This exercise will help you become familiar with defining LS-DYNA rigid walls using HyperMesh. It will also help you continue to learn how to define LS-DYNA model data, constraints, and output using HyperMesh.
In this exercise, you will define model data, loads, constraints, a rigid wall, and output for an LS-DYNA analysis of a bumper in a 40% frontal offset crash. The bumper model is shown in the image below.
Bumper model
Step 1: Load the LS-DYNA user profile.
1. On the Preferences menu, click User Profiles.
2. Select LsDyna.
Step 2: Import the LS-DYNA model bumper_start.key.
1. From the toolbar, enter files panel, import sub-panel.
2. Import… the LS-DYNA model file bumper_start.key.
Step 3: Define *PART_INERTIA for the vehicle mass component to partially take into account the inertia properties and mass of the missing parts.
1. On the Setup menu, click Card Editor , and select Comps.
2. Click on Comps and select the existing component vehicle mass.
3. Edit the component’s card image.
4. Under Options, select Inertia.
5. For the center of mass coordinates XC, YC, ZC, specify 700, 0, 170, respectively.
6. For translational mass TM, specify 800.
7. For the components of the inertia tensor, specify the following:
IXX IXY IXZ IYY IYZ IZZ
1.5E+07 -5.0E+03 -8.0E+06 5.0E+07 -900 6.0E+07
8. For the initial translational velocity along the X-axis, VTX, specify -10.
9. Return to the Card Editor panel.
10. Return to the main menu.
Step 4: Create a *DEFINE_BOX that contains all nodes but the barrier nodes.
1. On the Tools menu, click Create Cards.
2. From the Ls -Dyna keyword list, point to *DEFINE and click on *DEFINE_BOX.
3. For the block name=, type box velocity.
4. Make sure card image=, is set to DefineBox.
5. Optionally select a block color.
6. Toggle lower bound from corner node to x=, y=, z=.
7. Specify the lower and upper bounds as follows:
lower bound upper bound
-530 200
-800 800
0 300
8. Create the box.
9. Activate review nodes to see the nodes included in the box.
10. Return to the main menu.
Step 5: Create initial velocity on all nodes but the barrier nodes.
1. On the Tools menu, click Create cards.
2. From the Ls -Dyna keyword list, point to *INITIAL and click on *INITIAL_VELOCITY.
3. For Name, type velocity and click ok.
4. For the initial velocity in the global X direction, VX, specify –10.
5. In the BOXID field, specify the box velocity id.
6. Return to the main menu.
Step 6: View the closest nodes which are in the pre-defined node entity set (*SET_NODES_LIST) named Constrain Vehicle.
1. On the Setup menu, click entity sets.
2. Click review.
3. Toggle from display RLs to hide RLs.
This filters all nodal rigid body sets from the list.
4. Select the Constrain Vehicle set.
Notice the set’s nodes are highlighted.
5. Return to the main menu.
Step 7: Create *CONSTRAINED_EXTRA_NODES_SET.
1. On the Tools menu, click Create Cards.
2. From the Ls -Dyna keyword list, point to *CONSTRAINED and click on
*CONSTRAINED_EXTRA_NODES_SET.
3. For Name, type ExtraNodes and click ok.
4. For the part id (PID) of the rigid body to which the nodes will be added, specify the vehicle mass component’s ID.
5. Return to the interfaces panel.
6. Stay in the interfaces panel for the next step.
Step 8: Define the nodes in the Constrain Vehicle set to be a part of the vehicle mass rigid body.
1. Select the add sub-panel.
2. Make sure name=, is set to ExtraNodes.
3. Set the slave type to sets.
Step 9: View the extra nodes that are a part of the vehicle mass rigid body.
1. Click review.
Notice the extra nodes are temporarily displayed red while the PID (vehicle mass) is temporarily displayed blue. All other entities are temporarily displayed grey.
2. Return to the main menu.
Step 10: Create an entity set, *SET_PART_LIST, for just the vehicle mass component. All other components not in this set will be included in the contact.
