Nastran or Samcef with Python, Ruby, VBA, C#, excel...

FeResPost A Library distributed under LGPL license that allows you to automate the post-processing of Nastran and Samcef finite element results or FE model manipulations with the programming language of your choice (Python, Ruby, C++, C, C#, VBA in excel...)
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FeResPost library description

FeResPost library

FeResPost is a library that allows you to read Nastran and Samcef finite element models and results, and to automate post-processing operations.

Depending on the programming language being used (Ruby, Python, VBA, C#, C++...), FeResPost allows to program a wide variety of programs ranging from small scripts to large programs containing user-defined Classes and Modules, and allow to perform complex operations.

(The scripting capability of FeResPost can be very useful to automate simple tasks as automating the creation of connections, modifying element properties, creating temperature or force fields...)

Structural analysis

The structure analysis of complex structures often leads to repetitive tasks. This is related to :

The nature of the structure that is being analysed. Identical or similar components are often present several times, and sometimes many times, in the same structure (beams, panels, interfaces, connections...). These different parts or components are generally justified exactly the same way, and the corresponding calculation is often automated (with a programming language, excel...).
A structure is rarely sized for a single event, or checked again a single requirement. Generally, for static analysis, numerous load case are defined to ensure that the structure's strength is sufficient to sustain severel events in its life. This means that for each component, or each type of failure mode, the calculations is often done as many times as the number of defined load cases.
During the development of the structure, the design will be updated several times. Sometimes, several versions of a structure may be justified simultaneously, or consecutively. (Think, for example, at the different versions of the B737 Boeing or A320 Airbus planes that are flying nowadays.) This also contribute to the repititiveness of structural analysis calculations.

This explains why engineers involved in structural analysis are often also programmers. The need for automation leads them to use spreadsheets, use third party programs to accelerate the justification, or write its own post-processing programs. FeResPost can help in the development of these small programs!

How can FeResPost help?

The main purpose of the program is to download and manipulate Result entities in order to calculate margins of safety. Possible operations that can be performed on ``Result'' objects are, for example :

Extraction of the Results corresponding to a group of elements or nodes.
Modification of the reference coordinate system,
Calculation of total force and moment corresponding to a distribution of loads,
Derivation of criteria like Von Mises for a stress tensor, the norm of a vectors, the eigen-values and corresponding eigen-vectors for tensorial results...
Operations combining several results (sum, difference, product, merging of Results...),
Derivation of new Results (for example, laminated Results),
Extraction of maximum or minimum values, and corresponding finite element entities (elements, nodes...),
...

So far, these results can be read from Nastran HDF5, XDB or OP2 files, or from Samcef DES/FAC files. The corresponding finite element models can also be important from Nastran Bulk BDF files, or Samcef Bacon DAT files.

The groups of elements and nodes can be read from Samcef DAT or Patran session files. Manipulation of these Groups, by addition, substraction, intersection, associations are possible.

FeResPost allows the simultaneous manipulation of several models by defining several NastranDb and SamcefDb objects, and different Nastran and Samcef models can be manipulated simultaneously.

FeResPost also allows the calculation of composite structure by providing severeal classes for the Classical Laminate Analysis (CLA). Among other things, the CLA classes of FeResPost allow to :

Evaluate Laminate properties (equivalent moduli, stiffness and compliance matrices, coefficient of thermal expansion).
Calculate laminate analysis response corresponding to a specified loading (laminate loads and deformation, ply stresses and strains,...)
Evaluate laminate strength by calculating different failure criteria.
...

The CLA classes can be used separately from the finite element results, but also used together with finite element results. This allows for example to:

Calculate, at post-processing level, with a single command, the laminate response using shell forces, moments, temperatures on a large set of elements.
Do this calculation with the finite element model laminates, or with different laminates,
Estimate failure criteria that are now proposed by the finite element solver being used...

Who should use FeResPost?

The purpose of FeResPost is to automate post-processing operations by programming scripts. This means that FeResPost users must be ready to program his (or her) scripts. Fortunately, several programming languages and environments allow to use FeResPost (Ruby, Python, VBA, C#, C++...).

Some of the examples may give users the feeling that FeResPost provide tools that allow to perform complex operations without programming. It is sometimes true (excel examples). However, the user should keep in mind that those are just examples, and that there is a benefit in understanding how they work. In the case of excel examples, this means that the reading of documentation, the analysis of VBA code, and the testing of code and worksheet modifications will allow significant improved of what is provided.

Those who are not interested or alergic to programming should either "sub-contract" the programming work to their methodology service, or choose Nastran interactive pre- and post-processor (Patran, Femap, Hyperworks, NX...)

FeResPost library Classes and Modules

The library provides an access to 7 classes and 2 module allowing the manipulation of FE entities and results. The 7 classes are :

The ``DataBase'' class that is used to store a FE model and other entities (Groups, Results,...). This class is a generic class that can not be instanciated. Two classes inherit the DataBase class:
The ``NastranDb'' class that is used for the manipulation of Nastran models and Results.
The ``SamcefDb'' class that is used for the manipulation of Samcef models and Results.
The ``Result'' class that allows the manipulation of Results, thier transformation,...
The ``ResKeyList'' class, very useful to manipulate Result entities.
The ``Group'' class that allows the definition of Groups, thier manipulation, the extraction of Results on small parts of the structure.
The ``CoordSys'' class for the manipulation of coordinate systems.

The ``Post'' module gives access to several additional functions.

Four classes used to perform Classical Laminate Analysis calculations are also provided:

The ``ClaDb'' class that stores composite entities,
The ``ClaMat'' class used to mainpulate materials,
The ``ClaLam'' class to store laminates and perform CLA calculations
The ``ClaLoad'' class used to manipulate loadings applied to Laminates.

The CLA classes are interfaced with the rest of FeResPost and allow to post-process very efficiently composite finite element Results.

The program is mainly written in C++, and different wrappings are proposed around the C++ code (Ruby, Python, COM and .NET). This solution ensures that the program is easy to manage and that the program remains efficient because costly operations are done at C++ level (compiled language efficiency).