’s review our knowledge of the laws of the motion. First, we know that moving objects have momentum (the product of the mass and velocity of an object. Unless an outside force acts on an object, the object will continue to move its present speed and direction. Cars consist of several objects, including the vehicle itself, Loose objects in the car and, of course, passengers. If these objects are not restrained, they will continue moving at whatever speed the car is traveling at, even if the car is stopped by a collision.

Stopping an object’s momentum requires force acting over a period of time. When a car crashes, the force required to stop an object is very great because the car’s momentum has changed instantly while the passengers’ has not much time to work with. The goal of any supplemental restraint system is to help stop the passenger while doing as little damage to him or her as possible.

What an air bag wants to do is to slow the passengers’ speed to zero with little or no damage. The constraints that it has to work within are huge. The air bag has the space between the passenger and the steering wheel or dashboard and a fraction of a second to work with. Even that tiny amount of space and time is valuable, however, if the system can slow the passenger evenly rather than forcing an abrupt halt to his or her motion.

MAIN PARTS OF AIR BAG

There are three parts to an air bag that help to accomplish this feat:
1. Bag
2. Sensor
3. Inflation system

BAG
The bag itself is made of a thin, nylon fabric, which is folded into the steering wheel or dashboard or, more recently, the seat or door. The powdery substance released from their sir bag, by the way, is regular corn starch or talcum powder, which is used by the air bag manufacturers to
keep the bags pliable and lubricated while they’re in storage.

SENSOR
The sensor is the device that tells the bag to inflate. It works with the control module to discriminate between crash and non-crash events. These sensors measure the severity of the impact. Inflation happens when there is a collision force equal to running into a brick wall at 16 to 24 Km per hour.
They are setup so that sudden negative acceleration will cause the contacts to close, telling the control module that a crash before airbag deployment.

INFLATION SYSTEM
The air bag’s inflation system reacts sodium azide(NaN3) with potassium nitrate (KNO3) to produce large volume of nitrogen gas. Hot Blasts of the nitrogen inflate the air bag from its storage site up to 322Kmph. A Second later, the gas quickly dissipates through a tiny holes in the bag, thus deflating the bag so you can move.

CONSTRUCTION OF AIR BAGS
Airbag are assemblies consisting of the airbag (made of Nylon), inflator modules and sensor housing, electrical connectors (Clock spring), airbag retainer and the cover. The driver’s side bag is mounted in the center of the steering wheel as shown in fig.

WORKING OF AIR BAGS
Air Bags are designed to inflate in frontal or frontal-angle impacts in which the car strikes an immovable object at more than about 16 Kilometers per hour or another car at twice that speed. After a collision, sensors sense an electric current to an igniter system or, in some cases, to the computerized control unit. This unit evaluates the situation and then sends an electrical impulse to the igniter system. The electric current heats a filament (wire), which then ignites a capsule. The Ignited capsule supplies the heat to ignite gas-generating pellets. In most systems, the pellets are made of sodium azide and produce nitrogen gas when they burn. In other systems, pressurized argon gas is used instead. The gas then expands quickly and inflates the airbag, which then breaks through a plastic cover in the steering wheel or, the dashboard on the passenger side. The whole process takes about 0.1 second from the exact moment the crash is detected. The air bag starts to deflate immediately, venting the harmless gas through holes in the back of the bag of the through the fabric itself.