Article

Mode-Selective Excitation and Detection of Ultrasonic Guided Waves for Delamination Detection in Laminated Aluminum Plates

Department of Civil Engineering and Engineering Mechanics, University of Arizona, Tucson, AZ, USA.
IEEE transactions on ultrasonics, ferroelectrics, and frequency control (Impact Factor: 1.51). 03/2011; 58(3):567-77. DOI: 10.1109/TUFFC.2011.1839
Source: PubMed

ABSTRACT

Selective modes of guided Lamb waves are generated in a laminated aluminum plate for damage detection using a broadband piezoelectric transducer structured with a rigid electrode. Appropriate excitation frequencies and modes for inspection are selected from theoretical and experimental dispersion curves. Dispersion curves are obtained experimentally by short time Fourier transform of the transient signals. Sensitivity of antisymmetric and symmetric modes for delamination detection are investigated. The antisymmetric mode is found to be more reliable for delamination detection. Unlike other studies, in which the attenuation of the propagating waves is related to the extent of the internal damage, in this investigation, the changes in the time-of-flight (TOF) of guided Lamb waves are related to the damage progression. The mode conversion phenomenon of Lamb waves during progressive delamination is investigated. Close matching between the theoretical and experimentally derived dispersion curves and TOF assures the reliability of the results presented here.

Download full-text

Full-text

Available from: Tribikram Kundu, Jan 21, 2016
  • Source
    • "In this method, time of flight (TOF) of guided waves, such as Lamb waves and surface acoustic waves, are extracted from multiple surface-mounted sensors. In recent studies, real-time structural health monitoring frameworks based on guided waves' TOF have evolved by using various types of active and passive sensors [7] [8] [9]. However, the Lamb-wave-based triangulation method imposes critical limitations in anisotropic structures due to the directional dependence of their dispersion relationship and the resultant variations of wave speed as a function of wave propagation directions. "
    [Show abstract] [Hide abstract]
    ABSTRACT: A new diagnostic method to identify the location and magnitude of external impact on a sandwich structure using granular crystal sensors was studied. The granular crystal sensors are composed of one-dimensional chains of spherical particles that are inserted in a thick core of the sandwich structure. Given an external impact, the embedded sensors generate compact-supported, highly nonlinear solitary waves resulting from the dispersive and nonlinear characteristics of granular crystals. In this study, the propagating mechanism of highly nonlinear solitary waves in relation to various impact conditions was investigated. Particularly, it was reported that the flight time and magnitude of solitary waves are highly sensitive to the location and amplitude of impact. By analyzing measured solitary waves, the striker's impact location and drop height was successfully predicted nondestructively. It was found that the diagnostic results are in agreement with the numerical simulations obtained from a combined spectral element and discrete element model. The findings in this study imply that the granular crystal sensors can form a new type of impact monitoring system for a sandwich structure to achieve enhanced diagnostic accuracy and potentially to improve sensors' survivability under harsh mechanical and thermal environments.
    Full-text · Article · Oct 2014 · AIAA Journal
  • Source
    • "And then, Lamb wave monitoring signals can be acquired on-line when the structure is in service. The state of the structure can be determined by using some SHM algorithms [2] [3] [4] [5] [6] [7] to measure the difference between the Lamb wave baseline signal and the Lamb wave monitoring signals. Such a process can be implemented well in laboratory for the steady structural boundary condition. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Damage monitoring under time-varying structural boundary condition is one of the most difficult tasks in piezoelectric transducers (PZTs) and Lamb wave based SHM methods for engineering applications. Because the structural boundary changes such as variations in the tightness of bolts between structures can lead to false monitoring result even the structure is in health state. This paper proposes a Lamb wave based on-line continuous updating Gaussian Mixture Model (GMM) to study the problem. Based on the baseline GMM constructed by features of Lamb wave signals in structural health state, an on-line continuous updating GMM is studied to learn the dynamic changes of Lamb wave monitoring signals without any prior knowledge of damage patterns. The Kullback–Leibler (KL) divergence is used as a degradation index to estimate the structural damage by measuring the difference between the baseline GMM and the on-line GMM. The proposed method is validated on an aircraft steel beam. The validation results show that the method is effective for bolt hole crack growth monitoring under the time-varying changes in the tightness degree of the bolts.
    Full-text · Conference Paper · Jul 2014
  • Source
    • "In many cases the investigation by the means of the guided waves are performed using only fundamental A 0 and S 0 wave modes. In recent years some works have been done in the investigation of these waves broadband excitation using piezoelectric wafer active sensors (PWAS) [4]–[9], evaluating such factors as the size of the element, selective excitation and mode control schemes which are basically used in SHM applications. The objective of this research was to investigate the use of piezoceramic ultrasonic transducers for the broadband generation of Lamb waves in different thickness isotropic plates and to determine how efficiency of the generated guided waves asymmetric and symmetric modes changes due the change of the object thickness. "
    [Show abstract] [Hide abstract]
    ABSTRACT: In the case of non-destructive testing or structural health monitoring of plate-like structures measurements are often performed using broadband ultrasonic transducers for generation and reception of guided waves. In some cases, the measurements could be performed having access just from one side of the object and it affects the excitation efficiency of generated asymmetric and symmetric guided waves modes. The experimental investigation was performed in order to evaluate how the change of the thickness of the object under investigation will influence the efficiency of generated guided waves asymmetric and symmetric modes.
    Full-text · Article · Oct 2013
Show more