Hood design-Week 2
Hood design
Aim: To Design Hood outer panel, inner panel and the necessary reinforcements by following the Master section with the design parameter
Introduction: Hood is the main component of a car at the front portion. It is used to decorate the car and add a luxurious look. The shape of the Hood is made aerodynamic in order to minimize the air effect. Hood is generally used to access the parts easily such as radiator, engine and many other parts. A car hood, also referred to as a bonnet in some other countries, is the hinged cover that rests over the engine of a front-engine vehicle. Its purpose is to provide access to the engine for repair and maintenance. A concealed latch is typically used to hold down the hood. On vehicles with an aftermarket hood and on race cars, hood pins may be used to hold down the car hood. Hoods sometimes also contain a hood scoop, wiper jets, power bulge, and/or hood ornament. Car hoods are typically constructed from steel and sometimes from aluminum. Aftermarket car hoods may be constructed from various other materials, including carbon fiber, fiberglass, or dry carbon. The hood design may vary from one make and model to another.
while access for repairs and maintenance Hood can fix by two methods
1. Support Rod
2. Gas Stay
In the fig 1.1 shown Support Rod and Gas Stay
Fig.1.1: Support Rod and Gas Stay
In the fig 1.2 shown Hood and its parts
Fig.1.2: Outer Panel, Inner Panel & Reinforcement
Design requirements for Car Hood
1. Hood Head zone for lock striker: In the fig 2.1 shows Hood Head zone for lock striker
Fig.2.1: Hood Head zone for lock striker
From the Fig. The opening angle of hood will give A, C, B And D with respect to the ground. those A, B, C & D are decided in the head zone. Opening angle varies from region to region depending on average human weight. Depending on the standards we are deciding the angle. So from the angle data, Support rod or Gas stay is designed. The position of Support rod is on the other side of the battery which is shown in the fig. below.
2. Adding latches and stiffener pad: Latches are added where and all the weight is added. On the inner panel we have Hinges and striker, which are attached to the inner panel so due to this attachment the strength of the inner panel is going weak. In order to strengthen the inner panel Latches will play a very important role. Stiffener pad is the sponge-like material place b/w Inner and outer panel to reduce vibrations.
3. Mastic Seals: Mastic Seals place b/w Inner and outer panel to reduce Noise, vibration, and harshness. Every Mastic will have an effect of 80mm Dia locally. shown in the fig 3.1. Inner and outer panel gap is 2 to 5mm
Fig.3.1: Mastic Seals
4. Emboss definition: Emboss are provided in the inner panel of the hood assembly. This helps in weight reduction of the hood and also to dissipate the force during collision. Force dissipate is shown in the fig. 4.1 this project design.
Fig.3.1: Force dissipate
a. Deep Drawing: Deep drawing is a sheet metal forming process in which a sheet metal blank is radially drawn into a forming die by the mechanical action of a punch. It is thus a shape transformation process with material retention. The process is considered "deep" drawing when the depth of the drawn part exceeds its diameter.
b. 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.
5. Hood For Better Pedistain Rating:
Inlaid Hood:The line which is drawn 45 deg. from ground to Side Reference of carand which is meeting point on fender is called Inlaid Hood.
Wrap Around Hood: The line which is drawn 45 deg. from ground to front surface of the Hood and which is the meeting point on the outer panel is called Inlaid Hood.
Depending on the Inlaid Hood & Wrap Around Hood we can design hood for head impact in the fig 5.1 shown position of head impactor.
Fig.5.1: Position of head Impactor
Objective
Design hood outer panel, inner panel and reinforcements with the given outer hood skin, master section and design parameters.
Design parameters
Hood Thickness Information
Outer Panel Thickness = 0.75mm
Inner Panel Thickness = 0.75mm
Reinforcement Thickness = 1.5mm
Master Section
Components
1.Hood outer panel
Outer panels are the aesthetic elements of a car. It is the styling team who provides the skin for the outer panel. The shape, position and size of the hood should satisfy the safety norms. So while designing the hood we should give more importance to pedestrian safety. The outer panel is attached to the inner panel by hemming. So, it is necessary to provide required hemming flange and reliefs for the hemming operation. We also provide mastic sealants between outer panel and inner panel to reduce vibration.
2.Hood inner panel
Inner panel is the part that gives strength and rigidity to the outer panel. The master section represents the initial emboss shape and size. Then we provide the emboss for the latch and hinge elements after fixing the location.
Latch Trajectory
Latch trajectory is given by the circle drawn from the hinge axis point. Hinge axis point is the centre point of the hinge axis. First, we can fix either the latch or the hinge. If we have fixed the hinge position then we should plot the Trajectory circle for the latch. For proper mating condition the striker axis through the tip of the striker should be tangential to the latch trajectory.
Hemming
