Collaborators:

• • Profs. Fabrizio Vestroni and Annamaria Pau, La Sapienza University, Rome 

Funding:

• • Air Force Office of Scientific Research 

  • California Department of Transportation

Synopsis:

It is well established that nonlinear ultrasonic wave features are often more sensitive than linear ultrasonic wave features to material and structural conditions. Nonlinear behaviors (as those caused by higher-order elastic behavior or contact conditions) are, in fact, highly sensitive to the presence of structural flaws (including early damage precursors) and to the level of quasi-static applied stress (residual or thermal stress).Whereas the nonlinear behavior of bulk waves (longitudinal and shear) is well understood, that of dispersive and multimode guided waves necessitates further studies. We have carried out a series of theoretical analyses to specifically study the nonlinear higher-harmonic generation behavior of guided waves. Our results theoretically demonstrate, for example, conditions of existence and non-existence of specific guided wave modes in plates (Lamb waves) and rods. We have also used the SAFE modeling tool in combination with COMSOL (our CONOSAFE numerical framework) to identify higher-harmonic generation conditions of guided waves in structures with geometrical and/or material complexities (railtracks, composites). These analyses have enabled us to optimize nonlinear guided wave tests for maximum sensitivity to structural flaws and/or quasi-static applied stress in the structures. Finally, we have developed nonlinear wave propagation models applicable to solids under thermal stresses based on inter-atomic potentials considerations. 

Selected Publications:

Lanza di Scalea, F., Srivastava, A. and Nucera, C., “Nonlinear Guided Waves and Thermal Stresses,” Chapter 9 of Nonlinear Ultrasonic and Vibro-acoustical Techniques for Nondestructive Evaluation , T. Kundu, ed., The Acoustical Society of America, Springer Nature Publishing,  doi 10.1007/978-3-319-94476-0_9, 2019.

Pau, A. and Lanza di Scalea, F., “Nonlinear Guided Wave Propagation In Prestressed Plates," Journal of the Acoustical Society of America, 137(3), pp. 1529-1540, 2015.

Nucera, C. and Lanza di Scalea, F., “Nondestructive Measurement of Neutral Temperature in Continuous Welded Rails By Nonlinear Ultrasonic Guided Waves,” Journal of the Acoustical Society of America, 136(5), pp. 2561-2574, 2014.

Nucera, C. and Lanza di Scalea, F., “Modeling of Nonlinear Guided Waves and Applications To Structural Health Monitoring,” ASCE Journal of Computing in Civil Engineering, Special Issue on Computing, 29(4), pp. B40140011- B401400115, 2015. 

Nucera, C. and Lanza di Scalea, F., “Nonlinear Wave Propagation in Constrained Solids Subjected To Thermal Loads,” Journal of Sound and Vibration, 333(2), pp. 541-554, 2014.

Nucera, C. and Lanza di Scalea, F., “Nonlinear Semi-Analytical Finite Element Algorithm for the Analysis of Internal Resonance Conditions In Complex Waveguides,” ASCE Journal of Engineering Mechanics, 140(3), pp. 502-522, 2014.

Nucera, C., Phillips, R., and Lanza di Scalea, F., “Ultrasonic Guided Wave Monitoring Of Railroad Tracks,” Advances in Science and Technology, 83, pp. 198-207, 2013. 

Nucera, C., Phillips, R., Lanza di Scalea, F., Fateh, M. and Carr, G., “RAIL-NT System for the In-situ Measurement of Neutral Temperature in CWR: Results from Laboratory and Field Tests,” Transportation Research Record: Journal of the Transportation Research Board, no. 2374, Washington DC, pp. 154-161, 2013. 

Nucera, C. and Lanza di Scalea, F., “Higher Harmonic Generation Analysis in Complex Waveguides via a Nonlinear Semi-Analytical Finite Element Algorithm,” Mathematical Problems in Engineering, Special Issue on New Strategies and Challenges in SHM for Aerospace and Civil Structures, Hindawi Publishing Corporation, vol. 2012, doi:10.1155/2012/365630, 16 pgs., 2012.

Nucera, C. and Lanza di Scalea, F., “Monitoring Load Levels in Multi-wire Strands by Nonlinear Ultrasonic Waves,” Structural Health Monitoring International Journal, 10(6), pp. 617-629, 2011.

Srivastava, A. and Lanza di Scalea, F., “Higher-harmonic generation in Nonlinear Waveguides of Arbitrary Cross-section,” Journal of the Acoustical Society of America, 127(5), pp. 2790-2796, 2010.

Srivastava, A. and Lanza di Scalea, F., “On the Existence of Longitudinal or Flexural Waves in Rods at Nonlinear Higher Harmonics,” Journal of Sound and Vibration, 329, pp. 1499-1506, 2010.

Srivastava, A. and Lanza di Scalea, F., “On the Existence of Symmetric or Antisymmetric Lamb Waves at Nonlinear Higher Harmonics,” Journal of Sound and Vibration, 323 (3-5), pp. 932-943, 2009.