Turning operation element problem LS Dyna vs Autodyn

- October 31, 2018 at 2:53 pm
  
  dinler
  Subscriber
  
  Hello guys,
  
  It's my 1st post, i am greeting you all from Turkey.
  
  My problem is I am trying to simulate a 3d turning operation in which i machine an aluminum workpiece with a steel tool. First I model it with autodyn and then with ansys ls dyna. Autodyn result was close to reality however I could not achieve a similar result with LS-dyna. All parameters were identical.
  
  With ls dyna tool go into the workpiece material and make it stretch. What I expected was that plastic deformation and chip removal.
  
  I greatly appreciate any feedbacks.
- October 31, 2018 at 3:24 pm
  
  Sandeep Medikonda
  Ansys Employee
  
  Dinler,
  
  I moved your post to the Structural Mechanics category where it might get more traction.
  
  Coming to your question, what are the erosion criteria in your LS-DYNA model? Can you double check this and post the analysis settings for both simulations? Please see this discussion on the machining process.
  
  Regards,
  Sandeep
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- October 31, 2018 at 5:32 pm
  
  dinler
  Subscriber
  
  Thank you for your quick reply, you addressed the problem well that I dont have any erosion criteria in LS-DYNA. How can I add it?
- October 31, 2018 at 11:53 pm
  Sandeep Medikonda
  Ansys Employee
  Dinler,
  
  You can either include have failure criteria defined in your material model (i.e., use of *MAT_24) or you can insert a command snippet in WB LS-DYNA and use *MAT_ADD_EROSION to define the failure of the material, something like:
```
*MAT_ADD_EROSION

$#     mid      excl    mxpres     mneps    effeps    voleps    numfip       ncs

**       0.0       0.0       0.0       0.0       0.0       1.0     0.001

$#  mnpres     sigp1     sigvm     mxeps     epssh     sigth   impulse    failtm

0.0       0.0       0.0       0.1       0.0       0.0       0.0       0.0
```
  The above criteria specifies failure based on a max. a principal strain of 0.1. Now you need to find the correct material ID and input it where the ** is. You might have to write out the input deck(input.k) first to find this. One other way to estimate this is if you have 4 bodies in the Geometry object of the structure tree, and you want to apply failure to the 3rd body in it (from the top) its mid would typically be 3. Once you determine this, you command object should look something like this:
  
  Next, you need to specify eroding contact in your simulation as well:
  
  Hope this helps.
  
  Regards,
  Sandeep
  Best practices on the student community