An integral part of the flight verification process for a spacecraft is achieved through validation of the finite element model of the spacecraft structure. Modal survey testing is the method used to meet this requirement.
This course provides an in-depth look at modal survey testing of spacecraft systems and subsystems. Emphasis is on the practical aspects of test planning, execution, data analysis and
post-test data processing. The techniques discussed will provide the attendee with the
necessary tools to produce a set of verified natural frequencies and mode shape vectors that represent the mass and stiffness of the spacecraft in the test configuration.
Course logistics, Overview & Outline
Normal mode theory & description of the modal technique
3. Pre-test Analysis
Instrumentation and excitation locations, frequency range and modal density
4. Boundary Conditions
Quantifiable method to support / restrain structure
Accelerometers, force gages as well as alternative methods
6. Facilities and Support Equipment
Mechanical and electrical requirements
7. Data Acquisition
Hardware, software, data recording, sampling and dynamic range, noise and other problems
8. Spectrum Analysis of Recorded Test Data
FFT & Frequency Response Analysis
9. Structural Excitation Techniques
Discussion of available methods of structural excitation considering nonlinearities and modal density
10. Modal Analysis of Spectral Data
Methods of turning spectra response data into modal frequencies and deformation vectors.
11. Post Processing and Animation of Results
Making sense of modal frequencies and deformation vectors using graphical animation and correlation.
12. Verification of Modal Test Results
Gaining confidence in modal test results based on re-synthesis of spectra , Modal Assurance Criteria and graphical animation
13. Overview of Finite Element Model Correlation
Practical look at how test data is used to fine tune finite element models
14. Alternative Uses for Modal Testing
Many common (and not so common) issues that can degrade modal test data quality.
15. Avoiding Common Modal Test Problems
Response Location Problems
Test Setup Problems
Pitfalls in Data Acquisition, Processing
Practical Considerations and Tips
16. The Test Plan
17. Modal Test Demonstration
Data acquisition & processing on a test structure