Wide Range of Capabilities

ANSYS explicit dynamics helps engineers to explore a wide range of simulation challenges.

Crimping - complex contact
Airplane impact - Material failure
Blast loading inside a masonry structure

Superior Bidirectional CAD Interface

Existing native CAD geometry can be used directly with ANSYS explicit dynamics solutions with no need for translations to intermediate geometry formats such as IGES to ensure that parameters and other design information are not lost. ANSYS has provided native, bidirectional, integration with the most popular CAD systems for more than 10 years and also provides integration directly into the CAD menu bar making it very simple to launch world-class ANSYS simulation directly from a CAD system.
Because the geometry import mechanism from ANSYS is common to all CAD systems, the user has the flexibility to work within a single, common simulation environment while using multiple CAD packages and multiple ANSYS solution methods including explicit dynamics, structural mechanics, fluid dynamics and electromagnetics.

ProENGINEER® CAD model of perforating gun and cross section of one shaped charge mesh
Courtesy Schlumberger 

Circuit board CAD model and mesh in preparation of drop test simulation

ANSYS supports the following CAD systems: Autodesk® Inventor®, Autodesk Mechanical Desktop®, Autodesk Inventor Professional Stress, CATIA® v4 and v5, Pro/ENGINEER®, Solid Edge®, SolidWorks®, Unigraphics®, CoCREATE Modeling™ and SpaceClaim®. The ANSYS Workbench environment also supports the neutral format files of IGES, Parasolid®, ACIS® (SAT) and STEP to which any CAD system can export.

Geometries created with CAD tools are not always well suited for explicit dynamic simulations. For example, surfaces that do not meet or overlap may need to be corrected. Very small features may need to be removed to so that meshes can be created that can be used to generate accurate results efficiently. These operations can be done easily and conveniently with the ANSYS DesignModeler and ANSYS SpaceClaim Direct Modeler tools.

Robust Automatic Meshing

ANSYS provides a wide range of highly robust automated meshing tools — from tetrahedral meshes to pure hexahedral meshes and high-quality meshes for surface and line bodies. Using the explicit preference in meshing will generate meshes well suited for explicit dynamics. Additional productivity tools include the ability to control element size, to defeature unnecessary details, to generate swept hex dominant meshes, to use smoothing controls for gradual element size transitions and to apply multizone meshing for parts consisting of multiple bodies that need to be meshed uniformly. Multizone meshing also automatically will “slice and dice” parts to enable the generation of high quality hex meshes.

Multizone meshing of a complex bullet resulting in all hex elements

Auto Contact Detection for Parts

Once the geometry has been imported, the software automatically detects and performs setup for contacts, bonded contacts and interface definition for coupling between Euler and Lagrange regions for problems involving fluid–structure Interaction (FSI). Contact settings can be modified to improve computation speed by excluding parts or surfaces that are known not to come in contact.

Automated detection of contacts performed upon geometry import

Automated interface definition for coupling between fluid (Euler)  and structural (Lagrange) parts in FSI problems

Comprehensive Element Technology

The current generation of ANSYS element technologies used in explicit dynamics provides rich functionality with a consistent theoretical foundation coupled with the most advanced algorithms. ANSYS Explicit Dynamics solutions provide a variety of elements for use with line bodies, surfaces and solid elements. Element types include 8-node hex, 6-node penta or 4-node tet elements in 3-D as well as 4-node hex and 3-node tet in 2-D. The speed of calculations can be further improved with the use of 2-D axis symmetry, 2-D planer symmetry as well as 3-D quarter or half symmetry. These options can be easily set up in the ANSYS Workbench platform. Complex geometries are often difficult to mesh with all hex elements, which are generally desirable due to their accuracy and efficiency. Tet elements facilitate the meshing of complicated geometries, but have been avoided in the past for explicit solutions, because they tend to be too stiff and lock up. The recently implemented NBS tet eliminates problems with both volume and shear locking and enables easier problem setup without sacrificing accuracy.

