Scanning laser vibrometry imaging of fatigue cracks via nonlinear ultrasonic guided wave scattering and mode conversion

Yanfeng Shen; Mingjing Cen; Wu Xu

doi:10.1117/12.2514324

1 April 2019 Scanning laser vibrometry imaging of fatigue cracks via nonlinear ultrasonic guided wave scattering and mode conversion

Yanfeng Shen, Mingjing Cen, Wu Xu

Author Affiliations +

Proceedings Volume 10972, Health Monitoring of Structural and Biological Systems XIII; 109721I (2019) https://doi.org/10.1117/12.2514324
Event: SPIE Smart Structures + Nondestructive Evaluation, 2019, Denver, Colorado, United States

Abstract

This paper presents the Scanning Laser Vibrometry (SLV) imaging of fatigue cracks by taking advantage of the nonlinear ultrasonic guided wave scattering and mode conversion phenomena. The investigation starts with the numerical modeling using the Local Interaction Simulation Approach (LISA) to demonstrate the distinctive scattering and mode conversion features at rough fatigue cracks. During the wave crack interactions, nonlinear higher harmonics are generated from Contact Acoustic Nonlinearity (CAN). In addition, the microscale rough crack surface condition may introduce mode conversion between the symmetric and antisymmetric Lamb modes. After the theoretical analysis, SLV experiments are conducted on an aluminum plate, where fatigue cracks are nucleated from a rivet hole. The damage imaging scheme utilizes the post-processing techniques via Fast Fourier Transform (FFT), frequency domain filtering, and Inverse Fast Fourier Transform (IFFT) to eliminate the linear wave field, leaving only the scattered higher harmonics in the images. In this way, the fatigue cracks can be distinguished from structural features such as rivet holes and stiffeners. This paper finishes with summary, concluding remarks, and suggestions for future work.

Conference Presentation

Citation Download Citation

Yanfeng Shen, Mingjing Cen, and Wu Xu "Scanning laser vibrometry imaging of fatigue cracks via nonlinear ultrasonic guided wave scattering and mode conversion", Proc. SPIE 10972, Health Monitoring of Structural and Biological Systems XIII, 109721I (1 April 2019); https://doi.org/10.1117/12.2514324

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