How to activate element deletion at yield stress to simulate chip formation on machining in ABAQUS

[FlameOfAnor]

Hi everyone

I want to simulate chip formation on machining in abaqus. I found a youtube video which did exactly the same. But in the video they used Johnson Cook damage model for element deletion as shown in the below screenshot.

[URL unfurl="true"]https://res.cloudinary.com/engineering-com/image/upload/v1708669315/tips/jcn97b4pwgjc1_ivfjha.webp[/url]

I was wondering if I could use just the yield stress as a element deletion criteria instead of using the JC model. The idea here the material gets strained only in the linear elastic region before the chip forms, that is the element deletes. I hope this would also make the simulation finish faster ( my understanding was that straining the material in plastic region is what leads to high time consumption, the simulation done by following the youtube video takes almost a day to finish). Since the simulation is for a demonstration purpose a very accurate picture of the chip formation is not needed.

Is this possible? Any help is appreciated.

 

[FEA way]

Check this thread:

https://www.eng-tips.com/viewthread.cfm?qid=462351

 

[FlameOfAnor]

Hi there thank you for your reply.

I checked the mentioned post. Since I am a beginner to subroutines I am still learning the possibility of doing this simulation using this method.

But could you comment on the approach I am about to mention as well?
Since the failure that I want here is a perfect brittle damage I tried to utilize the Damage for ductile materials option with the plastic data and the failure strain given such that the elements can undergo failure and deletion at the yield stress.
Below shown are the data that I have used.

For plastic data I gave just the yield stress, which would be its fracture stress as well when thought of it as being perfectly brittle, of the material with zero plastic strain.

Why I used the mentioned value as the fracture strain is because when I did a trial simulation I found the maximum strain that is being occurring at the tool workpiece interface is in this range.

When i did a simulation using these, I obtained chip formation to some time steps as shown below

But then stopped due to excessive element distortion error. While I learned that it could be because of the mess refinement I would like to know your comment on this approach. A doubt that I am having about this approach is the damage evolution criteria value. I learned that it is the plastic strain multiplied by element characteristic length. So in my simulation should the value be zero? In the trial simulation I gave a random value compared to the fracture strain and it somehow worked. Though there are some youtube tutorials about this damage modelling I am not able to understand the intuition behind it.

Could you please provide your insights?

 

[FEA way]

Check the documentation section "Damage and failure for ductile metals". You can use the displacement damage evolution criterion and set it to 0 for instantaneous failure.