August 17, 2023 at 6:46 pm
javat33489
Subscriber

>>I say that because on your screenshot, I saw that you are in mks = meter / kilo / second and if we look the screenshot where the tools cuts the concrete your scale of stress is from 0 to 8756. In meter/kilo/second, the unit of Stress is Pa and if you have 8756 Pa at max it's really low. On the other side if it's 8756 MPa it's pretty high.

I checked all the data, everything matches mks. I know about agreed units, thanks. Here is the material:

Loads are also set correctly. WB has a menu for switching measurement systems, but this only changes the visual representation, does not affect the calculation.

I think there are large stresses due to the destruction of concrete, and the speed is very high, everything happens in 0.0001 seconds.

>>Another strange thing is the "ENDMASS" normally the default value in LS-DYNA is 1e+8 and it's a "Percent change in the total mass" meaning if you increase the mass of by 100 million percent, the simulation will end.

You should check the matsum and the added mass on each PARTs. As a rule of thumb, we tolerate 5% of mass increase for each PARTs.

Sorry for the stupid question, but how do you check the matsum and added mass on each PART in LS-Dyna ACT WORKBENCH?

>>Try with the default approximation theory for now (FORM=0 in *CONTROL_SPH in LS-DYNA format) as your model is too unstable.

It did not help

>>Also, for the contact try sfs=sfm=1e-9 and SOFT=1.

because of this, the bodies began to penetrate each other without deformation:

I also tried to solve the problem with these settings:

particles are still scattered.

My problem is changing the time. When I solve the problem at time 0.0001 without turning on the mass scale, everything is in order. When I change to a solution time of 1 s, I turn on the mass scale so that the calculation time is acceptable. Then the particles fly apart.

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PS

Here is another example why I wanted to switch to a solution time of 1sec. I rotate the part of the rigid drill with a deformable bit. The calculation time is 0.0001 sec, the feed rate is 2 mm per sec, I make 1 revolution by 360 degrees. I had to increase the speed to 20000 in order for it to work with a calculation time of 0.0001 sec. The results show what strong stresses and deformations the nozzle experiences, because to make a revolution in 0.0001 seconds is a space load, but the calculation ended without errors

Maybe I misunderstand the speeds when solving 0.0001 sec. I need your help.