A Lamb wave-based crack detection method for aluminum plates health monitoring is developed in this paper. Piezoelectric disks are employed to actuate and capture the Lamb wave signals. The position of crack is assumed to be aligned with the sensor and actuator.  Extraction of high quality experimental results of lamb wave propagation in a plate-like structure is considerably complicated due to...

Leaky Lamb waves are important research topics in the area of NDE and acoustic wave sensing technology. For waves propagating in a piezoelectric plate immersed in a fluid (dielectric or conductive), both mechanical and electrical loading effects present and result in phase velocity variation and wave attenuation. To quantitatively characterize these loading effects play an important role in var...

High Quality Factor Lamb Wave Resonators by Jie Zou Master of Science in Electrical Engineering and Computer Sciences University of California, Berkeley Professor Albert P. Pisano, Chair The small-in-size and CMOS compatible micro-electromechanical system (MEMS) resonators are likely to be the driving core of a new generation of devices such as radio frequency (RF) filters and timing references...

number of NDE applications. To excite Lamb waves, Ultrasonic Lamb wave techniques are widely used in a mode conversion of bulk waves or photo acoustic excitation are often used. Both of these approaches suffer from the need for liquid couplant or ablation of materials to reach good signal to noise ratio. In this paper, we propose a novel technique that utilizes point source excitation and detec...

In recent years, the Lamb wave analysis by the multi-channel analysis of surface waves (MASW) for concrete structures has been an effective nondestructive evaluation, such as the condition assessment and dimension identification by the elastic wave velocities and their reflections from boundaries. This study proposes an effective Lamb wave analysis by the practical application of MASW to concre...

This paper presents a forward calculation and analytic results of plate wave propagation in stressed plates of cubic materials. The single crystalline Ge films deposited on the Z-cut silicon wafers are investigated. Significant biaxial residual stresses in the film results from the lattice misfit between of the Ge film and the Si substrate. Phase velocity change of the acoustic waves due to mec...

The variation, with material parameters, of Lamb modes is investigated. Vibration spectra of traction-free elastic plates are generally presented, for a given isotropic material, as a set of dispersion curves corresponding to the various Lamb mode branches. Here, the spectrum variations, with the Poisson ratio nu, are plotted in a dimensionless co-ordinate system in the form of a bundle of curv...

Nondestructive evaluation (NDE) of aerospace structures using traditional methods is a complex, time-consuming process critical to maintaining mission readiness and flight safety. Limited access to corrosion-prone structure and the restricted applicability of available NDE techniques for the detection of hidden corrosion or other damage often compound the challenge. In this paper we discuss our...

As continuous health monitoring of aircraft components will provide substantial time and cost savings to the aircraft industry, the use of an integrated sensing technology with autonomous damage assessment is looked for. This study is part of the 6 STREP framework AISHA project, investigating the use of ultrasonic Lamb wave technology for the fast inspection of large shell structures. For the d...

In this paper, a liquid multi-parameter decoupling method with only one Lamb wave sensor is presented. In a Lamb wave sensor, antisymmetric modes (A(01) mode for low frequency, A(03) mode for high frequency) and symmetric modes (S(0) mode) are used to detect multiple parameters of a liquid, such as its density, sound velocity, and viscosity. We found they can play very different roles in the de...