LS Dyna

LS Dyna

Workflow for Importing Nastran Mesh Directly

    • tartan2020x
      Subscriber
      Hi,nI'm trying to import a Nastran file directly into Explicit Dynamics. I have read some other posts (https://forum.ansys.com/discussion/14809/i-need-help-please and https://forum.ansys.com/discussion/6685/importing-a-geometry-step-file-and-a-nastran-mesh-into-explicit-dynamics) and have been able to open the nastran file and run a simulation and get results. nHowever, when I use Explicit Dynamics or Mechanical, a new mesh of tetraheadral elements is generated and doesn't match the volume mesh of prism elements used in the nastran file. nIn the past, I believe the Workbench toolbox included a Fine Element Modeler, but it is no longer available. Is there a workflow or tool I should use in order to be able to run a simulation with the original nastran mesh preserved?nThank you.n
    • peteroznewman
      Subscriber
      nHow many nodes were on each Nastran Hex element? Was it a linear 8-node element or was it a quadratic 20-node element?nExplicit Dynamics can only use linear elements.n
    • tartan2020x
      Subscriber
      Thank you for your response! It is a linear 6-node penta element.n
    • peteroznewman
      Subscriber
      nAh, I didn't read your original post carefully enough.nThe problem is Nastran has a Prism element while Ansys does not.nThe Nastran linear prism element has 6 nodes.nANSYS creates a Prism element by using a Hex element and collapses one face to put two nodes at the same corner. There are still 8 nodes.nWhen ANSYS reads in a Nastran deck, the way they convert a Prism element is to split it into three Tet elements, keeping the same number of nodes.nIf you have the geometry that was meshed for Nastran, bring that into ANSYS. Meshing in ANSYS (either Hex or Tet elements) is going to create better quality elements than the triple split of a Nastran Prism element into Tets.n
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