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.
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Showing 1 to 20 of 23 for “"Lamb waves"”.
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Silence of the lamb waves
… investigates the use of ultrasound, specifically Lamb and longitudinal waves, as a sensing modality and measurement technique for thin film R2R manufacturing substrates. Contact (transducer-based) and non-contact (photoacoustic) generation methods along with deterministic and probabilistic …
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Optimum tuning of laser-generated Lamb waves
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2003.
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Experimental investigation of Lamb waves in transversely isotropic composite plates
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2001.
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Time-frequency analysis of Lamb waves using the Morlet wavelet transform
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, 2000.
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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 …
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Group Velocity Of Acoustic Waves In Plates Of Electronic Materials
… and dispersion characteristics of plate acoustic waves (PAW) in electronic materials are investigated experimentally. Plate acoustic waves are elastic waves that travel along a plate with thickness comparable to the wavelength of the waves. Lamb waves, a type of plate acoustic wave, have particle …
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A Comparison of Beamforming Characteristics in Isotropic and Composite Plate Structures for use in Structural Health Monitoring
… using phased array beamsteering of guided Lamb waves is useful in damage detection and evaluation efforts. Lamb waves can be effectively used for beamsteering using a linear array. The experimentation primarily focuses on beamsteering in the aluminum panel, which involves developing a …
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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 …
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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 …
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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 …
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Nonlinear ultrasonic guided waves for quantitative life prediction of structures with complex geometries
… from harmonic generation for propagating elastic waves. The long term goal of this study is to investigate the non-linear elastic propagation in parts with complex geometry. Cellular Automata is introduced as a new simulation method, in order to develop new analysis on quadratic non-linearities. …
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Structural health monitoring in commercial aviation
… including acoustic emission, ultrasonic, Lamb waves, piezoelectric and MEMS actuator/sensors. The limitations and challenges inhibiting introduction of SHM to industry and recommendations for the future are also discussed.
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Estudio de sistemas ultrasónicos basados en multitransductores para la detección de defectos en estructuras tipo placa
… de detección de defectos mediante ondas de Lamb. Su uso cobra especial interés en el caso de estructuras tipo placa debido a sus relevantes propiedades: propagación sobre largas distancias y sobre todo el espesor de la placa, y sensibilidad a daños internos producidos en la estructura. Este …
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Wave Propagation and Damage Characterization in Natural Fiber Hemp and LLDPE Composite
… The material is characterized by propagating Lamb waves generated using a dropped dead weight. Time-frequency information is extracted from a thin disc-like specimen using the Gabor Wavelet Transform (GWT) so as to characterize the material. Detection of defect is also established using the …
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Theory and application of quasi-elastic equations in terrain-folowing coordinates based on the full pressure field
… are filtered of vertically propagating acoustic waves. However, since Lamb waves are present, the equations may be termed quasi-elastic. In contrast to similar quasi-elastic pressure-based models, the equations and the numerical solution procedure presented here are formulated independent of the …
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Analysis of the spatio-temporal sea level variability in extreme regions using in-situ and satellite remote sensing data: South Shetland region (Antarctica)
… Ha’apai eruption generated atmospheric Lamb waves that were detected at Antarctic meteorological stations and triggered meteotsunamis at Livingston and Deception Islands. The responses at both sites highlight how atmospheric forcing generated long ocean waves that, once established, were …
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Dual-Use Strain Sensors for Simultaneous Strain Measurement and Acoustic Source Location
… test for determining the ability in measuring lamb waves for source location estimation. The NanoSonic USM sensor is further compared to commercial strain gauges and ultrasonic transducers during a PLB test under a tensile load where it is demonstrated the USM sensor yields similar measurements …
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Optimization and design of radio frequency piezoelectric MEMS resonators
… system (MEMS) resonators employing Lamb waves propagating in piezoelectric thin films have recently attracted much attention since they combine the advantages of the bulk acoustic wave (BAW) and surface acoustic wave (SAW) technologies: high phase velocity and multiple frequencies on …
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Structural Health Monitoring of Adhesively Bonded Joints With Piezoelectric Wafer Active Sensors
… The surface-bonded PWAS can produce guided waves traveling parallel to the surface and could detect damage that would escape some ultrasonic methods. The major focus of this research was directed towards the electromechanical impedance method for disbond detection. The electromechanical …
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Impedance-Based Structural Health Monitoring to Detect Corrosion
… is not as strong. Other NDE techniques like Lamb Waves could use the same sensors to quantify corrosion location, and perhaps surface coverage. The impedance method can detect and quantify pre-crack surface corrosion which leads to shortened fatigue life in structures; however, the sensors …
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