Z-mat ABAQUS interface#

Description#

The commands described in this chapter are used to enable a Z-mat material model for use within ABAQUS 1The Z-mat interface is also known as Z-aba or ZeBaBa in some older circles. The Z-mat name is however the official product name and symbolizes an approach which is a step beyond classical single code UMAT solutions, and one which is tied to the extensive Z-set software..

Syntax#

Z-mat jobs are launched via the Zmat command line script only.

% Zmat [ opts ] problem  \(\hookleftarrow\)

The command syntax for Zmat is given in more detail in the Release Notes & Zmaster handbook, including discussion of all the command line switches used to control the specifics of the Z-mat launch.

The script will initially launch ABAQUS, and then be called again by the ABAQUS pre-processor in compile and link mode. By default the launch submits the job to the ABAQUS queue, and therefore the script exits rapidly (even though the job continues in the background). To see the status of the calculation, look at the problem.log file (e.g. tail -f myprob.log), or run with the -fg switch.

ABAQUS Input#

The definition of a material for the Z-mat behaviors always uses an external file to establish the model components and coefficients. Z-mat never uses the material parameters defined in the ABAQUS .inp file. This is because the Z-set coefficient definitions are much more flexible in their definitions, and are integral to the actual structuring of the material model to be used. Global dependencies are established using the temperature parameter, or other global field variables.

Other commands are available in addition to the behavior definition which control the local integration method (implicit mid-point, Runge-Kutta explicit, etc), variable initializations, automatic time stepping parameters depending on the maximum allowable variable increments, and the local rotations.

Linking summary#

The Z-mat library is delivered as a dynamic shared object which can be linked to other programs. The library is entirely programmed in C++, but only a system linker (ld) is required for basic use of the program. The Zmat script prepares the proper link command in place of using the C++ or Fortran command lines. On Windows platforms no development software is necessary at all.

To have user routines attached to the basic library, a C++ compiler will be necessary, as a second add-on shared library must be prepared 2actually there is no limit to the number of plugins which can be used. There is a specific naming convention for Z-mat plugins however. For unix systems the user-library should begin with libZmat and on windows the DLL should start with zmat.. Since the standardization of C++, the compiler requirements are greatly reduced from what was previously the case. In most systems Z-mat plugins can be made which whatever C++ compiler is convenient. Normally the user would be best advised to use the most modern version possible. The general compiler level requirements specified by ABAQUS, Inc will most likely not be absolutely necessary, though we validate that those compilers do in fact work so they can be used as a guideline.

User plugins will always be compiled and linked before running ABAQUS, and the end-user will therefore not need any additional development tools in the same manner as running Z-mat without the plugins.

Current status#

Since the initial releases, many improvements have been made for the interface of Z-mat. Some issues still remain however.

Some of the additions with this version include:

  • Continuing streamlining and performance improvements. The distributed domain solvers in at versions 6.5 and above are well supported and are proven to give decent scalability with Z-mat.

  • Support for ABAQUS/Explicit is complete.

  • Improved automatic time stepping.

  • Improvements in the simulation/optimization tools, including support for finite strain problems.

  • Compatibility with the rest of Z-set, making one installation for sites with Z-set and Z-mat.

  • External disk storage for state variables. This allows models with thousands of state variables.

  • Finite strain has been improved, including now the addition of hyperelastic and Hyperviscoelastic models.

  • Direct reading of the .fil format is greatly improved. Abaqus ODB files can also be read and written by Zpost/Zmaster and Zebulon. This data file interface is without question the most robust of all the Z-mat interfaces.

  • All the Z-mat test cases use Z-post.

  • Support for all Abaqus 6.x versions.

  • Zebulon elements can be used as a UEL with output to an ODB file or other Zebulon supported output. This includes full state variable name and typing information.

  • Optional post processing step to translate all the Z-mat SDV# variable names to be the proper named and typed variable in a new ODB file.