Lamb Wave Ultrasonic System for Active Mode Damage Detection in Composite Materials (original) (raw)
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Sensors and Actuators A: Physical, 2005
In this work a new technology for designing and manufacturing ultrasonic interdigital transducers (IDT) is presented. The piezoelectric material used is a metallised piezopolymer film made of polyvinylidene fluoride (PVDF) with electrode pattern obtained with a laser ablation process. Piezopolymer transducer prototypes are designed with wavelength of 8 mm to operate with Lamb waves (symmetrical S 0 mode). An experimental validation of the piezopolymer IDT design is demonstrated with a transmitter-receiver IDT pair embedded in a 3 mm thick carbon fiber reinforced plastic (CFRP) composite laminate.
Piezo-composite transducer for mode and direction selectivity of Lamb waves
2018
Ultrasonic-based SHM (Structural Health Monitoring) applications commonly rely on the use of piezo-electric patches to emit and receive ultrasonic waves. The objective is to study the propagation of the waves through a structure to assess its structural integrity. Because of the elevated number of echoes and possible modes of propagation of the waves within the structure, those applications suffer from a burden of signal processing. This paper presents a composite piezo-electric patch that was designed and successfully tested for reducing the complexity of the SHM detection schemes by selecting the mode and direction of the Lamb waves received. The piezo-composite is composed of a row of eight independent ceramic pillars separated with polymer, so it is a 1-D matrix of independent piezo-patches. Used with adequate electronics and signal processing, it was shown that it allowed selecting the direction and the mode of the Lamb waves.
Direct-write piezoelectric ultrasonic transducers for impact damage detection in composite plates
2018
Internal damage in carbon-fibre reinforced polymer (CFRP) plates, induced by low velocity impact, becomes important to be detected and repaired before catastrophic failure happens. In this context, structural health monitoring (SHM) techniques have been developed that could monitor a structure over time by using a network of sensors. Discrete ultrasonic transducers made of piezoelectric lead zirconate titanate (PZT) ceramic, as currently widely used for SHM purpose, can generate and sense guided ultrasonic waves traveling in the structure. These waves are particularly affected by damage and discontinuities, but also by the anisotropy and complex structure of CFRP. Direct-write (DW) piezoelectric ultrasonic transducers have been developed on metallic structure for SHM to reduce transducers weight and profile for potential aircraft applications, to improve system reliability and to reduce the cost of introducing a large number of transducers, while they are directly produced during ma...
Sensors
This paper presents a method for measuring surface cracks based on the analysis of Rayleigh waves in the frequency domain. The Rayleigh waves were detected by a Rayleigh wave receiver array made of a piezoelectric polyvinylidene fluoride (PVDF) film and enhanced by a delay-and-sum algorithm. This method employs the determined reflection factors of Rayleigh waves scattered at a surface fatigue crack to calculate the crack depth. In the frequency domain, the inverse scattering problem is solved by comparing the reflection factor of the Rayleigh waves between the measured and the theoretical curves. The experimental measurement results quantitatively matched the simulated surface crack depths. The advantages of using the low-profile Rayleigh wave receiver array made of a PVDF film for detecting the incident and reflected Rayleigh waves were analyzed in contrast with those of a Rayleigh wave receiver using a laser vibrometer and a conventional lead zirconate titanate (PZT) array. It was...
Lamb wave transducers made of piezoelectric macro-fiber composite
Structural Control and Health Monitoring, 2012
During recent years, an intensive research activity concerning the application of Lamb waves (LWs) for SHM has been observed. LWs may be generated and sensed using different types of transducers, and their selection is essential for the SHM system's performance. Results of the investigation of three types of transducers based on macro-fiber composite (MFC) are presented in this paper; two types of commercially available MFC actuators are compared with a novel type of custom-designed interdigital transducer also based on the MFC substrate. After a short presentation of the piezoelectric transducer designed for SHM applications, details concerning the proposed interdigital transducer design are provided. Beampatterns of the investigated transducers are first compared using numerical FEM simulations, and next, the numerically obtained beampatterns are verified experimentally using laser vibrometry. In the final part of this paper, advantages and disadvantages of the investigated transducers are discussed.
Guided wave propagation in composite laminates using piezoelectric wafer active sensors
Piezoelectric wafer active sensors (PWAS) are lightweight and inexpensive transducers that enable a large class of structural health monitoring (SHM) applications such as: (a) embedded guided wave ultrasonics, i.e., pitch-catch, pulse-echo, phased arrays; (b) high-frequency modal sensing, i.e., electro-mechanical impedance method; and (c) passive detection. The focus of this paper is on the challenges posed by using PWAS transducers in the composite laminate structures as different from the metallic structures on which this methodology was initially developed. After a brief introduction, the paper reviews the PWAS-based SHM principles. It follows with a discussion of guided wave propagation in composites and PWAS tuning effects. Then, the mechanical effect is discussed on the integration of piezoelectric wafer inside the laminate using a compression after impact. Experiments were performed on a glass fiber laminate, employing PWAS to measure the attenuation coefficient. Finally, the paper presents some experimental and multi-physics finite element method (MP-FEM) results on guided wave propagation in composite laminate specimens.
Piezoelectric wafer active sensors for in situ ultrasonic-guided wave SHM
Fatigue & Fracture of Engineering Materials & Structures, 2008
A B S T R A C T In situ structural health monitoring aims to perform on-demand interrogation of the structure to determine the presence of service-induced damage and defects using nondestructive evaluation ultrasonic wave methods. Recently emerged piezoelectric wafer active sensors (PWAS) have the potential to significantly improve damage detection and health monitoring. PWAS are low-profile transducers that can be permanently attached onto the structure or inserted in between composite laminates, and can perform structural damage detection in thin-wall structures using guided wave methods (Lamb, Rayleigh, SH, etc.). This paper describes the analytical and experimental work of using PWAS-guided waves for in situ structural damage detection on thin-wall structures. We begin with reviewing the guided wave theory in plate structures and PWAS principles. The mechanisms of Lamb wave excitation and detection using PWAS is presented. Subsequently, we address in turn the use of PWAS to generate Lamb waves for damage (cracks and corrosion) detection in metallic structures. Pulse-echo, pitch-catch, phased array and time reversal methods are illustrated demonstrating that PWAS Lamb-waves techniques are suitable for damage detection and structural health monitoring. The last part of the paper treats analytically and experimentally PWAS excitation and tuning in composite materials. The research results presented in this paper show that in situ SHM methodologies using PWAS transducers hold the promise for more efficient, effective and timely damage detection in thin-wall structures.
Journal of Sensors, 2015
Interdigital transducers fabricated with piezopolymer film have been realized to excite ultrasonic Lamb waves in a composite laminate subjected to pure bending stresses. Lamb waves were generated and detected in a cross-ply [0°/90°] 4 mm thick carbon-fiber composite, by using two interdigital transducers in pitch-catch configuration. We demonstrate that the choice of the piezopolymer transducer technology is suitable for this type of investigation and the advantages of the proposed transducer assembly and bonding are described. A full set-up is described to determine the relationship between the time of flight of the recorded signals and the applied bending moment. Interdigital transducers were designed according to simulations of the dispersion curves, in order to operate at a central frequency of 450 kHz. This frequency corresponds to a central wavelength of 16 mm and to a group velocity of about 6000 m/s for the first symmetric guided wave mode. The variations in the time of flig...