Hood design-Week 2
Title - Hood Design
Objective
Design of Hood By considering given data of outer pannel and master sketch.
Hood is basically one type of door which is used to close the engine compartment. Hood consists of two mair parts inner panel and outer panel where inner panel givws strength to outer sheet and outer panel just sheet which gives look and design. Hood is the hinged cover over the engine of the vehicle. hood can open to allow access to the engine compartment for maintenance and repair also to cover the engine and give an aesthetic look to the vehicle. a concealed latch is typically used to hold down the hood. on vehicles with an aftermarket hood and on race cars. car hoods are constrructed fro steel and sometimes from aluminium. in special cases these are made with various materials like carbon fiber ,fiber glass or dry carbon.
Basic components of Hood:-
- Outer Panel
- Inner Panel
- Hinges
- Stricker(locking mechanism)
- Stay Ros or Gas Stay
- Mastic seals
- Reinforcement
Outer Panel
the outer panel is asheet which is for aesthetic purpose.we get this surface to design the inner panels and other componets.
the main shape of the outer panel comes from the basic sketch of car. As a BIW Designer we get the class AA surface as an input This class A surface consists of all the aesthetic shapes and boundries of the hood loke max size of hood.
Manufacturing process
First step is blanking in this process the main sheet is cut into peticular shape and size then stamping process is used. Stamping process used to givve basic shape to the outer panel.
Inner panel
this is the main structure of thr hood which gives strength to the outer surface. While designing the inner panel the main thing we need to make sure is uniformity and symmentry . The main input to design the inner panel is the class A surface of the outer panel. we need to take all refecrence from that class A surface . inner panel consists of holding purposes like cutouts for support rod or gas stay etc.
manufacturing process
the manufacturing process is quite similar to that to outer panel . First step is blanking in this process the main sheet is cut imto perpendicular shape and size then stamping process is used. Stamping process used to give basic shape to the sheet by pressing sheet metal innto the die. with addition to that variour cutouts are there in the inner panel.
Hinges:-
Hinges are the standard parts used in the hood assembly the main purpose of hinges is to give opening and closing to the hood. the one side of the hinge is mounted on the engine compartment and the other side is mounted on the hood of 2 hinges .Based on the hinge position we need to do embosses to the inner panel of the hood.
Striker(locking mechanism)
striker is the one part of the locking mechanism which helps to lock the hood to the engine bay. A strinker is also the standard part which mounts on the inner panel of the hood and the other part if locking mechanism is mounyed on the engine bay. The main criteria to mount the striker on the inner panel is that axis of the striker must be tangent to the rotational curvature of the inner panel.
Stay rod or Gas stay
the basiic application of the stay rod or Gas stay is to hold the hood in open position Stay rod is the rod eith a slightly bended in shape to get good strength and can provide support to the hood when it is in open position. the bend should not be more that 35 mm .
Gas stay is generally used where the weight of the hood is more to reduce effort we use gas stay insted of stay rod. while positioning the stay rod we need to make sure it is opposite to thr battery of the car so it is easy to put and remove the battery without any abstacle.
Mastic seal:-
Mastic seal is basically the glue used between the outer panel and innerpanel. we can apply a mastic seal where we need to provide stiffnessin 80mm diameter. we have to make sure we apply mastic seal in such a way all the are covered od the inner panel to give better results.
Reinforcement:-
this is added material to provide stiffness areas like under hinges and sticker etc. these are the simple strips which added to inner panel.
Design consideration for hood
Hood opening angle
the angle at which hood is opening should be sufficient that should not strike the person who is checking the engine height of the person.
Force distribution
while designing thr hood we need to consider that after impact like front impact to the hood the force should be distributed toward the hinges and not towards the person who is sitting in the vehicle we need to design aan embose in such a way that is to transfer a load to the hinges and absorb the load.
Placement of stay rod or Gas stay
the placement of stay rod sholud not comes between the battery removal and refit also need to consider the height and the rod depends on the angle at which the hood need to open.
Placement of mastic seal
the mastic seal gives stiffness in 80mm diameter. we have to make sure we apply mastic seal in such a way all the area covered of the innerr panel to give better results.
Pedestrian safetty:-
In pedestrian- car accidents head injuries are a common cause of death. the acceleration of the heads center of gravity resulting from a head hits is used to determine the HIC(head injury criterian) value, which is a measure of thr morality risk of a head injury direction.
during the majority of pedestrian-vehicle collisions the pedestrians entire body wraps around the car's front form. this has an effect on he vehicles head impact. Meanwhile the windscreen is a significant impact point that has undergone NCAP testing. Car contact speed vehicle type rigidity and shape nature of the vehicle front all influence the degree of injuries. One of the most essential parameters of assessing pedestrian protection is wrap Around Distance WAD.
INPUT DATA
Master Section
Hemming data
front relief:-
relief rear section
Emboss
sheet embossing is a stamping technique that creats ralsed or sunken images in sheet metal. this procedure can be accomplished using matched male and female roller dies or by sliding a sheet or a sstrip of metal between the desired pattren rolls.The geometry is based on the master section that was developed previously. We willl supply local emossed to strengthen the component when we complete the basic design stages. The Master portion will be used to reinforcement the component. when a face strikes the hood from the front the force travels upword.
Deep drawing
Deep drawing is a sheet metal forming technique in which a sheet metal blank is mechanically pilled radially into a forming die. As a result it's shape transition with material retention. When the depth of the drawn parts exceeds its diameter, the procedure is calling deep drawing. This is accomplished by using a sequence of dies to redraw the parts.Due to the material retention property ,the flange region(sheet metal in the die shouldr area ) experiences radial property drawing stress and tangential compressive stress. Flange wrinkles are caused by compressive stress(Hoop Stress) A blanker holder, whose purpise is to permit controlled mateerrial flow can help prevents wrinkles.
Hemming Process
Hemming is a shaping process in e=which the sheets edges are folded or folded over another section to create a sung fit. hemming procedures are commponly used to join parts, improve the look of a part and reinforce parts edges.
hemming is a secondry tehnique used in automotive partys assembly after deep drawing, trimming and fanging operations to unite two sheets metal sections(outer and inner ). hoods , doors, trunk lids and fender are common parts for thiss tyoe of assembly.
Roller Hemming:-
Types of hemming
Assembly of Hood Design
Front view
Side view
Hemming section view
Conclusion:-
In this project i learned abot different engineering parameters, safety parameters , sheet metal process used in manufacturing hood, design consideration that are used while designing Automotive Hood. and also the different commands used in catia V5.