How to get solution solved faster in 2D Explicit Dynamics
Hi, currently I'm solving a 2d explicit dynamics problem with approx. 9k nodes and 9k elements with 1.6058e8m mesh size on a server (32Gb Ram and 2 cores). Estimated Solution time is 1236 hrs (ofcrs not feasible).
Any way to solve it faster and get accurate results. Thanks.
Best Answers

peteroznewman Member
When you work with devices that have a dimension of 10 micrometers, and the element size is about 16 nanometers, Explicit Dynamics is not a good place to be.
The reason is the minimum time step depends on the element characteristic length. The smaller the length, the shorter the maximum time step and the longer the solution will take to compute to the End Time.
If you switch the solver to Transient Structural, then the element size is not a factor on how long the solver will take to solve to the end time.

peteroznewman Member
@FernandoTorres In Explicit Dynamics, element removal from the model is automatic.
In Transient Dynamics, element removal is not automatic. The article you enjoyed showed you how to do that with a script. This is more work for the user, but may end up taking less time compared with weeks of solution time in Explicit Dynamics.
Good Luck!

peteroznewman Member
@FernandoTorres AUTODYN 2D has no parallel processing, so one core is all you can use.
Answers
When you work with devices that have a dimension of 10 micrometers, and the element size is about 16 nanometers, Explicit Dynamics is not a good place to be.
The reason is the minimum time step depends on the element characteristic length. The smaller the length, the shorter the maximum time step and the longer the solution will take to compute to the End Time.
If you switch the solver to Transient Structural, then the element size is not a factor on how long the solver will take to solve to the end time.
Thanks Sir @peteroznewman
I'll try to go "transient"...
But what if I increase cores, and with a "reasonable enough mesh", will this solve the problem little faster?
i.e. does solution time of a 2d explicit analysis depends on ram, cores or both (I'm asking for hardware here not cfl equation parameters)
Thanks a lot.
@FernandoTorres
For any solver, if you go from 2 cores to 16 cores, you will reduce the solution time by less than a factor of 8.
If you double the computer clock speed from 2 GHz to 4 GHz, you will reduced the solution time by a factor of 2.
Implicit solvers need more RAM, but if the problem size fit in the existing RAM, increasing the amount of RAM will have no effect.
The maximum time step size is set by the minimum element length for Explicit, while for Implicit solvers, it is set by the highest natural frequency of interest in the structure. The ratio of the maximum time step of Implicit/Explicit for your nanoscale elements might be a factor on the order of 1000.
Thanks Sir @peteroznewman , shifted the model from explicit to transient but the tool is getting into the workpiece without cutting anything i.e. tool just moves inside workpiece without cutting the material. Tried to setup the contacts manually but it didn't work. What could be the issue?
Thanks.
@FernandoTorres
Read this Discussion.
Great Article Sir @peteroznewman , but I have issues in material removal (chip formation). When I run the same experiment in explicit dynamics, cutting is shown with proper chip formation, BUT ONCE I shift the model to TRANSIENT structural, there is no cutting like shown below (tool moves freely into the material without cutting). I know this is a childish question but it is what it is.
thanks for your help.
@FernandoTorres In Explicit Dynamics, element removal from the model is automatic.
In Transient Dynamics, element removal is not automatic. The article you enjoyed showed you how to do that with a script. This is more work for the user, but may end up taking less time compared with weeks of solution time in Explicit Dynamics.
Good Luck!
Thanks Sir @peteroznewman , I'll check that out in more detail. "Parallel processing is only available for 3d models" says the AUTODYN Solver for my 2d explicit dynamics problem. I know you have stated about the hardware on top of this page but I wonder if that is still valid for AUTODYN 2D Explicit Analysis.
Thanks.
@FernandoTorres AUTODYN 2D has no parallel processing, so one core is all you can use.