Experimental Demonstration of Superimposed Orthogonal Two-Dimensional Structure-Borne Traveling Waves

Several examples of structure-borne traveling waves (SBTW) are found in nature as a form of locomotion such as in rays, snails, and snakes. While researchers have been able to replicate these traveling waves in one- and two-dimensional structures, this work has been primarily focused on SBTW propagating along a single axis. In recent years, researchers have begun investigating methods of steering the propagation direction of traveling waves in two-dimensional structures. One method of steering these waves is to superimpose orthogonal traveling waves (OTW) and adjust the parameters of the individual SBTW to change the direction of the overall wave. However, until now, work on these superimposed OTWs relies only on simulations and a linear superposition to replicate multiple actuators under simultaneous excitation.

This chapter seeks to expand on the previous work by experimentally examining the behavior of superimposed orthogonal traveling waves. Previous theoretical work has sought to explain the overall propagation behavior resulting from these SBTW combinations using the structural intensity (SI) incited by the wave. This explanation has so far been examined using simulations, assuming that the SI induced by each contributing SBTW can be superimposed to produce an overall SI field on the surface. This work will challenge this assumption by experimentally updating the FE model before calculating the SI field for individual and combined traveling wave cases. To this end, a modal test will be performed on a real square plate to update a finite element model. This model will then be used to determine the excitation conditions necessary for suitable SBTW in the plate. These superimposed orthogonal SBTW will then be measured experimentally individually and then simultaneously. First, it will be examined if the superimposed excitation conditions result in an overall superimposed waveform. While this has been shown to hold for SBTW propagating along a single axis, it is yet to be shown for SBTW operating orthogonal until now. Finally, the SI will be calculated for the individual SBTW and the case with superimposed excitation conditions.