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Abilasha Ramdhas

Bio: Abilasha Ramdhas is an academic researcher from Indian Institute of Technology Madras. The author has contributed to research in topics: Bent molecular geometry & Lamb waves. The author has an hindex of 2, co-authored 2 publications receiving 51 citations.

Papers
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Journal ArticleDOI
TL;DR: This paper focuses on the faster bend-guided mode that is similar to the S0 (fundamental symmetric) Lamb mode in flat plates that is shown to be more strongly generated in smaller angle bends.

35 citations

Journal ArticleDOI
TL;DR: The influence of bends constituting annular polygonal structures on ultrasonic guided waves propagating along their axis is investigated and a slower bend-guided mode that is similar to the A0 (fundamental anti-symmetric) Lamb mode in flat plates is identified.
Abstract: The influence of bends constituting annular polygonal structures on ultrasonic guided waves propagating along their axis is investigated. Considering a single bend as a bent plate connects this problem to the better-understood physics of guided waves in straight plates. Using a three-dimensional finite element simulation validated with experiments, bends in plates are shown to act as features that can concentrate and guide ultrasonic energy along their length. Two interesting feature-guided modes are identified when the bent plate is subjected to “in-plane” or axial excitation applied uniformly along a through-thickness line bisecting the bent edge. Of these, the faster traveling mode has properties similar to, but travels at group velocities lower than, the S0 (fundamental symmetric) Lamb mode in flat plates. This paper however focuses on the slower bend-guided mode that is similar to the A0 (fundamental anti-symmetric) Lamb mode in flat plates. This mode is shown to be more strongly generated in smaller...

27 citations


Cited by
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Journal ArticleDOI
TL;DR: In this paper, the authors proposed a new method for detecting and locating delaminations in laminated composite beams using nonlinear guided wave, which employs a transducer network to detect and locate the delamination using the higher harmonic guided waves.

70 citations

Journal ArticleDOI
TL;DR: In this article, the feasibility of using ultrasonic feature guided waves (FGW) for rapid screening of typical 90° bends made of quasi-isotropic composite laminates is explored.

59 citations

Journal ArticleDOI
TL;DR: In this paper, a feature guided wave (FGW) was used for rapid screening of the bond line between a stiffener and a carbon fiber reinforced polymer (CFRP) composite panel.
Abstract: Adhesive bonding is widely used in aerospace composite structures. A continuous well-cured bond can offer good joint strength and improved fatigue and impact resistance, and is therefore crucial to the performance of the entire structure. This paper explores the feasibility of using feature guided waves (FGW) for rapid screening of the bond line between a stiffener and a carbon fiber reinforced polymer (CFRP) composite panel. Such FGWs are capable of focusing the wave energy along the stiffener and the bond layer, with limited radiation to the adjacent plate. The Semi-Analytical Finite Element (SAFE) approach is employed to understand the modal properties of FGWs that exist in the structure, and criteria are suggested to choose proper mode-frequency combination that is sensitive to adhesive defects. A shear horizontal type FGW mode is identified to be well suited, as it is easy to excite, and propagates with little dispersion and relatively low attenuation, while it retains sufficient energy around the bond layer. Both 3D Finite Element (FE) simulations and experiments are performed to study the interaction of the selected FGW mode with defects in the adhesive bond, and the results show excellent agreement. The reflection behavior and the wave-defect resonance phenomenon are investigated, which demonstrate the capability of the FGW for the bond line inspection.

50 citations

Journal ArticleDOI
TL;DR: In this paper, a holey structured metamaterial lens was used for ultrasonic characterization of subwavelength subsurface defects in metallic components. Butler et al. used numerical simulation to investigate the parameters that can help improve the resolution performance of the metammaterial lens, particularly, the addition of end-conditions.
Abstract: This paper presents the implementation of holey structured metamaterial lens for ultrasonic characterization of subwavelength subsurface defects in metallic components. Experimental results are presented, demonstrating ultrasound-based resolution of side drilled through-holes spaced (λ/5) in an aluminum block. Numerical simulation is then used to investigate the parameters that can help improve the resolution performance of the metamaterial lens, particularly, the addition of end-conditions. This work has important implications for higher resolution ultrasonic imaging in the context of practical non-destructive imaging and non-invasive material diagnostics.

43 citations

Journal ArticleDOI
TL;DR: A combination of plate-guided ultrasound and air-coupled ultrasonics is used to locate and visualize delaminations in composite laminates using wave visualization method as mentioned in this paper.
Abstract: This article reports on the characterization of delamination damages in composite laminates using wave visualization method. A combination of plate-guided ultrasound and air-coupled ultrasonics is used to locate and visualize delaminations. The study focuses on the physics of Lamb wave propagation and interaction with delaminations at various through-thickness locations and positions. Three-dimensional finite element simulations are used to study, in detail, the changes in wave features such as mode velocity, wavelength and wave refraction in the delamination region. These wave features provide information on the location, position and orientation of the delamination. These studies are validated by experimental measurements. The influence of position of source and delamination on wave refraction in the delamination region is examined. This method also correlates the results obtained from experiments and finite element simulations to theoretical dispersion curves in order to distinctly determine the delami...

38 citations