Exceedingly large (number of elements/nodes) models may not be able to complete an Explicit Dynamics solution in a reasonable amount of time for the following reasons:
As in any Mechanical application, you will start out with a coarse mesh and investigate convergence behavior while refining the mesh. This will typically lead to a satisfactory number of elements for a certain elapsed time. You may reduce the CPU time by distributing the model over multiple processors in parallel. With larger model sizes, the initialization time (which is typically a small fraction of the total run time) may increase significantly because the initialization is not running in parallel.
When performing convergence studies, you may run into hardware limitations. An Explicit Dynamics solution takes place in core memory, which means that RAM is the most limiting factor. Most modern workstations typically contain large amounts of RAM and will be able to cope with large models. Note that disk space is generally not a problem, since result files are typically not very large.
Although modern workstation hardware may allow large models to be meshed, the Explicit solver may not be able to handle such models because most integer numbers are still allocated on a 32 bit based definition. If a single internal array must be allocated with more than 29 entries, the solution will fail.
The current limitations can be summarized as follows, although these numbers are only a guideline as to what to expect:
Although Workbench can mesh a single part up to a maximum of 100 million solid elements, or 10 million shell elements, the Explicit solver may not be able to calculate a solution in a reasonable amount of time with a mesh of this size. Each element and node has a number of associated variables. The number typically depends on the type of solver chosen along with material models used and the number of options activated; for example, Failure models or the type of Interaction.
The AUTODYN component system can be used to generate structured meshes, which in turn can be converted to unstructured. The limit for the number of elements that can be converted lies between 50 million and 60 million.
The number of SPH objects used to create zoning regions for SPH meshes in the AUTODYN component system is limited to 99 in 3D.
The number of bodies in an Explicit Dynamics analysis in Mechanical with the Reference Frame set to Particle is limited to 99.
If the Explicit solver detects that more than 500,000 nodes are packed in an SPH object a warning will be given, since it will affect CPU and RAM resources.
Note: These limitations are approximate and serve as a guideline when modeling for Explicit Dynamics and AUTODYN component systems. To reduce the solution time, consider using a coarser mesh or Mass Scaling in your model.