1. On the Tools menu, click Create Cards.
2. From the Ls -Dyna keyword list, point to *SET and click *SET_PART_LIST (Non-Ordered).
3. For name=, type Exempt Parts.
4. Make sure card image, is set to Part.
5. With the comps selector active, select the vehicle mass component.
6. Create the set.
7. Return to the main menu.
Step 11: Create *CONTACT_AUTOMATIC_GENERAL contact.
1. On the Tools menu, click Create Cards.
2. From the Ls -Dyna keyword list, point to *CONTACT and click on
*CONTACT_AUTOMATIC_GENERAL.
3. For name=, type impact.
4. Create the group.
5. Return to the interfaces panel.
6. Stay in the interfaces panel for the next step.
Step 12: Define the slave surface with slave set type 6, part set id for exempted parts.
1. Select the add sub-panel.
2. Make sure name=, is set to impact.
3. Set the slave type to sets.
4. Select the Exempt Parts set.
5. Update the slave selection.
6. Select the card image sub-panel.
7. Edit the group.
8. Activate the option ExemptSlvPartSet.
Notice the slave surface type SSTYPE value changes from 2 (part set ID) to 6 (part set ID for exempted parts).
9. For the static coefficient, FS, specify 0.15.
10. Return to the interfaces panel.
11. Return to the main menu.
Step 13: Create an entity set, *SET_PART_LIST, to specify the elements that will contribute to the cross-sectional force results.
1. In the Analysis page, enter the entity sets panel.
2. For name=, type XsectionPlane-Parts.
3. For card image, select Part.
4. With the comps selector active, select the components interior crashbox and exterior crashbox.
5. Create the set.
6. Return to the main menu.
Step 14: Define a section by creating *DATABASE_CROSS_SECTION_PLANE.
1. On the Tools menu, click Create cards.
2. From the Ls -Dyna keyword list, point to *DATABASE and click on
*DATABASE_CROSS_SECTION_PLANE.
3. For Name, type Xsection_Plane and click ok.
4. Create the group.
5. Return to the rigid walls panel.
6. Stay in the rigid walls panel for the next step.
Step 15: Define the location and size of the section’s plane.
1. Select the geom sub-panel.
In this sub-panel, the plane’s origin (the tail of the normal vector) is defined by a base node.
Create a node from the create nodes panel by following steps 2 - 5 below and then select it for the base node.
2. Make sure name=, is set to XSection-Plane
3. Press the F8 key to enter the create nodes panel in the Geom page.
The rigid walls panel, geom sub-panel is interrupted.
4. Select the type in sub-panel.
5. For x=, y= and z=, enter the values –320, -500 and 100, respectively.
6. Create node.
Notice the node is created and is displayed.
9. Switch normal vector: to x-axis.
This defines the wall’s normal vector.
10. Leave shape set to plane.
11. Toggle from infinite to finite.
12. Toggle from corners to dist/axis.
13. Switch local x axis: to y-axis.
This defines the edge vector L.
14. For len x= and len y=, specify 100 and 200, respectively.
Doing this defines the extent of the section. The values are the length of the edges a and b in the L and M directions, respectively.
15. Update the group.
16. Stay in the rigid walls panel for the next step.
Step 16: Specify the parts slave to the rigid wall.
1. Select the add sub-panel.
2. Set the slave type to sets.
3. Select the set XsectionPlane-Parts.
4. Update the slave selection.
5. Stay in the rigid walls panel for the next step.
Step 17: View the entities slave to the rigid wall.
1. Click review. Notice the slave entities are displayed red while the rigid wall is displayed blue. All other entities are temporarily displayed grey.
2. Return to the main menu.
Step 18: Create a *DEFINE_BOX containing the nodes making up the barrier and bumper’s left side. These nodes will be slave to the rigid wall.
1. On the Tools menu, click Create Cards.
2. From the Ls -Dyna keyword list, point to *DEFINE and click on *DEFINE_BOX.
3. For block name=, type half model.
4. For card image =, leave it set to DefineBox.
5. Optionally select a block color.
6. Specify the lower and upper bounds as follows:
lower bound upper bound
-600 -460
-800 0
0 400
7. Create the box.
8. Activate the option review nodes to see the nodes included in the box.
9. Return to the main menu.