An invariance transformation algorithm for defect characterization of ultrasonic signals for the nondestructive evaluation of concrete

Michael Dominic Ciocco An invariance transformation algorithm for defect characterization of ultrasonic signals for the nondestructive evaluation of concrete 2002 Dr. Shreekanth Mandayam College of Engineering Nondestructive evaluation (NDE) techniques offer cost-effective strategies for monitoring the integrity of a variety of civil infrastructure, such as natural gas and sewer pipelines, without the need to take the system off-line. However, interpretation of NDE signals in terms of the location, size, and shape of underlying flaws in the material being inspected is fraught with difficulty. Typically, variations in the testing signal due to operational parameters have created a significant challenge for defect characterization. This thesis proposes, develops, and validates a defect characterization algorithm that compensates for operational variables and maps the test signal to a visual defect profile. This algorithm takes a two-step approach: 1. The raw NDT signal is processed via an invariance transformation feed forward artificial neural network that removes the effects of operational parameters and produces a signal containing defect related information only. 2. A second feed forward artificial neural network processes the defect signature developed by the invariance transformation network and predicts defect profiles representing the location, size, and shape of material flaws. The algorithm is validated with experimental data from two separate NDT sources, magnetic flux leakage (MFL) testing of metal gas pipeline specimens and ultrasonic testing (UT) of concrete wastewater pipeline speciments. A selection of three papers is provided describing the invariant defect characterization technique. The results obtained demonstrate that the invariance transformation technique can be used to accurately characterize the depth of defects in concrete or metal, irrespective of variations in the material properties of the test specimens. Recommendations for future research related to this technique are also provided. MINI ABSTRACT Michael Dominic Ciocco An invariance transformation algorithm for defect characterization of ultrasonic signals for the nondestructive evaluation of concrete 2002 Dr. Shreekanth Mandayam College of Engineering Nondestructive evaluation methods offer cost-effective approaches for examining the integrity of a variety of civil infrastructure such as natural gas and sewer pipelines. However, extracting defect related information, such as location, size, and shape of a flaw, from NDE signals remains a considerable challenge as a result of variations in the signal due to material properties and the testing environment. This thesis presents a defect characterization technique that renders NDE signals invariant to operational parameters and predicts a defect profile from the flaw information in the signal.