Learning Forum

[javat33489]

Hi all.

Ls-dyna ACT WB.

I solve a simplified model of a drill with nozzles.

The body of the drill is rigid, the nozzles are deformable bodies.

I use content and contact snippets.

Nozzle material:

I'm trying to return the drill in space along with the nozzle. The nozzle is attached to the drill with a contact:

But during rotation, the nozzle experiences enormous stresses and is greatly deformed. Why? It does not contact with anything, it only rotates with the drill. The rotation is set to the drill. There are no restrictions on the nozzle other than contact.

PS

Previously, I cut with a rigid body when I trimmed the cement material.

Then I made the tip of the chisel deformable and made the same TIED contact. And it worked well:

Why does not work on a drill?

[Chris Quan]

Regarding to "But during rotation, the nozzle experiences enormous stresses and is greatly deformed. Why? It does not contact with anything", were you using Program Controlled for the Precision under Analysis Settings?

If yes, can you change it to Double so double precision is used, rather than single precision (default). 

For typical mechanical simulations, velocity is usually low. Thus the change of all variables (displacement, stress, strain) at each time step is very small. Use of double precision can prevent any possible round-off error from floating point calculations.

 

[javat33489]

Yes, of course I use double precision. All of this happens with double precision turned on.

[javat33489]

HELP PLEASE

[Ram Gopisetti]

Hi 

imporove the mesh on those buttons and try again, you may find some impovements 

cheers, ram 

[javat33489]

Yes, of course I did a fine grid on the bits.

In addition, I tested the bits on another working model. I had a rigid drill that cut concrete and I added deformable bits to it. All the same. When rotating, they experience enormous stress:

I also tried using the classic contact workbench, it doesn't help.  and i also tried using rigid body additional nodes to connect the bits and the drill, that doesn't help either

 

[javat33489]

HELP PLEASE 

[javat33489]

I found a clue in solving the problem. I increased the solution time from 0.0001s to 0.1 and 1s. I set the timestep to 0.00001. Under this condition, the solution takes longer, but during rotation, the teeth suffer much less. As I understand it, I forced the drill to make a rotation in 0.0001 s, which greatly affects deformable bodies, they are strongly deformed in space, as if flying into space.

But now I need to test it on rotation speed. The rotation speed of the drill is 27 rad/s. Drill with teeth does not rotate. I used Rotation Velocity, Rigid Angular Velocity, no rotation happens. Why? If I set the Rotation in degrees using the Remote Displacement, then the rotation is there.

I'm tired, please help.

I have attached the file with the model.

ARCHIVE

[javat33489]

Looking forward to your tips and advice! Thank you.