Learning Forum

[maheshwarj]

Hello!

I am trying to simulate a seatbelt tightening process around a seat that is modeled as a rigid body using solid tetrahedral elements and MAT_20 material. Since I do not want the rigid body to be displaced, I applied constraints in all directions to this material. I've applied a boundary-prescribed motion to a piece of seatbelt (modeled using shell elements as MAT_FABRIC) that tries to tighten the seatbelt around this rigid body. I've defined different types of contacts between these bodies, but the contact keeps breaking, and the seatbelt goes right through the rigid body. If I use a deformable material to define my seat, the contacts work appropriately. Any help on trying to resolve this issue would be great!

Thanks!

[Neetu Jha]

Hi Maheshwarj,

To address the issue of contact breaking and the seatbelt penetrating the rigid body in your simulation, consider the following adjustments:

1. Mesh Discretization: Ensure that the mesh is sufficiently discretized to handle the anticipated contact interactions. A finer mesh can help distribute the contact forces more evenly and prevent penetration. This is particularly important for rigid bodies where contact accuracy is crucial. 

2. Material Properties: Use realistic material properties, especially the elastic modulus, as they are critical in contact simulations. Even with soft constraints, the material properties play a significant role in how the contact is resolved. 

 

3. Contact Settings: Adjust the contact settings to ensure that the contact stiffness is appropriate for the materials involved. If you are using a very soft material against a hard one, consider using different contact algorithms or settings like 'soft' options to improve contact behavior. This can help prevent deep penetration and ensure the contact remains intact. 

By implementing these adjustments, you should be able to improve the contact interaction between the seatbelt and the rigid body, preventing penetration and maintaining contact integrity.

[Alex R.]

Hi Maheshwarj,

Could you please show us the contact card that is handling the seatbelt -rigid dummy interaction? 

Thank you,
Alex 

[maheshwarj]

Here's the contact card between the two bodies:

*CONTACT_SURFACE_TO_SURFACE_ID
$HWCOLOR GROUPS50000022       5
$      CIDHEADING                                                               
  50000022Seatbelt_to_seat                                                       
$     SSID      MSID     SSTYP     MSTYP    SBOXID    MBOXID       SPR       MPR
  50000098  40000000         2         3                                        
$       FS        FD        DC        VC       VDC    PENCHK        BT        DT
       0.2       0.1                                                            
$      SFS       SFM       SST       MST      SFST      SFMT       FSF       VSF
                                                                                

MSID corresponds to the rigid component (seat) and the SSID corresponds to the seatbelts set. The seat is constrained in all directions, and the seatbelts are moved into the seat. The reason I'm confused why this isn't working is that when I constrain the seat in all directions, the contact breaks. If I remove the constraints and allow the seat to move say in the Y direction, the contact works fine. I need the seat to be constrained in all directions though.

[Alex R.]

Hi Maheshwarj,

I would try using CONTACT_AUTOMATIC_NODES_TO_SURFACE. Please check the contact used in this example https://ftp.lstc.com/user/lstc-dummies/LSTC.LEARNING_AID_VEHICLE_AND_50TH_BELTED_DRIVER.100112_V1.0.zip

Username: user 

Password: computer

Please let us know how it goes, 
Thank you,
Alex 

[maheshwarj]

Hello,

Contact still fails. The belt goes right through the seat as if no contact is defined. If helpful, I could upload the model if you want to take a look.