Hood design-Week 2

Hood and its component -The hood is the hinged cover over the engine of motor vehicles. Hoods can open to allow access to the engine compartment for maintenance and repair. A typical hood assembly consist of hood outer panel, inner panel, latch and striker, hinge. It is the most critical part of the car as it is always exposed to the frontal crash, climatic conditions, heat generation by the engine compartment, etc. This gives access to the engine, battery, and other components which are always needed to be inspected at regular intervals.

Hood mainly consist of 4 components:

Inner panel, Outer panel, Hinges and Latch striker.

Outer panel- Outer panels are the aesthetic elements of a car. The shape, position and size of the hood should satisfy the safety norms. During designing the hood we give more importance to pedestrian safety. The outer panel is attached to the inner panel by hemming. Then mastic sealants are provided between outer panel and inner panel to reduce vibration.

Inner Panel-Inner panel is the part that gives strength and rigidity to the outer panel. Then we provide the emboss for the latch and hinge elements after fixing the location.

Reinforcement-Reinforcements are provided according to the design requirements. Hinges are provided for the movement of hood to smoothen the opening of hood and as the limit of hood that can open . Striker are provided as the constraint to lock the hood in close position. According to the design requirement here it is given 1.5mm thickness to both hinge and latch reinforcements.

Mastic Data- We cannot use other joining techniques like welding, riveting because they leave marks on the outer panel which spoil its aesthetic appearance. So, mastic sealants are used to stick the inner surfaces of outer panel and inner panel. Mastic sealants are elastic compound that behave like rubber. It is applied between the inner and outer panels at specified spots. Each spot of mastic sealants has its effect around a circular region of 80mm diameter. Thus, the mastic points are arranged in such a way that it covers the areas away from the hemming which are more vulnerable to vibrate.

Hemming - Hemming is a forming operation in which the edges of the sheet are folded or folded over another part in order to achieve a tight fit. Normally hemming operations are used to connect parts together, to improve the appearance of a part and to reinforce part edges. The accuracy of the hemming operation is very important since it affects the appearance of the surface and surface quality. Typical hemming defects are splits or wrinkles in the flange, material overlaps in the corner areas or material roll-in.

Emboss- Embosses are provide throughout the inner panel . Main aim to provide emboss is to increase the stiffness of the inner panel .The shape and size of the embosses also determines the direction of the force distribution resulted from frontal collision. The force should be always distributed away from the passengers. Here in the figure the embosses are designed in such a way that the force is directed to either sides of the car.

Final assembly-