SIDE CRASH ANALYSIS OF CHRYSLER S NEON

SIDE CRASH OF CHRYSLER NEON

The Chrysler Neon is a front-engine, front-wheel-drive compact car introduced in January 1994 for the model year 1995 by Chrysler's Dodge and Plymouth divisions in two and four-door body styles over two generations.

BIW :

BIW (Body in White) is a stage in automotive design and manufacturing. BIW refers to the body shell design of an automotive product such as cars. It is just a sheet metal welded structure. BIW will not have doors, engines, chassis or any other moving parts.

OBJECTIVE :

The main aim of the project is to run the simulation for the side crash of Chrysler's Neon and record the following errors and energy changes.

EXPLANATION:

  • The single unit system is followed [Kg mm ms] for the entire simulation.

CONTACT INTERFACE :

  • Type 7 contact interface is used and the following parameters are set. 
  • The important interface parameters are

     Igap      ----      Determines how the size of the gap is calculated

    Gapmin  ----      Minimum gap for activation of the surface

    Inacti     ----      Action to take if any initial penetration occurs

    Istf         ----      Affects how the stiffness of the interface is calculated

    Iform     ----      Friction Formulation

    STmin    ----     Minimum stiffness to use in the interface

    Idel       ----      What to do with the slave node and master segments if the elements get                              deleted

 

  Igap : 0

  • It is a constant gap method 
  • The gap is defined by Gapmin and is constant for all the contact. This is the default value.
  • If the Gapmin value is not defined or not set, then Gapmin = min(tm,lmin/2) 

  Igap = 1 

  • It is a variable thickness method
  • The gap varies according to the movement of the master surface and slave node
  • the variable gap = max[(tm,(gs+gm)]
  • This case will not give you an accurate result because the variable gap may not be correct all the time.

   Igap = 2

  • It is a variable thickness with scale factor

   Igap = 3

  • It is a variable thickness with a scale factor as well as the mesh size factor.
  • The scale factor helps to avoid the resistive force in case if there is any kind of initial penetration.
  • The mesh size factor helps to make mesh finer so that it creates the possibilities of all the node gap is detected or penetrated into the master surface gap
  • Igap = 3 is preferred.

 

   Inacti : Action to take if initial penetration exists

   Inacti: 0

  • No action takes place and running the simulation even though there is any initial penetrations.
  • This is the best option if it is possible.   

    Inacti: 3

  • Automatic removal of the initial penetrations
  • It destroys the model geometry.

    Inacti: 6

  • The gap is reduced and scaled.
  • When the scale factor is provided, the solver tries to reduce the gap that it won't affect the geometry and making it considered.
  • Thus resulting in the best accuracy.

    Iform : Sliding force computation

  •  Iform = 1, viscous method
  •  Sliding forces are computed using viscous parameters of the interface.
  •  Iform = 2, Stiffness method
  •  Sliding forces are computed using stiffness parameters of the interface, usually results in a bigger time step.                

    Idel :

  • Idel =0, the master node and slave node are kept as such leading to instability of the simulation and the model
  • Idel = 2, the master segment is removed from the contact when the link is deleted and the slaved node is deleted when it is free from the contact.  

thus the recommended parameters used are

RIGID WALL :

  • The cylindrical rigid wall is created normal to X-axis to the frontal car.
  • The co-ordinates of the rigid wall are (2250,1020,1500).
  • Friction parameter is given as 0.1
  • Dsearch is 1000mm which means it creates a search tolerance level of 1000mm around the rigid wall.

ADD MASS:

  • The mass is added to the system such a way the total mass of the system must be 700kg throughout the system.
  • At initially, the total mass of the system was 182kg. The mass is to be increased but the center of gravity of the car must lie in the back of the driver seat and must be low almost to the base of the car.
  • So the mass is added along the base of the cars and the b-pillar of the car to increase the mass.
  • Thus the center of gravity is almost maintained behind the driver seat and mass is brought up to 700Kg.

INITIAL VELOCITY:

  • The initial velocity is given to the car thus it creates an impact with the rigid wall at some speed.
  • The initial velocity of the car is given as 15.636 mm/ms along the Y-axis according to the global axis.
  • The entire nodes of the cars are selected.

TIME STEP :

  • The time step of the simulation is maintained at  0.5 to 0.1 milliseconds.

 

OUTPUT REQUESTS:

1.Sectional force in the cross member.

                                                                CROSS MEMBER

The forces at the cross member are shown above                                                                                                                                                                                                                  The hikes in the cross member is due to the resistive force and the deformation of the component. The maximum force is 16 Newtons at the time of  26 milliseconds. This is the point where the deformations gradually increase throughout the cross member.

 

2. Intrusion at B pillar 

    

     

 

      

 

Displacement keeps on increasing due to the initial velocity

At the point of 30 milliseconds, the graph remains almost constant because the B-Pillar is almost hit the rigid wall and hence cannot move further.

Thus the total intrusion is 1021mm inside the driver cabin.

3.The intrusion at the hinge pillar

 

The displacement at the hinge pillar is kept on increasing because even after the impact, The B-pillars get impact and forms V-shaped structured where the hinge, A-Pillars and rear fender are still moving beyond the cylindrical rigid wall. The displacement is a maximum of 1000mm.

The total intrusion is found to be 305mm inside the cabin.

 

4.The intrusion at the fuel tank region:

 

The displacement curve keeps on increases and the time of 30 milliseconds, the element displacement remains constant till up to the time of 47 milliseconds. It is because the component undergoes deformation and requires more forces to get more deformation, which is next to the lower yield point of the material and increase a bit more.

The total intrusion is found to be 711 mm from the initial position.

5.Peak velocity of the inner node of the door

 

Due to the initial velocity applied, the graphs start at 15 mm/ms^2 remains almost constant.

The curve starts to decrease due to the impact, the velocity has been reduced at the time of 8 milliseconds from the impact and gradually keeps decreasing.

Thus the spikes are due to the resistive force offered by the material due to the impact.

 

Energy Curves:

 

Hourglass Energy: The hourglass energy remains constant throughout the simulation. This is because of the properties assigned as Qeph= 24

Kinetic Energy:  The elements are in motion due to the initial velocity, so the kinetic energy is high and keeps reducing due to the impact of the car on the rigid wall.

Internal Energy: The internal energy of each element keeps on increasing due to the impact, the reaction force is created. Due to the reaction force, the resistive force is kept on increasing in the elements.

 

Result:

Thus the simulation of the side crash for Chryslers Neon is executed and the following observation has been made. The car fails for the side crash due to the intrusion of components into the driver's cabin. It can be neglected by adding a few more cross member in the base and also making B-pillar components stronger by using different grades of sheet metal.

 

Energy Error  ---  -0% to -1.0%

Mass Error     ---  0.0091% to 0.0097%

 

https://drive.google.com/open?id=1WwKWFCeHrfHufA5cdjdWE3ODgYK_Wv1M


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