https://digital.library.adelaide.edu.au/dspace/bitstream/2440/103882/3/hdl_103882.pdf

Locating delaminations in laminated composite beams using nonlinear guided waves

https://dr.ntu.edu.sg/bitstream/10356/83470/1/Damage%20detection%20in%20quasi-isotropic%20composite%20bends%20using%20ultrasonic.pdf

Damage detection in quasi-isotropic composite bends using ultrasonic feature guided waves

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.

Feature guided wave inspection of bond line defects between a stiffener and a composite plate

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.

Holey-structured metamaterial lens for subwavelength resolution in ultrasonic characterization of metallic components

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...

Characterization of delamination-type damages in composite laminates using guided wave visualization and air-coupled ultrasound:

Symmetric low-frequency feature-guided ultrasonic waves in thin plates with transverse bends.

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...

Antisymmetric feature-guided ultrasonic waves in thin plates with small radius transverse bends from low-frequency symmetric axial excitation

This paper studies the influence of cross-section ovalness or ellipticity on lower order axisymmetric guided wave modes in thin pipes. The second longitudinal mode L(0,2) and the fundamental torsional mode T(0,1) are studied, as these are of interest to current pipe inspection. The semi-analytical finite element (FE) method is mainly used, with three-dimensional FE simulations for visualization and cross-validation of results. The studies reveal that even a small degree of ovalness can affect mode shapes and velocities. The effect is more pronounced on the L(0,2) mode than on T(0,1) and this may be important for practical inspection applications.

Ultrasonic guided waves in elliptical annular cylinders

This paper studies the effect of axially uniform eccentricity on the modal structures and velocities of the lower order axisymmetric guided wave mode L(0,2) in circular tubes or pipes. The semi-analytical finite element method is mainly used, supported by fully three-dimensional finite element models and validated using experiments. The studies show that even a small eccentricity in the pipe can cause a loss in the L(0,2) mode axisymmetry, leading to its confinement in the thinned side of the pipe cross-section and also a reduction in mode velocities. The physics of this phenomenon is related to the feature-guiding and mode confinement effects noted in recent years in the literature, particularly studies on waveguides with local cross-section variations and curvature.

Low frequency axisymmetric longitudinal guided waves in eccentric annular cylinders.

This paper studies the feasibility of using ultrasonic guided waves to rapidly inspect tubes and pipes for possible eccentricity. While guided waves are well established in the long range inspection of structures such as pipes and plates, studies for more complex cross sections are limited and analytical solutions are often difficult to obtain. Recent developments have made the Semi Analytical Finite Element (SAFE) method widely accessible for researchers to study guided wave properties in complex structures. Here the SAFE method is used to study the effect of eccentricity on the modal structures and velocities of lower order guided wave modes in thin pipes of diameters typically of interest to the industry. Results are validated using experiments. The paper demonstrates that even a small eccentricity in the pipe can strongly affect guided wave mode structures and velocities and hence shows potential for pipe eccentricity inspection.

Roson Kumar Pattanayak

Papers

Symmetric low-frequency feature-guided ultrasonic waves in thin plates with transverse bends.

Antisymmetric feature-guided ultrasonic waves in thin plates with small radius transverse bends from low-frequency symmetric axial excitation

Ultrasonic guided waves in elliptical annular cylinders

Low frequency axisymmetric longitudinal guided waves in eccentric annular cylinders.

Ultrasonic guided waves in eccentric annular pipes