Seat Deformation

Seat Deformer (Pre-Simulation)

Export an input deck, for the appropriate solver, in order to simulate the deformation of the seat under the dummy. The simulation result files can be imported to update the initial FE model and remove the intersections and penetrations between the dummy and the seat.

When a dummy is positioned to its H-Point location on a seat, intersections between the dummy and seat foam parts generally occurs.

  1. From the menu bar, click Safety > Pre-Simulation (Seat Deformer) if you are using the Crash user profile. From the menu bar, click Tools > Pre-Simulation (Seat Deformer) if you are using the Aerospace user profile.
    Restriction: Only available in the LS-DYNA and Radioss solvers.
    The PreSimulation tool opens.
  2. Define pre-simulation setup settings.
  3. Click Export.


Figure 1. . Shows the initial model with the dummy positioned at its correct H-Point location, and shows intersections with the seat.
The selected dummy components move following the direction that you move them in until no penetrations between the dummy and seat components are detected. The dummy components are rigidified. A contact between the seat and dummy is automatically created with user defined parameters as well as a fix boundary condition on the selected fixed nodes of the seat. Finally, an imposed displacement is applied on the dummy components to bring them back to the initial position.


Figure 2.
The pre-simulation load case is ready and the dedicated input deck is exported to the user specified location, as shown below. When the solver analysis is done, you can import the dedicated solver output file to update the initial model with the deformed geometry and initial stresses of the seat parts.


Figure 3.

PreSimulation Tool

Overview of the PreSimulation Tool user interface.

LS-DYNA

Option Description
Unit System Selecting a unit system will automatically set up the default simulation parameters to the correct unit. In any case, you can still modify these values manually.
Dummy Dummy components that are selected in contact with the seat will be exported for the pre-simulation. The selection can be done via:
Components
Mechanism
Opens a dialog to select a complete dummy
Assemblies
Set
Opens a dialog to select a set of type *SET_PART_LIST
Seat Select the seat components that will be exported for the pre-simulation. The selection can be done via:
Components
Mechanism
Opens a dialog to select a mechanism defining the seat. Only the bodies that are defined by components or sets of components will be taken into account.
Assemblies
Set
Opens a dialog to select a set of type *SET_PART_LIST
Fixed Nodes of Seat Select the nodes that will be fixed during the simulation. The selection can be done via:
Nodes
Set
Opens a dialog to select a set of type *SET_NODE_LIST
Dummy Displacement Direction Defines the vector to move the dummy from its initial position to the final position on the seat.
Export Files Defines the pre-simulation deck name and location.
Dummy Velocity Defines the imposed velocity value applied on the dummy parts during the simulation. Default value = 0.1mm/ms.
Time Step Defines the control time step value. Default value = 0.001ms.
Scale Materials Density Scale factor to scale the material density values in order to increase the critical time step of the model. Default value = 10.
Dummy Displacement Step Displacement increment used to move the selected dummy components along the prescribed vector. After each increment, the penetration check between the dummy and seat will be performed and the dummy motion will be stopped when penetrations are no longer detected. Default value = 10.
Soft Defines the Soft parameter value in the generated contact between the dummy and seat. Default value = 2.
Friction Defines the FS parameter value in the generated contact between the dummy and seat. Default value = 0.0.
Imposed Contact Thickness Defines the value of parameters SST, MST and SLDTHK in the generated contact between the dummy and seat. Default value = 0.0.
Contact Stiffness Scale Factor Defines the value of parameter SFS in the generated contact between the dummy and seat. Default value = 0.0.
Import *INITIAL_STRESS_SOLID If this checkbox is activated, initial stresses for solid elements will be imported from the dynain file. This option is activated by default.
Import *INITIAL_STRESS_SHELL If this checkbox is activated, initial stresses for shell elements will be imported from the dynain file. This option is deactivated by default.
Import *INITIAL_STRESS_BEAM If this checkbox is activated, initial stresses for beam elements will be imported from the dynain file. This option is deactivated by default.
Export Starts the export process of the pre-simulation deck at the specified location.
Import dynain File Allows the LS-DYNA simulation to update the initial model.
Close Closes the dialog.

Radioss

Option Description
Unit System Selecting a unit system will automatically set up the default simulation parameters to the correct unit. In any case, you can still modify these values manually.
Dummy Dummy components that are selected in contact with the seat will be exported for the pre-simulation. The selection can be done via:
Components
Mechanism
Opens a dialog to select a complete dummy.
Assemblies
Set
Opens a dialog to select a set of type /GRPART.
Seat Select the seat components that will be exported for the pre-simulation. The selection can be done via:
Components
Mechanism
Opens a dialog to select a mechanism defining the seat. Only the bodies that are defined by components or sets of components will be taken into account.
Assemblies
Set
Opens a dialog to select a set of type /GRPART.
Fixed Nodes of Seat Select the nodes that will be fixed during the simulation. The selection can be done via:
Nodes
Set
Opens a dialog to select a set of type /GRNOD.
Dummy Displacement Direction Defines the vector to move the dummy from its initial position to the final position on the seat.
Export File Defines the pre-simulation deck name and location.
Generate XREF for initial stresses Enables the creation of /XREF cards for the seat components that are compatible with this Radioss feature in terms of material type and element formulation. This checkbox is activated by default.
Dummy Velocity Defines the imposed velocity value applied on the dummy parts during the simulation. Default value = 0.1mm/ms.
Time Step Defines the control time step value. Default value = 0.001ms.
Scale Materials Density Scale factor to scale the material density values in order to increase the critical time step of the model. Default value = 10.
Dummy Displacement Step Displacement increment used to move the selected dummy components along the prescribed vector. After each increment, the penetration check between the dummy and seat will be performed and the dummy motion will be stopped when penetrations are no longer detected. Default value = 10.
Friction Defines the friction value in the generated contact between dummy and seat. Default value = 0.0.
Stmin Defines the minimum contact stiffness in the generated contact between dummy and seat. Default value = 1.0kN/mm.
Gap_Min Defines the minimum gap in the generated contact between dummy and seat. Default value = 0.5.
IGAP Defines the IGAP value for the generated contact between dummy and seat. Default value = 2.
Export Starts the export process of the pre-simulation deck at the specified location.
Import h3d File Allows the Radioss simulation to update the initial model.
Close Closes the dialog.