Side crash analysis of a Neon model as per the required parameter values and settings using HyperMesh and Radioss.
Project Report
Side crash analysis of a Neon model as per the required parameter values and settings using HyperMesh and Radioss
Objective:
To do the Side crash analysis of the given Neon model, requesting required outputs and assigning appropriate parameters as asked.
Theory:
A crash simulation is a virtual recreation of a destructive crash test of a car or a highway guard rail system using a computer simulation in order to examine the level of safety of the car and its occupants. Crash simulations are used by automakers during computer-aided engineering (CAE) analysis for crashworthiness in the computer-aided design (CAD) process of modelling new cars. During a crash simulation, the kinetic energy, or energy of motion, that a vehicle has before the impact is transformed into deformation energy, mostly by plastic deformation (plasticity) of the car body material (Body in White), at the end of the impact.
Data obtained from a crash simulation indicate the capability of the car body or guard rail structure to protect the vehicle occupants during a collision (and also pedestrians hit by a car) against injury. Important results are the deformations (for example, steering wheel intrusions) of the occupant space (driver, passengers) and the decelerations (for example, head acceleration) felt by them, which must fall below threshold values fixed in legal car safety regulations. To model real crash tests, today's crash simulations include virtual models of crash test dummies and of passive safety devices (seat belts, airbags, shock absorbing dash boards, etc.). Guide rail tests evaluate vehicle deceleration and rollover potential, as well as penetration of the barrier by vehicles.
Given model:
The side section of the car was taken because of the limitations of the student version of the software but the balancing was done appropriately so the the condtions obtained were as good as that of a fill model.
Unit system:
Open the file neon_front_0000.rad. We can check that unit system is kg, mm, ms either from the notepad file or from the Benign card as the following image shows.
Penetrations check:
There should not be any initial penetration. This gives rise to a simulation with sliding energy present at the initial conditions which is physically wrong and hence it should be strictly seen that the penetration check is applied through the pre-processor.
HyperCrash was used for the penetration check. To check it select all interfaces in the browser tab and run click check penetration for selected objects. As a result, we got the following results as in the figure below. It can be seen that there were no initial penetrations present which was a good sign.
Runtime:
To set runtime, Go to cards and then select ENG_RUN and enter the required value in Tstop. Here we see that the value was already set to 80ms which is good to go.
Definition of Initial Velocity:
The initial velocity is 35 mph=15.6464 mm/ms.
To give initial velocity ,create > boundary conditions > INIVEL
Then the value in Vy is entered as shown below:
After the create Grnod_id, Go to Entity IDs and select all the nodes of the model so the initial velocity is assigned to them
Rigid wall creation:
To create rigid wall , in the model browser go to create, then select rigid wall.
As shown in the figure below, The Engineering data and the support data is entered by taking the reference of the full car model provided. Slide value was set as 2 and Dsearch value as 100 are entered.
Friction is entered as 0.1 as shown below.
The obtained cylindrical rigid wall looked like this:
Interface Creation:
In RADIOSS an interface is created by defining the master segment and slave node set. The master segment can be parts components, elements, contact surface, node surface sets and slave entities can be parts components and node sets. The contact algorithm will check every time step for potential penetration of a slave node through a master segment
In this case Goto model browser, and create a contact. In the contact section, enter the recommended parameters like Type of contact, Istf , Igap , Idel , Stmin , Fric , Gapmin , Inacti , Iform etc. Now select Masters and slaves through Surf_id(M) and Grnod_id(S) respectively and under Entity IDs components for master and slaves respectively as shown below:
Centre of Gravity:
On taking a node at the cordination of the centre of gravity it was seen that it was not at a proper position, and also total mass wat quite less by around 512kg, so to correct that that much of mass was added uniformly at the back portion of car to obtain proper mass as well as the center of gravity at a proper position.
Goto Tools > Mass Details > Mass, COG and inertia to obtain the window below.
