Simulation of Roof Crash of Dodge Neon BIW model using Radioss
Aim:
1. To perform roof crash analysis on neon dodge BIW model by setting up the following parameters.
1) To import both BIW and FMVSS Impactor in Radioss.
2) To give the following the transformations to bring the impactor at the desired location:
• A 180° rotation about the global z-axis
• A 5° rotation about the axis through axis AB
• A 25° rotation about the axis through axis AC
• A translation to put point A at global ( -3500.00, 584.822, 1343.06)
3) To setup interfaces and provide the following boundry conditions and also give imposed displacement to the impactor:
• Keep the suspension shock tower nodes locked in Z.
• The impactor assembly contains a spring attached for stability. Create a BCS
collector to fix the free end of the spring.
• Create a moving SKEW to define the direction normal to the impactor’s
face.
• 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.
• 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.
• Avoid abrupt changes in the acceleration of the impactor.
4) To check the following controls cards:
• /ANALY card
• /DEF_SHELL card,
• /DEF_SOLID card, and
• /IOFLAG card
• /SPMD card
• /TITLE card
5) To check for penetrations and intersections in the model and checking for any errors & warnings in the model checker.
6) To check for the following values in the engine keywords:
• 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.
7) To run the simulation and to provide the following animations and plots:
• Elemental Energy.
• Elemental equivalent plastic strain.
• Elemental hourglass energy.
• Elemental von Mises stress.
• Nodal added mass.
• 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.
Theory:
The roof crash analysis is done for the estimating how the forces and other parameters act on the roof of the vehicle. It also shows deformaions happening near the passengers seat.
Procedure:
1. Setting up the model:
1) We first import the roof crash model and the impactor using the import option.
2) We then perform the transformations given in the aim for that, we first rotate the impactor for 180° about the z-axis, then we give 5° rotation about the axis through axis AB, then we give 25° rotation about the axis through axis AC and finally, we give translation to put point A at global ( -3500.00, 584.822, 1343.06). The A, B & C are given in the image given below.
3) We finally get the impactor positioned in the correct way according to the FMVSS 216 roof crash standards as shown in the image given below.
4) We need to create the Interface type 7 contact between the roof and the Impactor and a self impact also needed to be created in the car model.Self contact is to prevent the penetrating of nodes into the elements while the deformation caused by the impact.Also the contact between the impactor and the roof is essential because the roof and impactor will interact when the crash happens. The interface is shown in images given below.
5) We then give the boundry conditions for the model first, we give rigid body to the three suspension shock towers and then, we lock them in translation along the z axis. For that, we first create a BCS Collector and in that we select the node and skew ID's we also create a moving skew on the master node and then, finally we lock the z-axis translation of the element as shown in the image given below.
6) We then need to tie that impactor spring on one end to a point.For that we need to arrest the D.O.F of the spring in all the 6 d.o.f. So another BCS is needed and in that we need to check all the 6 D.O.F. The BCS Collector definition is shown in the image given below.
7) We then, need to arrest the all D.O.F except the z direction for the Impactor Rigid body. While creating this we should also create a moving SKEW to represent the normal to the face of the impactor.This normal should be the z axis of the Skew.The Skew created is of Moving skew. The BCS Collector definition is shown in the image given below.
8) We then, need to define the Imposed displacement for the impactor. While creating this we need to define the function with the displacement is 0mm at 0mm/ms velocity to 200mm displacement at 200 ms time as shown in the image given below.
9) We then, define the imposed displacement as shown in the image given below.
10) We then, check for the control cards i.e. /ANALY card, /DEF_SHELL card, /DEF_SOLID card, /IOFLAG card, /SPMD card and /TITLE card in the Solver Browser. We find that, all the cards mentioned abov are available so we proceed further for checking penetrations and intersections in the model.
11)We check for the penetrations and inersections using the penetration checker. We find that there are no penetrations and intersections in the model as shown in the images given below.
12) We then, perform model checking using the model checker and we find that there are 3 errors & 5 warnings in the model. The errors and warnings are shown in the image given below.
13) We clear all the errors and warnings and we proceed further to check the simulation time and time step. We check the value of run time, time step and time history print values and find that all the given correct as shown in the images given below.
14) We also turn on the parallel arithmetic i.e. IPARITH in the /ANALY card as shown in the image given below.
15) We finally, create a new folder for simulation of the model and for creating out files, animation files, h3d file and T01 file on running the simulation. For running the simulation by going to the Analysis module and clicking on Radioss option as shown in the image given below.
2. Simulation Results:
1) On running the simulation, we get the values of energy error and mass error in 1.out file as shown in the image given below.
Energy Error: -4.4 %
Mass Error: 0.04490
No of cycles: 2,00,001
2) We go to Hyperview and import the file '.h3d' then, we check for contour plot on Von mises stress with simple average method, Plastic Strain,and Node Mass in the form of animations as shown below.
Max Node Mass: 0.9315 kg
Max Plastic Strain: 0.07107
Max Von Mises Stress: 0.2697 GPa
3) We then, proceed to plot the graphs the results with the help of Hypergraph 2D.
4) We plot graphs for all the energies which include internal energy, kinetic energy, Contact energy, Hourglass energy & total energy are shown in the image given below.
In this plot, there energy that is stored in the system therefore the Kinetic Energy is ~0 J, the Hourglass energy is also 0 J since we are using the default recommended shell formulations, the Contact energy is 92 J which is less since the contact only happens when the impactor touches the BIW model, the Internal Energy of the systems increases after 45 ms from 0 J to 1990 J since energy is released and finally, the Total Energy as follows the same path as of the Internal Energy, it increases from 0 J to 2021 J.
5) We plot graph for Force vs Displacement by plotting the displacement vs time & Total Resultant Force vs time of Contact Interface created between car and impactor. We use the cross plot for two curves under the math menu and plot the graph as shown in the image given below.
The contact is not made until the 45 th milli second since the impactor is in travelling phase.And the maximum value is obtained equals to 18.3 KN at 140 mm .As soon as the impactor makes the contact the contact force reaches maximum.The roof nodes try to penetrate the impactor mesh but it opposes with the contact force.This is happening throughout the coarse of the impactor motion.
The total vehicle mass is 175 kg = 1716 N. For the vehicle to pass the Roof crush test, it has to have the capability to withstand loads equal to 3 times its own weight, which in this case is 3 * 1716 = 5150.2 N or 5.15 kN. The peak force registered for the simulation is 18.3 kN which is well above the calculated value. Thus the model has passed the Roof crush test successfully.
Conclusion:
1) We setup the model for the Roof Crash Test, according to the parameters provided in the aim.
2) We checked for penetrations and intersections and found no penetrations in the model.
3) We used model checker and found out the errors & warnings in the model and cleared one by one manually and finally, we checked the engine runtime, animation time step, print time of time history files and parallel arithmetic switched on or not.
4) We ran the simulation and obtained the animation contour for Plastic Strain, Node Mass, and Von Mises Stress.
5) We plot the graphs for all the Energies and Graph for Force vs Displacement was plotted and a maximum force of 18.3 kN at 140 mm displacement was noted. Since this force is very higher compared to the 3*GVW value for the car, the roof crush test is a success.
Model Link:
https://drive.google.com/file/d/15Vk12E1WD2SK9W5eN-LxC_7XQmL72Ky1/view?usp=sharing