Assignment 7-Side Pole Crash Simulation Challenge

Project 2 : Side pole crash simulation with given BIW frame in RADIOSS

 

Aim :-  To perform a side pole crash simulation with the given BIW frame in Radioss and request for outputs as mentioned in problem statement.

Software used :- Altair hyper-works student version 2020 and Hyper-Crash 2020

Problem statement :-

Neon side crash -BIW

• Check unit system and either follow [Mg mm s] or [Kg mm ms].
• Create appropriate interface ,friction 0.2 and recommended parameters.
• Make sure of no penetration and intersections.
• Create rigid wall with friction 0.1 as per referance model.
• Compare the model weight with the referance model and use added masses to reach target weight 700kg while getting CG about the required range.
• Initial velocity as shown in picture.
• Use model checker to ensure good quality.
• Timestep :0.5 to 0.1 microseconds.
• Run 80ms.

Output requests:

• Sectional force in the cross member.
• Intrusion at B-pillar, hinge pillar and fuel tank region. Provide recommendation on what can help to reduce Fuel tank intrusion.
• Peak velocity of inner node of the door.

Introduction :-

I'm utilising the BIW framework to develop a Side Crash for this project. The side crash analysis is crucial for passenger and occupant safety. If the holding structure is poor, the whole force of the crash may transfer to the main compartment, injuring the person.At junctions and in corridors, crash analyses are frequently conducted. They are a crucial component of safety analysis. The crash analysis may be used to evaluate issues and identify viable solutions. A destructive test called a crash test is frequently carried out to make sure that safe design criteria are met.

FMVSS ( Federal Motor Vehicle safety standards)

Federal Motor Vehicle Safety Standards (FMVSS) are US federal Vehicle Regulations specifying design, construction, performance, and durability requirements for motor vehicles and regulated Automobile safety-related components, systems, and design features. They are the U.S. counterpart to the UN Regulations developed by the World Forum For Harmonization of Vehicle Regulations and recognized to a varying degree by most countries except the United States.

BIW (BODY IN WHITE)

Body in white (BIW) is the stage in Automobile Manufacturing in which a car body's frame has been joined together, that is before painting and before the motor, chassis sub-assemblies, or trim (glass, door locks/handles, seats, upholstery, electronics, etc.) have been integrated into the structure. Assembly involves different techniques such as Welding (spot, MIG/MAG), Riveting, clinching, bonding, and laser Brazing.

 

Solution :-

 

Step 1 :- Intersection and penetration checking :-

Before opening model check units for further results from starter input file.

 

 Import the given model "neon_side_reduced_0000" into Hypermesh.

 

To check for penetrations in the model, we will go to Tools menu on Menu bar and click on Penetration Checkoption. In Penetration check panel, we will select all the components and click on Check command. The software will check for penetrations and then display the results as shown below,

There are no penetration or intersection error found.

Balancing COG

The BIW model does not include the precise weight of the vehicle; thus, additional mass should be added to the BIW model in order to account for the body's weight after production, including the weight of the seats, the weight of the people, and all other weights under realistic conditions. The desired weight is listed as 700 kg, however the real mass is 120 kg without the external weight. To build a new object, click on added mass after adding the mass. After providing the mass in the balancing menu, choose Type 0 - Mass is distributed to each node of the node group, and then click saveCheck COG simultaneously. As needed, add mass until the point is in the centre and the mass has reached the desired value. Below is an image that COG is present on required location i.e. under the driver seat.

 

Creating contact surfaces.

To examine the contact energy, a contact interface has to be established. Because of its great precision and accurate physical representation, type-7 Contact (Node to Surface) is chosen in this situation. The Contact interface describes the self-impact as the body acting as both a master and a slave. interface attributes modified the issue description to reflect the suggested circumstances, and created a new interface for bumper and rail connections as seen in the figure below.

 

 Rigid wall

We will require the outermost node at the front left door of the car in order to construct a cylindrical stiff wall at the left side of the vehicle. So, using the temp nodes option, we will generate the outermost node on the edge of the element. Next, we will use the solver browser's right-click menu to select Create > RWALL > CYL. We will enter the coordinates of the pole, which will be located a distance from the side door's outermost node, under Engineering data in the RWALL panel. After that, we will set the pole's normal orientation in the Y-axis and its diameter to 254 mm. As stated below, the FRIC value will be 0.1 and the Dsearch value will be 1000.

