Hood design-Week 2

OBJECTIVE:

• Designing and modeling the hood concerning its parameters and requirements.

INTRODUCTION:

• Hood is an automobile component and it is called the bonnet in British countries.
• It is assembled in a tapered position to the windscreen of the car it has enclosed around the engine compartment.
• A hood is meant to protect the vehicle's performance parts like the engine or battery.
• They also provide easy access to car repair and maintenance.
• The hood is made up of aluminum materials.
• They serve a great deal of purpose in protecting the passengers inside the car and pedestrians in event of an accident.

HOOD COMPONENTS:

• Hood outer panel
• Hood inner panel
• Latch and striker
• Reinforcements

OUTER PANEL:

• The outer panel has an aesthetic look to it but on its own is very weak and not capable of handling force during impact.
• It is installed over the inner panel and made up of aluminum alloy.
• Aluminium alloy has excellent corrosion resistance and it possesses high strength and excellent stretch forming and lightweight characteristics.

INNER PANEL:

• The inner panel is mounted under the outer panel.
• It has been designed and modeled with overlapping flanges connected.
• The emboss is created under the manufacturing process of sheet metal stamping dies.
• The purpose of the hood inner panel is providing to improve rigidity, durability, and pedestrian protecting performance by comprising a composite structure.
• The inner hood panel also protects the engine compartments during the collision.
• Generally the hood inner panel has a multi-cone structure.

HINGE:

• The working system of the hood is completely baes on its hinges.
• The hinge mechanism is provided that allows a lawn and garden tractor hood to be pivoted between closed and open positions.
• The construction of hinges to allow easy separation or connection of parts at the hinge axis in a radial direction requiring a specific angular position the pin having a non-circular cross-section
• The hinges are properly aligned on a single reference axis path.

To assemble the hinges, two constraints are used.

• Touch constraint
• Parallel constraint.

LATCH AND STRIKER:

• A vehicle hood latch and release mechanism are latched when the hood striker engages the latch portion of the mechanism as the hood is moved to its closed position.
• The mechanism is actuated to release the hood striker by pushing action on the cable.
• When the latching mode of the hood latching and releasing mechanism latches the hood striker holds the hood closed.

REINFORCEMENTS:

• The striker reinforcements material that can enhance strength and rigidity in the vicinity of the striker and secure pedestrian protection performance.
• The reinforcement is included for the less thickness of material where the deformation occurs at the time of the collision to protect pedestrians.

ASSEMBLY TREE OF HOOD:

LATCH TRAJECTORY MOTION:

• The significance of the trajectory concept is open and close the hood along the curved path to its motion concerning gravity.
• The circle is sketched at the center section of the hood using the datum plane and the line is drawn tangent to the circle.
• A perpendicular line is drawn at the center of the striker using the datum plane.
• By using the align constraint, coincident the tangent line and perpendicular line of striker.

MASTIC DATA:

• The mastic sealants are in the form of paste.
• The mastic sealants either join one surface to another or adheres to nearly any material.
• The mastic sealants are applied in between the outer panel and inner panel to join with each other.
• The mastic data are applied on the hood and it solidified fills the gap of 5mm between the outer panel and inner panel.

EMBOSS:

• This command enables modifying the sheet body by adding faces of a solid body.
• The target sheet body intersects with tool bodies when pressed.
• The shape of the tool bodies is to be transferred onto the sheet body.
• It increased the metal panels and stiffness and rigidity.

• Increase the surface area for heat transfer or acoustic applications and improve the traction.

MASTER SECTION:

• Outer panel thickness=0.75mm
• Inner panel thickness=0.75mm
• Reinforcement thickness=1.5mm

HEMMING PROCESS:

• Hemming is a technology used to join inner and outer closure panels together.
• It is the process of bending/folding the flange of the outer panel over the inner panel.
• Hemming is performed to
• Achieve a better final geometry in the vehicle part.
• Allow safe handling of the part.
• Add resistance and rigidity to the part.
• We are using the roller hemming operation for the hood to get the desired final shape of the product of the sheet.
• When force is applied during hemming process there may be change of shape which is examined and relaxation is given those areas to decrease stress concentration.

Numerical quantification of model and experiment of external force

• To prevent the formation of buckling during hemming make the corner relief at the sharp corners.

PEDESTRIAN SAFETY:

• The term pedestrian generally refers to a person walking, running, skating, skateboarding, and other similar devices.

Kinematics of pedestrians in an impact

• It describes when a passenger car collides with an adult pedestrian standing erect.
• The contact between the leading edge of the hood and the upper legs/pelvis of the pedestrian.

Adult and child head impact

• The impact area for the child's head is between 1000WAD-1700WAD.
• The adult head impact area is between the 1700WAD-2100WAD. The impact area does not include the windscreen.

Virtual crash simulation

Requiring factors of the virtual crash test

• Creating the three-dimensional geometric models of all the required components to replicate structure as accurately as possible.
• Converting the geometric models into FE models.
• Implement the mass properties and representative materials properties.
• Constraining the components together.
• Post-processing to analyze the crash results.

Contour plot of hood displacement using hyper view

Conclusion:

• Designed and modeled the hood panel using Siemens NX CAD as per the design parameters.

https://drive.google.com/drive/folders/1ljdnxxxQwSrJFkwkeWrJpqNbp-KDhVmx?usp=sharing