LS Dyna

LS Dyna

Negative Contact Energy at Explicit Dynamics

    • OnurErol91
      Subscriber

      Hello All,

      This is my first post at here. I am new at explicit dynamics and I have created a model about bullet hitting to thin metal sheet. Metal sheet has been constrained at its edges in 6 DOF by remote displacement. Velocity (960m/s) has been given as initial condition to bullet. I am using explicit dynamics module(Autodyne solver).

    • Akshay Maniyar
      Ansys Employee

      Abrupt increase in negative contact energy may be caused by undetected initial penetrations. Care in defining the initial geometry so that shell offsets are properly taken into account is usually the most effective step to reducing negative contact energy. Can you please check if you have any penetration, then rerun the analysis.
      regards amaniyar
    • OnurErol91
      Subscriber
      Hello Amaniyar Thanks for your reply. Actually, I have but decent gap as you can see in .
      Best Regards Onur
    • Akshay Maniyar
      Ansys Employee

      Can you share the contact definition that you have defined. Do you have body interaction and contact both or just one? May be you have defined more than one contact definition between same parts.
      regards amaniyar

    • OnurErol91
      Subscriber
      Amaniyar I was still work on subject. So I have taken caps when simulation running.
      I tried both body interaction and manual contact definition. I also tried other settings inside of body interaction. I had still negative energy.

      Regards Onur

    • OnurErol91
      Subscriber
      Hello Again
      Interestingly, I saw some explicit tutorials with negative contact energy.

      Onur
    • Akshay Maniyar
      Ansys Employee

      Please check the below link for contact energy calculation in Explicit dynamics module.
      https://ansyshelp.ansys.com/account/secured?returnurl=/Views/Secured/corp/v201/en/wb_sim/ds_Energy_Results.html?q=contact%20energy%20calculation
      Negative contact energy in LS-Dyna shows that there are issues like initial penetration, redundant contact conditions. If you run same simulation with LS-Dyna, you will get positive contact energy.
      regards amaniyar

    • OnurErol91
      Subscriber
      Hello Amaniyar Thanks for your support. I have checked the link you shared.
      Delta x over here is penetration of contacts, right? I searched is there any explanation. But I couldn't find.

      Best Regards Onur



    • Akshay Maniyar
      Ansys Employee

      It is the incremental distance moved during current time step. Similar to the description you can find in LS-Dyna theory manual.
      regards amaniyar

    • OnurErol91
      Subscriber
      Amaniyar Thanks for your help.

      Best Regards Onur
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