Hood design-Week 2
INTENT :
To design and model an aesthetic Passenger Car Hood with the Outer Panel, Inner Panel, Hinge, and Striker assembled and finally Provide the required emboss definitions and the Mastic data as given.
Major software used :
CATIA V5
Introduction :
The hood refers to a fabric cover over the passenger compartment of the car known as the 'roof' or 'top' In many motor vehicles the resemblance to an actual hood or bonnet is clear when open and viewed head-on. In modern vehicles it continues to serve the same purpose but no longer resembles a head covering The Hood is an opening body panel which is the frontal BIW enclosure component in a front engine vehicle. It consists of an outer and inner panel. The inner panel provides strength while the outer panel functions as a metal cover. It is a very critical component because of the frontal crash requirements and pedestrian and passenger safety requirements. The design of the hood is vital since it affects the aerodynamic flow around the car
Design parameters :
Hood Thickness Information
Outer Panel Thickness = 0.75mm
Inner Panel Thickness = 0.75mm
Reinforcement Thickness = 1.5mm
Master Section
Hood also embodies several parts :
Inner and Outer Panel
The inner panel provides strength while the outer panel functions as a metal cover. They are of 0.65-0.75 millimeters (mm) thick. To improve NVH (Noise, Vibration, and Harshness) i.e to reduce these levels Mastic Sealants are used Mastic Sealants improve the strength locally at around 80mm diameter. They are positioned between the inner and outer panels of the hood in such a way that it covers most of the hood region. They are made of hard Rubber and are introduced as a paste thereby joining the inner and outer panels with a thickness of 5mm
1.Hood outer panel :
2. Hood inner panel :
Inner panel is the part that gives strength and rigidity to the outer panel. The master section represents the initial embossed shape and size. Then we provide the emboss for the latch and hinge elements after fixing the location
3. Reinforcement:
Reinforcements are provided according to the design requirements. Mainly it is provided at the hinge and latch regions to improve the strength locally. Usually, the thickness of reinforcements will be higher than that of the inner panels and the value varies according to cost and requirement. According to the design requirement here, it is given 1.5mm thickness to both hinge and latch reinforcements
4. Latch Trajectory :
The latch trajectory is given by the circle drawn from the hinge axis point. The hinge axis point is the center 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 conditions, the striker axis through the tip of the striker should be tangential to the latch trajectory.
6. Mastic Data :
Hood commonly possesses a large surface area and hemming can only be provided through its boundary. We cannot use other joining techniques like welding, riveting, etc because they leave marks on the outer panel which spoils its aesthetic appearance. So, mastic sealants are used to stick the inner surfaces of the outer panel and inner panel. Mastic sealants are elastic compounds that behave like rubber
7. Deep Drawing :
Deep drawing is one of the most widely used processes in sheet metal forming. Apart from its use in many other sectors, it is applied in the automotive industry for the manufacturing of car body parts. The deep drawing process is a forming process that occurs under a combination of tensile and compressive conditions
8. Hemming & Corner Cutout :
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, improve the appearance of a part, and reinforce part edges. In car part production, hemming is used in assembly as a secondary operation after deep drawing, trimming, and flanging operations to join two sheet metal parts (outer and inner) together. Typical parts for this type of assembly are hoods, doors, trunk lids, and fenders. The accuracy of the hemming operation is very important since it affects the appearance of the surface and surface quality. Material deformations, which occur during the hemming process, can lead to dimensional variations and other defects in parts. Typical hemming defects are splits or wrinkles in the flange, material overlaps in the corner areas, or material roll-in This is why it is important to provide the required relief at the corners.
There are two types of hemming operations,
- Conventional die hemming
In conventional die hemming, the flange is folded over the entire length with a hemming tool.
- Roll hemming
It is the roll hemming process that is used for automotive sheet metals. Roll hemming is carried out incrementally with a hemming roller. An industrial robot guides the hemming roller and forms the flange. Roll hemming operation can also be divided into several pre-hemming and final hemming process steps. Roll hemming is very flexible to use and tool costs are significantly lower as compared to those of conventional die hemming. However, the cycle times are much higher since the hemming is realized using a hemming roller which follows a defined path
TREE STRUCTURE :
