Nonlinear Ultrasonic Characterization of Damage Evolution in Consolidated Granular Media

This paper is a summary of the main results achieved in the past ten years about the practical application of a nonlinear ultrasonic technique denoted as Scaling Subtraction Method (SSM), developed at Politecnico di Torino. Several case studies are reported, involving various types of consolidated granular media and different damage mechanisms. The effectiveness of the SSM in describing damage evolution is compared with other techniques and discussed with reference to both diffuse damage, as induced by mechanical loads, thermal actions or corrosion, and localized damage, as due to degradation of the interfaces between different portions of a masonry system under chemical attack. The reverse process of crack repair due to a healing agent is also analyzed.