A1040 MIRA – Ultrasound Tomography
How it works
The tomograph is based on the reflection of short elastic waves impulses due to cracks, holes and other discontinuities of the material (pulse-echo method). The intensity of the waves reflected out of such a discontinuity depends on their contrast with the starting material in terms of acoustic impedance (acoustic impedance – Z- = density ∙ elastic waves velocity). In particular, the air in the empty spaces has basically no impedance and the impulses are entirelly reflected: R = (Z2 – Z1) / (Z1 + Z2) = – 1. Is possible to obtain eaker indications (R ~ 0.5) in correspondence with the scaffold bars, which acoustic impedance is about 4 to 5 times the concretes.
Source: Prof. Roberto Felicetti – Dipartimento di Ingegneria Civile e Ambientale – Politecnico di Milano