cutting contact

[halleluja]

Hi everyone,

i am doing a simulation of cutting. See t0.png, the nodes of the cutting tool are fixed and the workpiece goes towards the cutting tool. I use Node to Segment strategy without friction as

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PAIR 1
NTOS 1 2
SOLM PENAlty 5e3 .
The result of the simualtion is shown in t0.png, t1.png, t2.png and t3.png.
But why the nodes of upper right of the workpiece don't as experted in rightone.png move up but move down? Could  you give me some advice? Thanks^^

[Prof. R.L. Taylor]

Post your input file

[JStorm]

Is this an elastic solution?

it seems that in your simulation (t0-t3) no material cutting, degradation, damage, etc. is active.

[halleluja]

Post your input file

You would find the inputfile in attachments.

[halleluja]

Is this an elastic solution?

it seems that in your simulation (t0-t3) no material cutting, degradation, damage, etc. is active.

Yes it is a elastic solution.

I know we cannot use only the finite element method to simulate cutting process because the mesh will be so distorted that the Determinant of the deformation gradient will be negative. But at the beginning of the cutting process (from time t0 to t3) the mesh deforms not very large, so i think it should work just using finite element method.

[Prof. S. Govindjee]

Is there a reason that t2 and t3 have different meshes from t0 and t1?

[halleluja]

Is there a reason that t2 and t3 have different meshes from t0 and t1?

If i modify the master surface

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SURFace 2
LINE
FACEts
1 0 553 554
2 0 554 555
3 0 555 556
4 0 556 553to

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SURFace 2
LINE
FACEts
1 0 556 553, the upper right corner of the workpiece moves up as expected and is shown in moveup.png.

[Prof. R.L. Taylor]

In order for your cutting tool to pass over the mesh the deformations will become very large.  Trying to do this with an elastic material and with 3-node triangles will probably not have any chance of success.

What are you using as a reference to learn how to solve such complex problems?

[halleluja]

In order for your cutting tool to pass over the mesh the deformations will become very large.  Trying to do this with an elastic material and with 3-node triangles will probably not have any chance of success.

What are you using as a reference to learn how to solve such complex problems?

Dear Prof. R.L. Taylor,

yes, you are right. At a later time step i will use a so called particle finite element method to remesh the workpiece. But at the first few time step the deformation is not so large, that it should work fine just using finite element method. But output is very strange. See in attachment at time step 25 no deformation, but at time step 26 the upper right corner moves down when deformation happens. Here i have used

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plot pair 1 to plot the slave nodes and the master segment.

[JStorm]

You can write out the contact state of the nodes to have more informations for the interpretation of the results.

my guess is:

• there is no slave node in contact in time step 25 and, thus, there is no deformation
• there is just one node in contact in time step 26, which get pressed into the block.

then both results look plausible.

[halleluja]

You can write out the contact state of the nodes to have more informations for the interpretation of the results.

my guess is:

• there is no slave node in contact in time step 25 and, thus, there is no deformation
• there is just one node in contact in time step 26, which get pressed into the block.

then both results look plausible.

Thanks for your info. Could you tell me how to write out the contact state of the nodes?

See timestep25.png in attachement. What happens in the next time step? Maybe the node 460 will be first in contact, and this node will be pushed up from the cutting edge, which causes that the node 414 comes in contact and this node will be pushed down from the horizonal segment of the cutting tool. Maybe the pushdown force to node 414 is much larger than pushup force of node 460, sothat the upper right corner of the workpiece moves down.