Assignment 6-Frontal Crash Simulation Challenge

Aim: To perform frontal crash analysis on body in white component by considering recommended parameters.

OBJECTIVE:

1. Check unit system and either follow [Mg mm s] or [Kg mm ms].
2. Create appropriate interface with recommended parameters and friction force is 0.2.
3. To check the penetration and intersection between components.
4. To create rigid wall with friction 0.1 between car and rigid wall.
5. Adding extra mass to attain target mass of 700kg.
6. Adding initial velocity of 35 mph.
7. Run model checker to ensure good quality.
8. To apply timestep between 0.5 to 0.1 microsecond.
9. To add a sectional force in the rails at location of indicated node 174247.
10. To add axial force received on the rail from bumper.
11. To find cross sectional forces in shotgun.
12. To find sectional forces in A pillar.
13. To find acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).
14. To calculate intrusions on the dash wall at node 66695 and 66244.

PROCEDURE:

Open the hyperwork software, and then we have to set user profile interface i.e. Optistruct or RADIOSS. Optistruct is implicit solver which handles small deformations. And RADIOSS is explicit solver which handles large deformation. So we will use RADIOSS as user interface.

First we have to import the required file i.e. neon_front_0000, which is in .rad format. So to import the .rad file format model in hyperworks, we have to follow:

File--->Import---->Solver Deck---->File: select file--->Import.

Once model is opened, it will look like as shown picture in below.

1. Check unit system and either follow [Mg mm s] or [Kg mm ms].

In order to check unit system, we have to follow:

Model Browser---->Cards---->BEGIN_CARD

2. Create appropriate interface with recommended parameters and friction force is 0.2.

Once unit system is checked. Now we have to create appropriate interface. In model there are different interfaces are present, so we have to delete the default interfaces as shown in picture below.

Therefore, in order to create the interface of Type 7, we have to display solver browser by clicking

View---->Browsers---->HyperMesh---->Solver.

Once solver browser is displayed. Now we have to create appropriate interface i.e. Type 7 with recommended parameters as shown in picture below.

Solver---->INTER---->press right click on INTER---->Select create---->TYPE7.

3. To check the penetration and intersection between components.

There should not be penetration and intersection between components. In order to check the penetration, we have to follow.

Tools---->Penetration check---->Select group---->Check.

4. To create rigid wall with friction 0.1 between car and rigid wall.

In order to create rigid wall, we have to follow:

Solver---->Create---->RWALL---->PLANE

To make a rigid wall, we need to create a reference node. First we will create a temporary node at the middle of bumper. After then we will translate that node to create a gap between car and rigid wall as shown in picture below.

In rigid wall, we have to create the recommended properties by selecting the temporary node in XM,YM,ZM then enter the search distance Dsearch of 1000 and friction value of 0.1.

5. Adding extra mass to attain target mass of 700kg.

In order to check the mass, we have to follow:

Tools---->Mass Details---->Mass, COG and inertia

Therefore, in this model we have a total mass of value approximate 188 kg as shown in picture below. But in 300k nodes model we have a target mass of value 700 kg.

Therefore, in order to create the mass. First we have to select the nodes by creating GRNOD. In order to create masses on nodes, we have to create GRNOD by following.

Solver---->GRNOD---->Create---->GRNOD---->nodes: select node.

Now we have to add masses to increase overall weight of car by assigning GRNOD ID

We have to follow:

Solver---->press right click to create---->ADMAS.

Now we have to assign recommended parameters by assigning GROND ID as shown in picture below.

So, finally we have a total mass of the component as shown in picture below.

6. Adding initial velocity of 35 mph.

First we have to create a INIVEL card as shown in picture below, by following:

Solver---->Create---->BOUNDARY CONDITIONS---->INIVEL.

Now, we have to create a GRNOD id by select all components as entity id. And procedure to create GRNOD id is same as explained above. Also we will provide initial velocity of 15.65 mm/ms in translational x-direction and remaining two dimensions will remain constrained.

7. Run model checker to ensure good quality.

We will use hypercrash to run the model checker. In order to switch model from hyperworks to hypercrash. We will export the .rad format file by following:

File---->Export---->Solver Deck---->File: select location---->Export.

Then we will open .rad file in hypercrash. Now in order to run the model checker we have to follow steps as shown in picture below.

Once model checker is done, report will generate as shown in picture below.

8. To apply timestep between 0.5 to 0.1 microsecond.

We have different methods to create time step such as INTER, NODA, BRICK, QUAD, SHELL, TRUSS, BEAM, SPRING etc.

And we have different time step control such as CST, CST1, CST2, DEL, STOP, AMS.

In this case we have created INTER and NODA as a type of time step control.

8.1. ENG_DT_INTER

This method is used in order to control the time step.

A type of time step option is “INTER” and time step control “DEL” is used.

We have to keep 0.67 as time scale factor and 0.0005 as a minimum time step control.

If time step gets reduced below the minimum time step, then this algorithm will add some mass to the element which leads to maintain time step more than minimum time step.

8.2. ENG_DT_NODA:

This method is used to control the time step from the nodes.

A type of time step option is “NODA” and time step control type “CST” is used.

In order to create ENG_DT_NODA we have to follow steps as explained below.

