How do you validate and update your modal parameters from experimental data?

Last updated on Sep 26, 2024

Modal analysis and vibration testing are essential tools for aircraft design, as they help you identify and avoid potential resonance problems, optimize structural performance, and validate your numerical models. But how do you validate and update your modal parameters from experimental data? In this article, you will learn the basic steps and methods for modal parameter estimation, validation, and updating.

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If you’re looking to learn more about modal analysis and vibration testing, there are many resources online to explore, such as books, journals, courses, webinars, or tutorials. For example, Modal Testing: Theory, Practice and Application by D. J. Ewins; Modal Analysis by Zhi-Fang Fu and Jimin He; Experimental Vibration Analysis for Civil Structures: Testing, Sensing, Monitoring, and Control by Joel P. Conte and Rodrigo Astroza; Modal Analysis Topics by The Modal Shop; or Introduction to Modal Analysis by Brüel & Kjær.

Propose using Craig-Bampton reduction to create reduced-order models for complex structures like aircraft, which speeds up the iterative process of model updating. In a full-aircraft vibration study, the initial high-fidelity model was computationally expensive to update after each experimental validation. By reducing the model using Craig-Bampton techniques, we retained the critical dynamic characteristics while significantly reducing the computational load, allowing us to make updates 40% faster while maintaining accuracy. This approach is particularly useful when handling large-scale models, ensuring efficient validation without sacrificing detail.

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Validating & updating modal parameters from experimental data is a meticulous process:- Case Study - The Millennium Bridge in London experienced unexpected swaying on opening day. Engineers used experimental data to update the bridge's modal parameters, pinpointing the synchronisation of pedestrian footsteps as the cause. Insight - In automotive industries, companies like BMW perform modal analysis during crash tests. They update their vehicle models based on the data, enhancing safety features. Example - Aerospace firms, such as Boeing, conduct ground vibration tests on new aircraft. The data collected helps validate & refine their computational models, ensuring the aircraft's structural integrity & performance.

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