Mass addition and balancing:
In order to add mass to the components, in the model browser, right click and go to solver mass. Under that select the required mass type (type 1 was taken in this case), mass and grnd_ID and under that go to Entity_ID and select the Nodes on which mass is to be added. COG relocates to a position as shown in the figure below.
In the figure below it can be seen that Mass id almost proper as required and centre of gravity is also shifted at a proper position i.e. at the middle and behind the portion of the driver’s seat.
Section selection:
Moving frame was specified and selected at each of the selected section. Also appropriate elements were selected. Values of deltaT and alpha were entered as 0.1 and 1.65 respectively.
Time history:
To get the above created sections in the result, the cross sections were selected and assigned to the TH->SECTIO->crosssections.
Similarly acclerometer’s and the instrusion nodes were assigned in the TH to get their time history result in the output block, as shown in the images below:
Intrusion Nodes:
Cross sections:
Model Checker:
Finally before simulation run , model checker was used check the model for looking for errors or warnings and their rectification so that problems are not encountered during simulation run. To run model checker goto Tools -> Model checker -> Radioss and checker appears as shown below and then it is run to check for errors etc.
Animation after running the simulation was as follows:
The car model is crashed from the front region, the deformation starts from the bumper and hence move along as shown the the images below. Initially the stress was maximum at bumper but was later distributed in other portions too as shown in the contour plot.
Mass Error: 0.3083E-01
ELAPSED TIME: 3054.62 s
Contours :
Displacement Contour Plot:
Max Displacement: 1.326E+3
Mass Contour Plot:
Max Mass: 6.255E-02
Min Mass: 3.687E-05
Von Mises Contour plot:
Max Von Mises stress: 4.366E-01
Graphs:
Internal and kinetic energy variation:
It is obvious that due to crashing the Kinetic energy decreases, it gets converted to internal energy which is increases as shown below:
The is a decrease in Total energy as it can be seen.
Contact and hourglass variation:
There is a sudden hike in the contact energy because too much of the elements come in contact toward the end time of the crash.
Total resultant forces on Cross sections as well as intrusions asked along with the cross sections where they are measured:
Cross Rail 1:
Here it can be seen that from 0 to 15th ms there is an increase in the forces and then a decrease. And after that there is are variations but not such steep but there are some jerks present but are under limits. This may be because at 15th ms the part is hitting the rigid wall so the forces are high. Max force: 8.2 kN
Cross Rail 2:
Similarly, compared to the previous case here also due to initial collision there is an increase in force but then a decrease. At the end there is an increase in one of then because maybe the rear part come in close contact of that component so the force again increases. There are somewhat more jerks here because this rail is in line with the rigid wall so variations are more. Max Force: 3.5kN.
Intrusions on the nodes asked in the problem statement:
Fuel Tank Displacement:
Node numbers and variations are mentioned in the graph.
It is very clear from the graph that as the collision proceeds the displacement of the given nodes happen at almost a very decent pattern as seen from the graph.
Initial intrusion – Final intrusion = 1314.821-225=1089.8 mm (approx)
B-Pillar Displacement:
Node numbers and variations are mentioned in the graph.
It is very clear from the graph that as the collision proceeds the displacement of the given nodes happen at almost a very decent pattern as seen from the graph.
Intrusion: 1307.847-270=1037.847mm
Hinge Displacement:
Node numbers and variations are mentioned in the graph.
It is very clear from the graph that as the collision proceeds the displacement of the given nodes happen at almost a very decent pattern.
Intrusion: 1312.65-570=742.654
Velocity of Node on the Door:
Node numbers and variations are mentioned in the graph.
Velocity at time of impact is high quite high i.e. 15.8 mm/ms, it is maximum at around 5ms time which is 16 mm/ms. As the crash proceeds and the car comes to rest, the velocity decreases with some jerks and hence we obtain the velocity time history graph as shown above.
Conclusion:
For the given model of Neon, the Side crash analysis was carried out successfully using Hypermesh, HyperCrash and Radioss, and the required results were plotted and analysed accordingly.