Description:

Topics in Condition Monitoring of Solids and Structures Using Elastic Waves

The detection and quantification of internal defects as well as the measurement of in-situ stresses in solids and structures can be well accomplished by using elastic waves propagating in the ultrasonic regime (> 20 kHz). The talk will present three research topics related to this kind of condition monitoring of solids and structures. The first topic is the passive-only extraction of the Green’s function (or transfer function) of the test piece subjected to an unknown, and generally nonstationary excitation. This concept is being successfully utilized to defect internal defects in rail tracks using solely (non-contact) ultrasonic receivers and exploiting the natural train wheels as the acoustic excitation. Several other opportunities exist to passively monitor structures subjected to natural operational loads. The second topic deals with the nonlinear wave propagation regime and the increased sensitivity that this brings to nondestructive material state awareness compared to the conventional linear wave regime. Nonlinear wave propagation will be presented for the case of waveguides, affected by multimode and dispersive behavior, and for the case of constrained solids subjected to thermal excursions. One application of the latter case is the nondestructive assessment of in-situ thermal stresses for the prevention of thermal buckling failures. The third topic will present improvements to the application of ultrasonic Synthetic Aperture Focus (SAF) that utilizes multi-element ultrasonic arrays to image defects in engineering solids and biological materials. These improvements will be proposed in terms of physics-based adaptive weights to apply to the array and compounding information from multiple wave modes. Applications will be shown to image internal defects in aluminum and steel bulk parts, as well as in panels representative of new composite aircraft construction.

Francesco Lanza di Scalea (Ph.D. 97 Univ. of Palermo, Post-doc 98-99 Johns Hopkins Univ.) is currently a Professor of Structural Engineering and the Director of the NDE & Structural Health Monitoring Laboratory at the University of California San Diego. His research and teaching interests are in the fields of structural health monitoring, non-destructive evaluation, and experimental mechanics. Lanza di Scalea was awarded the UCSD Structural Engineering Teacher of the Year Award (2011), the Structural Health Monitoring Person of the Year Award (2007), the American Society for Nondestructive Testing Research Fellowship Award (2002, 2006 and 2010), the American Society for Nondestructive Testing Faculty Grant Award (2003), the UCSD Hellman Faculty Fellowship (2000 and 2002), and the Fulbright Scholarship (1995). He currently serves on the Editorial Board of the following journals: Journal of Intelligent Materials Systems and Structures, Structural Health Monitoring: An International Journal, Research in Nondestructive Evaluation, ASME Journal of Nondestructive Evaluation, Diagnostics and Prognostics of Engineering Systems, and SEM’s Experimental Mechanics. He is a Fellow of the following societies: American Society for Nondestructive Testing (ASNT), Acoustical Society of America (ASA), and Society for Experimental Mechanics (SEM).