Warped-wigner-hough transformation of lamb waves for automatic defect detection

2011 ◽  
Author(s):  
Alessandro Perelli ◽  
Luca De Marchi ◽  
Emanuele Baravelli ◽  
Alessandro Marzani ◽  
Nicolo Speciale
Keyword(s):  
Defect Detection ◽  
Lamb Waves ◽  
Hough Transformation

scholarly journals Defects Detection and Localization in Underwater Plates Using Laser Laterally Generated Pure Non-Dispersive S0 Mode

2019 ◽  
Vol 9 (3) ◽  
pp. 459 ◽  
Author(s):  
Qingnan Xie ◽  
Chenyin Ni ◽  
Zhonghua Shen
Keyword(s):  
Defect Detection ◽  
Lamb Waves ◽  
Mode Conversion ◽  
High Sensitivity ◽  
Laser Source ◽  
Dispersion Characteristics ◽  
High Attenuation ◽  
Corrosion Defects ◽  
Detection And Localization ◽  
Lateral Excitation

When working in humid environments, corrosion defects are easily produced in metallic plates. For defect detection in underwater plates, symmetric modes of Lamb waves are widely used because of their characteristics including long propagating distance and high sensitivity to defects. In this study, we extend our previous work by applying the laser laterally generated S0 mode to detection and localization of defects represented by artificial notches in an aluminum plate immersed in water. Pure non-dispersive S0 mode is generated in an underwater plate by lateral laser source irradiation and its fd (frequency·thickness) range is selected by theoretical calculation. Using this lateral excitation, the S0 mode is enhanced; meanwhile, the A0 mode is effectively suppressed. The mode-converted A0 mode from the incident S0 mode is used to detect and localize the defect. The results reveal a significantly improved capability to detect defects in an underwater plate using the laser laterally generated S0 mode, while that using A0 is limited due to its high attenuation. Furthermore, owing to the long propagating distance and the non-dispersion characteristics of the S0 generated by the lateral laser source, multiple defects can also be detected and localized according to the mode conversion at the defects.

Extension of Lamb Waves Defect Location Techniques to the Case of Low Power Excitation by Compressing Chirped Interrogating Pulses

2013 ◽  
Vol 569-570 ◽  
pp. 940-947
Author(s):  
Luca de Marchi ◽  
Nicola Testoni ◽  
Alessandro Perelli ◽  
Alessandro Marzani
Keyword(s):  
Signal Processing ◽  
Structural Health Monitoring ◽  
Low Power ◽  
Defect Detection ◽  
Health Monitoring ◽  
Lamb Waves ◽  
Signal Processing Algorithm ◽  
Imaging Algorithm ◽  
Passive Networks ◽  
Time Waveform

In this work a signal processing algorithm for Lamb waves based defect detection/localization procedures is proposed. In particular, the proposed signal processing allows active-passive networks of piezosensors to use chirp shaped pulses in actuation, instead of classically applied spiky pulses. Thus, defect detection/localization can be achieved by using low power voltages in actuation. Basically, the proposed processing is capable to compensate the acquired time-waveforms from the dispersion due to the traveled distance as well as to compress the additional pulse spreading due to the chirp actuation. A processed time-waveform is thus directly transformed into a distance of propagation. Next, the compensated and compressed signals are exploited to feed an imaging algorithm aimed at providing the position of the defect on the plate. As a result, an automatic detection procedure to locate defect-induced reflections is demonstrated and successfully tested by analyzing experimental Lamb waves propagating in an aluminum plate. The proposed method is suitable for defect detection and can be easily implemented in real applications for structural health monitoring.

Beam Forming of Lamb Waves for Nondestructive Testing of Plates

2014 ◽  
Vol 490-491 ◽  
pp. 1512-1516
Author(s):  
Qing Zeng Ma ◽  
Jing Pin Jiao ◽  
Ping Hu ◽  
Jing Yang
Keyword(s):  
Experimental Data ◽  
Phase Shift ◽  
Defect Detection ◽  
Lamb Waves ◽  
Optimization Technique ◽  
Beam Forming ◽  
Acoustic Beam ◽  
Transducer Array ◽  
Wide Range ◽  
Weighted Optimization

For wide range defect detection in plate, acoustic beam optimization technique was investigated. The synthesis wave field obtained from the basic phased-addition is prone to be influenced by the noise and the resolution is low. To improve the performance of beam forming of array, the synthesis acoustic field is processed with amplitude weighting. The experimental data have been processed with phase shift and amplitude weighted optimization. It is shown that the proposed beam forming technique with transducer array can recognize the features in plate.

DEFECT DETECTION ON CARBON FIBRE REINFORCED PLASTICS (CFRP) WITH LASER GENERATED LAMB WAVES

2011 ◽  
Author(s):  
O. Focke ◽  
P. Huke ◽  
A. Hildebrandt ◽  
Donald O. Thompson ◽  
Dale E. Chimenti
Keyword(s):  
Carbon Fibre ◽  
Defect Detection ◽  
Lamb Waves ◽  
Reinforced Plastics ◽  
Carbon Fibre Reinforced Plastics
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