Reply To: What calculation model do i need?

[Reno Genest]

Hello Daniel,

LS-DYNA has an explicit and an implicit solver. In explicit, it is possible to simulate events longer than 1 second; we have customers simulating 30s or longer events, but they run on hundreds of cores. Also, it depends on element size (which determines the timestep) and your patience :).

With SPG, we have done a simulation of a screw in wood, metal, and concrete that lasted 2.4 seconds or more. With these problems, we typically increase the density of the SPG material quite a bit and it does not seem to affect the results too much. You can do a parametric study where you increase the density of the SPG material, record the computation time, and your results of interest. Does increasing the SPG material density affect your results of interest for your model? Then, you can judge by how much you can increase the SPG density and still get good results.

Also, with SPG, we typically distribute the SPG part to many CPUs using the following keyword:

*CONTROL_MPP_DECOMPOSITION_ARRANGE_PARTS

In LS-PrePost, it looks like this (this is an example; it might look different for your model):

Have a look at the LS-DYNA user manual Vol I for more information on this keyword.

The default decomposition for MPP LS-DYNA might put the entire SPG part on only 1 CPU which is not effective. This is why we use the above keyword to make sure the SPG part is being distributed on many CPUs for faster solve time.

 

Let me know how it goes.

 

Reno.