Learning Forum

[zmohamma]

I am simulating a very simple model in LS-DYNA:

Slave: a sample modeled with Shell_Beta elements

Master: a steel plate, modeled first with solid elements and then also tested with shell elements

Contact: *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE with both SSTYP=0 and MSTYP=0 (segment option)

Friction: static = 0.30, dynamic = 0.23

Penetration check: 0 mm (initially)

Both versions (shell–solid and shell–shell) run without any errors. However, the results are not what I expect:

Reaction force = 0 N

No change in stress or strain in either part

It seems as if the contact card is not working at all

What I tried:

Changing the plate from solid to shell

Verifying that the segment option is active

Checking for initial penetration (none)

Ensuring friction coefficients are correctly defined

Problem: Despite these checks, the contact appears to never activate, and output quantities (reaction force, stresses) remain zero.

Question:
Do you have any suggestions on what I might be missing? In particular:

Are there special settings needed for shell thickness in segment-based contacts?

Could the lack of a normal load be preventing frictional contact forces from appearing?

Any other contact-control parameters I should enable to make sure the surfaces “see” each other?

Any advice would be appreciated!

[Satvik]

Hello User,

I'm checking with this. I'll get back to you with my comments shortly!

Regards,

Satvik.

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[Satvik]

Hi User,

As mentioned earlier, the run terminated without any errors. To proceed effectively, could you please confirm the following details:

1. Contact Visualization:
   During post-processing, do you observe actual contact between the master and slave surfaces? Or is there a noticeable gap between them?

2. Part Details:

   • What are the thicknesses of both parts involved?
   • What element formulation (ELFORM) is being used for each?

3. Loading Conditions:

   • What type of load is being applied?
   • What is its magnitude?

---

Meanwhile, here are a few suggestions you can try:

• Change the SOFT parameter to SOFT=1 or SOFT=2.
• A commonly used reference setup in the automotive industry is:
  *CONTACT_AUTOMATIC_SURFACE_TO_SURFACE with
  SOFT=2, SBOPT=3, DEPTH=35, and PSTIFF=1.
  This can be a good starting point.
• If the impact speed is high and the timestep is large, contact may not be detected. Try reducing the timestep.
• Experiment with different SSTYP/MSTYP values:
  • First iteration: SSTYP=2, MSTYP=2 (Part Set ID)
  • Second iteration: SSTYP=3, MSTYP=3 (Part ID)
• Try switching the contact type to *CONTACT_AUTOMATIC_SINGLE_SURFACE.

Let me know once you’ve reviewed the above points or if you need help implementing any of the suggestions.

Best regards,
Satvik Koli
Technical Support Engineer