Imaging of elastic wave guides interconnected by a junction

A method for imaging a structure composed of at least one wave guide connected to a junction, the structure supporting elastic wave guided propagation modes, the structure having at least one defect, the method comprising the following steps:

• for at least one operating frequency, acquiring a plurality of measurements of signals propagating in the structure by means of a plurality of pairs of non-colocalized elastic wave sensors, the measurements being organized in a measurement matrix with dimensions equal to the number of transmitting sensors by the number of receiving sensors,
• determining a plurality of propagation modes guided by the structure, correcting the measurements on the basis of ultrasound signals measured or simulated for the same structure in the absence of any defect,
• converting the measurement matrix into a wave field scattering matrix U,
• determining, at each point of a sampling grid, a test vector F characteristic of the structure without any defect, the components of which are the projections of a Green tensor from the defect-free domain onto the transverse functions of the guided propagation modes, applying a numerical inversion method to determine a vector H of modal components such that U.H=F at each point of a sampling grid, determining an image of the structure on the basis of the vector H.