Hood design-Week 2

 

A car hood is meant to protect the performance parts of your vehicle, including the engine, while also providing easy access for repairs and maintenance. It is possible for the hood to incur damage as well. One of the most common types of damage is to the hinge, which is the device that connects the hood to the body of the vehicle. Over time, the hinge can become loose or may fall off completely. The hood is also prone to receiving scratches and dents. Although this might appear to be a minor problem, dents and scratches can lead to depreciation in the value of your vehicle. Scratches and dents can also lead to exposure to the elements that can result in rust and corrosion. This can be a serious problem that can ultimately expose the engine in your car to snow, sunlight, and rain. When this happens, it can impact the performance of your car's engine.

 

 

To reduce the death of pedestrian and injuries in the traffic, measures from the automotive industry as well as environmental changes are required.
The European Enhanced Vehicle Safety Committee has developed test procedures to estimate the level of pedestrian protection for the front parts of
the vehicles. Based on the EEVC WG 17 report, legal requirements havebeen derived.The European directive consists of head impact, upper leg impact and lower leg impact [10].
To test how good the cars is at pedestrian protection, the car industries performs different tests on the cars that simulate an real life accident with head impact, upper leg impact and lower leg impact. In the hoods perspective, the head impact protection is the most common and is in the highest priority.

 

To estimate the potential risk of pelvis and upper leg injuries in the event of a vehicle striking an adult, a series of impact tests is carried out at 40 km/h using an adult upper leg form impactor as shown in Figure 9. Impact sites are then investigated and the protection offered is rated as good, adequate,marginal, weak or poor.

Upon lifting the hood, the hood struts extend, assisting you with raising the hood. Also called hood lift supports, the hood struts act as a prop rod to hold the hood up when fully extended. These deceivingly simple parts house some interesting science. The strut cylinder is filled with oil and nitrogen gas, creating a stable compressible material. The rod coming out of one end is connected to a piston that increases or decreases the internal volume, which increases or decreases the pressure on the gas. Closing the hood telescopes the rod into the cylinder, which pushes the piston against the gas, increasing pressure. On opening the hood, the gas pressure forces against the piston, pushing the rod out and the hood up.

 

A hood stay is an apparatus for an engine room of a car , which can safely keep an engine hood in an open state if an external force is abruptly generated due to vibration, wind & can facilitate an opening/closing operation of the engine hood.It Is the basic and most commonly used support for the hood in low cost and mid range cars,  Since it is cost effective. 

These type of Hood Support does not require much of Man power and is very useful when the weight of the hood is more and difficult to lift. This is usually seen in bigger cars and also it is expensive. These gas stays are provided in the back door to all car segements these days.

It has two ends where one end is fixed to engine compartment and the other to the hood itself. The length C & D is kept constant and only the (B-A) length is varied. We could say that if the length of the Hood increases , (B-A) length also increses. 

 

1) The gap between the hood outer and the inner panel is minimum of 2 mm

2) The distance from the hood outer to the hood innermost surface is 25 mm. Engine compartment is installed below this 25 mm surface. Hence the dimension is fixed.

3) The geometry is defined at almost 45 degree or angled outwards to enable tool to stamp and come out of the part.

1.HOOD OUTER PANEL

2.HOOD INNER PANEL

3.Hinge Assembly

4.Striker

Opertaions Done on Hood

1.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.

2.Embossing

Embossing is a metal stamping process for producing raised or sunken designs or reliefs by passing metal sheet or strip between rolls of the desired pattern. The process enables repeated production without variation and does not change the metal's wall thicknesses.

3.Hemming

Hemming is the process of joining both the outer and inner panel together. The hemming process roles and wraps the hood outer panel around the inner panel and holds it tightly together. The following are the dimensions followed for hemming.After the hemming process is done, now we need to provide corner relief on the corners of the hood so that the part is manufactural.

Mastic Sealent

The Mastic sealant or the Mastic point is an elastic compound that behaves like a rubber. The mastic points are defined on the hood inner panel where the hood can easily deform. They help the hood outer panel to come back to its original shape after it gets deformed. The mastic has an influence area of 80mm.

Isometric View