An Experimental Method for Stereo-DIC Measurement of Large-Scale Thin-Film Structures

Abstract

Background

Due to their flexible configuration and lightweight characteristics, film structures have gained significant attention in the field of aerospace engineering. The scales of film structures typically range from several meters to over ten meters. Stereo-digital image correlation (stereo-DIC) methods offer distinct advantages for obtaining full-field measurement results. However, challenges persist in fabricating high-quality speckle patterns and addressing the problem of imaging reflections, particularly for large-scale transparent or semi-transparent film structures.

Objective

This paper presents an experimental measurement method for large-scale, transparent thin-film structures. The method focuses on fabricating high-quality digital speckle patterns without altering the vibration characteristics of thin film, as well as addressing the problem of imaging reflections.

Methods

A combined large-scale backlighting system and transmission imaging are introduced to solve the problem of reflections. To avoid altering the characteristics of the thin film, a single-particle transfer printing technique is developed. A large umbrella thin-film structure with a diameter of 6 meters is selected to validate the effectiveness of the proposed method. The structure is composed of multiple steel trusses and fan-shaped films.

Results

With high-quality speckle patterns and solving the problem of reflections, the full-field displacement results of the umbrella thin-film structure are measured. The first-order and second-order natural frequencies along with corresponding mode shapes are further obtained.

Conclusion

The effectiveness of the experimental method is demonstrated through rotational and vibration tests conducted on the large umbrella thin-film structure. This method provides a powerful means for studying the mechanical behavior and vibration characteristics of large-scale thin-film structures.