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| CREA is experienced
in the use of the ANSYS Parametric Design Language for the extension of the programs
capability. This page discusses a few of the issues involved in the use of APDL and
some of the advantages. CREA can provide consultancy,
advice and assistance in the extension of the ANSYS capability to the benefit of our
clients. (It can even be used such that CREA carry out
the first pass on the project, then our clients receive the macros and input files to
carry out re-runs!!) |
Macros in ANSYS |
| Parametric Modelling |
| Solution Control |
| Post Processing |
| Code Checking |
| Design Optimisation/What if? Studies |
Macros
in ANSYS |
| Macros within ANSYS provide a sound means of
extending the capability of the program. The ANSYS macro language is based on
FORTRAN in that most of its structure, if not syntax, is similar to FORTRAN. The
language, ANSYS Parametric Design Language (APDL), obviously doesn't have the overall
scope and power of FORTRAN, however, it does enable complex processes to be carried
out. APDL has developed over its relatively short life, and can now access a large
portion of the data held on the ANSYS database (.db) and results files, (.rst,
etc.). It is for instance possible to make modelling or solution discussions based
upon the results of a previous analysis, on previous modelling activities, or on partial
solutions. APDL allows the
capability of ANSYS to be extended without the complexity of understanding the ANSYS
program data structures, which is necessary if you are using high level languages such as
FORTRAN or "C". Further, for some of the high level programmed extensions,
re-linking of the ANSYS program can be necessary, requiring the purchase of compatible
compilers and risking all of the QA implications of changing the program.
APDL is essentially an interpreted language,
therefore, its main drawback is that it is slow and can seriously affect solution times.
Engineers at CREA Consultants
(CREA) have many years of experience in using APDL, (from its inception in fact),
and we can provide macro programming services, or provide advice on how to use APDL. |
Parametric
Modelling |
| Using APDL for modelling allows generic models to
be built. Such models are of significant advantage if a series of analyses are to be
performed, for say differences in geometries or parametric studies. Using APDL it is
possible to set up a table of values, or to pass arguments to a macro, which influence the
manner in which the model is built, influence material properties or boundary
conditions. APDL parameters can also be set from the ANSYS command line, allowing
batch running of problems with varying properties. The macro language does not have to be used in a macro file, with a few
exceptions, all macros commands are available in either batch or interactive input
streams. In a batch input, it is possible to use the macro branching commands to
alter the path through the input stream, allowing modelling discussions to be
automated. Calling macros from an input stream allows repetitive tasks to be
programmed once, then repeated, and isolates complex tasks to ease development and
checking. Macros can also be made available system or network wide, thus allowing
common tasks to be standardised across the organisation. |
Solution
Control |
| Using APDL to control a solution allows the user
to change the operation of the solver as the solution progresses. APDL also allows
the solver to be run in a parametric manner. For instance setting solver controls by
using parameters allows the user to try different solution settings when solving complex
non-linear problems. In multi-phase
solutions, APDL can be used to pass information between phases or between different
solution types. For example, from a modal solution to a transient solution.
APDL can also be used to control birth and death,
vary loading, time-steps, iteration controls, and much more. |
Post
Processing |
| APDL is ideal for customising
post-processing. It has access to the majority of the results and geometry
databases, it can therefore be used to calculate results that ANSYS does not calculate as
a matter of course. Coupled with careful model building, such as the grouping of
elements and the use of components, complex relationships can be derived, tested and in
many instances plotted. Using the "etable" capability, new stress items
can be derived. It is also possible to alter the results database, something that is
carried out at the users own risk. APDL
can be used for code checking, thus allowing the program to operate in
different engineering fields where the design codes are used in different ways, or where
different Country codes are to be used.
Results can be stored in the APDL parameters and
passed on to future pre-processing, post-processing and solution phases, allowing complex
modelling or data comparisons to be made. (See also Design
Optimisation/What if? Studies) |
Code
Checking |
| Running super complex, detailed FE solutions is
one thing, getting the results past the regulator is another. For many designs it is
necessary to demonstrate that the design complies with various National and International
codes of practice, or with a clients own design code. ANSYS is equipped for some
code checking to ASME and ANSI standards, but this is about all that is hard coded.
APDL can be used to carry out design code checks and thus to produce tables of factors of
safety, identify over-stressed elements, and much more. By using macros for the code
checking, then different code requirements can be used for different analyses. CREA has experience in the
writing of code checking macros for use in design or for use within the solution being
performed. |
Design
Optimisation/What if? Studies |
| Design optimisation is one of the most useful
auxiliary features of ANSYS. It can be used in many ways to improve designs.
Primarily designed to optimise designs, by repetitively running an analysis with
automatically varying parameters, the intention is that an optimum design is
achieved. Here the program will compare results from the analysis,
and results of design code checks to defined allowable limits to
establish variations to defined design parameters. These parameters are varied
between set limits to produce a viable design, or to indicate that a design is not
possible. The level of control passed to the program is fully within the control of
the analyst. The design optimisation
process is essentially a looping process, and the process can be fully controlled by the
user. Once the process is complete, it is possible to graph the variations of
optimisation parameters. This makes it an ideal tool for What If? and parametric
studies, where features are varied and the various results are compared. The
comparisons can then be graphed or further manipulated by APDL.
CREA have experience in the use of the design optimisation procedures to carry out
many analysis tasks, for instance:
- Design optimisation
- Automated parametric studies
- De-tuning of structures
- Trouble shooting designs
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