Design of Broadband Transducers for Complex Testing Problems

Abstract

Integral transform methods are applied to calculate the sound field in a solid half-space generated by a transducer [1]. To overcome the restriction of plane interfaces and to calculate an extended three-dimensional transient field in a layered body with non-parallel and curved interfaces a separation approach was developed [2]. The separation method was applied successfully to obtain calculation programs for the design of ultrasonic transducers with time-harmonic excitation. Figure 1 shows the different approaches to calculate the sound field generated by a transducer. While the approaches A and B are suitable to simulate the time-harmonic sound field in a two-layered problem (angle beam probe coupled on a half-space) [3], the approach C yields the time-harmonic sound field in a layered test object with curved interfaces [4,5]. In continuation of way C, a superposition of time-harmonic wave fields (harmonic synthesis) yields the transient sound field in a layered body with curved interfaces [6]. This is an optimized approximation method. The direct method D is based on transient Green’s functions. This approach is an exact calculation of the transient sound field in a half-space or in a layered medium with plane interfaces [6,7]. Therefore, it is used to evaluate the optimized approximation method [6].