Assignment 7

Aim- Crash simulation using Hypermesh/Hypercrash/Radioss over a CAR side body BIW structure.

Objective-

1- Check the unit system (Kg, mm, ms or Mg, mm, s )

2- Create an appropriate interface with the recommended parameter, make sure there is no penetration and intersection.

3- Create a rigid wall ( as cylinder /pole) as per requirment.

4- Add mass for proper COG.

5- Giving initial velocity to the vehicle.

6- Use the model checker to ensure there is no error.

7- Create the Timestep ( 0.5 to 0.1 ) and run time to 80ms.

8- Run the simulation and plot the required results.

Introduction-

Crashworthiness is a term that describes a vehicle’s ability to protect its occupants during a collision. This means that the airbags and tires as well as the structure of the car must all prevent serious personal injuries in the event of a crash. Manufacturers must test all vehicles for crashworthiness before they enter the marketplace. However, car defects can result in a vehicle that does not provide adequate protection from the force of a collision. If you sustain injuries in a car accident due to the vehicle’s lack of crashworthiness, then you may have a claim against the vehicle’s manufacturer.

Crashworthiness concerns the safety of a vehicle during a car accident, not crash prevention. Product liability law requires that all manufacturers ensure their products are safe for all reasonable consumer use. Since millions of car crashes happen every year, it is reasonable for vehicle manufacturers to ensure occupant safety in their automobiles even during a wreck.

Body In White (BIW)-

Body in white 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, or trim (glass, door locks/handles, seats, upholstery, electronics, etc.) have been integrated into the structure. Assembly involves different techniques such as welding (spot, MIG/MAG), riveting, clinching, bonding, and laser brazing.

The term derives from manufacturing practices before steel unibody monocoques — when automobile bodies were made by outside firms on a separate chassis with an engine, suspension, and fenders attached. The manufacturers built or purchased wooden bodies (with thin, non-structural metal sheets on the outside) to bolt onto the frame. The bodies were painted white prior to the final color.

Side Crash-

Side impact car crashes (also called "T-bone accidents" or "broadside collisions") tend to have a more devastating effect on the human body than all other types of car accidents, according to researchers at Monash University Accident Research Centre in Melbourne. Side impact car accidents kill between 8,000 and 10,000 people each year, more than rear-end and head-on collisions combined. Even at speeds as low as 30 km/h, side-impact car crashes routinely cause serious injuries to the occupants of the struck car. While modern automobiles have many safety features to protect drivers and passengers from the front and rear accidents, such as airbags, seatbelts, and bumpers, side-impact car crashes leave occupants relatively unprotected. Some automotive feature side curtain airbags, but most vehicles offer no protection from side-impact crashes besides the car door.

Due to the lack of standardized safety installations to protect occupants, the types of possible injuries suffered in a side impact car crash can vary greatly, ranging between head injuries, ear injuries (most often caused by broken glass and airbags), neck injuries, back injuries, rib injuries, shoulder and arm injuries, or hip and leg injuries. For people riding on the struck side of the car, severe injuries are most commonly delivered to a person’s neck, followed by the head, chest, legs, and abdomen/pelvis. For car occupants riding on the non-struck side of the car, head injuries are most common, followed by chest injuries.

Procedure-

A- Unit check-

First, we need to check the unit for the model, it should be matched with the software in which we going to perform the analysis, we can check the unit from a hyper crush or we can also check it from the input.RAD file.

B- Center Of Gravity-

The model we get here is not the full model, so we need to match the COG so for that we need to increase the vehicle mass, here we added the mass in HYpercrash so that we can get proper COG. We can see that the model we were given has 187kg mass and the full model has 700kg so we need to balance the mass so that we can achieve a better COG.

C- Contact Interface and Penetration Check-

After the mass balancing, we moved for interface assignment, for that we use contact interface with Type-7 interface, the reason behind using type-7 is its frequently used interface for elastoplastic material and the reason why we giving the contact interface for the model so that they can not collapse with each other and behave like rigid and not collide to each other.After giving the interface we went to check the intersection and penetration between the node/element, if there is any penetration then we need to clear it.

D- Initial Velocity-

To impact with the wall we need to give the vehicle some speed, here we gave 15.65mph as initial velocity to the model so that it can impact on a pole, with appropriate direction ( in the direction of the pol -Y direction ).

F- Rigid Wall-

So to crash test we need to create a rigid wall a cylinder body in side of the vehicle, here we used a rigid pole as an impactor with appropriate input with some distance.

G- Contact Forces-

To measure the forces on the BIW structure we need to assign some input to the model to measure the forces on the structure for that we first created FRAME ---SET---CROSS-SECTION using hypermesh.

H- Output Request-

To see all these parameters we need to give an output request in simulation, so created an output request for all we need to see in the result in post-processing.

Energy Capturing-

Here we can see in the initial stage some energies are increasing due to strikes and some increasing, so the total energy remains constant.

Cross-Section Forces-

These are the forces that induce at various places in the BIW structure as we assign the cross-section.

Results-

These are the contour plot for von misses stress and displacement which are plotted using Hyper View. Here we can see vehicles moving at 15.65mph and strikes with the pole the maximum stress developed is 0.38164 N/mm2 at 80ms .

Conclusion-

1- Model has been imported in the Hypermesh and Hypercrash.

2- Model gas checked for error and penetration also for any free parts.

3- Added mass located with proper COG.

4- Simulation Terminated normally with negative error with 7000 no. of cycles and time elapsed is near to 3800s.