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Harmonic Scattering of S0 Lamb Wave — A Computational Study (ISTAM 2021 Young Scientist Award Paper) Pravinkumar Ghodake (3701242) Engineering education Mechanical engineering asset management Mechanical engineering not elsewhere classified Applications in physical sciences Other physical sciences not elsewhere classified Acoustics and noise control (excl. architectural acoustics) Acoustics and acoustical devices; waves Computational modelling and simulation in earth sciences Numerical and computational mathematics not elsewhere classified Data visualisation and computational (incl. parametric and generative) design Numerical modelling and mechanical characterisation Solid mechanics Theoretical and applied mechanics Nonlinear optics and spectroscopy Numerical analysis Numerical computation and mathematical software Numerical solution of differential and integral equations Computational complexity and computability Engineering design Computer aided design Design practice and methods Design not elsewhere classified Design history, theory and criticism Models and simulations of design Theory and design of materials Young Scientist Award harmonic scattering harmonic scattering intensities Harmonic Scattering Angle-resolved Harmonic Scattering S0 Lamb wave S0 Lamb wave mode Lamb waves (LW) Lamb Waves guided waves nonlinear ultrasonics Nonlinear ultrasonics Nonlinear Ultrasonics nonlinear elastic inclusion One-Way Two-Wave Mixing Two-Wave Mixing backscattered waves forward-scattered waves higher harmonics higher harmonics generation Higher harmonics early-stage damage Early-Stage Damage Detection micro-cracks micro-voids Micro-voids dislocation substructures Dislocation substructures damage quantification structural health monitoring Structural Health Monitoring (SHM). Structural Health Monitoring Sensors Structural health monitoring Aircraft availability Structural health monitoring systems Structural health monitoring; Interfacial debonding; ACTs; Vibration-based structural health monitoring, data-driven methods, thermal response, bridges Structural health monitoring. Structural Health Monitoring (SHM) structural health monitoring (SHM) Structural health monitoring (SHM) Structural health monitoring Structural Health Monitoring STRUCTURAL HEALTH MONITORING non-destructive evaluation non-destructive evaluation inspection Non-destructive evaluation (NDE) Non-Destructive Evaluation (NDE) Non-destructive Evaluation Non-Destructive Evaluation Non-destructive evaluation thin plates finite element analysis numerical simulation Numerical simulation-based techniques numerical simulation investigated Numerical simulation of stress state Numerical Simulation Analyzed Combinatorial Material Science Study Raman scattering analogy raman scattering spectrometer Nonlinear optics -- Mathematical models Nonlinear optics integrated waveguides nonlinear optics, pulse propagation and solitons nonlinear optics, 2D materials Nonlinear Optics Nonlinear nonlinear optics, Nonlinear OpticsThe synthesis strategy nonlinear optics ISTAM 2021 solid mechanics problems Solid mechanics and dynamics Solid mechanics solid mechanics Solid Mechanics Pravinkumar Ghodake Pravinkumar Ramchandra Ghodake Design Optimization Design & Technology Generative design research Elastodynamics simulations This conference contribution is a Young Scientist Award paper presented by Pravinkumar Ghodake (Department of Mechanical Engineering, IIT Bombay) at the 66th Congress of the Indian Society of Theoretical and Applied Mechanics (ISTAM 2021), hosted at IIT Kharagpur. The work was submitted under the "Paper for the Young Scientist Award" category in the Solid Mechanics (SM) session. Title of contribution: "Harmonic Scattering of S0 Lamb Wave — A Computational Study" Abstract: Harmonic scattering of S₀ waves from local early-stage damage modeled as nonlinear elastic inclusion is demonstrated using numerical simulations for the interaction of single-frequency waves and one-way two-wave mixing, by varying intensity of local damage and damage size. Recent advances in nonlinear ultrasonic techniques such as harmonic generation show sensitivity towards the detection of micro-scaled damages like dislocation substructures, micro-cracks, and micro-voids. Interaction of a