LS-DYNA Tiebreak Surface to Surface

Alsendi1989Alsendi1989 Member
edited October 22 in Explicit Dynamics

Hi All,


I need to connect the steel plate that shown attached to a solid element that sits on the top of this plate. The dimensions of the plate are 20 in x 10 in and subjected to a tension force of 100,000 Ib. I used Tiebreak Surface to Surface to provide this connection between the plate and the solid element. So, I selected the top surface of the plate as the slave segment and the bottom surface of the solid element as the master segment. The connection area is 200 in^2, so setting the shear stress failure (SFLS) less than 100,000 Ib/200 in^2 = 500 psi will cause a shear stress failure for the module. Furthermore, I don’t want my model to fail by normal stress so I neglected the normal stress failure (NFLS) by setting it to 1e+10 psi.

My question is, what did I miss? Because even if I set the SFLS to 1000 psi the model is still failing. In other words, the generated shear stress due to the 100,000 Ib tension force should not exceed 1000 psi so why it is failing?


Stay Safe,



  • cxquancxquan Berkeley, CAForum Coordinator

    Use LS-PrePost to conduct Contact Check. Make sure the number of the nodes being tied is large than zero.

  • jdayjday Member

    First, does rcforc indicate that contact forces are even being transmitted?

    Secondly, you're assuming the shear stress distribution is spatially uniform when it very likely isn't. To get stress stress for each segment, write and postprocess an intfor database. To do this:

    1. Add a *database_binary_intfor command to your input deck

      (If this command is not provided, the output interval for intfor will be the same

      as for d3plot, provided steps 2 and 3 are followed.)

      It's not mandatory to so so, but you can also add

      *database_extent_intfor can be added to control content of the intfor database

      to some extent.

    2. Set the appropriate print flag(s) on Card 1 of *contact.... (see SPR and MPR).  Only those contact

      surfaces so flagged will be output to the intfor database.

    3. Include "s=intfor" on the LS-DYNA execution line.

    4. After running the analysis, open the intfor database in LS-PrePost as you would a d3plot database,

      e.g., by typing "lsprepost intfor".

      Use Selpar to select the contact surface of interest.

      There are options for fringing and time history plotting of normal and tangential

      contact forces and contact stresses.

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