Assignment 7-Side Pole Crash Simulation Challenge

Objective:

To perform a side crash analysis on the BIW of the dodge neon car as per given requirements. To carry the crash analysis at the speed of 35 Mph. To generate the output requests are as follows

• Sectional force in the cross member.
• Intrusion at B pillar,hinge pillar and fuel tank region.
• Peak velocity of the inner node of the door.

Theory:

Side Crash analysis:

The crash analysis is performed using a side pole with a diameter of 254mm. The vehicle has an initial velocity of 35mph. Analyze the occupants and body damage when the side body impacts over the pole.

Procedure:

Case setup:

In this project, We need to create a rigid wall, interface type 7 contact, check for penetrations, create initial velocity at 35mph, carry out mass balancing to ensure the body weight of 700 kgs & move the cog point to the correct area by adding mass under 700kgs. Finally create sections, intrusions, create a node at inner door for output request purposes to plot the graphs.

Model image:

Creating type 7 contact:

Import the model using import>solver deck>0000.rad file and select import in hypermesh. Now the file is imported.

Check the units in Begin card>solver browser for kg,mm,ms.

At first delete any type 7 contact that is already created. Now right click solver browser>create>Inter>type 7. Here assign the recommended values for the type 7 contact. The image is shown below. Assign all components for slave and master node selection. Therefore the interface card covers all the components that are selected.

We need to create an output request for type 7 contact in time history. So select create>TH>Inter. After the interface attributes tab appears below, we need to right click entity id and assign a group that is created.

Creating the Rigid wall:

A rigid wall is an entity that is used to define an interaction between a non-deformable entity and deformable entity. Nothing can go beyond Rwall and it is non-yielding. It has multiple types like infinite plane, infinite cylinder, infinite sphere, infinite parallelogram. Here we should use infinite plane for frontal crash.

Here we need to create a Rigidwall for the side crash analysis. At first right click solver browser>create>Rigid wall>Cylinder. Now select the node to create an axis at the centre of the B pillar. Now assign Normal values for this x & y as 0, z as 1. Assign diameter as 254mm. Now we need to assign Dsearch as 2000, Sliding as 2 (sliding friction), friction as 0.1. Assign nodes as all the nodes by box selection.

We need to create an output request for Rwall in time history. So select create>TH>Rigid wall. After the rigid wall attributes tab appears below, we need to right click entity id and assign a rigid wall that is created.

Assigning initial velocity for the BIW:

Now assign initial velocity for the car because here the car is the movable object not a rigid wall. Select create>Boundary conditions>INIVEL.

Here assign type as translational, Vy (y axis) velocity as 35mph.Here we will perform side crash so the rigidwall take place at y axis so velocity vector is in y axis. We need to convert 35 miles per hour to mm per ms by converting the value. the value is 15.64 mm/ms. Assign other two Vx,Vz as 0. Assign nodes and select all nodes for initial velocity.

Mass balancing:

Now open hypercrash by selecting applications>hypercrash in hypermesh. export the model export>solver deck>.rad file in hypermesh. We need to import it to hypercrash for mass balancing. import>Radioss> .rad. Now the target mass of the model is 700 kgs. We need to check the mass of the model and place of the cog point by selecting Mass>Balancing from the toolbar of the hypercrash.

Here we have only 166kgs so we need to add some masses in the model to balance the mass in the overall model under 700 kgs.Centre of gravity point is shown above image. We need to move the cog point in the correct position by adding more mass and balance the weight to move the cog point. Now select Load case>Added mass. Select create a new object option and select type as type 1 for adding mass. Now assign the additional mass in kgs. Now select the node for adding the mass to those nodes. Here I need to select cross members separately. We can add masses at some other floor areas to balance the model.

The following the current mass of the model and cog point where we want are shown below.

Creating sections on cross members:

At first creating sections we need to create a moving frame( local coordinate) for sections. Select create>Frame>mov to create frame.

Doing this the moving frame window appears on the screen. We need to select the origin node and select node for z axis & select node for yz plane. For the origin node, we have a node to select for cross member sections. Select the other two nodes to define the plane.

After creating a moving frame, we can create a section for the moving frame by selecting create>sect>sect. Now select N1 node is an origin node that is defined for a moving frame. N2 & N3 nodes are selected to define a plane. After this, select a frame id by selecting the frame that we already created. Put the Delta t as 0.1 and alpha value as 1.67. Now we need to select grshel_id. It will be selected by two rows of elements, of which the nodes are a part. Now check the arrow that would be perpendicular to the force acts or parallel to the Rigid wall.

After creating the sections, we need to create output requests in time history by selecting create>TH>SEC. After this, right click out blocks. select entity ID and we need to assign all the sections that we created (2 sections).

Screenshot will all cross sections that are created shown below.

Creating Intrusions on B pillar, Hinge pillar, Fuel tank:

Here we have different kinds of methods for adding intrusions. But we go on using the spring element method.

We need to create a 1D spring element. Here select 1D>springs>two nodes. Now select the first node in the bottom of the B pillar (like hinge pillar, fuel tank). Select the second node that is parallel to the selected node. Now select create.

Now we need to rename it in model browser>components>undefined. Now create a property id for the spring element part. Assign mass as 0.001 and stiffness k1 as 0.001. After this, assign property id for the spring element part.

Now we need to create output requests in time history by selecting create>TH>Spring. Now select the entity id and assign two spring elements.

