Roof Crash Simulation

AIM:

        1)  To perform the roof crash analysis on Neon Dodge BIW set-up the model by following parameters.

             i) Import both NEON-BIW model & FMVSS 216 Impactor in Radioss

        2) By following the transforms bring the impactor at the desired location.

             i) A 180° rotation about the global z-axis with the point opposite to C as base point 
            ii) A 5° rotation about the axis through axis AB
           iii) A 25° rotation about the axis through axis AC
           iv) A translation to put point A at global ( -3500.00, 584.822, 1343.06)

        3) To create interfaces & provide the boundary conditions for the imposed displacement to the impactor

               i) keep the suspension shock tower nodes locked in Z.

              ii) The impactor assembly contains a spring attached for stability. Create a BCS collector to fix the free end of the spring.
             iii) Create a moving SKEW to define the direction normal to the impactor’s face.
             iv) Create a BCS collector to guide the master node of the impactor rigid body so that it is free to translate normal to the face of the                               impactor, but is fixed in all other DOFs.

              v)  Impose the velocity of the impactor starting from 0 mm/s at t = 0. The displacement of the impactor should be 200 mm @ 200 ms.
             vi)  Avoid abrupt changes in the acceleration of the impactor.

         4) To check the following control cards:

                • /ANALY card
                • /DEF_SHELL card,
                • /DEF_SOLID card, and
                • /IOFLAG card
                • /SPMD card
                • /TITLE card

          5) To check the following values in engine file:

                • Use a constant nodal time step
                • Print time history every 0.0001 seconds
                • Solve for 200 ms
                • Create an animation file every 0.005 seconds 

          6) Run the simulation & provide following animations & plots

                 • Elemental Energy
                 • Elemental equivalent plastic strain
                 • Elemental hourglass energy
                 • Elemental von Mises stress
                 • Nodal added mass
                 • Turn on parallel arithmetic

                 • Plot force vs. displacement. Check that the FMVSS 216 target load of 47,000 N (= 3 * GVW) has been met.
                 • Plot the energy vs. time curves

DESCRIPTION:

                        Roof crush is the failure and displacement of an automobile roof into the passenger compartment during a rollover incident. Roof crush has also been identified as a cause of both full and partial ejection in rollover accidents because of ejection portals created by the collapsing roof structure. These chiefly involve broken windows but occasionally also involve the body structure. The current Federal regulation involving roof strength - 49 CFR 571.216 (FMVSS 216) - has been found to offer little benefit and is currently being reviewed. Many European manufacturers provide stronger roofs than do U.S. or Asian manufacturers despite the fact that there is no European (EEC) roof strength regulation for light vehicles.

 PROCEDURE:

Import the roof crash model & as well as imapctor in Hypermesh

 Then we are performing the transformations as per in the given. First we rotate the impactor for 180°  about the global z-axis with the point opposite to C as base point. Next we rotate 5° about the axis through axis AB, Then we give 25° rotation about the axis through axis AC. Atlast we give  translation to put point A at global ( -3500.00, 584.822, 1343.06)

Once the impactor has been set-up near to the roof of the car, Create Type-7 contact interface between the car & the impactor. choose the appropriate values for stiffness definition, minimum gap, co-efficient of friction & friction penalty formulation.

Self impact of the car:

Car & the imapctor:

Then we give boundary conditions & give rigids to the shock-towers & lock them in the z direction.

Then we have to fixed the spring at one end, so we have to arrest all DOF's

Then we defined imposed displacement for the imapactor with displacement is 0/mm at 0mm/ms  velocity to 200 mm at 200 ms time.

Then we check for the control cards which has been mentioned in the given. All cards are in the solver, so we can furtherly proceed to check penetrations & intersections.

Then we check errors & warnings, if any we neglect them & furtherly proceed to the simulation of the model to create out , animation, h3d & T01 files. By selecting analysis module & click radioss option to run the simulation.

Once the simulation is done, we calculate energy & mass error in out file.

Energy error - 4.4%

Mass error - 0.04490

No of cycles - 200001

Then we import the h3d model in Hyperview for contour plot on von misses stress with simple average method, plastic strain & node mass in the form of animations.

NODE MASS:

PLASTIC STRAIN:

VON MISES:

Then we plot graphs for internal, kinetic, contact, hour glass & total energy. 

By observing the plot, kinetic energy remains zero. Contact energy increases upto 92.2052 which is less, because contact happens only when the impactor touches the model. Total energy slightly increases upto 2021.

Then we plot the graph for force vs displacement, displacement vs time & total resultant force vs time of the contact interface, which has been created between for the car & impactor.

The contact is not made initially for some peroids, since the imapctor is travelling & maximum value is obtained. As sooner the imapctor reaches the contact force reaches maximum. For the vehicle to pass the roof crash test it should have some withstand capability of loads. Thus the model passes the roof crash test.

RESULTS:

•    The model has been setted up for roof crash test according to the parameters which has been mentioned in the given.
•    Then the model is checked for penetrations & intersections.
•    By using model checker, we are observing any errors & warnings occurs. If any we are neglecting those & running the simulation.
•    Once the simulation is done the animation for plastic strain, node mass & von mises in simple average method by using contour plot.
•    Then we plot the graphs for internal, kinetic, contact, hour glass & total energy & force vs displacement was obtained. Since the force is         very high compared to the 3*GVW value for the car, roof crash test is succesfully obtained.