Designing of Car Hood by following EURO NCAP Standards using NX-Cad

Designing of Car Hood by following EURO NCAP Standards using NX-Cad

Aim:

To design a car hood by following EURO NCAP Standards with inner and outer panel by placing latch, hinge and its reinforcement using Siemens NX-Cad.

Software used: NX-Cad

Hood (Bonnet)

The hood or bonnet is the hinged cover over the engine of cars. Hoods can open to allow access to the engine compartment on rear-engine for maintenance and repair. It is hinged thin sheet which covers and protects the main parts of car like engine. Its main function is to direct access to the engine, battery and other crucial parts of the cars for repair and maintenance and to protect these parts from direct sunlight and dust. It consists of Support rods or gas stays to hold the hood while it is opened. A hood may contain a hood ornament, hood scoop, power bulge and wiper jets etc.

Body in White:

It is the stage in automobile manufacturing in which a car body's frame has been joined together, that is before painting and before the motor, chassis sub-assemblies have been integrated into the structure. It helps to ensure that the welding process meets the pre-defined standards of high-quality. They provide the necessary support and stability to avoid distortions in the welding process, which can often lead to expensive iterations.

Parts of Hood:

• Outer panel
• Inner panel
• Latch &Striker with its reinforcement
• Hinge with its reinforcement

Functions of Hood:

• It helps to design car aerodynamically stable.
• Sometimes it is required to supply pure air so filter is provided on the bonnet to supply filtered inlet air.
• Hoods are provided with different vent designs for cooling purpose of an engine and carburetor at high speed.
• scoops on hood having another function of supply of air for supercharger in case of supercharged engines.
• The function of hood is to handle this type of heavy engines with supercharger outside
• And lastly it also gives good looks

Design Approach

Top down Approach

Procedure for Designing Hood

Hood Thickness Information

• Outer Panel Thickness = 0.75mm
• Inner Panel Thickness = 0.75mm
• Reinforcement Thickness = 1.5mm

Master sketch:

The master sketch is prepared based on the requirements that received from marketability team and on basis of manufacturing requirements. It is a master section used for designing these Hood.

Design of hood outer panel

• It is created on basis of styling and it wraps around inner panel for fixing both together by applying mastic between them.
• Some reliefs are applying at the edges.

Mastic Sealant

It is an elastic compound that behaves like a rubber. These points are defined on the hood inner panel where hood easily can deform. It helps hood outer panel to come back to its original shape after getting deformed. It also helps the inner panel fixed with the outer panel. The main function of mastic point is to reduce NVH(Noise ,Vibration and Harshness) that created on hood. So, by providing more in number of mastic points at center area of hood will increase the performance of car. It has capability to reduce the NVH for the radius of 80mm.

Design of hood inner panel

• At first wave geometry is used to extract the styling surface as a linked body.
• Then these surfaces were trimmed into half along x-axis by using trim body.
• By using offset geometry of 0 mm were generated and separated to feature group for forming parent group and other one for working surface.
• On basis of master section their surfaces were offset at 2mm ,4mm and 25mm downwards.
• Then for creating flange the corner of the tangent curve will be offset inwards at distance of 20mm by giving filleted corner of 30mm further remaining portion to be trimmed.
• Though curves are applied to create flanges at 80 degree by applying tolerance for easy manufacturing.
• On third surface 55mm offset distance for curve has given and by removing unwanted portion.
• Then required embosses are created in a way that force dissipates and passes through corners which the energy is dissipated to outwards. Hence to satisfy the requirements of NASC regulations that embosses must have outward draft.
• By using edge blend with three corners all required surfaces are selected with proper directions and smoothened out as per manufacturer requirements.

Hemming Data:

Hemming is a process of joining the both outer and inner panel together. These process roles and wraps the hood outer panel around the inner panel for holding it tightly together.

Front relief

Relief rear section

Design of Latch & Striker

• It is used to locking the hood with the car body.
• In this striker exactly fits into hole provided in the car body.
• The Latch & striker is fixed on hood inner panel using some fasteners and Reinforcements.
• These reinforcements are made about thickness about 1.75 mm.

Design of Hinge

• Hinges are used to connect the hood and cowl panel of an automobile.
• It enables the hood to swing open and close.
• Normally hinges are positioned in a way that the striker fits into hole provided.

1. The line joining the midpoint of the hinge axis and tip of the striker should always normal to circular trajectory of the hood which rotates about the hinges.
2. In simple words the line joining the midpoint of axis and tip of the striker should be always perpendicular to tangent of circular trajectory of hood of the tip of the striker.

• Hinge reinforcements are used to provide more strength to assembly.
• Reinforcements are made with sheet metals of thickness about 1.75mm.

Positioning the Hinge Assembly

• Hinge assembly is carried out by applying required constraints.
• Initially inner panel was fixed, and line was created horizontally that connects the hinges were constrained with a parallel mate to x-axis.
• Then the top surface of hinge is constrained to hood part that is emboss on the inner panel.

Positioning the Latch and Striker

• At first the latch was positioned roughly on basis of constraints and exporting the rear surface of latch using wave geometry linker.
• Then emboss for the latch was created before doing this some surface is extended all around for creating clearance for edge blends.
• Required circle from center point on hinge axis is selected and a line tangent to circle and a line vertical to striker point from latch were created.
• Then both the lines were aligned then latch will have its perfect position for striking with the engine compartment.
• Now if we move the hood as closing then the striker will meet the exact location of striker point in the engine compartment.

Hood Assembly:

Isometric view

Front view

Right view

Top view

Back view:

Bottom view:

Conclusion:

Thus, Body in white of complete Hood of a car was designed as per the industrial manufacturing requirements by following the EURO NCAP Standards.