monochromatic elastic wave with uniformly distributed micro-scaled early-stage damages generates higher harmonics, and the amplitudes of the higher harmonics can be correlated to the intensity of the averaged damage present inside the material.In practice, thin plates under impact, fatigue, and fracture contain highly local early-stage damages. To understand and gain more insight into the interaction of the nonlinear ultrasonic S₀ guided wave and the resulting harmonic scattering from local damages, this investigation models the damage as a nonlinear elastic material while maintaining the same linear impedance as the surrounding linear elastic material. The existence of backscattered waves is shown due to the interaction of monochromatic waves and one-way two-wave mixing. Amplitudes of harmonics are highly sensitive to the input frequencies, frequency combinations, intensity of local damages, and damage sizes. The presence and absence of backscattered higher harmonics are demonstrated by considering different case studies of harmonic scattering from local damage. Similarities of the observed harmonically scattered elastic Lamb waves are drawn by comparing with the harmonic scattering of nonlinear light waves, well known as 'Raman Scattering' in nonlinear optics. Key Contributions:<ul><li>Numerical simulation of S₀ Lamb wave interaction with localized nonlinear elastic inclusions</li><li>Demonstration of backscattered harmonic generation under single-frequency and dual-frequency one-way two-wave mixing</li><li>Sensitivity analysis of harmonic amplitudes to input frequency, frequency combination, damage intensity, and damage size</li><li>Case studies showing presence and absence of backscattered higher harmonics</li><li>Behavioral analogy between harmonically scattered elastic Lamb waves and Raman scattering in nonlinear optics</li></ul> Methodology: A finite element method (FEM) framework is used to simulate the interaction of nonlinear ultrasonic S₀ guided waves with localized, early-stage material damage in thin plates. The damage is modeled as a nonlinear elastic inclusion with matched linear impedance to isolate the nonlinear effects from linear scattering. Monochromatic wave excitation and one-way two-wave mixing configurations are studied across varying damage intensities and sizes. Backscattered and forward-scattered harmonic wave fields are analyzed to identify sensitivity trends and to establish the Raman scattering analogy. Conclusions:<ul><li>Backscattered harmonic waves exist and are highly sensitive to input frequency and frequency combination</li><li>Harmonic amplitudes correlate strongly with local damage intensity and damage size</li><li>The observed behavior parallels Raman scattering in nonlinear optics</li><li>The study provides a computational baseline for nonlinear ultrasonic guided-wave damage detection in thin plate-like structures</li></ul> Award Recognition: Submitted as a "Paper for the Young Scientist Award" at ISTAM 2021. Published abstract (ISTAM 2021 official): <a href="https://istam.iitkgp.ac.in/resources/2021/proceedings/Award_session/Abstract/SM/138abstract.pdf" target="_blank" rel="noreferrer">https://istam.iitkgp.ac.in/resources/2021/proceedings/Award_session/Abstract/SM/138abstract.pdf</a> ResearchGate record: <a href="https://www.researchgate.net/publication/356786945_Harmonic_Scattering_of_S0_Lamb_Wave_-_A_Computational_Study" target="_blank" rel="noreferrer">https://www.researchgate.net/publication/356786945_Harmonic_Scattering_of_S0_Lamb_Wave_-_A_Computational_Study</a> Research portfolio: <a href="https://sites.google.com/view/pravinkumarghodake/research" target="_blank" rel="noreferrer">https://sites.google.com/view/pravinkumarghodake/research</a> Keywords: harmonic scattering, S0 Lamb wave, Lamb waves, guided waves, nonlinear ultrasonics, nonlinear elastic inclusion, one-way two-wave mixing, backscattered waves, early-stage damage, structural health monitoring, non-destructive evaluation, finite element analysis, Raman scattering analogy, ISTAM 2021, Young Scientist Award 2026-09-30T03:53:39Z Text Conference contribution 10.6084/m9.figshare.34028979.v1 https://figshare.com/articles/conference_contribution/Harmonic_Scattering_of_S0_Lamb_Wave_A_Computational_Study_ISTAM_2021_Young_Scientist_Award_Paper_/34028979 CC BY 4.0