Papers by Keyword: Surface Wave

Abstract: The bending fatigue of Al6061 alloy has been evaluated by the acoustic nonlinearity of laser-generated surface wave. The surface wave is very attractive for field applications since it enables to pulse and receive signals at the same surface of materials, and has strong acoustic nonlinear effects on the surface. A relative acoustic nonlinear parameter was measured successfully on the surface of fatigue-damaged aluminum 6061 alloy. The results show that the acoustic nonlinear parameter increased with fatigue damage accumulation in relation to dislocation evolution. Consequently, this study suggests that the acoustic nonlinearity technique of a laser-generated surface wave can be potentially used to characterize surface damage resulting from bending fatigue.

Abstract: With the change of the relation between the Bond numbers and 1/3, the different control equations with different dispersion item for the surface wave was obtained. The equation under tension and bottom was reduced from the potential flow theory with the little parameter perturbation technique, and then was solved by using the pseudo-spectral method. The waterfall of the surface wave was simulated with software. The results show, that different surface tension has significant effect on the film surface and there are some solitary-like wave.

Abstract: Free surface motion of a liquid metal submerged in an alternating magnetic field has been examined. A copper vessel filled with a liquid gallium is set in a coil for the imposition of the alternating magnetic field. The alternating magnetic field penetrates into a liquid gallium only from an upper free surface because thickness of the copper vessel is larger than the electromagnetic skin layer of copper. Time variation of displacement of the standing wave loop excited on the free surface is detected by a laser level sensor. The standing wave was suppressed not only by intensification of the magnetic field magnitude but also increase of the magnetic field frequency.

Abstract: This paper describes a study of laser generated ultrasonic waves in an 2-layer elastic, isotropic biomaterial model, in order to establish a modelling technique to simulate the thermoelastic response of high-power short pulse laser beams in human skin. The theory proposed in this paper takes into consideration the fundamental understanding of the laser/material interface. A finite element model using the commercial finite element code ANSYS is used to study the effects of laser pulse duration and energy flux contribution to the surface waves. The simulation comprises a set of boundary conditions that approximate a heat flux point source located on top of the surface of the material. Because of the time scale of interest, the elastic effects do not feed back into the thermal problems, so that a sequential coupled-field analysis was performed where the thermal and elastodynamic fields are uncoupled and treated separately. The initial finite element analysis involves a transient thermal analysis using a heat flux with Gaussian spatial variation to simulate the laser pulse heating. The results from the thermal analysis were read and applied to the structural analysis where the out-of-plane displacements histories are analyzed in the skin model with varying thicknesses