 

Initial velocity

In this simulation the initial velocity given to the model is 35Mph or 15.6464 mm/ms.To set the initial velocity of the model LoadCase>Initial Velocity>Set the value of the velocity in Y-Direction>Select all nodes>Yes>Save

Step 6 :- Section creation. :-. The results which we want on required cross sectional parts will be calculated based on a frame of reference. So before creating cross section, we will create moving frames on a particular node of that section. Now as we have to create the moving frames which are also called as local axis, we have to perfectly align our local axis to the global axis. Now we can create moving frame using these nodes. In Solver browser, we will right click and navigate to Create > FRAME > MOV.

Run model checker to ensure good quality

To check the quality of the model in Hypermesh, in Menu Bar we will navigate to Tools > Model Checker > RadiossBlock. This will open a new Model Checker browser.

Set time step and runtime

We'll go to Cards in the Model browser in Hypermesh to verify these parameters. We'll access the ENG RUN card to examine the run time, and there we'll notice that the model already has the run time in Tstop set to 80 ms. We will access the ENG DT NODA card and adjust the Tmin value to 0.5 ms for the time step.

Output request

Peak velocity of inner node of the door.

To find peak velocity at the inner node of the door, we will create a moving frame at the node location by using the same procedure as we used in cross section creation. Then we will create output block for the peak velocity by specifying the node and the frame or skew based on which the peak velocity is calculated as shown below.

 

Intrusions at B-pillar, hinge pillar and fuel tank

Here, we need to find the intrusions at B-pillar, hinge pillar and fuel tank. So to find the results at the specified parts, we need to have a frame of reference. Thus we will create moving frames at the opposite side which are at right B-pillar, hinge pillar right side and fuel tank opposite side as shown below.

Sectional forces in cross members

For this we will go to Output Blocks under Model browser. Then we will right click and create a new output block. Under Entity IDs option, we will select the cross section which we created and thus we will be able to plot graphs of the cross-sectional forces in Hypergraph.

RUN THE SIMULATION:

Click on the analysis panel in the Hyper mesh.Save the model in the local directory.Type -nt 4 in option and click on Radioss.From side_crash_0001.out file, the Total number of cycle was 159000. The energy error is -1.0% which is in acceptable limit. The mass error is 0.411e-4% which also less than 5% it is acceptable. The run was normal terminated which implies the processor successfully completed. There was no sudden changed in energy as well as in error. as shown below

 

Simulation in Hyperview:

Animation of the crash simulation is as follows:

Displacement contour plot

We can see that the vehicle's body is colliding with a pole in the collision scenario shown above. Following the collision, the vehicle's structure deforms, contracting around the pole with the left B-Pillar serving as the pivot. Since the vehicle's centre of gravity (CG) is aligned with the pole's axis or direction, we may see even frame deformation around the pole.

Von mises stress

the stress is more in B-pillar and cross members as B-pillar takes the initial impact and then the impact is transferred to the cross members.

Plots in Hyperview 2D :

The plots like energy differences, displacements, velocity and the normal forces are analysed.

 TOTAL ENERGY OF THE SYSTEM:

From the above plot, we can see that there is high amount of Kinetic energy at the start of the simulation but as the simulation progresses, the kinetic energy in the vehicle decreases and gets converted into internal energy, so the internal energy increases in the same proportion. Thus the total energy in the system is almost constant at 85000 kg*mm²/ms² and due to some energy loss which we can see in energy error, there is some decrease in total energy. We can also see some amount of contact energy in the model as we have defined the value of friction in Type 7 interface due to which contact energy is generated.

Sectional forces acting in cross members :-

From the above plot, we can see that the total resultant force in the rear cross member is more than the cross-member A. As the cross-member B is in line with the Pole, it experiences more force.

Intrusions

To prevent this failure, we need to reduce the intrusion which we can achieve by adding another cross member in fuel tank region which absorb some energy and resist the movement of fuel tank region and also the cross member can take some deformation. Also we can increase the strength of the support element near the Fuel tank region by changing the material or by adding a small support bracket over that region

Peak velocity of inner node of door :-

This plot helps to understand, with how much the actual inner side of the door moves in the direction of the Driver during the pole impact. 

CONCLUSION :

In order to develop the model for a side pole collision test, the outcomes were considered. I can infer from the output file that the simulation is quite stable because the energy and mass errors are both within acceptable bounds. Cross-members A and B play a significant function in absorbing impact force. Therefore, strengthening the cross-member material or adding an additional support element next to the cross-member can enhance their performance. As we previously discussed, the fuel tank side also needs some reinforcement. Since the B-pillar is the component that is closest to the force of the side impact, we may also concentrate on improving its properties.