Side Pole Crash Simulation on Car BIW.

Aim: Side Pole Crash Simulation

Procedure: In this project, we need a car model and it should be a solver deck file ( 0000.rad and 0001.rad). So in our case, we have used BIW of a car only. A complete file will be too big to handle and take more processing time. So to start analyzing the result for the side crash we need to set up our solver deck and model first.

We will start by checking the unit system as per specifications, in my case, it was allowed to be in [Mg mm s] or [Kg mm ms]. So we can check for the unit system for our model in the starter file i.e. 0000.rad file.

So, after finding our unit system to be correct we need to create the appropriate interface, friction 0.2, and recommended parameters.
For this model, we are using the Type 7 interface. It is an interface between the master surface and slave nodes. We can also use other interface cards individually or in combination to type 7 as they help to remove intersections and Inacti helps in removing penetrations. Using more cards will increase simulation time but will also improve results. Intersections are when a node penetrates into elements and Penetrations is when a surface with thickness penetrates another surface.

Here we see 7 interfaces and it is of no use for our case so we will delete all interfaces and create a new Type 7 interface. And give surface id and ground id by selecting for the whole model. And other parameters as recommended for type 7 interface.

Recommended Values for Type 7 Interface are :
Istf = 4
Igap = 2
Idel = 2
Stmin = 1
Gapmin = 0.5
Inacti = 6
Iform = 2
And for our model, we need to give Fric = 0.2.
Now after setting the interface card we need to check for penetrations and intersections if any. This can be done by opening HyperCrash under Applications. In HyperCrash we need to go in Loadcase - Contact Interface and click person symbol in Contact Interface window for penetrations and intersections check.

So, for our case, we got no intersections and penetrations. Now we need to correct rigid bodies manually if any. It was not there in our case. Now we will be creating a rigid wall with friction 0.1. This can be done by right-clicking in the solver tab and creating a Rwall of the required type. For this side pole crash scenario, we are using a Cylindrical-type RWall.

Next, we need to compare the model weight with the full-scale 300k nodes model and use added masses to reach the target weight of 700kg and also placing CG in the required area. This can be done in HyperCrash easily. First, we need to check for COG and Computed mass value. This can be checked under Mass - Balancing - Show COG Point.

Now we notice here the mass is 166Kg instead of 700Kg. So we need to add mass to nodes in the model in such a manner that it reaches 700kG FOR 300K nodes model and also COG shifts to a position where it should be in a full car model with mass addition. So mass addition is done under loadcase - Added Mass - Create new mass by right-clicking type 1 where mass is distributed to each node of node group.

In this we can change the title of added mass and give the mass amount in added mass and in support, we need to provide the node id to which we want to apply mass. For this, we need to right-click and select the area by using add nodes by box selection. And select nodes to which you want to apply weight. So in our case, we added mass at 4 different locations i.e., Near driver seat area indicating weight for seat and driver, Co-Passenger sitting area indicating weight for Co-passenger seat and person, Back seat area/Fuel Tank, and center mass indicating weight for gearbox, etc. And the values were decided based upon standards for that area.

Now we need to set the initial velocity as 20mpH. Specifically 20mpH because is an industrial standard value after several experiments by companies. This is done by creating an INVEL card by right-clicking in the solver tab. And applying it to our model. As our unit system is in mm Kg ms so we need to convert 20mpH to a given unit and it comes out to be 8.88mm/ms.

Now we need to change the time step to 0.5-0.1ms and also Run for 80ms. As both of them are a control file so they will come under Engine Keywords. DT for Timestep and Run for simulation time.

Now all the setting is done now we need to use a model checker to ensure good quality. For this we again use HyperCrash and it can also be done in HyperMesh. This is necessary because while defining things for the model which we did tell now we may make mistakes or we forget the unnecessary cards to be removed after updating things. So by the model checker, we will come to know all the errors and warnings for our model. If we have only warnings then our model will easily run and if we have errors then the model won't run. Now how to check this? For this, we can check models from both HyperCrash and HyperMesh but we have used HyperCrash here.

So, luckily we have not got any error for this model and only warnings showed up for our model, now we need to eliminate the necessary one very carefully. And never use the autocorrect option as it will ruin all settings and we need to go all steps again. So, if any error would have come up in that case we usually understand each and every error first and dig the reason why it came. And see if we can correct the same or we usually create that step again. At last, it should be all warnings no errors and we successfully achieved it.

Now the time comes for outputs and analyzes things happening to the model. We will start with setting the things for getting sectional force in the cross members. Now this statement itself says that first, we need to create a frame of reference for the informed node and later define a section for the same node along which study will be done and to have this in output we need to declare the same in TH (Time history).

While creating a frame you have multiple methods which need a careful selection of node and axis selection as when you make a section out of the frame the direction of normal or local coordinate i.e. frame, should be in the direction of the crash. As we are taking output requests with reference to this section only.

Other than this we need to find intrusion at the B pillar, hinge pillar, and fuel tank region. For this we actually have 2 methods: first, we can directly define it under TH/Node or we can do a better approach by creating a spring in between the asked node and a node on the surface which is exactly perpendicular to the asked node. Spring definition has to be done in that case. But the results are much better than TH approach. We are using TH approach here. While defining intrusion we just need to give a node id in entity id in our case.

We also need to find the peak velocity of an inner node of the door. For this also we will repeat the same process for that creating intrusions.

Now all the output request setup is done and we just need to check results for our model now.

Animation File Links: https://drive.google.com/file/d/1_H8PVgIPAiGrp2MQ5qG4H_m-6PKIXO5n/view?usp=sharing

In the results, you will see changes in the curve behavior of intrusions in the B pillar, hinge pillar, and fuel tank region. 123359 is intrusion for the fuel tank, 123370 is intrusion for Hinge Pillar and 123402 is intrusion for B Pillar. 338478 shows peak velocity at door. So here we see maximum displacement for the Hinge pillar that is because when we see simulation the model actually bends from the contact area and starts folding. Because of this hinge pillar location, and our intrusion point on the hinge pillar deviates due to folding most as it is far from the area of contact during a crash. And others show less displacement. And also in the case of sectional force we see both the cross members shows almost the same curve i.e. because when we see simulation minimum damage happens in cross members and the vehicle instead starts folding and roof cross members show maximum buckling i.e. because cross members are a bit stiff in nature due to property assigned to withstand higher loads. And peak velocity is as per expectations it will increase with contact and time.

Observed values of mass error and energy error in run1_0001.out file.
Mass Error : In the range of = 0.9508E-02 - 0.1030E-01.
Energy Error : In the range of = 0.0% - (-2.4%). Negative because energy is dissipated during a crash.

These small values of mass error and energy error are in acceptable range so no need to worry about the same.

Model Drive Link: https://drive.google.com/drive/folders/1BS-3HsNmmkhcwrRmiqaI1fuSk5kLjoX3?usp=sharing