Analysis and modeling of diffuse ultrasonic signals for structural health monitoring

Article · January 2007with23 Reads
Source: OAI
Structural Health Monitoring (SHM) refers to the process of nondestructive autonomous in situ monitoring of the integrity of critical engineering structures such as airplanes, bridges and buildings. Ultrasonic wave propagation is an ideal interrogation method for SHM because ultrasound is the elastic vibration of the material itself and is thus directly affected by any structural damage occurring in the paths of the propagating waves. The objective of this thesis is to provide a comprehensive damage detection strategy for SHM using diffuse ultrasonic waves. This strategy includes a systematic temperature compensation method, differential feature extraction methods optimized for discriminating benign surface condition changes from damage, and data fusion methods to determine the structural status. The temperature compensation method is based upon a set of pre-recorded baselines. Using the methods of baseline selection and baseline correction, a baseline that best matches a monitored signal in temperature is provided. For the differential feature extraction, three types of features are proposed. The first type includes basic differential features such as mean squared error. The second type is derived from a matching pursuit based signal decomposition. An ultrasonic signal is decomposed into a sum of characteristic wavelets, and differential features are extracted based upon changes in the decomposition between a baseline signal and a monitored signal. The third type is a phase space feature extraction method, where an ultrasonic signal is embedded into phase space and features are extracted based on changes of the phase portrait. The structural status is determined based on a data fusion strategy consisting of a threshold selection method, fusion at the feature level, and fusion at the sensor level. The proposed damage detection strategy is applied to experiments on aluminum specimens with artificial defects subjected to a variety of environmental variations. Results as measured by the probability of detection, the false alarm rate, and the size of damage detected demonstrate the viability of the proposed techniques. Ph.D. Committee Chair: Michaels, Jennifer; Committee Member: Durgin, Gregory; Committee Member: Jacobs, Laurence; Committee Member: Michaels, Thomas; Committee Member: Vachtsevanos, George
    • It is noted that AU is not sensitive to discrete defects but can sense distributed damage resulting in localized changes to elastic properties of the material. The receiver does not sense the excitation signal, but rather the response of the structure to the acoustic disturbance (Lu 2007). The AU technique is often attributed to Vary (1982) and was developed primarily for the inspection of composite materials.
    [Show abstract] [Hide abstract] ABSTRACT: Licensees of commercial nuclear power plants in the US are expected to submit license renewal applications for the period of operation of 60 to 80 years which has also been referred to as long term operation (LTO). The greatest challenges to LTO are associated with degradation of passive components as active components are routinely maintained and repaired or placed through maintenance programs. Some passive component degradation concerns include stress corrosion cracking (SCC) of metal components, radiation induced embrittlement of the reactor pressure vessel (RPV), degradation of buried piping, degradation of concrete containment structures, and degradation of cables. Proactive management of passive component aging employs three important elements including online monitoring of degradation, early detection of degradation at precursor stages, and application of prognostics for the prediction of remaining useful life (RUL). This document assesses several nondestructive examination (NDE) measurement technologies for integration into proactive aging management programs. The assessment is performed by discussing the three elements of proactive aging management identified above, considering the current state of the industry with respect to adopting these key elements, and analyzing measurement technologies for monitoring large cracks in metal components, monitoring early degradation at precursor stages, monitoring the degradation of concrete containment structures, and monitoring the degradation of cables. Specific and general needs have been identified through this assessment. General needs identified include the need for environmentally rugged sensors are needed that can operate reliably in an operating reactor environment, the need to identify parameters from precursor monitoring technologies that are unambiguously correlated with the level of pre-macro defect damage, and a methodology for identifying regions where precursor damage is most likely to initiate.
    Full-text · Article · Jan 2011 · Structural Control and Health Monitoring
    • The strategy is to compute multiple differential features from the six total transducer pairs, and apply threshold and data fusion techniques to ascertain whether or not damage is present. A summary is presented here, and details may be found in[17]. Seven differential features are computed from the time domain signals, the local temporal coherence[14], and from a matching pursuit wavelet decomposition[18].
