A travelling Lamb wave tactile display has been developed. To indicate smooth or braking sensation, the device is controlled in order to impose the relative speed between the finger and the wave, so that a variable shear force appears on the fingerpulp. Moreover, at low frequency, an amplitude modulation of the travelling Lamb wave is achieved so as to excite alternatively shear forces on the s...

Lamb-wave testing for structural health monitoring is complicated by the dispersion nature of the wave modes. The dispersion effect will result in a propagated wave with longer time duration, deformed envelop shape as compared to its excitation counterpart, and hard to be interpreted. This paper first reviews the dispersion compensation and removal algorithms. Second, it compares these two meth...

An original method is presented to determine the complex Lamb wave spectrum by using a numerical spectral method applied to the elasticity equations. This method presents the advantage to directly determine complex wave numbers for a given frequency via a classical matricial eigenvalue problem, and allows the wave numbers to be determined at relatively high frequencies (i.e., corresponding to m...

We discuss waves created in relatively thick plates by edge excitation at frequency-thickness (fd) products that correspond, in principle, to multiple Lamb wave modes. For relatively low values of the fd product it is clear that Lamb wave modes will be generated, while at large values of the fd product we observe a bulk (longitudinal wave) in the solid, but influenced by reflections from the pl...

earthquakes travel times inversion for determination of velocity structure of crust is one of the most important objectives in seismology. in the simultaneous inversion method, the parameters of earthquakes and velocity model are determined initially and are improved during inversion steps. in this study, we have used more than 22000 calculated travel times for first arrivals of 6000 earthquake...

Guided waves in a free isotropic plate (symmetric S(n) and antisymmetric A(n) Lamb modes) exhibit a resonant behavior at frequencies where their group velocity vanishes while their phase velocity remains finite. Previous studies of this phenomenon were limited to isotropic materials. In this paper, the optical generation and detection of these zero-group velocity (ZGV) Lamb modes in an anisotro...

There are many advantages to adhesively bonding stiffeners onto aircraft structures rather than using traditional mechanical fastening methods. However there is a lack of confidence of the structural integrity of adhesively bonded joints over time. Acousto-ultrasonic Lamb waves have shown great potential in structural health monitoring applications in both metallic and composite structures. Thi...

This study presents a novel monitoring method for hole-edge corrosion damage in plate structures based on Lamb wave tomographic imaging techniques. An experimental procedure with a cross-hole layout using 16 piezoelectric transducers (PZTs) was designed. The A0 mode of the Lamb wave was selected, which is sensitive to thickness-loss damage. The iterative algebraic reconstruction technique (ART)...

Hertzian, dry, pointlike contacts are used to couple ultrasonic energy efficiently to plate wave modes in anisotropic solid plates. A new transducer configuration using a piezoelectric PZT-5H transducer and a quartz buffer rod is realized for this purpose. In particular, the lowest order antisymmetric Lamb wave (A0) mode is excited and detected in anisotropic plates at a frequency of 200 kHz an...

Compared with conventional linear ultrasonic inspection methods, which are sensitive only to severe defects, nonlinear ultrasonic inspection methods are better for revealing micro-cracks in thin plates. However, most nonlinear ultrasonic inspection methods have only been experimentally investigated using bulk or Rayleigh waves. Numerical studies, especially numerical simulations of Lamb ultraso...