Assignment 7-Side Pole Crash Simulation Challenge

Aim: To perform a crash analysis test using HYpermesh Riadioss for Side Impact Crash as per the following criteria shown below.

Neon side crash -BIW

• Check the unit system and either follow [Mg mm s] or [Kg mm ms].
• Create an appropriate interface, friction 0.2, and recommended parameters.
• Make sure of no penetration and intersections.
• Create a rigid wall with friction of 0.1 as per the reference model.
• Compare the model weight with the reference model and use added masses to reach the target weight of 700kg while getting CG about the required range.
• Initial velocity - 20mph, as per the standards.
• Use a model checker to ensure good quality.
• Timestep:0.5 to 0.1 microseconds.
• Run 80ms.

Output requests:

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

Step 1:- Intersection and penetration checking:-

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

2. Import the given model "neon_side_reduced_0000" into Hypermesh GUI.

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

We can also verify in the Hypercrash:

Select the tree which we have to verify and then go to Quality -> Check intersection of Tree Selection

Addition of Mass to the body:

1. The BIW model doesn't consist of the exact weight of the vehicle so Additional mass should be added to the BIW model considering the weight of the Body after manufactures e.g. with the weight of the seats, the weight of the persons, and all other weights in realistic condition.
2. The targeted weight is given 700kg whereas the actual mass before adding the external weight is 166kg.
3. To Add the mass, Click on added mass, and to create a new object Select Type 1 - Mass\N is distributed to each node of the node group, and click save
4. Check COG, simultaneously after giving the mass in the balancing menu.

After the addition of a Mass of 700Kg:

Creating a Contact Surface:

1. A contact interface should be defined to view the contact energy. Here the type-7 Contact is used (Node to Surface), because of its high accuracy and correct physical representation. The self-impact is defined in the Contact interface as the body acts as both master and Slave.
2. Interface properties Changed to recommended conditions as per mentioned in the problem statement and create another interface for bumper and rail contacts. which is shown in the image below.

Creation of Rigid Wall:

To create a cylindrical rigid wall at the left side of the car, we will need the outermost node at the front left door of the car. So we will create the outermost node on the element edge using the temp nodes option. Then we will right-click in the solver browser and navigate to Create > RWALL > CYL. In the RWALL panel, under Engineering data we will specify the coordinates of the pole which will be at some distance from the outermost node on the side door. Then we will give the normal direction to the pole in the Z-axis and the diameter of the pole to be 150 mm. The FRIC value will be 0.1 and the Dsearch value will be 1000 as shown below.

Applying Initial Velocity:

• In this simulation, the initial velocity given to the model is 35 mph 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

Creation of Section :

• The results which we want on required cross-sectional parts will be calculated based on a frame of reference. So before creating a 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 a moving frame using these nodes. In the Solver browser, we will right-click and navigate to Create -> FRAME -> MOV. So here, we will create frame by node reference and select the nodes for the x-axis and xy plane and then click on create.
• Thus a moving frame will be created. Now we will create a cross-section for this frame. To create a cross-section, we will right-click on the Solver browser and navigate to Create -> SECT -> SECT. In the section panel, we will specify the Frame_ID as the moving frame which we created and the delta value as 0.1. From the HyperWorks help menu, we get that the general value of alpha is taken as 2π10">2*3.14/10. Thus we will specify alpha as 0.628. We will right-click and create grshel_id, then we will select the elements where we want the cross-sectional results. Thus the cross-section will be created as follows.

Creation of Output request:

1. Peak velocity of an inner node of the door.

To find the 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 an 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.

2. Intrusions at B-pillar, hinge pillar, and fuel tank:-

Here, we need to find the intrusions at the 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 on the opposite side which are at the right B-pillar, hinge pillar right side, and fuel tank opposite side as shown below.

Check for Errors and Warnings:

Run the Results:

From the side_crash_0001.out file, the Total number of cycles was 80001(With 8 Internal cores). The energy error is -1.2% which is an acceptable limit. The mass error is 0.0238% which is also less than 5% it is acceptable. The run was “normal terminated’ which implies the processor completed. There was no sudden change in energy as well as in error. as shown below

Results:

Simulation view in Hyperview:

In the above crash simulation of the vehicle, we can see the vehicle body is impacting a Pole. After the impact, the frame of the vehicle deforms and the vehicle body gets contracted around the pole with the left B-Pillar as the pivot point. The CG of the vehicle is in the same axis or direction as the pole, so we can see even deformation of the frame around the pole.

Von-Mises Stress:

Here the stress act on the car by hitting the poll acts along the frame of the body.

Max Stress of 3.82e-1 N/mm^2 and Min Stress of 0 N/mm^2 which acts on the polls.

Plastic Strain:

Here is the strain of 1.167 mm/mm of Max and 0 mm/mm of Min.

Belong image is shown where the Strain acts on the bottom as between in Hinge and B-pillar.

Plots in Hyperview 2D :

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

Total Energy plots:

From the above plot, we can see that there is a 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 87000 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 the Type 7 interface due to which contact energy is generated.

Sectional displacement acting in cross members:-

Sectional Forces:

Intrusion Displacement Plots required nodes:

Blue Line - Fuel Tank

Red Line - Hinge Parts

Green Line - B-Pillar

• The intrusion at Hinge Pillar – The final displacement at the Hinge Pillar region is 1 mm and the initial distance of the fuel tank from the frame of reference is 397.67 So total intrusion is 397.67 – 655.12 = -257.45.00 mm. Thus the total intrusion at the hinge pillar region is 257 mm but the minus sign indicates that the intrusion increased after the crash.
• Intrusion at B-Pillar – The final displacement of node at B-pillar is 1070.33 mm and the initial distance of the fuel tank from the frame of reference is 397.67 So total intrusion is 397.67 - 1070.33 = -672.66 mm. Thus the total intrusion at the B-pillar region is 672 mm but the minus sign indicates that the intrusion increased after the crash.
• The intrusion at Fuel Tank – The final displacement at the fuel tank region is 397.67 mm. Thus the total intrusion at the fuel tank region is 142.34 mm but the minus sign indicates that the intrusion is increased after the crash. This increase in intrusion can lead to the failure of the fuel tank and fuel may drop out of the tank. To prevent this failure, we need to reduce the intrusion which we can achieve by adding another cross member in the fuel tank region which absorbs some energy and resists the movement of the fuel tank region 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, how much the actual inner side of the door moves in the direction of the Driver during the pole impact. The peak Velocity measured at the inner door point is 15.79mm/ms to 8 ms. After that, the speed is starting to reduce to a great extent.

CONCLUSION :

Thus, the model was simulated for a side pole crash test and the results were discussed. From the output file, the energy error and mass error are in an acceptable range so I can conclude that the simulation is pretty stable. Cross-members A and B are playing important roles in the Impact force absorption. So, improving the cross-member material or adding some extra support element near the cross-member can improve their performance, also the Fuel tank side as we discuss earlier needs some reinforcement. We can also work on the B-pillar property improvement as it's the closest part which comes in contact with the force during the side crash.