Advanced Signal Interpretation Algorithm for Automated Impact EchoTesting System: Application to Concrete Bridge Decks

The purpose of this study is to develop an advanced signal interpretation algorithm for an automated impact-echo (IE) testing system. It will be a part of a multi-purpose air-coupled ultrasonic testing system for assessment of concrete bridge decks. An intelligent signal processing algorithm is an essential part of the automated IE testing system. As such it will provide reliable and consistent results by eliminating human errors, and significantly save time for post-processing (i.e., signal processing, data interpretation, and decision). For this purpose, a numerical model, finite element analysis (FEM) is developed to simulate transient behavior of stress waves in air-concrete domain. Using this model, a series of numerical simulations is conducted to investigate the effects of source locations over delamination defects at various depths (60 and 160 mm) and widths (300, 450, and 600 mm). Frequency responses from numerical IE tests are presented as 2-D spectral B-scan images. From those, parameters important to estimate the presence and geometry of delamination defects are qualitatively investigated. After quantitatively testing these parameters through sensitivity analyses, an effective signal interpretation algorithm for the automotive IE testing system is proposed. The validity of the algorithm is verified through a series of numerical blind tests, and the results are discussed in this study. The developed algorithm is demonstrated to be a reliable and time-effective solution of evaluating the areal extents and depth of delamination defects in concrete bridge decks.