Infrared Thermography applied to transport infrastructures monitoring: outcomes and perspectives

International audienceLong term monitoring of transport infrastructures by infrared thermography has been studied and tested on different structures. A first standalone infrared system architecture developed is presented and discussed. Results obtained with such system on different Civil Engineering structures are presented. Some data processing approaches and inverse thermal model for data analysis are introduced and discussed. Lessons learned from experiments carried out in outdoor with such system are listed and analyzed. Then, a new generation of infrared system architecture is proposed. Finally, conclusions and perspectives are addressed

On the feasibility of defect detection in composite material based on thermal periodic excitation

International audienceImplementation of periodic thermal excitation to identify thermal properties (conductivity, heat capacity, diffusivity) of complex composite materials at different investigation scales (from micrometer to millimetre) presents many advantages. These methods are usually based on the thermal waves phase lag observation compared to a reference signal. In fact, phase lag evolution versus distance to the heating source or versus excitation frequency is quite informative about numerous material characteristics. For example, considering that a structural defect can modify heat propagation inside a material, diagnosis can be performed from phase lag observations and comparisons between samples with and without defects. Numerous studies have been performed considering global heating (a quite large surface of the investigated composite material is heated and defect depth or size can be detected). The proposed approach is original since periodic heating is local and aims to detect defects in the periphery of the excitation. Based on a mathematical model for thermal waves propagations and introducing complex temperature for numerical resolution (finite element method), a feasibility study has allowed a sensitivity analysis. This preliminary study also provides information on the operating protocol, for heating(frequency, power, size of the source), and observation (transmission or reflection). Then, experimental device and early experimental results are briefly exposed

Outdoor thermal monitoring of large scale structures by infrared thermography integrated in an ICT based architecture

International audienceAn infrared system has been developed to monitor transport infrastructures in a standalone configuration. Results obtained on bridges open to traffic allows to retrieve the inner structure of the decks. To complete this study, experiments were carried out over several months to monitor two reinforced concrete beams of 16 m long and 21 T each. Detection of a damaged area over one of the two beams was made by Pulse Phase Thermography approach. Measurements carried out over several months. Finally, conclusion on the robustness of the system is proposed andperspectives are presented

The detection and thermal characterization of the inner structure of the ‘Musmeci’ bridge deck by infrared thermography monitoring

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Heat transfer 1D modeling for Non Destructive Testing and Structural Health Monitoring for civil engineering structures improved by GPGPU

International audienceSince the past decade, infrared thermography coupled with inverse models based on 1d thermal quadrupoles have shown their usefulness in civil engineering by first showing their ability to assess the quantitative non destructive testing of concrete repaired by bonded CFRP plate over a wide area (i.e. repaired or reinforced concrete beams). On the other hand early implementations of long terms monitoring methods based on such approach have given their first results over a whole bridge deck. The experimental method, allow us to have the apparent surface temperature field evolution with time for a wide area divided in pixels. Knowing this specificity, the procedure aims to apply an independent model to each pixel in order to retrieve physical properties map. Such treatment can have a high computational cost. In this paper we propose various improvement of our procedure based on GPGPU paradigm in order to shorten the computational time. This study will detail an experimental procedure able to assess the long term thermal monitoring of a bridge deck over days and to draw properties maps of the inner structure

Surveillance thermique de structures par thermographie infrarouge couplée au suivi des paramètres environnementaux : du déploiement à la standardisation

National audienceLe vieillissement des structures de génie civil, leur utilisation de plus en plus intensive et lessollicitations environnementales nécessitent de développer de nouveaux outils de suivi etdiagnostic. Apparu avec l’avènement des technologies de l’information et de lacommunication, le « Structural Health Monitoring » (SHM), intègre les méthodes de contrôleau sein de systèmes d’information complets permettant, par exemple, l’utilisation del’historique des mesures.Au sein d'I4S, équipe de recherche commune de l'Inria et de l'Ifsttar, le projet Cloud2SM a pourobjectifs d’étudier et proposer une architecture décentralisée et normalisée permettant lesuivi sur le long terme des structures in-situ. Il associe une approche capteurs et modèles. Lelogiciel Cloud2IR, un des composants de cette architecture, a été conçu et développé au seinde ce projet. Il permet de mettre en œuvre sur site extérieur, de manière autonome, desacquisitions de données issues de caméras infrarouges et d’autres capteurs de suivi desparamètres environnementaux.En plus de découpler la gestion des capteurs et leurs données en s’appuyant sur l'utilisationd'un « framework » dédié, Cloud2IR à la particularité d'encapsuler automatiquement lesdonnées dans des formats normalisés et/ou orientés web services. Intégré à une architectureréseau nationale, Cloud2IR est déployé et testé, depuis mi-2015, sur différents sites (Nantes,Rennes et Paris). Les essais conduits associent des mesures par thermographie infrarougepour le suivi thermique plein champ avec des capteurs environnementaux.Après avoir exposé la philosophie de Cloud2IR ainsi que la nécessité de standardisation deslarges volumes de données, un exemple de déploiement sur site sera présenté

