Hood design-Week 2

INTRODUCTION:

HOOD:

Acar hood also referred to as a bonnet in some other countries is the hinged cover that over the engine of a front engine vehicle . its purpose is to provide access to the engine for repair and maintenance . A concerealed latch is typically used to hold down the hood. on the vehicles with an aftermarket hood and on racecars , 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 . the hood design may vary from one market and model to another , including SUV truck , minivan,, and pasenger - car models.

Concerns regarding the severity of a potential pedestrain head injury during a collision with a motor vehicle have led to advanced hood design on many models such design on many models such design may include a multi- come inner hood panel design . an active structure that is capable of pushing the surface of the hood away from the vehicle hard motor components in the event of a pedestrain crash is also in use pyrotechnic or spring force design are often used in the active - hood .

HOOD DESIGN CONSIDERATION:

The hppd of car is considered the frontal BIW enclosure component. bonnets are designed to reduce air resistance as the air flows around the car . apart from this , bonnets are also designed to meet several other requipments . they serve a great deal of purpose in protecting the passenger inside the car and the pedestrains in the event of an accident . it also acts as the cover for the engine .

The Europen new car assement programme (Euro NCAP) is a Europen car safety performance assement programe that has developeded test specification rating system for assessing pedestric injuries during impact with the front of vechicles such tests include a serices of tests using impacts designeds to bio - mimic a collision at speed of 40 km/h.

. They described a situation in which a pedeestration is situated laterically and car first hits one the leg , upper leg and most importantly the head trauma is most commmonly responsible for casualites.

. So to avoid servise injuries to thehead , the high impact area for adults and childeren is subjected to less thickness . also no reinforecemnt shpould be provided in that area as during head collision , the hood will absorb the head collision the head impact energy leading to the collapse of the hood and thus protecting the severe head injury.

. Another important critertrion for the hood design is the protection of the occupants inside the car during a front collision the design of the hood dhould be in such a way that during this collisions , the force should travel in the upward directaion through the embosses and directly towards the body of the car . thus protecting the occupants inside .

HEMING:

Hemming is a forming operation in which the edges of the sheet are folded or folded over another part to achieve a tight fit normally hemming operation are used to connect parts , improve the opperance of a part , and reinforce part edges.

in car part production , hemming is used in assembly as a secondaryoperation after deep drawing , trimming , and flanging operation to join two seets 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 apperance of the surface and surface quality . materilas deformation , 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 meterial rooll- inn the corner . this is wy it is important to use simulation tools to , on the one hand , better understantand the hemming process and , on the other hand significantly reduce the number of trial and error loops during tryout and producation.

DEEP DRAWING:

Deep drawing is a sheet metal forming process in which a sheet metal blank radically drawn into a forming die by the mechanical action of a punch. it is thus a shape transformation process with material retentaion . the process is considerd deep drawing when the depth of the drawn part exceeds its diameter .

PROCEDURES OF DESIGN HOOD:

Hood is one of the major components of the vechicles body . it mainly covers 2 major power transmitting components ie. engine and radiator assembly . along with covering them through its inner panel , the hood outer panel also serves a major role in the aesthetics and ergonomics of the vehicle.

it has 3 supportive components viz.

1. A) HINGS-for easy opening and closingg of the hood .

2.B) LATCH- to keep hood in corect closed position

3. C) Support rod- helps in keeping the hood in the open psition

we will be mainly discussing

1. Hood outer panel

2. Hood inner panel

3. Hinge Assembly

4. Latch assembly

Hood inner panel is designed as per the given master section sketch concerning the hood outer skin provided.

HOOD INNER PANEL:

. In the inner panel only we can reserch and implement the safety of pedestrains and as well as the driver . in this panel only we can attach the reinforcement , embossed , mastic point, etc.

. It is an object of the present invention provide a hood inner panel capable on reduction of a reaction force of the hood inner panel even if alevel of deformation of a hood of a vehicle increases and ensuring a sufficient energy absorption . first we have to crate a hood inner panel with the given master section and create embosses for forces impact in the hood.

offsets the given outer panel which given master section 1.7mm,4.7mm,26.5mm and 21.5mm . split the offsets surface 15mm form edge, the second surface between 17mm and 30mm fromthe edge use third surface 50mm from the outer edge. use multi section tool from the split edges and join three surfaces with the surface fillet option . the fillet value is min 3mm and max 5mm in the sheet metal.

then for the embossing surface draw a sketch excludiong are for hinge and latch emboss position . extrude the sketch and split joined offset surface . create sweep in split edges and trim with a 21.5mm offset surface.

THE NECESSITY OF EMBOSS AND ITS DESIGNING:

After the basic mater layout is done we have to provide emboss section to dissipate the collision force to outercornets towerds hinge portions . thus impact force passing to passenger cabin be reduced majorly.

While creating these emboss we hwve to keep in mind the draft direction and draft angle so that the stamping tool will create proper embossed structures on the pannel considere the following image for reference of embossed sections on the inner panel.

Create a sketch for embossing on the above surface . as same extrude the sketch and split with surfaces, sweep emboss split edges with the angle of 7 degrees concering the surface . trim with 5.7mm offset surface.

MASTIC CREATION:

MASTIC DATA.

To reduce NHVi.e noise vibration and hardness between the hood inner panel and an outer one , matic sealants are needed to be applied . Every mastic sealant improves the strength locally by around 80mm. it joins the inner panel with the outer panel also redusing the vibration noise .

thus while designing embosses on the inner panels we have to design mastic portion where sealant can be made as shown in thwe image ; ,astic data.

Mastic regions are designed such that they will be closer to the outer panel . rubber sealant is applied on the mastic regions of the hood inner panel which will glue both panels together.

HINGE POSITIONING:

Hinge positioning is needed to be properly designed so that the opening and closing of the hood will occur correctly . also , it will decide if the latch and striker get closed correctly or not.

To have proper hinge location , algin hinges on the inner panel such that the mid point of an axis passing through both hinges with striker centere point be radius which will create a trajectory.

LATCH EMBOSS:

Similar to hinge emboss we have to design latvh emboss to improve the local strength of the inner panel providing a support structure for latch mounting.

LATCH ASSEMBLY;

Latch and strike is used for locking the hand with car . kit is usally placed on the space provided on the inner panel.

REINFORCEMENT:

To furthermore reduce the impact on the occupants inside the car , additional latch and hinge reinforcement to the hood when latch and striker are placed , therfore is a drop in strength at that position thus reinforcement is requred . also stiffnes pads are placed to reduce NHV. hinge and latch reinforcement thickness is kept at 1.5 mm but it may vary

HINGE REINFORCEMENT:

HEMMING:

Hemming is the process in which the edge is rolled flush to itself , while a seam joins the edges of two materials . normally hemming opertaion are used to connet parts together , improve the appearance of a part , and reinforce part edges . in hood design , hemming is used in assembly as a secondary operation after deep drawing , trimming , and flanging operation to join two sheet metal parts (Outer and inner) together . dimensions of hemming are given below.

RELIEF DATA:

Relief is provided onto the part or component in order to remove any stress develpoed in aparticular area ie sharp corners that take place during the hemming process is caried our. thus corners are rounded or charferd.

CONCLUSION:

Therfore , we have designed the hood outer panel , inner panel , and the necessary reinforcemnets by following the master section design section mentioned with the design parameter . submited an assembly of hood inner panel , outer panel, latch , hinge , and reinforecemnt.