Hood design-Week 2

HOOD DESIGN

Aim: - The main objective of this project is to learn the basic tools, commands, and surface modelling of Hood designing using Siemens NX Cad. This project is come up with a design idea of hood BIW that satisfy the manufacturing requirements functional requirements and as well as EURO NCAP standards.

The objective of this project –

• To understand and learn the basic Graphical user interference of NX CAD.
• To learn basic tools, command feature, surface modelling and its application.
• To understand and learn about the industrial approach how to design hood of a car using siemens NX cad.
• To design the hood using surface modelling feature of NX cad.

Introduction: -

Hood is the engine cover, hinged to the body of car (front engine automobile). It gives you the access to the engine of the car and is also important for the safety against the frontal impact of the car.

The hood (North American English) or bonnet (Commonwealth English) is the hinged cover over the engine of motor vehicles. Hoods can open to allow access to the engine compartment, or trunk on rear-engine and some mid-engine vehicles for maintenance and repair. In the generally for passenger car hood may be held down by concealed latch. But in race car or car in aftermarket the hoods may be held down hoods pin. 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 fiber, fiberglass, or dry carbon. The hood design may vary from one make and model to another SUV. The hood is also designed for several requirement. 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. They serve as a great deal of purpose in protecting the passenger inside the car and the pedestrian in the event of the accident.

Types of hoods support-

There are two types of support available of the hood support-

• Gas Stay
• Support Rod

Gas Stay

Gas stay is the device for supporting the engine hood of a motor vehicle in its open position by means of an actuator which is activated by gas. This is mostly used when the car hood is heavy. In this no men power is required. Spring stays are designed to be used on upward lifting doors, once the door is open n slightly the spring will push the door to the fully open position. Euro fits stock various size spring depending on the door size requirement.

Support Rod

Support Rod is a device for supporting the engine hood of a car in its open position by means of a rod. We have to lift hood by ourselves and place the support provided either in the hood or engine component. This is mostly used where the car bonnet weight is small.

Design constraint to be followed: -

• Passenger safety
• Pedestrian safety
• Manufacturing feasibility
• Positioning the striker along the Trajectory of the center of hinge axis.
• Joining techniques of inner and outer panel.

Passenger Safety-

Whenever the frontal crash takes place in car the first part which will got effected will be hood. So must be designed in such a way that it should not come of from the body from the car and must absorbs the energy as far as possible ad diverting the force towards the side panel of the car so that the amount of force which is sent to the cabin is lesser since the force lesser the passenger will experience less amount of force so that passenger safety is ensured.

Pedestrian Safety-

Safety of the pedestrians need to be considered during the design as per the NCAP Euro assessment. Hood is of two types based on the side reference line. Side reference line is an imaginary line drawn from ground at angle of 45degree.If this line falls on the fender, then the hood is inlaid hood and if the line falls on the hood, then hood is wrap around hood

Child and adult impact area on the hood are defined by wrap around distance. Area between the wrap around distance 1000-1500mm in child head impact zone and from 1500-2100 WAD is the adult head impact zone. We now the zone where the pedestrian going to hit, as a design engineer, we must make sure that they are exercising the least force such that they were not getting any serve injury without compromising the strength of hood so that passenger safety must be assured. For this reason, the inner panel kept 25mm from the outer panel and creating the embosses to improve the strength of the hood.

Head impact area is defined the side reference line and wrap around distance. This zone will get red, yellow, green rating using the head injury criteria calculated using the expression.

There are important hood parts-

Outer Panel: -

The outer panel of the hood is the coverage for the inner panel, it is attached to the inner panel through Heming process. It is also the initial part in the hood design on the basis of which the dimension and the curvature of inner panels are designed. It is also important for the car from the point of view of external looks.

Inner panel: -

Basically, this can be termed as the skeleton of the hood, it is the inner panel on which the embosses, Hinge and latch are attached and finally it is covered by the outer panel, Inner panel gives the main strength to not only the bonnet but it is very important part from the car safety perspective, inner panel is designed considering all of the safety measures in the mind as it is the first part to be impacted in case of frontal collision.

Reinforcement: -

The reinforcements give additional fortitude inner panel of the centers where various parts for instances, the lock and rotate will be put. The reinforcement ensures that the turns and the snare have better assistance to avoid frustration.