    [Show abstract] [Hide abstract] ABSTRACT: Several different strategies are being considered for ultrasonic structural health monitoring systems using a variety of approaches. Guided wave techniques for interrogating large plate-like structures have probably generated the most interest; these methods have the potential of monitoring large areas with a low sensor density while remaining sensitive to defects. The acousto-ultrasonic nondestructive evaluation method has motivated the use of long-time, reverberating waves which "fill" a structure and hence monitor large areas. Local methods based upon several different wave modes have been considered for monitoring known "hot spots" such as fastener holes and critical bonds. Presented here are examples of these three strategies where the purpose is to both show progress which has been made and illustrate key issues, mainly in the context of aerospace applications. The progress and problems thus far show both the promise of ultrasonic structural health monitoring and the significant challenges in moving from the laboratory to deployed systems.
    Full-text · Article · May 2008
  • [Show abstract] [Hide abstract] ABSTRACT: L'interférométrie par ondes de coda est une technique qui exploite les changements inhérents aux ondes dispersives afin d'évaluer les variations de propriétés du milieu de propagation. Cette technique a été précédemment mise au point dans le domaine de la géophysique, dans le contexte d'une caractérisation non destructive [1], [2]. En effet, un des potentiels de cette méthode réside, entre-autre, dans sa capacité à évaluer les modifications du temps de parcours des ondes élastiques dans des milieux soumis à des changements de température aussi bien qu'à des modifications structurelles. Une première étude a montré la capacité de l'interférométrie par ondes de coda à estimer avec précision la température dans une plaque d'aluminium [3]. Ce travail préliminaire, dans un milieu homogène et isotrope, a permis alors de confronter les mesures à un modèle analytique. Le travail présenté dans cet article s'inspire de ces résultats pour étudier l'effet de la température sur la propagation des ondes acoustiques dans une plaque composite de type verre époxy. La sensibilité de la méthode ouvre des perspectives très intéressantes en termes de contrôle de santé des matériaux en présence d'endommagements faibles ou précoces. Références [1] Grêt, A., R. Snieder, and J. Scales, Time-lapse monitoring of rock properties with coda wave interferometry, J. Geophys. Res., 111, 2006. [2] Grêt, A., R. Snieder, and U. Ozbay, Monitoring in-situ stress changes in a mining environment with coda wave interferometry, Geophys. J. Int., 167, 504-508, 2006. [3] E. Balaa, A. Le Duff, G. Plantier, R. El Guerjouma, Interférométrie par onde de coda : effet de la température sur la propagation d'ondes acoustiques dans une plaque d'aluminium, 22ème colloque sur le traitement du signal et des images, Dijon, septembre 2009.
    Full-text · Conference Paper · Apr 2010 · Structural Control and Health Monitoring
  • [Show abstract] [Hide abstract] ABSTRACT: Damage assessment can be considered as the main task within the context of structural health monitoring (SHM) systems. This task is not only confined to the detection of damages in its basic algorithms but also in the generation of early warnings to prevent possible catastrophes in the daily use of the structures ensuring their proper functioning. Changes in environmental and operational conditions (EOC), in particularly temperature, affect the performance of SHM systems that constitutes a great limitation for their implementation in real world applications. This paper describes a health monitoring methodology combining the advantages of guided ultrasonic waves together with the compensation for temperature effects and the extraction of defect-sensitive features for the purpose of carrying out a nonlinear multivariate diagnosis of damage. Two well-known methods to compensate the temperature effects, namely optimal baseline selection and optimal signal stretch, are investigated within the proposed methodology where the performance is assessed using receiver operating characteristic curves. The methodology is experimentally tested in a pipeline. Results show that the methodology is a robust practical solution to compensate the temperature effects for the damage detection task.
    Article · Feb 2015
May 2013 · Applied Acoustics · Impact Factor: 1.02
    One of the most important difficulties faced by in situ structural health monitoring approaches when establishing a relationship between a specific damage mechanism and its acoustic signature is the lack of an appropriate signal processing method able to deal with the non-stationary acoustic signals. The purpose of this paper is to use the Hilbert–Huang transform for the extraction of new... [Show full abstract]
    January 2013 · Applied Acoustics · Impact Factor: 1.02
      In Structural Health Monitoring (SHM) of materials, estimating the effects of environmental and operational conditions such as temperature is important. Indeed, temperature changes induce modifications of the mechanical properties of the material and therefore causes a dilation of the acoustic signals characterized by a scale factor. This paper described four scale factor estimators able to... [Show full abstract]
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