Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
Results
Showing 1 to 20 of 34 for “"Lamb Wave"”.
-
Analysis of optimum Lamb wave tuning
Guided waves are of enormous interest in the nondestructive evaluation of thin-walled structures and layered media. Due to their dispersive and multi-modal nature, it is desirable to tune the waves by discriminating one mode from the others. The objectives of this thesis are (1) to develop schemes …
-
Lamb wave propagation in laminated composite plates
Low frequency Lamb waves in composite laminates were investigated theoretically and experimentally. To have a general solution for Lamb wave propagation in multilayered composite laminates is not practical due to a large number of boundary conditions needed to be satisfied at the interlaminar …
-
Fundamental Studies In the Lamb-Wave Interaction Between Piezoelectric Wafer Active Sensor and Host Structure During Structural Health Monitoring
… the structure by exciting and receiving Lamb waves propagating in the structure or by passively listen to changes in the structure. PWAS-structure interaction modeling is fundamental in order to achieve single mode excitation, i.e., tuning, a requirement for most of the SHM algorithms …
-
Interaction of acoustic waves and anisotropic multilayered composite plates immersed in water.
… dissertation a theoretical analysis of elastic wave propagation in multilayered anisotropic composite plates is presented. Reflection and transmission coefficients as a function of the plane wave incident angle and ultrasonic wave frequency are computed for single layered and multilayered …
-
Piezoelectric-based in-situ damage detection of composite materials for structural health monitoring systems
… for the application of modal analysis and Lamb wave techniques to quasi-isotropic graphite/epoxy test specimens containing representative damage. These results were then verified experimentally by using piezoelectric patches as actuators and sensors for both sets of experiments. The passive …
-
Ultrasonic sensor platforms for Non-Destructive Evaluation
… inspection is not practical. A reconfigurable Lamb wave scanner, using autonomous robotic platforms is presented. The scanner is built from a fleet of wireless miniature robotic vehicles, each with a non-contact ultrasonic payload capable of generating the A0 Lamb wave mode in plate specimens. …
-
Development of Structural Health Monitoring Systems Incorporating Acoustic Emission Detection for Spacecraft and Wind Turbine Blades
… of SHM systems employing the impedance and the Lamb wave methods. An acoustic emission sensor of the proposed system continuously monitors acoustic events, while the SHM system is in sleep mode. The SHM system is evoked to perform the SHM operation only when there is an acoustic event detected …
-
Phased Array Damage Detection and Damage Classification in Guided Wave Structural Health Monitoring
… Among the methods developed, the guided Lamb wave based SHM can be a promising technique for damage evaluation since it provides reliable damage information through signals propagating over large distance with little loss of amplitude. While this method is effective for damage assessment, …
-
Characterisation of micromechanical materials and MEMS structures using optically generated ultrasound
… using laser-generated and detected ultrasonic Lamb waves, is described in this thesis. Laser generated ultrasound is an attractive approach for material testing as it provides a non-contact non-destructive characterisation method. In the work reported here, Lamb waves are generated using a …
-
Super-high-frequency lithium niobate microelectromechanical system resonators
… Chapter 3 will discuss characteristics of Lamb wave modes and detail the first-order antisymmetric (A1) Lamb wave mode which can be employed in designs of SHF LiNbO3 MEMS resonators. Chapter 4 will present and describe the microfabrication process of the SHF LiNbO3 MEMS resonators. Finally, …
-
Structural health monitoring of polymer-matrix composites (PMCs) using embedded piezoelectric transducers: experimental and numerical approaches
… the efficacy of the numerical approach. Lamb wave propagation analysis further contributes to the understanding of smart isotropic and composite structures. The investigation of the impact of the numerical model parameters on the obtained results enriched the interpretation of the …
-
Guided Wave Structural Health Monitoring with Environmental Considerations
… variations and applied stress create on Lamb wave propagation velocity in plates is analytically modeled and validated. Two methods are developed for the analytical derivative of the Lamb wave velocity; the first uses assumes a thermoelastic material while the second expands thermoelastic …
-
Gallium Nitride phononic crystal resonator
We present a Gallium Nitride (GaN) Lamb Wave resonator using a Phononic Crystal (PnC) to selectively confine elastic vibrations with wide-band spurious mode suppression. A unique feature of the design demonstrated here is a folded PnC structure to relax energy confinement in the non-resonant …
-
Advancing acoustic filters for 5G front-ends: Lithium niobate piezoelectric MEMS resonators and filters
… by employing the first order asymmetric (A1) Lamb wave mode in the Z-cut and Y-cut lithium niobate (LiNbO3) thin films. The fabricated devices based on Z-cut LiNbO3 demonstrated an electromechanical coupling (kt2) of 30%, which is more than three times of current commercial solutions. The …
-
Ultrasonic inspection methods for defect detection and process control in roll-to-roll flexible electronics manufacturing
… investigates the use of ultrasound, specifically Lamb and longitudinal waves, as a sensing modality and measurement technique for thin film roll-to-roll manufacturing. A variety of custom wedges were designed and machined from multiple materials to test their suitability at launching ultrasonic …
-
ALN/ALSCN Acoustic Resonant Systems Based on Ultra-Thin Piezoelectric Films
… (MEMS) acoustic resonators — surface acoustic wave (SAW), thin-film bulk acoustic resonator (FBAR), and Lamb wave resonators— were investigated by employing the ultra-thin piezoelectric films targeted for mobile filtering application toward the 5th generation (5G) millimeter wave bands. We …
-
Durability testing of an aircraft structural health monitoring system
… testing of a surface-mounted piezoelectric Lamb-wave SHM system are presented. Environments tested include temperature extremes, humidity, fluid susceptibility, altitude, and mechanical strain.
-
High quality integrated LiNbO3 acousto-optic platform for visible light spectrum
… acousto-optic devices such as efficient microwave converters, optical isolators, and wavelength scale acousto-optic frequency shifters, which were not realizable before. However, all of these devices target the 1550 nm optical wavelength or mid IR spectrum, and there is no integrated …
-
Damage assessment in reinforced concrete using contactless ultrasound
… method (FEM or FE) simulations of mechanical wave-based NDE methods are developed and described in order to support the system construction, theory verification, and experimental work. The FE models simulate generation and detection of air-coupled transient waves in air and wave interactions …
-
K-band lithium niobate microelectromechanical system hybrid filters
… is built with the seventh-order antisymmetric Lamb wave mode (A7) resonators with an electromechanical coupling of 0.7%. The measurements show a 3 dB FBW of 2.4% at 19 GHz, and a compact footprint of 1.4 mm2.
Page 1 of 2