Engineering the acoustic field with a Mie scatterer for microparticle patterning.

The utilization of acoustic fields offers a contactless approach for microparticle manipulation in a miniaturized system, and plays a significant role in medicine, biology, chemistry, and engineering. Due to the acoustic radiation force arising from the scattering of the acoustic waves, small particles in the Rayleigh scattering range can be trapped, whilst their impact on the acoustic field is negligible. Manipulating larger particles in the Mie scattering regime is challenging due to the diverse scattering modes, which impacts the local acoustic field.

Air-Coupled Ultrasonic Arrays for Assessment of Pipe Internal Geometry and Surface Condition.

This article explores what useful information can be retrieved from pipeline interiors using an air-coupled ultrasonic array. Experiments are performed using an array, custom array controller, and supporting electronics controlled by a Raspberry Pi 4, mounted on board a crawler robot. A 64-transducer 40-kHz array configuration is selected based on uniformity of imaging amplitude over the circumference of the pipe wall.

Envelope correction for shear-longitudinal collinear wave mixing to extract absolute nonlinear acoustic parameters.

This paper addresses the effect of the excitation envelope on the generated nonlinear resonant signal (NRS) for collinear wave mixing of shear and longitudinal waves. The aim is to explore how the absolute material nonlinearity can be extracted accurately for any enveloped sinusoidal excitation signal. A finite difference time domain (FDTD) model was built to simulate the effect of input waveforms on the NRS.

Numerical model of nonlinear elastic bulk wave propagation in solids for non-destructive evaluation.

Nonlinear ultrasonic techniques can be difficult and non-intuitive to understand due to the range of wave mixing combinations available between similar or different wave modes. To overcome this, a numerical model that uses a Finite Difference Time Domain (FDTD) scheme, without a staggered grid system, to solve the nonlinear elastic bulk wave equations in two dimensions is proposed in this paper, with the purpose of better understanding nonlinear ultrasonic techniques. Both material and geometrical nonlinearities are considered and a stress-type boundary condition is used to model the excitation.