title: Transmission analysis of ultrasonic Lamb mode conversion in a plate with partial-thickness notch.
abstract: Mode conversions of Lamb waves can occur upon encountering damage or defect such as a notch, leading to newly-converted modes apart from wave reflection and transmission. In this paper, the transmission of the fundamental Lamb modes symmetrical S0 and anti-symmetrical A0 with anti-symmetrical notches were investigated in steel plates within the relatively short propagation distance. The group velocity and modal energy of the converted modes were analyzed using simulations and experiments. Two-dimensional finite difference time domain (2D-FDTD) method was employed to calculate the scattering field and extract numerical trends for simulation study and experimental confirmation. Both simulations and experiments revealed that the apparent group velocities of the converted modes in the transmitted signals subject to the notch positions. To describe the mode conversion degree and evaluate the notch severity, wave packets of the originally-transmitted modes and newly-converted modes were separated and corresponding mode energy percentages were analyzed at different notch severities. Frequency-sweeping measurements illustrated that the modal energy percentages varied monotonically over the notch-depth increase with a statistically consistency (R=1.00, P<0.0004).
authors.affiliation: Department of Electronic Engineering, Fudan University, Shanghai 200433, China.
authors.forename: Kailiang
authors.initials: K
authors.lastname: Xu
authors.forename: Dean
authors.initials: D
authors.lastname: Ta
authors.forename: Zhongqing
authors.initials: Z
authors.lastname: Su
authors.forename: Weiqi
authors.initials: W
authors.lastname: Wang
mesh_terms: D003198:Computer Simulation; D008420:Manufactured Materials; D008962:Models, Theoretical; D012542:Scattering, Radiation; D013016:Sound; D014463:Ultrasonography / Q000379:methods*; D014732:Vibration
keywords: Group velocity; Mode conversion; Mode energy; Notches; Ultrasonic Lamb waves