Assignment 7 - Lu s Figueiredo
Assignment 7
Unit system
For reasons of simplicity, the unit system used is the same as in the provided files.
Rigid wall
The rigid wall is a vertical cylindrical surface with a diameter of 25 cm.
This rigid wall was created in a way that the pole hits the car in the front door panel, as shown in the next image.
The properties of the rigid wall are defined as shown in the following image:
Penetration check
By performing a penentration check, it was seen that, in the whole model, there were 73 penetrations.
Manipulating the meshes by hand to solve each penetration individually would be extremely time-consuming, so I chose to create an interface between all components. So, the solution that I chose to deploy is to make sure that INACTI = 6 in the Type 7 interface involving all the components. This ensures that, if initial penetrations occur, there is a spring that\'s created between the penetrating nodes and the surface they\'re penetrating, the stiffness of that spring is calculated according to the depht of the penetration.
Mass and CoG adjustment
By using the mass calc functionality of Radioss, it was determined that the total mass of the model was 106,308 Kg. Since the target mass is 500 Kg, a 393,692 Kg distributed mass should be added in the model and distributed by all the nodes in the model.
The type of the mass was set to 1 to make all the added mass equally distributed by all the nodes.
Initial velocity
The side pole crash test is performed at a speed of 20 mph (= 8.94 mm/ms) and the car is throwed against the pole at an angle of 75º, giving an initial velocity of (vx,vy) = ()
Main controls
Be reading the file neon_side_reduced_0001.rad, it was found that the simulation time and the time step were already set to 80 and 5 miliseconds respectively.
Model checker
When running the model checker, it was seen that the model had some errors that would stop the program from running.
All these issues were solved in order to run the simulation properly.
Cross member force
The cross section in the cross member component was created as shown in the next image. To maintain the reliability of the forces obtain in this cross section, the skew (reference axis system) was defined in the opposite side of the crash.
Intrusions
The intrusions were measured in the following nodes:
All the intrusions were measured in the same component (side member)
In the output block definition, only the displacements in the x and y directions were requested. But the result presented will be the magnitude of the displacement.
Velocity of the inner door node (node 337773)
It was also created an output block for the velocity of this node, from which the maximum velocity will be obtained.
Results
Hyperview
Hypergraph
1. Cross member cross-section force
2. intrusions in the front, middle and back nodes
Front node
Middle node
Back node (fuel tank)
3. Node 337773 velocity
Conclusions
From the hyperview results, it can be seen that this is, usually, a much worse case scenario than the front crash case, because the passengers are now sitting closer to the impact zone than they were in the previous case.
To prevent further intrusions in the fuel tank area, one possible solution is to add stiffners in the fuel tank area, so that the structure around that zone increases its striffness and, therefore, the nodes that are located in that area can have a smaller displacement.
In the inner node of the door, the y component of the velocity quickly decreases to zero after the impact, and from that moment on, the x and y components os the velocity are approximately the same.
The forces registred in the cross section don\'t exceed 1.3e-15 KN, which is quite low. But these values makes sense because the impact occurs with the car moving in a near-y direction and the forces are being measured in the x direction.