Which Explicit Tool is Right for Me?
In my Explicit Dynamics and Ansys: Part I blog post, I discussed the fundamentals of the theory behind the explicit dynamics method for structural simulation, and some of the scenarios in which the method can be useful. However, the question remains: of all the explicit dynamics tools available through Ansys, which is the correct tool for any given application? Luckily, the options available can easily compared by highlighting a few of the key features of each. The four tools or environments I’ll cover are:
- Explicit Dynamics in Workbench
- Workbench LS-DYNA
- LS-DYNA (LS-Prepost and LS-Run)
- Autodyn
Pictured: Ballistics study performed using Explicit Dynamics (left) and LS-DYNA (right).
Explicit Dynamics
What is it?
Explicit Dynamics is a system component in Workbench that becomes available with the installation of the Ansys Structures package and an Ansys Mechanical Enterprise license. It uses the “Explicit STR” solver, which is essentially a modified version of the Autodyn solver. The pre-processing and post-processing is done using the Ansys Mechanical environment.
Who should use it?
Users that are new to Explicit but are familiar with the ANSYS Mechanical environment especially will benefit from the workflows used in this tool. It leverages the ease-of-use inherent to ANSYS Mechanical, while simultaneously using program-controlled solver settings for several scenarios to take the burden off less-experienced users. This is also the system component used with the “Drop Test” Wizard available in ANSYS Mechanical.
Workbench LS-DYNA
What is it?
Workbench LS-DYNA is very similar to the “Explicit Dynamics” component in that it is a system component available in Workbench. It becomes available with the purchase of an LS-DYNA license as well as the installation of Ansys Mechanical and the loading of the Workbench LS-DYNA ACT extension. Like Explicit Dynamics, this component also uses Ansys Mechanical for the pre/post-processing environment.
Who should use it?
Like Explicit Dynamics, Workbench LS-DYNA is a great tool for less-experienced users who want to start leveraging the explicit method. It combines the ease-of-use of Mechanical and Workbench with the power and versatility of the LS-DYNA. LS-DYNA should be considered as an alternative to Explicit Dynamics for a couple reasons:
- For simulations that involve relatively low-rate or low velocity events (longer than 0.100s is sometimes used as a very general guideline), LS-DYNA may improve solve time over the Explicit STR solver.
- Prestressing the model using an implicit solution is more easily accomplished with Workbench LS-DYNA
- Users with some LS-DYNA experience may prefer it over Explicit Dynamics
LS-DYNA using LS-DYNA Preppost
What is it?
This option leverages the exact same solver as Workbench LS-DYNA, but it allows the user to use the LS-DYNA Preppost environment to setup and review the results of their simulation. This option becomes available with the purchase of an LS-DYNA license and the installation of the LS-DYNA Preppost environment from the Ansys Structures installer.
Who should use it?
Obviously, experienced LS-DYNA users will prefer this option over the others. However, this version of LS-DYNA (as well as the Workbench version) are particularly useful for relatively low-speed simulation as compared to Autodyn and Explicit STR. It is the automotive industry standard for crash-test simulation, is leveraged for simulating bird-strikes on aircraft, and is often preferred for some ballistics and other impact studies. It also uses an open input solver file format, which allows for customization and scripting that Autodyn and Explicit STR are not capable of.
Autodyn
What is it?
Autodyn includes both a pre/post-processing environment as well as a solver. This tool is available with an Autodyn license and the installation of Autodyn from the Ansys Structures installer.
Who should use it?
Autodyn is an extremely powerful asset when very high rates of change are introduced. It is especially useful for blast/explosive simulations, hypervelocity simulations, and those that involve the use of Euler domains (fluids or extreme deformations) or Smooth Particle Hydrodynamics (SPH) for when something is expected to get blown into pieces. LS-DYNA can also simulate using Euler and SPH domains, but it is a key area of strength for Autodyn. While Explicit Dynamics uses the same solver technology as Autodyn, it does not allow for the use of mesh-free domains or the full breadth of the equations of state used to simulate blasts that Autodyn has.