Data to used-

Hood Thickness information

• Outer Panel thickness=0.75
• Inner panel thicknes-0.75
• Reinforcement thickness =1.5

Master Sketch: -

Design Approach: -

The styling gathering will give us the skin data. The arranging engineer will mull over the engineering common sense of the part with furthermore considering the NCAP standards and will give analysis so they can change the styling of the hood properly.

The master sketch territory is obliged different areas. Moreover, various predefined values are given to us as demonstrated by which we need to engineer and plan the sketch and model the hood.

Starting there forward, the CAE engineer will do an examination and testing on the part showed and subsequently report analysis to the hood engineer and do the significant changes.

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 into the condition the pass on by driving the punch down on it. To avoid the sheet wrinkling on 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 way of the striker 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 normal 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 is dependent). This circular trajectory has the radius equal to the length from the center point of the center axis of the hinge to the striker point on Latch. The striker point is also tangent to the trajectory.

Mastic sealant: -

The mastic points are region where mastic is put to interference the outer panel to the inner panel. We can’t use spot welding because this gives less elegantly fulfilling result. Accordingly, mastic is used to join the panel as it doesn’t modify the real metal.

Embosses: -

The design of embosses are done in accordance with the force distribution of frontal impact, it is designed in such a way that the reduction of force starts when it is directed till the corner i.e., up to the hinges and loses maximum amount (of force) till the end.

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 sort of the vehicle. The reinforcements give additional fortitude inner panel of the centers where various parts for instances, 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 the joining of the outer and inner panel of the hood by bending their corner curvature areas to 180 degrees. For this process 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 properly in the required area. Hemming is a sheet metal operation that is widely used in automobile sector because welding or joining operation can not be done on styling parts as it may affect the aesthetics of the car

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 roller passes through certain portion.

Features Description: -

Offset surface- The offset surface gadget makes a copy of the picked surface at a provided distance and guidance.

Emboss- The embossing contraption makes a punched surface of the picked shut contour. The punch is produced using a picked surface containing the contour surface. Sketch. a draft can be obliged the punch from either the end cap or the base surface.

Trim sheet- The trim sheet gadget parts the target surface along the intersection curve of the target surface and the gadget surface. The piece of the surface on either side of the intersection can be either discarded or retained according to need.

Through curves- This contraption creates a surface between two assorted surface sections where the shape can change in section.

Law Extensions- Creates an extended surface subject to an open chain contour or a shut contour on the picked target surface. A draft can be obliged by the extension.

Face blend- Creates a curved blend or fillet along two picked surfaces in gave direction vector. The curve of the blend can be changed regarding reach, width, and continuity.

Extend sheet- Creates an extension of picked sheet up to a given distance.

Offset in the face- Creates an offset in the face or edge on the target face up to a to a provided distance.

Bridge curve- Create a roundabout portion between two intersecting and non-intersecting curves. The beginning and end point of the roundabout changed by providing distanced.

Projected curve- Creates a projection of curved profile onto a goal surface. The surface can be linear and curved. The direction can be changed by reasonable vector.

Sew- combines sheet bodies by using sewing common edges together, or combines solid bodies using sewing faces. Any opening between the surfaces can be closed.

Mirror Geometry- Mirror a geometry along a face.

Curve on surface- Creates a surface spline feature directly on face.

Thicken- creates a strong body using thicken.

Extracted body- Creates a body of picked geometry that can be changed by editing the parent feature and rebuilding the extracted feature.

Hood Design Assembly

The hood is designed or modified by different tools like offset surface, offset curve in face, projected curve, curve in face, through curves, face blend, edge blend, sew, law extension, mirror geometry, trim sheet, trim body, thicken which provide desire shape and size to unexpected deformation.

Top view

Front View

Isometric View

Draft Analysis-

Conclusion-

Thus, the hood is designed considering passenger and pedestrian safety as per the master section. We were sufficiently set up to plane the inner panel of the hood with assistance with given master sketch and different assessments. Organized the way of hood design by NCAP rules feasibly amassed the hood inner panel, hood outer panel, hinge assembly. we gain more knowledge and industrial requirement while designing the hood design.