Detecting Cracks on Plates using Reflections of Fundamental Symmetric and Anti-symmetric Lamb Waves from Defect

Title:Detecting Cracks on Plates using Reflections of Fundamental Symmetric and Anti-symmetric Lamb Waves from Defect

Volume: 19 Issue: 5

Author(s): Xuexin Li*, Yu Zhang, Qi Jing and Xinhan Zhang

Affiliation:

• National Engineering & Technology Research Center for Disaster & Rescue Equipment, Army Logistics Academy, Chongqing, China

Keywords: Lamb wave, steel plate, crack detection, defect reflection, finite element, dispersion.

Abstract:

Introduction: Ultrasonic Lamb waves can achieve long-range inspection on plate-like structures and can even detect unreachable cracks and defects. There are multiple modes under a certain generation frequency with most of them dispersive.

Method: The dispersion curves of Lamb wave in a steel plate were given by numerical calculation. A 2-D finite element (FE) model of a steel plate was promoted. The fundamental symmetric and antisymmetric Lamb waves were generated by uploading symmetrical and anti-symmetrical displacements on one side of the plane. The wave reflects when it comes across the defect and the edge of the plate. Mode conversion will occur after the asymmetrical discontinuities of the structure.

Result: The theoretical and numerical results of the values of group velocities of S₀ and A₀ in a steel plate show well agreement. The maximum amplitude of the converted A₀ wave from the interaction of the incident S₀ wave with the cracks was observed. The amplitude will first rise then fall under any depth of the defects. The relationship between the defect reflection and the length as well as the depth of defects were simulated based on the FE model. Phase reversion and phase delay were discovered by controlling the defect size changing in one dimension. The reflection coefficient increases linearly with the defect length while the depth is constant, as well as the defect depth while the length is constant.

Conclusion: Experiments on steel plates with artificial defects including thorough holes and tapered holes were carried out using ISONICA STAR. The results also show that when the defect size changes in one dimension such as the thorough holes, the reflection coefficient increases linearly correspondingly. However, the testing results of the taper holes were inconsistent with the regulation as the size increases in both the length and the depth.

Cite this article as:

Li Xuexin*, Zhang Yu, Jing Qi and Zhang Xinhan, Detecting Cracks on Plates using Reflections of Fundamental Symmetric and Anti-symmetric Lamb Waves from Defect, Recent Patents on Engineering 2025; 19 (5) : e150324228039 . https://dx.doi.org/10.2174/0118722121290852240308100436