I have developed a 3D half symmetric scratch model using Abaqus/Explicit consisting of two parts an analytically rigid conical indenter and an elastic-plastic deformable specimen. I have NOT defined any failure criterion for the material. The normal load is applied on the indenter along –Y (load control), indenter moves along –X to generate the scratch in the specimen (displacement control). I have the following questions and I would be grateful if someone could help me out
1. At higher loads (say > 10 N), when the linear displacement of the indenter begins, the job gets aborted due to Excessive element distortion. I have implemented ALE adaptive mesh but the mesh moves along the -Y (probably because the load is applied in that direction). Is there a way to allow the mesh to adapt in –X direction? If yes, how should it be implemented?
I have tried mesh constrains but the following error message is displayed as soon as the job is submitted:
Spatial adaptive mesh constraints cannot be specified on nonadaptive nodes.
Adaptive mesh constraints cannot be applied to more than one degree of freedom on nodes that lie on a Lagrangian or geometric edge
2. Secondly, sliding velocity of the indenter is 0.5 mm/s so I implement a timeperiod based on scratch length and sliding velocity.
For example Scratch length = 3 mm; Sliding velocity = 0.5mm/s; Timeperiod = (3/0.5) +2 = 8s; 2 seconds for loading and unloading the indenter. Is this correct?
3. If time scaling needs to be implemented to reduce the KE of the model to < 10% of Total Energy of the model then should the time period of simulation be increased or decreased?
Please let me know if any further explanation is required regarding the model or the questions.
I solved the problem by completely changing my model. These are some of the changes I implemented.
1. Converted my rigid body to deformable with high elastic radius (5 times of E of diamond)
2. Surface to surface contact definition was much better when I changed the rigid body to a deformable body
3. Did not apply ALE any more
4. Kept the time scale similar to that of the real experiment i.e lenght of the scratch x 1/speed of the scratch
5. Varied the mass scaling factor until the problem of distortion was not encountered
6. Optimized the model by varying mesh size and mass scaling factor
I hope this helps!
In my experience, ALE does not help too much in problems that are similar to machining processes. You can try to simply switch it off.
In general, excessive distortions are a common problem in Explicit, you may try to use Eulerian analysis instead.
Dear Martin, Thank you for your reply. I did come across some examples of machining simulations in literature, will give it a try!
According to my experience, better than ALE results can be achieved by applying hourglass control coupled with element distortion (yes); if in your model 3D elements can be used, than the best results ( in terms of the accepted distortion) due to conversion to SPH (in mesh module - element type)
This line in .inp file will help you manage this Problem.
*SECTION CONTROLS, NAME = Hourglass, HOURGLASS = STIFFNESS, KINEMATIC SPLIT = CENTROID
Info: KINEMATIC SPLIT=CENTROID to use the centroid strain formulation and the hourglass base vectors in the hourglass control in Abaqus/Explicit.
Give me feedback if it does help. Have a nice day
Dear Tamer, Thanks for the reply!
I implemented the hourglass and the kinematic split = centroid but still the problem of distortion continues the job gets aborted once the indenter starts its displacment.
Thanks again and good day to you too!
I have been going through the same problem but with changing the ALE frequency value and remeshing sweeps value I am getting results only upto some extent but the problem remains.
I solved the problem by completely changing my model. These are some of the changes I implemented.
1. Converted my rigid body to deformable with high elastic radius (5 times of E of diamond)
2. Surface to surface contact definition was much better when I changed the rigid body to a deformable body
3. Did not apply ALE any more
4. Kept the time scale similar to that of the real experiment i.e lenght of the scratch x 1/speed of the scratch
5. Varied the mass scaling factor until the problem of distortion was not encountered
6. Optimized the model by varying mesh size and mass scaling factor
I hope this helps!
Hi Kannaki,
Did you use finite sliding or small sliding in this model?
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