Design of flexural ultrasonic phased array for fluid-coupled applications

A design of a 4×4 ultrasonic phased array working in flexural mode is presented. The array consists of an elastic metal sheet, a baffle with 16 holes, a back plate and 16 piezoelectric discs. The active area of each flexural array element is defined by the diameter of the holes of the baffle and the back plate provides an additional clamped-edge-like boundary condition through the baffle for each flexural element. A finite element analysis is utilized to investigate the influence of the dimensions and the materials on the performance of the array. Optimal ratios of the radius of piezo disc to the radius of elastic element working at (0, 0) mode and (1, 0) mode are obtained. A direct comparison of the radiation patterns of the flexural transducers working at (0, 0) and (1, 0) modes proves that the (0, 0) mode is preferable as working mode for the array. The dimensions and the materials of the baffle and the back plate are chosen to effectively reduce the mechanical cross talk between the neighboring array elements. A flexural ultrasonic phased array prototype is fabricated and characterized. Experiments indicate that the ultrasonic beam of the array can be continuously steered from 0° to 50°. This proof-of-concept design demonstrates our low-cost flexural ultrasonic phased arrays design to be sufficiently robust for various fluid-coupled applications.