Penetration check:

We need to check for any initial penetration in the model. For these select tools>penetration check on top of the tool bar. Now select the check type as intersections and penetrations. Entity type as components and assign all the components. Thickness>size option to ignore initial penetrations. Now select check for check the entities.

Check Simulation time:

Go to solver browser>engine keywords>DT. Check Tmin in DT NODA, DT BRICK, DT INTER. Assign value as 0.1 to 0.5 micro seconds.

Go to solver browser>engine keywords>ANIM>ANIM/DT. Check Tfreq as 5.0.

Go to solver browser>engine keywords>RUN. Check Tstop as 80ms.

Model checker for errors:

Finally we need checking for errors in the model before doing analysis. Go to tools>model checker> right click RUN.

Here we have warnings only so we can ignore the warnings. If any errors arise, we need to rectify the errors.

Running the model analysis in Radioss:

Now select the analysis section in the bottom panel. Here select Radioss.Here we have to save the simulation files by selecting save as tool. We should create a folder for saving analysis files separately. because we will get a lot more files after simulation. select the correct directory to save those files. After that choose export options as all, check the include connectors checkbox, type -nt 4 in options tab (it runs the solver using 4 cores on the CPU). Now select Radioss to run the simulation.

Analysing the energy error in the output file:

The next is to carry out the energy error and mass error in the simulation. So we need to go to the analysis saved files directory and open _0001.out file to check the file by using text editor. By opening the file, go to page down. We can see the energy and mass values for the end time step. The resultant energy error is -2% which is acceptable. The energy error is acceptable between -15% to 5%. The closer to 0% is better. The mass error is almost 0.

Viewing the simulation:

To view the simulation, we need to switch to hyperview by using a client selector.

Here we have to import the h3d file in the saved directory. After importing, select the contour tool in the toolbar. We can switch to von mises contour. We can analyze the model using this contour.

The animation is shown below,

In side crash analysis, The force flows through B pillar usually. After BIW hits the rigid wall, The maximum stress is flowing from the B pillar through Door panel,floor panel and top area. Maximum stress value is 0.347 Gpa at Node 121498.

Generating the graphs:

Next we should plot the energy graphs and output request graphs using hypergraph 2D view. Go to the client selector, we can switch to hypergraph 2D. We should import the T01 file in the saved directory in the load files tab.

Select global variables and select internal, kinetic, total, hourglass, contact energy and select mag and click apply to plot the energy graphs.

When the rigid wall make contact with BIW of the car, the kinetic and internal energy changes occurs at that exact moment. The Kinetic energy loses gradually throughout the simulation due to decrease in velocity of the car. During initial velocity the kinetic energy is high at that point. The Car absorbs forces after hit the rigid wall, the internal energy increases gradually due to the energy absorption after hitting the rigidwall. The maximum internal energy peaked at 27360 J at 80ms. The minimum kinetic energy at around 55000 J at 80ms. The affect of contact energy in the model, it lead to slight difference in total energy. Hourglass energy is constant because of the presence of recommended shell properties.

Contact energy is created when one element get contact with other element or neighbouring element. The opposite force created by the element forms the contact energy.Contact energy starts 0 at 0ms. After the crash, the contact energy takes off at 3ms and peak around 1700 J at 80ms. Due to the elements getting in contact with other elements during the crash, The element penetrations lead to increase in contact energy. The elements penetrated each other while the car hit the rigid wall. the elements got deformation and contact with other elements.

Rigid wall forces graph:

The forces spikes up at 3ms due to the side pole impact. The rigid wall forces suddenly peaked at 50ms after that its stabilize. At 45ms the sudden peak of force due to the floor panel buckled and amy be impact the Rwall. when the car had exhausted its deformable capabilities in the door region. After that the forces were transferred to the floor panel regions in the BIW. Due to that the rigid wall experienced the stabilized curve during the end of the time step.

Output requests:

sectional forces on two cross members:

Both cross members take off at 3ms. After that both cross members absorbs some forces due to the impact. The cross member 1 peaked at 30ms after that a lot of fluctuations happened due to the vibrations over the body. The cross member 2 peaked at 20ms because this cross member located near B pillar. so the force peaked earlier due to the impact. after that some fluctuations were there because of the body vibrations.

Intrusions on the B pillar, Fuel tank, Hinge pillar:

The Elongation of the B pilar spring takes off at 3ms and gradually increases and peaked at 800mm at 80ms. The fuel tank spring takes off at same time 3ms but it located slightly far from B pillar so it absorbs less impact than B pillar due to this the elongation gradually increases and peaked at 650mm at 80ms. It less than B pillar spring elongation. Now the Hinge pillar elongation takes off at 7ms. it peaked at 250mm at 80ms. Because it is located somefar from the B pillar. the deformation exactly taken place at B pillar due to this, elongation of hinge pillar less than both fuel tank and b pillar.

Peak velocity of the inner node of the door:

The node at the inner side of the door starts at 15.64 mm/ms due to initial velocity. after the side pole impact, the car defromed rapidly due to this the velocity of the car decreases gradually so that the velocity of the node suddenly dropped at 10ms after that the velocity got some fluctuations due to the body vibrations over the impact and it got velocity of around 5mm/ms at 80ms.

Conclusion:

The side crash analysis was performed in the given dodge neon car model as per the requirements.The energy graphs were plotted as per the requirements. The output requests were generated using the sectional areas. The intrusions of the given nodes like B pillar, hinge pillar, fuel tank are also generated in the model.