GPGPU implementation of modal parameter tracking by particle based Kalman filter

International audienceThis paper presents a method based on the use of Bayesian modal parameter recursive estimation basedon a particular Kalman filter algorithm with decoupled distributions for mass and stiffness. ParticularKalman filtering is a combination of two widely used Bayesian estimation methods working together:the particle filter (also called sequential Monte Carlo samplings) and the Kalman filter. Usual systemidentification techniques for civil and mechanical structures assume the availability of large set of dataderived from a stationary quasi steady structure. On the opposite, several scenarios involve time varyingstructures. For example, due to interaction with aerodynamics in aeronautics, some critical parametermay have to be monitored, for instability monitoring (leading possibly to flutter) of in flight data due tofuel consumption and speed change. This relates to the monitoring of time varying structural parameterssuch as frequencies and damping ratios. The main idea of a particular Kalman filter is to considerstochastic particles evolving in the parameter space. For each particle, a corresponding linear state isrecursively estimated by applying a Kalman filter to the mechanical system, whose modal parametersare driven by the evolution of this time-varying particle. The weight of each particle is computed fromthe likelihood of the parameter sample it represents and its corresponding state. This result in a bank ofadaptive coupled Kalman filters combined with their particle filter. However, the system parametrizationis relatively large. In order to provide fast and convincing results for large time varying structure, suchas an airplane, the execution time of the method has to be improved. In particular, the particle evolutionscan be run in parallel, Within the Cloud2sm project, A Quadro k6000 card of 3072 cores clocked to 3GB/s has been used. This paper will show a GPGPU implementation of the particular Kalman filter andthe first results will be discussed

Study of an optimal heating duration indicator for square pulsed thermography applied to CFRP gluing quality control

International audienceDuring previous works, square pulsed thermography was used to carry out non destructive testing of bonding quality of CFRP glued on civil engineering structures during reinforcement operations [1,2]. The use of such wave form excitation was motivated by " on-site " requirements, but also by measurements duration, number of composite layers to test, depth of possible faulting areas versus temperature elevation allowed at composite level according to inner heat diffusion. Nevertheless, square pulsed excitation implies to choose an adapted heat duration. This duration is directly linked to the reliability of the parameter estimator [3]. In fact, after a certain duration the standard deviation of the estimation procedure stagnates. According to these observations, an indicator able to predict the sufficient heating time when the reliability of the parameter estimator reached an asymptotic evolution behavior was studied. Based on the absolute thermal contrast, the proposed indicator Iph is defined with the maximum thermal contrast ∆Tmax and the time delay (tph) between the heating time tc and the appearance of the maximum contrast, as shown in figure 1 (left). A typical evolution of the Iph indicator is proposed in figure 1 (right). This indicator allows to take into acount the detectability as well as the induced flaw temporal effect on the thermal contrast shape evolution. It has been observed that the maximum of Iph is connected with the sufficient heating time when the standard deviation of the estimation procedure tends to be minimized. This paper will present the establishment of this indicator for optimal square heating time and present an analysis of results obtained with numerical simulations and laboratory experiments. Figure 1 Absolute thermal contrast characteristics (left) and indicator Iph evolution with heating time duration References [1] A. Crinière, J. Dumoulin, C. Ibarra-Castanedo and X. Maldague , " Inverse model for defect characterization of externally glued CFRP on reinforced concrete structures: Comparative study of square pulsed and pulsed thermography " ,] L-D. Théroux, J. Dumoulin and X. Maldague , " Square heating applied to shearography and active infrared thermography measurements coupling: from feasibility test in laboratory to numerical study of pultruded CFRP plates glued on concrete specimen " ,Strain journal, Wiley editor, 2014. doi:10.1111/str.12086. [3] V. Feuillet, L. Ibos, M. Fois, J. Dumoulin, Y. Candau, " Defect detection and characterization in composite materials using Square Pulse Thermography coupled with Singular Value Decomposition analysis and thermal quadrupole modeling " , NDT&E International, Volume 51, Octobre 2012, pp 58–67, Elsevier, http://dx

Robust uncertainty evaluation for system identification on distributed wireless platforms

International audienceHealth monitoring of civil structures by system identification procedures from automatic control is now accepted as a valid approach. These methods provide frequencies and modeshapes from the structure over time. For a continuous monitoring the excitation of a structure is usually ambient, thus unknown and assumed to be noise. Hence, all estimates from the vibration measurements are realizations of random variables with inherent uncertainty due to (unknown) process and measurement noise and finite data length. The underlying algorithms are usually running under Matlab under the assumption of large memory pool and considerable computational power. Even under these premises, computational and memory usage are heavy and not realistic for being embedded in on-site sensor platforms such as the PEGASE platform. Moreover, the current push for distributed wireless systems calls for algorithmic adaptation for lowering data exchanges and maximizing local processing. Finally, the recent breakthrough in system identification allows us to process both frequency information and its related uncertainty together from one and only one data sequence, at the expense of computational and memory explosion that require even more careful attention than before. The current approach will focus on presenting a system identification procedure called multi-setup subspace identification that allows to process both frequencies and their related variances from a set of interconnected wireless systems with all computation running locally within the limited memory pool of each system before being merged on a host supervisor. Careful attention will be given to data exchanges and I/O satisfying OGC standards, as well as minimizing memory footprints and maximizing computational efficiency. Those systems are built in a way of autonomous operations on field and could be later included in a wide distributed architecture such as the Cloud2SM project. The usefulness of these strategies is illustrated on data from a progressive damage action on a prestressed concrete bridge

Thermographie infrarouge synchronisée avec la mesure de paramètres météorologiques : Application à l'auscultation du tablier d'un pont ouvert au trafic

International audienceCet article présente un monitoring thermique conduit pendant plusieurs jours sur le tablier du pont de « Musmeci » à Potenza (Italie). L’analyse des données est conduite en exploitant la mesure de paramètres météorologiques synchronisée avec l’acquisition d’images thermiques. Une analyse par FFT, permet de détecter sur les séquences de cartes d’amplitude et de phase la structure interne du tablier. Un modèle thermique exprimé dans le domaine fréquentiel a été développé et couplé à une procédure d’estimation de paramètres.Une cartographie de la distribution spatiale de la conductivité thermique apparente est ainsi calculée puis comparée avec l’analyse d’images par approche fréquentielle