9. To add a sectional force in the rails at location of indicated node 174247.

First we have to display the nodes i.e. 174247. In order to display the node, we have to follow:

Tool---->numbers---->By id---->Type node number---->Display---->on.

In order to create SECTION first we have to create the FRAME CARD. In this moving frame is attached with the nodes which is selected as origin.

Now, we have to create FRAME card in solver browser. In order to create FRAME card, we have to follow:

In order to assign parameters in FRAME---->MOV, we have to follow. In this we have to define origin node and then define the z-axis with second node which is in the direction of crash. And then we have to define the third node for plane as shown in picture below.

Once axis has created at node 174247, it will look like as shown in picture below.

Now we have to create the SECTIONAL force at RAIL_1. In order to create SECTIONAL force we have to follow:

First we have to create GRSHEL card by selecting elements as shown in picture below.

Now we have to assign this GRSHELL id in the SECT parameters as shown in picture below.

Now we have to give output blocks request in model browser as shown in picture below.

10. To add axial force received on the rail from bumper.

First we have to create a MOV collector in FRAME card as shown in picture below.

Now we have to assign parameters in SECT as shown in picture below.

Now we have to give output blocks request as shown below.

11. To find cross sectional forces in shotgun.

First we have to create a MOV collector in FRAME card as shown in picture below.

Now we have to assign GRSHELL id by selecting element as shown in picture below.

Now we have to assign parameters in SECT as shown in picture below.

Now we have to give output blocks request as shown below.

12. To find sectional forces in A pillar.

First we have to create a MOV collector in FRAME card as shown in picture below.

Now we have to assign GRSHELL id by selecting element as shown in picture below.

Now we have to assign parameters in SECT as shown in picture below.

Now we have to give output blocks request as shown below.

13. To find acceleration curve received on the accelerometer at base of B pillar (on B pillar rocker).

First we have to create ACCEL card in solver browser as shown below.

Now we have to assign accelerometer parameters as base of B pillar.

Now we have to give output Blocks request as shown in picture below.

14. To calculate intrusions on the dash wall at node 66695 and 66244.

In order to show these nodes at number 66695 and 66244, we have to follow steps already explained in step 9. Once nodes are generated, it will look like as shown in picture below.

Create a node time history, select the node and assign the newly created skew to that as shown in picture below.

Similarly, we will do same step for node 1 and 2. Then we have to assign output blocks request for both intrusion as shown in picture below.

Simulation on the FRONTAL CRASH:

Now we can check the animation by run the simulation with default properties by following:

Analysis---->Radioss

Now we have to give location to export the input file:

Options helps to choose number of cores to solve this problem, here we have chosen 4 number of cores by (-nt 4).

Then click on Radioss, and new window will get pop-up. A simulation will start to show result,

After run the simulation on model, solver has generated different files such as engine listing file, animation, time history and then restart file.

Now, in order to check the energy error and mass error. We have to open the output file in notepad.

Once output file is opened, we can see the results.

Time step is calculated at every cycles. If model time step value is less than 0.001, then solver will take default time step value i.e. 0.001. Because we are using “CST” which means solver will use default time step value, if model time step value falls below nodal time step. To keep time step constant, it will add some mass on the node for which control the time step.

In zeroth cycle model time step is less than nodal time step. Control method has to be used constant time step having value of 0.001 and mass has been added on the nodes. If mass percentage lies in between 1 to 3, that means results will be acceptable.

An error is positive which means some energy is generated in the body.

Now we have to switch from Hypermesh mode to Hyperview mode. Then we have to select the appropriated (.h3D) file. And then we have to click on Apply to view the results.

By using different animation controls, we can check and animate the results as shown in picture below.

Contour plot for Displacement

Maximum displacement reaches upto 1250 mm over the period of time.

Contour plot for Von Mises

Stresses are distributed in the entire model. More stress is generated on the front rail, shotgun, bumper and other front components. Generated stress is less because initial velocity applied is less.

And balancing masses are added at the end of panel. If mass applied is higher, then inertial will also high. In this case model is obeying second law of motion because mass added is trying to move the car in the forward direction, when a car collided with wall.

HYPERVIEW

Now we have to switch from HyperView mode to HyperGraph 2D mode.

ENERGY PLOT:

As we can see, from below graph that kinetic energy is decreasing from starting time to termination time. Because a velocity is decreased over a period of time. Kinetic energy is directly proportional to velocity. Kinetic is started at 85000 and ended up with 45000.

Internal energy is increased over a period of time. Because it has some work done in the car.

And no hourglass energy is dissipated, since QEPH formulation has been used.

As we know total energy is the combination of internal, kinetic energy which has been plotted below.

Once all parameters are filled, we have a required graph as shown in picture below.

Dash wall intrusion at 66695 and 66244 node:

ACCELEROMETER 1 and ACCELEROMETER 2

A Pillar LH and RH:

Rail to bumper:

Shot gun:

Rail_1

CONCLUSIONS

1. Simulation has been done successfully on given BIW model as per given requirement.
2. All the output requests have been calculated such as sectional forces, axial forces, acceleration and intrusion of the dash wall.
3. From the simulation it has been observed that there was minimum deformation in the cabin and also minimum intrusion was found in the driver seat area.