Detection and imaging of microcracking in complex media using coda wave   interferometry (CWI) under linear resonance conditions
  This letter presents the development of ultrasonic coda wave interferometry to locate and image microcracks created within consolidated granular media, polymer concrete. Results show that microcracks can be detected through coda waves when the polymer concrete is submitted to a linear resonance. In addition, the multiple scattering revealed to be dependent on the plane in which the resonance is excited. In that sense, Acoustic emission measurements were performed under flexural resonances generated in (XY) and (XZ) planes to verify the existence of a possible structural anisotropy related to microcracks. Recorded acoustic signatures revealed important differences in the frequency contents, depending on the considered plane, with a consequent wealth on the involved mechanisms during the microcracks vibrations. 
S. Toumi, C. Mechri, M. Bentahar, F. Boubenider and R. El Guerjouma
cond-mat.mtrl-sci