Hood design-Week 2
HOOD DESIGN
Aim:
The main objective of this project is to learn the essential tools, commands, and surface modelling of Hood designing using Siemens NX Cad. This project is to develop a design idea for hood BIW that satisfies the manufacturing requirements, functional requirements, and EURO NCAP standards.
INTRODUCTION:
Hood is the engine cover hinged to the car's body (front-engine automobile). It gives you access to the vehicle's engine and is also vital for the safety against the frontal impact of the car.
Types of hoods support
There are two types of support available for the hood support
- Gas Stay
- Support Rod
Gas Stay:
Support Rod :
Design constraints to be followed:
- Passenger safety
- Pedestrian safety
- Manufacturing feasibility
- Position the striker along the Trajectory of the centre of the hinge axis.
- Joining techniques of the inner and outer panel.
Components of Hood:
1. Outer Panel
2. Inner Panel
3. Hinge
4. Latch
5. Reinforcement
Outer Panel:
A car hood panel is one of the most important components of the BIW (body in white), it is considered the closure sheet-metal component. The outer panel has the aesthetic look to it but on its own is very weak and not capable of handling force during impact. Most automobile hood outer panels are made of traditional steel plates, and their quality does not meet the needs of lightweight development. For this reason, it is necessary to obtain lightweight effects through the application of automotive aluminium sheets. The most widely used car aluminium alloys in the market are deformed aluminium alloys of 6111, 6016, and 5182. The production process of the outer panel of the hood mainly includes blanking, deep drawing, trimming, turnup, and side turnup. Among them, deep drawing is a key process to ensure the quality of parts.
Inner Panel:
The inner panel of the hood is not visible to the customer, but this is the engineering feature of the outer panel. The hood panel is required to have a high initial reaction force against the impact exerted on the hood to enhance the energy absorption capacity. The hood is further required to minimize a reduction of a reaction force by deformation in a collision. A hood inner panel according includes an inner panel main body forming part of a hood of a vehicle, a front bead provided on the inner panel main body and extending along a vehicle width direction, and a rear bead provided on the inner panel main body, located on a rear side of the front bead and extending along the vehicle width direction. The front bead includes a centre portion in the vehicle width direction that is curved toward the front of the vehicle and located in front of each end portion in the vehicle width direction, and the rear bead includes a centre portion in the vehicle width direction that is curved toward the back of the vehicle and located behind each end the portion in the vehicle width direction.
Hinge:
A hinge is a machine element that connects two bodies allowing angular movement about a fixed axis of rotation, all the while preventing translations and rotations on the remaining two axes. A hinge can be considered as a journal bearing with only one degree of freedom where a shaft is rotating in a hole. Hinges only allow one rotation, either yawing (the most common), pitching, or rolling. Hinges are a jointed and flexible device that is attached to any swinging part. Hinges are mechanical bearings that are used to connect two swinging objects or points and give them the freedom to move relative to each other. Hinges have limited movement, allowing the joint to move only at one angle and restricting the other movements of swinging parts.
Latch:
Latches are mechanical components that allow the temporary joining of parts that are moving relative to each other. They are actuated to release the coupling and allow the two parts to separate. Latches are mostly seen on doors and enclosure openings. They are also used in devices such as seat belts, clamps, straps, and objects with retractable parts. Different designs feature various methods of actuation, holding style, and mounting. The hood latch is extremely simple. When the hood is closed, the latch slides over what is called a catch, and spring covers the latch to keep it snug. When we pull the knob inside the car to open the hood, the hood latch cable opens the latch, allowing it to bypass the catch and open.
Data used-
Hood Thickness
- Outer Panel thickness=0.75
- Inner panel thickness-0.75
- Reinforcement thickness =1.5
Master Section:
Parts description:
Deep drawing:
In this corporation, a sheet is pulled into the ideal shape using a punch and pass-on gadget. The sheet is outlined in the condition the pass on by driving the punch down on it. To avoid the sheet wrinkling itself, the sides of the sheet are held someplace close to folios. In the automotive industry, deep drawing is usually carried out using rigid tools.
Latch Trajectory:
The latch trajectory shows the striker's way when the hood is opened and shut on a vehicle. The range of the round Trajectory is controlled by the set standard dependent on the typical stature of an individual. The range is estimated from the pivot hub up to the Latch. It is the Trajectory on which the movement of the hood (opening and closing are dependent). This circular Trajectory has a radius equal to the length from the centre point of the centre axis of the Hinge to the striker point on Latch. The striker point is also tangent to the Trajectory.
Mastic sealant:
Hood commonly possess 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 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.
Embosses:
Throughout the inner panel we provide different embosses. We can increase the stiffness of the inner panel through these embosses. 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.
Reinforcement:
The Zone near the turn and Latch has more chances of disillusionment in the hood panel. Consequently, to avoid any failure to rotate and latch region upheld with extra materials whose thickness is regularly directed by the vehicle. The reinforcements give additional fortitude inner panel of the centres where various parts, for instance, the lock and rotate, will be put. The reinforcement ensures that the turns and the snare have better assistance to avoid frustration.
Hemming:
The Heming process involves joining the outer and inner panels of the hood by bending their corner curvature areas to 180 degrees. There is also some corner relief given to the sheet to get stationed so that the rollers that do the Heming of sheets can roll appropriately in the required area. Hemming is a sheet metal operation widely used in the automobile sector because the welding or joining process can not be done on styling parts as it may affect the car's aesthetics.
Reliefs:
Reliefs are provided at the front and side portion of the panel for smooth rolling operation .so that no tearing of the sheet happens when the roller passes through a specific portion.
Piercing:
Piercing is the kind of shearing process in which the unwanted material with a particular shapes are removed from the sheet metal by using the blanking punch and dies.
Hood Assembly views:
ISOMETRIC VIEW:
FRONT VIEW:
TOP VIEW:
SIDE VIEW:
Conclusion:
Hence, the hood design has been completed by considering the criteria, dimensions, procedures and standards. By the process of this design, have learnt about the hood mountings, sheet metal operations like hemming, embossing, deep drawing, piercing, Pedestrain safety and its ratings.