Session: 10-01: Nonlinear Ultrasonic Techniques for NDE I

Paper Number: 135199

135199 - Amplifying Nonlinear Ultrasonic Signatures for Fatigue Damage Detection via a Graded Elastic Meta-Enhancer 

Abstract: 

Fatigue cracks pose a significant threat to engineering structures due to their inconspicuous nature and difficulty in detection. Hence, the development of effective methodologies for detecting fatigue cracks holds paramount importance. Among the current solutions, ultrasonic inspection technology has emerged as a promising approach. In contrast to linear ultrasonic techniques, which primarily detect major defects, the nonlinear counterpart exhibits a higher sensitivity to the onset of fatigue cracks, and has garnered increased attention within the Structural Health Monitoring (SHM) and Nondestructive Evaluation (NDE) communities. However, for the nascent stage of fatigue crack growth, the nonlinear attributes are faint and challenging to discern and characterize, thereby compromising the practical effectiveness of the detection methodology. Consequently, the amplification of these subtle nonlinear features becomes imperative to improve the detection efficiency. Conversely, elastic metamaterials, comprising artificially engineered structures, have demonstrated considerable potential in controlling wave modes and frequencies. Leveraging the metamaterial concept, this paper proposes a wave modulating device termed a meta-enhancer (ME), showcasing the improvement of sensitivity in detecting fatigue cracks.

In this study, an elastic ME featuring special wave dispersion properties is meticulously designed to facilitate effective wave collection for second higher harmonic through a graded array of resonators attached to an elastic plate. The amalgamation of resonance and spatial grading within surface arrays of structures enable meta-units to demonstrate broadband wave trapping, resulting in substantial amplification of out-of-plane displacement within the host plate medium at resonator positions, where the second higher harmonic component accumulates. A straightforward implementation involves employing a series of rod resonators with increasing height, effectively engaging the motion of the A₀ mode within the plate foundation. This induction causes a wavenumber transformation along the structure, accompanying an amplitude reduction in the rods coupling with a notable amplification within the waveguide. Harnessing the interplay of these effects — deceleration in the resonators and amplification in the host beam — the numerical and experimental findings demonstrate that, given a sufficiently prolonged excitation time, the elastic ME can amplify the faint magnitude of the second higher harmonic produced by fatigue cracks within the host plate structure. The suggested capability for wave energy enhancement using the elastic metamaterial exhibits promising potential for future applications of nonlinear ultrasonic technique within the SHM and NDE communities. The paper concludes with a summary, concluding remarks, and recommendations for future research directions.

Presenting Author: Yiran Tian Shanghai Jiao Tong University

Presenting Author Biography: Yiran Tian is working as a postdoc at University of Michigan-Shanghai Jiao Tong University Joint Institute in China. He graduated from Shanghai Jiao Tong University in 2023 and received his PhD degree. Currently, he is working with his adviser Dr. Yanfeng Shen and doing his research work in AMIS laboratory. His research interests cover elastic metamaterials, structural health monitoring, guided waves, and nonlinear ultrasonics.

Authors:

Yiran Tian Shanghai Jiao Tong University
Haoyu Fu Shanghai Jiao Tong University
Yanfeng Shen Shanghai Jiao Tong University