LS Dyna

LS Dyna

How to set up seemingly simple grinding/turning scenario?

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    • wyatt
      Subscriber

      Hello, I am having difficulties determining how to set up a grinding/turning scenario. I used a microhardness test on this forum for setting up the contact scenario, except I used a frictional contact.

      I would like to simulate a fixed-axis rotating cylinder, with a small tool in contact. I have the student version of Ansys, so I need to keep the mesh elements within the limitations of the program.

      I first attempted a static structural analysis, where I had the tool contact the workpiece, and things seemed to work without issues. For this I followed a tutorial for a microhardness test that I found on this forum, but I used a smaller cylinder to get results faster. From here I tried a remote displacement, and ran into issues.

      The materials would be structural steel or something similar for the cylinder, and something like silicon nitride or tool steel for the tool. I believe I could make the cylinder a thin walled tube, and reduce the mesh size.

      I am interested in the stresses and strains in the tool, but I would also like to see if I could run a short simulation with material removal (if there would be any). If someone could provide me with some ideas or instructions on how to continue, I would really appreciate it!

    • wyatt
      Subscriber
      I managed to get a simulation to run, however I only used a small section of the cylinder, and I increased the density to speed up the processing. The simulation ran fine in explicit dynamics, however the tool is the only part that seemed to show stress/strain, and no material erosion occurred. nI tried running the same simulation in transient structural, but after processing, the cylinder did not move at all. I saw in another forum post that with smaller elements the time step is longer, i.e., the longer the processing for explicit dynamics. nI hope this is rehasing something that has come up before, and someone could direct me to the relevant discussions. I am still looking through the forums as there is a lot of useful information.nI also ran an explicit simulation on a much smaller cylinder, and the processing took nearly half a day. The results were not great, and only the tool showed damage, not the cylinder.nMy questions are:nCould a contact condition or the mesh be preventing the cylinder from displaying stress/strain/erosion?nHow would you recommend meshing?nIs there a method to perform this explicit dynamic simulation in transient structural?nthanks!n
    • wyatt
      Subscriber
      I have managed to run two explicit dynamic simulations.nThe first simulation took a long time, and only showed material erosion in the tool. I believe I can improve the mesh for this. I used a small cylinder with a small penetration into the cylinder with the tool.nThe second simulation I used a section of the cylinder shown in the above image. To speed up the processing, I increased the density of the cylinder and tool. The simulation ran without any error messages, however the cylinder experienced no stress/strain/erosion, and the tool only experienced some stress/strain. The tool is quite small, and as I have seen on other threads, the time step increases with small elements. As recommended in another thread, I tried using transient structural instead, however I could not reproduce the motion of the cylinder section in the explicit analysis. I also saw in another thread that material erosion/failure can be seen in structural analysis, so for both time and convienince this would be great.nCould someone direct me to related forum posts? or perhaps guide me through improving the mesh/simulation parameters/using a transient structural analysis with material erosion in this scenario?nthanks!n
    • Chris Quan
      Ansys Employee
      Since the removal of materials is expected in this simulation, make sure Failure Model with reasonable maximum strain/stress is added to the materials in Engineering Data. Also, make sure Erosion is activated under Analysis Settings to remove the material that has failed. Activate Erosion by Material Failure.n
    • wyatt
      Subscriber
      Ok, Thank you. I really appreciate the support.nIn general, are these mesh and contact conditions enough, or should the cylinder have a finer mesh? Also, would you recommend changing anything in my analysis settings?nn
    • Chris Quan
      Ansys Employee
      Both part should have the similar mesh density (element size) on their contact faces. Analysis Settings OK.n
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