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8/14/2019 Airbags and Seatbelt
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BY
K.SUGANESWARAN
AIRBAGS AND SEATBELT
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AIRBAGS
In the 1980s the first commercial air bags appeared inautomobiles.
Air bags are most commonly used for cushioning, in
particular after very rapid inflation in the case of an
automobile collision.
The safety belts, primarily restrain the occupants torso and
pelvic movements, however, the instantaneous head, neck
rotations cannot be prevented by the safety belts.
The air bags supplements seat belt in this function byproviding soft cushion between occupants head and
steering / dash board.
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CONT
This prevents direct contact between occupantshead and rigid vehicle interiors and evenly
distributing the forces on occupants face.
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TYPES
Frontal air bags
Door mounted side head airbags
Knee air bags
Side curtain air bags
Air bag for pedestrian protection on front hood of
vehicle(under research)
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WORKING
The bag itself is made of a thin, nylon fabric Polyamide(PA) or Polyester (PETP) partially with blow-out holes for
controlled cushion, which is folded into the steering wheel.
The sensor is the device that tells the bag to inflate.
The sensors receive information from an accelerometerbuilt into a microchip.
The air bag's inflation system reacts with Sodium Azide
(NaN3) with Potassium Nitrate (KNO3) to produce nitrogen
gas.
Hot blasts of the nitrogen inflate the air bag.
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CONT
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CONT
The air bag system ignites a solid propellant, which burnsextremely rapidly to create a large volume of gas to inflate
the bag.
The bag then literally bursts from its storage site with the
speed up to 322 km/h - faster than the blink of an eye. A second later, the gas quickly dissipates through tiny holes
in the bag, thus deflating the bag .
Cornstarch or talcum powder is used for effective
lubrication.
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TECHNICAL COMPLEXITIES
The decision whether to deploy or not to deploy are doneby airbag triggering algorithm.
Inputs coming from the crash sensors which in turn dependon crashworthiness of individual vehicle structures.
Many times real life accidents do not generate crash forcesenough to trigger the airbag to deploy.
If occupant is sitting close to the airbag less than teninches, the risk of occupant getting seriously injured by thedeployment of airbag itself increases many fold.
Children can get seriously injured even fatal injuries cantake place if unbelted child is sitting very close to theairbag.
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SEATBELT ANCHORAGES
Restraint systems integrated with occupants seat haveshown improved occupant safety and decreased risk of
injuries during motor vehicle impacts .
A seat belt or safety belt is a safety harness designed to
secure the occupant of a vehicle against harmful movementthat may result from a collision or a sudden stop.
Seat Belts are intended to reduce injuries by stopping the
wearer from hitting hard interior elements of the vehicle.
Seat belts also absorb energy by being designed to stretchduring any sudden deceleration.
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CONT
Spreads the loading of impact on the passengersbody.
An arrangement of straps with a securing buckle, adjusting
devices and attachments which are capable of being
anchored to the interior of a motor vehicle .
Designed to diminish the risk of injury to the wearer in theevent of collision or of abrupt deceleration of the vehicle,
by limiting the mobility of the body of the wearer.
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TYPES
Two Point (Lap) Belt
Three Point Belt
Harness Belt
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CONT
A seat belt retractor is a device having a gas generator forgenerating a high pressure gas when a vehicle is in
emergency.
Chamber cylinder for conducting the high pressure gas
from the gas generator, a piston received movably withinthe chamber cylinder and pressed and moved by the high
pressure gas.
Piston having an O ring sealed end portion engaging walls
of the chamber cylinder and a rack portion extending intothe chamber cylinder and finally tighten the belts.
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Cont
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