Next Article in Journal
Comparative Experimental Study of a High-Temperature Raman-Based Distributed Optical Fiber Sensor with Different Special Fibers
Next Article in Special Issue
Design, Fabrication, and Evaluation of Multifocal Point Transducer for High-Frequency Ultrasound Applications
Previous Article in Journal
Discrimination of Two Cultivars of Alpinia Officinarum Hance Using an Electronic Nose and Gas Chromatography-Mass Spectrometry Coupled with Chemometrics
Previous Article in Special Issue
Dual-Modal In Vivo Fluorescence/Photoacoustic Microscopy Imaging of Inflammation Induced by GFP-Expressing Bacteria
Article Menu
Issue 3 (February-1) cover image

Export Article

Open AccessArticle

Laser Ultrasound Inspection Based on Wavelet Transform and Data Clustering for Defect Estimation in Metallic Samples

1
Physics Department, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 22, 08222 Terrassa, Barcelona, Spain
2
Electronic Engineering Department, Universitat Politècnica de Catalunya, Rambla Sant Nebridi 22, 08222 Terrassa, Barcelona, Spain
*
Author to whom correspondence should be addressed.
Sensors 2019, 19(3), 573; https://doi.org/10.3390/s19030573
Received: 22 December 2018 / Revised: 14 January 2019 / Accepted: 24 January 2019 / Published: 30 January 2019
(This article belongs to the Special Issue Ultrasound Transducers)
  |  
PDF [2385 KB, uploaded 30 January 2019]
  |  

Abstract

Laser-generated ultrasound is a modern non-destructive testing technique. It has been investigated over recent years as an alternative to classical ultrasonic methods, mainly in industrial maintenance and quality control procedures. In this study, the detection and reconstruction of internal defects in a metallic sample is performed by means of a time-frequency analysis of ultrasonic waves generated by a laser-induced thermal mechanism. In the proposed methodology, we used wavelet transform due to its multi-resolution time frequency characteristics. In order to isolate and estimate the corresponding time of flight of eventual ultrasonic echoes related to internal defects, a density-based spatial clustering was applied to the resulting time frequency maps. Using the laser scan beam’s position, the ultrasonic transducer’s location and the echoes’ arrival times were determined, the estimation of the defect’s position was carried out afterwards. Finally, clustering algorithms were applied to the resulting geometric solutions from the set of the laser scan points which was proposed to obtain a two-dimensional projection of the defect outline over the scan plane. The study demonstrates that the proposed method of wavelet transform ultrasonic imaging can be effectively applied to detect and size internal defects without any reference information, which represents a valuable outcome for various applications in the industry. View Full-Text
Keywords: laser ultrasound; damage visualization; spectral signal processing; ultrasound propagation; time of flight; wavelet transform; non-destructive testing laser ultrasound; damage visualization; spectral signal processing; ultrasound propagation; time of flight; wavelet transform; non-destructive testing
Figures

Figure 1

This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).
SciFeed

Share & Cite This Article

MDPI and ACS Style

Selim, H.; Delgado Prieto, M.; Trull, J.; Romeral, L.; Cojocaru, C. Laser Ultrasound Inspection Based on Wavelet Transform and Data Clustering for Defect Estimation in Metallic Samples. Sensors 2019, 19, 573.

Show more citation formats Show less citations formats

Note that from the first issue of 2016, MDPI journals use article numbers instead of page numbers. See further details here.

Related Articles

Article Metrics

Article Access Statistics

1

Comments

[Return to top]
Sensors EISSN 1424-8220 Published by MDPI AG, Basel, Switzerland RSS E-Mail Table of Contents Alert
Back to Top