Abstract: A method for performing tomography on a structure supporting modes of guided propagation of elastic waves, the method includes the steps of: acquiring a plurality of signals propagating through the structure by means of a plurality of pairs of non-collocated elastic-wave sensors; for each pair of sensors, i. selecting one mode of guided propagation, ii. converting the measured signal into wave field for the selected mode, iii. determining an anisotropic calibration coefficient on the basis of a wave-field propagation model evaluated depending on the anisotropic wavenumber and on the distance between the sensors of the pair, and on the basis of the wave field or of a reference wave field corresponding to a healthy state of the structure, calibrating the wave fields using the determined calibration coefficients, performing tomography on the structure on the basis of the calibrated wave fields.

Abstract: Methods and systems for analyzing an industrial structure are provided. With a plurality of sensors (e.g. FBGs and/or piezoelectric transducers and/or electromagnetic acoustic transducers) deployed in, on or in proximity to the structure, sensors are interrogated and a function representative of the impulse response of the structure is determined by passive inverse filter. Subsequently, a map of the propagation of the elastic waves through the structure is determined via various modalities, and in particular by tomography (of bulk or guided waves, by analysis of time of flight or of the complete signal). Embodiments especially relate to the management of the number and position of the sensors, to the use of artificial noise sources, and to automatically controlling the sensors and/or noise sources to monitor the health of the structure, or even to view the dynamic behavior of the structure.

Abstract: Methods and devices are provided for analyzing a tubular structure including at least two electromagnetic-acoustic transducers (EMAT) and, called sensors, attachable or attached in, on or in the vicinity of the tubular structure; and computation and/or memory resources, that are accessed locally and/or remotely and that are configured to determine, for the pair of sensors, a function representing the impulse response of the tubular structure on the basis of the diffuse acousto-elastic noise present in the structure. Developments describe the use of rings supporting the sensors; translation and/or rotation movements; permanent or temporary installations; hinged rings; various computation modes, e.g., intercorrelation, a passive inverse filter, or correlation of the coda of the correlation; the use of artificial noise sources, imaging (e.g., tomography) for determining the existence of one or more defects in the structure. Software aspects are described.

Abstract: A method for monitoring the structural health of a structure that supports guided propagation modes of elastic waves, includes the following steps: a) acquiring an ambient noise propagating through the structure by means of at least one pair of non-collocated elastic-wave sensors; b) estimating a function representative of an impulse response of the structure for elastic propagation between the constituent sensors of said pair; c) extracting at least one dispersion curve of the elastic propagation through the structure by time-frequency analysis of this function representative of an impulse response; and d) estimating at least one parameter indicative of a mechanical property of a constituent material of the structure from the dispersion curve obtained in step c). A system for implementing such a method is also provided.

Abstract: A method and system for inspecting a rail by guided waves, the rail being instrumented by sensors. The method comprises the steps of receiving elastic wave measurements from one or more sensors, as a train passes, releasing energy as guided waves into the rail; and of determining a function representative of the impulse response of the rail and the sensors. Developments describe how to determine the existence, position and characterisation of a defect in the rail (e.g. fracture, incipient fracture, etc.), the use of inter-correlation analyses, correlation of the coda of correlations, Passive Inverse Filter, imaging techniques. Other aspects are described for exploring rail defects: sensor position and movement, acquisition time, sampling frequency, frequency filters, amplifications, techniques for learning during successive train passes, signal injection by transducers. Software aspects are described.

Abstract: Methods and systems for analyzing an industrial structure are provided. With a plurality of sensors (e.g. FBGs and/or piezoelectric transducers and/or electromagnetic acoustic transducers) deployed in, on or in proximity to the structure, sensors are interrogated and a function representative of the impulse response of the structure is determined by passive inverse filter. Subsequently, a map of the propagation of the elastic waves through the structure is determined via various modalities, and in particular by tomography (of bulk or guided waves, by analysis of time of flight or of the complete signal). Embodiments especially relate to the management of the number and position of the sensors, to the use of artificial noise sources, and to automatically controlling the sensors and/or noise sources to monitor the health of the structure, or even to view the dynamic behavior of the structure.

Abstract: A method for monitoring the structural health of a structure that supports guided propagation modes of elastic waves, includes the following steps: a) acquiring an ambient noise propagating through the structure by means of at least one pair of non-collocated elastic-wave sensors; b) estimating a function representative of an impulse response of the structure for elastic propagation between the constituent sensors of said pair; c) extracting at least one dispersion curve of the elastic propagation through the structure by time-frequency analysis of this function representative of an impulse response; and d) estimating at least one parameter indicative of a mechanical property of a constituent material of the structure from the dispersion curve obtained in step c). A system for implementing such a method is also provided.