×
INTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS

Are you an
Engineering professional?
Join Eng-Tips Forums!
• Talk With Other Members
• Be Notified Of Responses
• Keyword Search
Favorite Forums
• Automated Signatures
• Best Of All, It's Free!

*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail.

#### Posting Guidelines

Promoting, selling, recruiting, coursework and thesis posting is forbidden.

# Extracting matrices from MSC Nastran/Patran (Circulatory, mass, stiffness, gyroscopic)

## Extracting matrices from MSC Nastran/Patran (Circulatory, mass, stiffness, gyroscopic)

(OP)
I am currently using Nastran rotor dynamics for my thesis and require the following matrices to be extracted:
[KC]R = Circulatory matrix due to damping in rotating frame.
[KC]S = Circulatory matrix due to damping in fixed frame.
[G] = Gyroscopic Matrix.
[K] = Stiffness matrix.
[M] = Mass matrix.

### RE: Extracting matrices from MSC Nastran/Patran (Circulatory, mass, stiffness, gyroscopic)

May I ask which Nastran? MSC?

DG

### RE: Extracting matrices from MSC Nastran/Patran (Circulatory, mass, stiffness, gyroscopic)

Sorry, you put MSC Nastran in the title of your post and I didn't catch it right away.

Look in the MSC Nastran Rotordynamics User’s Guide in the chapter "Theoretical Formulation"; there you will find the equations for a fixed and a rotating reference frame along with the circulatory and gyroscopic terms for which you are looking. This will help fix the nomenclature of the different rotor specific terms.

Now you will need to use some DMAP to obtain the various matrices you need. DMAP is a macro like language that allows you to change or add to the solution steps carried out by MSC Nastran. It is Fortran like, but also has a number of quirks specific to the language.

First, create a rotor model, one defined in a fixed frame and one defined in a rotating frame of reference. If you want circulation terms generated for things like bearing stiffness (which are part of the stator), define a stator as well, otherwise a boundary condition will suffice. Run this model in a solution sequence that generates the various items you are looking for (something like SOL 107 to extract the complex eigenvalues of the rotor) and make sure there are no errors in the run.

Write DMAP alters to add some instructions, probably to subDMAP GYROMAT. This subDMAP is where most of the rotor specific matrices are generated. You can write the various matrices to one or more different files.

1. The pch file (in DMIG format) - this is ASCII, human readable and generates MSC Nastran bulk data DMIG entries which contain the matrix data
2. An op2 (OUTPUT2) file - this can be a binary or ASCII encoded and not human readable; you will need a program (python, C, Fortran,...) to read the data and make it available in human readable form.
3. An op4 (OUTPUT4) file - this can be a binary (not human readable) or ASCII (human readable) file; you will need a program (python, C, Fortran,...) to read the binary data and make it available in human readable form.
4. An HDF5 file - this is a binary file and will need pytables + python, or clever C, to read the data and make it available in human readable form. An HDF5 viewer will assist in this.

If you don't know how to write DMAP alters, you are going to need some help to do this, and it is going to be an uphill journey. Decide on the items above and come back here for help with your input file.

DG

#### Red Flag This Post

Please let us know here why this post is inappropriate. Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework.

#### Red Flag Submitted

Thank you for helping keep Eng-Tips Forums free from inappropriate posts.
The Eng-Tips staff will check this out and take appropriate action.

#### Resources

Low-Volume Rapid Injection Molding With 3D Printed Molds
Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. Download Now
Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a partâ€™s function at the center of their design considerations. Download Now
Taking Control of Engineering Documents
This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. Download Now

Close Box

# Join Eng-Tips® Today!

Join your peers on the Internet's largest technical engineering professional community.
It's easy to join and it's free.

Here's Why Members Love Eng-Tips Forums:

• Talk To Other Members
• Notification Of Responses To Questions
• Favorite Forums One Click Access
• Keyword Search Of All Posts, And More...

Register now while it's still free!