NBS tet elements avoid shear locking problems

All HEX mesh of complex automotive brake rotor assembly
Courtesy PTC.

Extensive Library of Material Models

It is vital to understand and accurately characterize material behavior while designing or analyzing an engineering application. ANSYS Explicit Dynamics solutions provide a vast library of mathematical material models to aid the user in simulating virtually all kinds of material behavior as shown in the table below. In addition, in order to aid in finding parameters for these materials models, ANSYS also provides a set of curve-fitting tools. 

The engineering data library included with the ANSYS Workbench platform not only contains an extensive list of material models but displays the material response properties in a tabular and graphical form.

Advanced Numerical Methods for Nonlinear Dynamics

With a solid foundation of element and material technology, ANSYS Explicit dynamics solutions offer various advanced solver technologies to best simulate a comprehensive list of dynamic applications. The multiple solution methods described and pictured below can be combined in several ways through the use of part interaction. The interactions can be through contact, bonded contact and coupling between Euler and Lagrange regions for problems involving fluid–structure interaction (FSI). For parts that interact via contact, the contact surfaces that are automatically redefined as elements on the surface are removed through erosion. The table below shows the solvers that are available with each of the three explicit dynamics products, through the ANSYS Workbench interface.

 * LS-DYNA does have SPH and ALE capability - it is not currently accessible from the ANSYS Workbench interface

Available Solution Methods

The Lagrange solver utilizes a mesh that moves and distorts with the material it models as a result of forces from neighboring elements. This is the most efficient solution methodology with accurate pressure history definition. If however, there is too much deformation of any element, it results in a very slowly advancing solution and is usually terminated because the smallest dimension of an element results in a time step that is below the threshold level. For problems with too much deformation involving gases and liquids, the Euler solver is better suited.

The Euler (multi-material) solver utilizes a fixed mesh, allowing materials to flow (advect) from one element to the next. The Euler solver is very well suited for problems involving extreme material movement, such as those involving fluids and gases. Euler is generally more computationally intensive than Lagrange and requires higher resolution (smaller elements) to accurately capture sharp pressure peaks that often occur with shocks.

The ALE (Arbitrary Lagrange, Euler) solver utilizes the advantages of both the Lagrange and Euler solvers. It works as a Lagrangian solver but periodically repairs the mesh as it becomes distorted. This solver is well suited for problems that lie between the Lagrange and Euler sweet spots.

The Euler–FCT solver, used for ideal gases, is a special-purpose Euler solver that is very fast and highly accurate. It is best suited for use in problems simulating blast loadings.

SPH (smooth particle hydrodynamic) mesh-free method is ideally suited for certain types of problems with extensive material damage and separation such as cracking. This type of response often occurs with brittle materials and with hypervelocity impacts.

The Shell solver is assigned to two-dimensional parts such as membranes. It enables efficient computation in spite of the very small dimension of the membrane.

The Beam solver is used for one-dimensional parts such as reinforcements. When used in conjunction with solid elements, beams can be located inside a solid element and need not be aligned with the nodes of the Lagrangian elements, making their use unlimited, while requiring very little effort to set-up.

Lagrange (structures)
Euler (fluids)
ALE (auto remesh)
SPH (brittle)
Shell/Surface (thin 2-D)
Beam - Reinforcement (long 1-D)

The numerical methods accessible for the three explicit dynamics products cover almost all possible areas of application appropriate to explicit simulation.

Efficiency Tools

The interactive user interfaces offered by ANSYS Explicit STR and ANSYS AUTODYN software offer a powerful collection of tools for increasing productivity by reducing the effort to set up, run and analyze simulations. This increases accuracy, reduces simulation time and makes the jobs of the engineer or scientist easier and more enjoyable. The list below contains just a few of the numerous tools available to the user.

