General Mechanical

General Mechanical

Element failure – Explicit analysis

    • Francisco Donda
      Subscriber

      Hi all, could you please help me with an explicit analysis? Im trying to approve an A36 structure for a dropped object analysis. The problem here is that the object is passing through it. It seems that the elements are "dying" after reaching some level of strain, could it be some type of auto ekill? If so, how to turn it off?

    • Francisco Donda
      Subscriber

    • peteroznewman
      Subscriber

      Click on Analysis Settings and in the Details window, look at the settings under Erosion Controls.  The default settings are shown below.
      Erosion is the automatic removal of elements during the analysis that have exceeded the thresholds in this section.
      The default setting has erosion when the strain exceeds 150% (1.5) but you can turn that off by setting Yes to No.

      If you define Material Failure limits in Engineering Data, then you can turn that on in this panel.

      I also show the Output Controls because the Result Number of Points is a setting I always change on any new analysis because 20 is way too few output frames. A better number here is somewhere between 200 and 2000, the bigger number for when you are uncertian how long the impact event will last and it gives you enough frames so you can see something if it turns out to be a very brief time relative to the End Time you set.

    • Francisco Donda
      Subscriber

      Hi peteroznewman, Thank you for your help but Im still facing some issues, could you please give me a hand?
      The analysis is currently with 9e-3s at end time giving enough time for the project to clash with frame (this is taking 25e-6s). Looking at the total deformation and equivalent stress It is shown some deformation of the frame but at the directional velocity of projectile there inst a big change. Going to Energy Summary and Energy conservation all curves are pretty much stable. Does this means the impact is not being read? Not sure what is the problem here.
      Thank you!

    • peteroznewman
      Subscriber

      Hi Francisco, you can see that the impact is present because the sheet metal is bending at the impact site. What is the diameter of the projectile? What is the mass of the projectile?  What is the impact velocity?  What is the wall thickness of the sheet metal? 

    • Francisco Donda
      Subscriber

      Hi Peteroz, I am following normative requirements of 5 kJ on the impact. To meet this Im using a 616.54 kg projectile with 100 mm (also a normative requirement), velocity of 4 m/s and wall thickness of 12.5 mm with material A36.
      My main concern is that I expected a energy summary showning a cross point between Internal energy and kinetic energy which I was reading as impact moment (added an example below), dont know if this interpretation is mistaken.

    • peteroznewman
      Subscriber

      The example you show is the Energy Summary, but the chart you ask about is Energy Conservation. Please show the Energy Summary for your model.

    • Francisco Donda
      Subscriber

      In the model discussed it is shown the same behavior both in Energy Summary and Energy Conservation. Please see below the requested information

Viewing 7 reply threads
  • You must be logged in to reply to this topic.