NASTRAN, a powerful finite element analysis (FEA) software, utilizes include files to manage and organize large and complex models. These files enhance code reusability, improve readability, and simplify the modification process. However, understanding the different types and purposes of these files is crucial for efficient and effective model creation. This article delves into the various types of include files in Nastan, explaining their functionality and best practices for their implementation.
What are Include Files in Nastran?
In essence, include files in NASTRAN act as modular components. They contain blocks of NASTRAN commands, such as element definitions, material properties, or boundary conditions, which can be incorporated into the main input deck. This modular approach promotes better organization, reduces redundancy, and facilitates easier model modification and management. Instead of repeating the same code segments multiple times, you simply include the relevant file.
Types of Include Files and Their Usage
NASTRAN doesn't explicitly define "types" of include files in the way some programming languages might. The "type" is determined by the content of the file. However, we can categorize them based on their common usage:
1. Bulk Data Include Files
These are the most common type of include file. They contain Bulk Data entries, which define the model's geometry, element properties, material properties, and loading conditions. These files are often used to:
- Organize model components: Separate files can be created for different parts of the model (e.g., a file for the wing, another for the fuselage). This improves readability and maintainability.
- Reuse model components: Once created, a Bulk Data include file can be reused in multiple analyses. This saves time and reduces errors.
- Manage complex models: For extremely large models, breaking them into smaller, manageable include files is essential for efficient processing.
2. Executive Control Section Include Files
While less frequent than Bulk Data include files, these files can contain portions of the Executive Control Section. This section dictates the overall analysis process, including solution sequences and output requests. Separating parts of this section into include files can be useful for:
- Parameterization: Include files can contain parameters that control the analysis, allowing for easy modification without altering the core code.
- Modular Analysis: Specific analysis steps, like pre-processing, solution, or post-processing, can be modularized and managed through separate include files.
3. User-Defined Subroutines and Functions
Although not strictly "include files" in the same way as the above, user-defined subroutines and functions, written in FORTRAN or other compatible languages, can be linked to the NASTRAN analysis. These are crucial for:
- Custom Element Development: Creating and implementing custom finite elements to model unique phenomena.
- Advanced Post-processing: Developing specialized post-processing routines for specific analysis requirements.
- Automation: Creating scripts to automate repetitive tasks.
Best Practices for Using Include Files
- Descriptive filenames: Use clear and descriptive filenames to easily identify the contents of each file (e.g.,
wing_geometry.dat,material_properties.dat). - Consistent formatting: Maintain a consistent formatting style within your include files to improve readability.
- Version control: Use a version control system (like Git) to track changes to your include files and manage different versions of your models.
- Error handling: Implement robust error handling mechanisms to catch errors early in the analysis process.
- Documentation: Thoroughly document your include files, explaining the purpose and content of each file.
How to Include Files in a NASTRAN Deck
The inclusion of a file typically uses a directive such as INCLUDE or a similar command depending on the specific NASTRAN version. The exact syntax is specified in the NASTRAN documentation for your version. The command usually involves specifying the path to the include file.
By effectively utilizing include files, engineers and analysts can dramatically enhance the organization, modularity, and efficiency of their NASTRAN models, especially those of significant size and complexity. Remember to consult the NASTRAN documentation for precise syntax and details pertinent to your software version.