Tool/Description	Picture
Interactive problem set-up (pre-processing) solution and analysis (post-processing)  Working interactively with a graphical user interface, instead of preparing a text input file, makes it easy and convenient to immediately identify and correct bad input values, thus resulting in a working solution in the shortest possible time.
Remapping in space  High resolution fast running 1-D problems can be mapped into 2-D or 3-D, enabling highly accurate results to be created extremely fast. The remapping is accomplished with just a few clicks of the mouse. 3-D problems can also be remapped into 3-D for extending the physical size of the problem.
Remapping solution method The solution method for a part can be changed when the problem requires a different methodology. In the example to the right a 2-D axis-symmetric Euler solution is mapped into a 3-D Lagrange solution enabling the simulation of an oblique impact. Running this problem in 3-D with the same result resolution and accuracy would require 1,000 times as much computer time.
Import of data from Geographic Information System (GIS) services  For modeling large city structures information from a GIS data base can be imported, making the creation of a mesh and solution space virtually automatic. Manual set-up of this type of a problem would make it totally unpractical.
Mass scaling  Mass is artificially added to individual elements to ensure their timestep is at least equal to a user defined value. This is a valuable technique for problems with a limited number of small elements. A contour plot of the time step for each element enables quick identification of the scope of the problem and whether this technique is practical and safe.
Dezoning Parts using the Euler solver can be “dezoned” increasing the size of each element and reducing the number of elements. This process tool provides a way to increase the computational speed during the later stages of a calculation when less resolution might be required.
Erosion  Erosion is a numerical method to eliminate elements that have become degenerate, or have caused the time step to be reduced below a minimum value. Erosion criteria can be based on minimum time step values, strain or material failure. The eroded element can optionally be retained as a point mass, enabling more accurate momentum conservation and potential loading from the eroded nodes.
Natural Fragmentation  Natural fragmentation provides a statistical way to model failure due to impurities. This technique is invaluable when modeling symmetrical parts under uniform strain, where normally all elements would fail at the same time. Natural fragmentation introduces minor variance in the failure criteria randomly in the elements that make up the part, resulting in “natural fragmentation.”

Advanced Post-Processing

ANSYS provides a comprehensive set of post-processing tools to display results as contours or vector plots and provide summaries of the results (like min/max values and locations). Powerful and intuitive slicing techniques allow the user to obtain more detailed results over given parts of the geometries. All the results can also be exported as text data or to a spreadsheet for further calculations. Animations are provided for static cases as well as for nonlinear or transient histories. Any result or boundary condition can be used to create customized charts.

Contour plots on bodies

Results can be displayed on any part of the geometry.

Path plot

Automatic Report Generation

A design can be explored in multiple ways. Then the results must be efficiently documented. ANSYS provides instantaneous report generation to gather all input data specifications, material models used and a copy of all the images and graphs that were generated in the set-up and post-processing of the model in a convenient format (HTML, Microsoft Word®, Microsoft PowerPoint®).

Advanced Pre-Processing for Composites

Setting up parts consisting of complex layups for modeling composites is greatly simplified with the use of the ANSYS Composite PrepPost program. Explicit dynamics can now use the results of ANSYS Composite PrepPost and simulate the response of composites exposed to impact or other severe loadings.

Bat made of a composite and the layup within ANSYS Composite PrepPost
Composite layup

Solving Large and Complex Models Efficiently

ANSYS Explicit Dynamics solutions offer a comprehensive set of tools that facilitate reduction of solution time and increase in accuracy of the results generated. Parallel processing using domain decomposition can reduce the solution time for large problems. Parallel solutions can be used with any computer configuration, such as multi-core, multi-CPU or networked computers.

Domain decomposition of model with performance improvements as a function on number of processors used

Solution Customization and Open Architecture

ANSYS Explicit Dynamics solutions offer an open architecture that enables customers to extend the standard capabilities of the program easily and conveniently. Customization capabilities through user-defined subroutines are available for a list of functions, such as materials equation of state, material failure model, erosion model, strength model, boundary conditions, input and output functions and many more. Templates are provided for all user definable subroutines with documentation on how they can be used, the variables available for use and the variables that must be defined within the subroutine.