Page relationship that a vehicle experiences during

Page  of 6ZOOMASSIGNMENT – 2DESIGN OF AUTOMOBILE BODY FOR SAFETY? Design of automobile body structure is the first and crucial step in improving the safety of the vehicle. It is this part of the vehicle which is ultimately responsible for safety of its occupants, so needless to say, it becomes imperative that the design process should be taken in a more holistic way.? Vehicle occupant safety can be classified into two broad areas: the degree to which a vehicle protects its occupants in a crash, known as crashworthiness, and the extent to which the vehicle enables the driver to lower his or her chances of being in a crash, known as crash avoidance. Much academic and industrial research has been devoted to optimizing the performance of safety systems that aid in crashworthiness, including the designs of vehicle structural systems and restraint systems.? The first thing to consider is the basic energy relationship that a vehicle experiences during a collision. The kinetic energy of a vehicle destroyed during a collision can be expressed as: K.E = (m – Ñm) V^2/2 Where m = total mass of vehicle Ñm = moveable mass (passenger or load) V = Velocity? The kinetic energy of a vehicle destroyed during a collision is absorbed by the work done on materials by elastic deformation.? In addition to the energy considerations, there are various loads that a vehicle faces: ? Load cases:? Bending case – Due to weight of components along vehicle frame (static load).? Torsion case – When vehicle traverses on an uneven road.? Combined bending and torsion – All load of lighter axle is applied to one wheel.? Lateral loading – Due to cornering, generated at tyre to ground contact.? Longitudinal loading – When vehicle accelerates and decelerates, inertia forces are generated and adds to additional bending.? Asymmetric loading – Results when one wheel strikes a raised object or drops into a pit.? Keeping in mind these considerations, the frame and chassis is designed for a particular vehicle (heavy or light). This leads to 2 types of body designs: ? Body over frame design (generally heavy vehicles) – ? ADVANTAGES:? Easier to design, build and modify (less of an issue now that computer-assisted design (CAD) is commonplace, but still an advantage for coach-built vehicles).? Quieter, because the stresses do not pass into the body, which is isolated from the frame with rubber pads around the attachment bolts.? Easier to repair after accidents. This is crucial for first responders (police, fire, EMS) and taxicabs, because damaged bolt-on fenders can be replaced in the firm’s own garage for petty cash, with the cab returned to earning status immediately, whereas a unibody body would require straightening by paid specialists on a machine expensive to rent.? DISADVANTAGES:? Heavier than unibody, causing lower performance and/or higher fuel consumption, although reconstruction of a chassis in a metal like titanium can ensure a more lightweight material.? Far less resistant to torsional flexing (flexing of the whole car in corners), compromising handling and road grip.? Lack of a crumple zone causes higher rate of death and serious injury. Some cars have adopted a “front clip” and “rear clip” format similar to what is used in NASCAR where the car is split into three sections, and the clips absorb the impact, allowing the “clip” to be replaced when repairing the car.? Unibody design (light vehicles):? ADVANTAGES:? The first is weight savings: Since every part of the car is key to structural integrity, there’s no need for the added mass of a dedicated frame. Also offers good handling and control.? Unibody designs make it much easier to protect passengers by directing crash energy away from the cabin.? The absence of a separate frame frees designers in terms of styling and usage of space, allowing for more unique-looking automobiles and larger interiors and trunks.? DISADVANTAGES:? Harder to repair after accidents.? Requires heavy engineering to deal with stresses the body will be subjected to.? All the points taken are weigh out for the vehicle to make a suitable body. After this, there are various parts and systems of the body / vehicle which are also carefully designed to reduce the effects of collision and avoid sharp edges, ornaments and edges or projected elements inside or outside a vehicle. ? Some of the parts and systems include: safety features of a door system which prevents opening of doors while in motion due to transmission interlock and proper design to minimize side impacts, stronger roof system for rollover protection, window glasses (should be shatter-proof) and windscreen (freedom from faults which interfere with vision), bumpers, seat back and head restraints, rear view mirrors etc.THE END