Hood design-Week 2

Hood:- It is opening body that covers engine in front side of vehicle. It open to allow access to the engine compartments for the maintenance like replace of cooling water, engine oil & repaire the parts. Hood is also consider as another type of door.

It consist of 4 part are following-

• Outer Pannel - It is outer skin of the hood. It provide luxurious look to the vehicle.
• Inner pannel - It provide the strength of hood. It distribute the force toword the hinged.
• Striker - It is U shape bend that attached to the latch. It lock the hood & any loose motion of hood.
• Hinge- It is pivoting point where hood open & close.

Designe consideration:-

• Opening Angle- It is depends upon average human height. In india is 5.8 feet where as in europian countries is 6 feet. It important criteria becouse opening angle is less, a chance of head injury of human. 
• Hood Stay- It is device for supporting the engine hood in its open position. Two types of hood stay are following- 

1. Supporting rod- It is cost effective & simple design. length depends upon opening angle & radius of curvature is less than 35mm becouse of if more, than rod is bend due to hood weigth.
2. Gass stay-Easily lifting the heavy hood and there is no human effort needed. 

• Reinforcement- It is an additional of material to the compansate the strength. Provided mainly in hinged & latch region. Stiffer pad improve the strength to reduce noise & vibration. 

Pedestrian safety:-

Designe should be such way that it should reduce the injury to the pedestrian in the event of pedestian vehicle collision. following parameter consider for predestian safety in hood design.                                                                                                                                                                                Wrap around distance(WAD)- It is the geometric trace from contact point with graund Graund Reference Plane.                                                                        Side referance line- line draw from graund at 45 degree and tangent to end point of fender.                                                                                                    Child head impact zone - 1000 WAD to 1500 WAD                                                                                                                                                              Adult head impact zone - 1500 WAD to 2100 WAD 

Latch trajectory- It is circle, follows the latch striker path. It is draw from hings axis at radius of distance between hing axis and striker. 

Mastic - It is use between outer and inner panel. It is a hard rubber to join inner & outer pannel becouse other joining process like welding or riviting are not good for asthentic design. It also improve NVH characterstics. It effective around circuler region of 80mm diameter.

Manufacturing process:-

• Deep drawing- It is metal forming process which occurs under a combination of tensile & compressive condition. In deep drawing depth is gratter or equal to the diameter. Form cup like product from thin sheet metal known as deep drawing. 
• Hemming- It is metal forming process inwhich sheet are join by bending it usualy to 180degree. It involves rolling of edge sheetmetal over and itself, creating an area of two layer. During this process, the edge of sheet metal is folded over. The typicaly tree step of bending process of hemming are following-

1. Comprising of Flange
2. Pre-hemming
3. Final hemming