Assignment 6-Frontal Crash Simulation Challenge
Assignment No.6 - Frontal 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 penetrations and intersection.
>correct rigid bodies if any issues.
>Create a rigid wall with friction 0.1.
>Compare the model weight with the full-scale 300k nodes model and use added masses to reach target weight 700kg while getting CG about the required range.
>Initial velocity 35 mph.
>Use model checker to ensure good quality.
>Timestep :0.5 to 0.1 microseconds.
>Run 80ms.
Solution
Check with the unit system first, either use [Mg mm s] or [kg mm ms]
This can be done using the starter file neon_front_0000.rad in notepad as shown below.
For this assignment, we are using the unit system as [kg mm ms]
Create an appropriate interface, friction 0.2 and recommended parameters
Delete the available interfaces in the original model, and create a new one with the Type 7 interface.
Recommended properties as follows
To create the interface of Type 7 you can create in Hypermesh or Hypercrash
1. To create in Hypermesh right-click > create >contact>Type 7, apply appropriate properties and friction as 0.2
2. To create in Hypercrash select load case from top menu>contact interfaces > create new>Multi usage (Type 7), apply appropriate properties and
friction as 0.2
Make sure of no penetrations and intersections
To run the analysis, we should make sure that there is no intersection and penetrations between two bodies of parts
To check for penetrations and intersections in a hyper crash go to LoadCase in upper tab menu>Contact Interface > Select the contact Type 7>Click on Check
penetrations for selected objects
As there are no 0 penetrations and intersections we can run the analysis. If the quality check shows any intersection or penetration we can fix it by using an auto
fix tool.
>If the auto-fix is failed to clear the penetrations or intersections then we have to correct as per the manual method.
Check rigid bodies if any issues
As checked in the model, there are no issues with the rigid bodies in the given model
Create a rigid wall with friction 0.1
Now we to crate the rigid wall in the given model with the friction 0.1
>We can create in both Hypermesh and Hypercrash
1. To create a rigid wall in Hypermesh go to Create> Rigid Wall
Select the type of the rigid wall you want as a cylinder, infinite plane, or sphere.
For this application, we need an infinite plane type of rigid wall.
Select the base node from which you want to create the rigid wall.2. To create the rigid wall in Hypercrash
Right, click >Create New>M-R>Rigid Wall>Plane.
Set the parameters as per Hypermesh setting for a node, D search as 800 and friction as 0.1
Comparing the weight with a full-scale model for weight balancing
The weight of the full car model is 1216.55 kg as shown in below image
The weight of the model we are using for the analysis is 188.42 kg
We need to balance the remaining weight to reach the value of 700kg of a working model.
We need the extra weight of 511.68kg
This weight can be added to get the position of CG value near to the driver seat location line.
So we can add the weight to the lower panel as shown.
The mass added is at bottom support, rail, and nodes at the cut section. They are added as follows
Weight added to bottom= 461.58kg, to rail= 35kg and to set of nodes= 15kg
So the weight of our model is matched to 700kg as shown in the below image.
Also, you can see the CG of the model shown as a pink dot in the model.
Apply initial velocity if 35mph
As we are following the system [kg mm ms] we need to input the value of velocity in mm/ms.
So after conversion the velocity 35mph= 15.65mm/ms.
In Hypercrash go to Load Case > Initial Velocity > Select the whole model and apply velocity in X-Direction as 15.65mm/ms as shown in the below image.
Use model checker to ensure good quality.
Before going to the actual run we should ensure the quality of the model.
In Hypercrash go to Quality> Model checker> Run. Then the system will show the error and warning. Try to find out the error and correct
Conclusion:
The energy error and mass error are in an acceptable range.
The sectional forces in the bumper to rail for both RH and LH side plays an important role in absorbing the max impact.
The role of shotgun design also plays an important role to keep the impact less transmitting to the interior parts of the vehicle.
The max impact is taken by the frontal cross-sections hence the forces in the A-pillar section for both RH and LH side are very less.
The position of the Center of Gravity of a vehicle is vital in the crashworthiness, so maintaining the weight balancing of a vehicle is the skill of design
engineer.
As we are using the half model and with added masses, if we can go for full vehicle body analysis then more realistic results can be obtained.
For accurate validation always try to use the full-scale model of the vehicle.