Jerzy Dziewierz

Correspondence: Computationally efficient solution of snell's law of refraction

An algorithm for an efficient parallel implementation of Snells law of refraction, applicable to planar interfaces, is found by algebraic manipulation. The algorithm is tailored for general-purpose graphics processing unit (GP-GPU)-type processors. Numerical singularity in the solution is addressed. Performance is compared against other implementations. Application areas include real-time total focusing method implementation, phased-array probe computer-aided design (CAD), and data fusion.

Automated full matrix capture for industrial processes

Full matrix capture (FMC) ultrasound can be used to generate a permanent re-focusable record of data describing the geometry of a part; a valuable asset for an inspection process. FMC is a desirable acquisition mode for automated scanning of complex geometries, as it allows compensation for surface shape in post processing and application of the total focusing method. However, automating the delivery of such FMC inspection remains a significant challenge for real industrial processes due to the high data overhead associated with the ultrasonic acquisition. The benefits of NDE delivery using six-axis industrial robots are well versed when considering complex inspection geometries, but such an approach brings additional challenges to scanning speed and positional accuracy when combined with FMC inspection. This study outlines steps taken to optimize the scanning speed and data management of a process to scan the diffusion bonded membrane of a titanium test plate. A system combining a KUKA robotic arm and a reconfigurable FMC phased array controller is presented. The speed and data implications of different scanning methods are compared, and the impacts on data visualization quality are discussed with reference to this study. For the 0.5 m2 sample considered, typical acquisitions of 18 TB/m2 were measured for a triple back wall FMC acquisition, illustrating the challenge of combining high data throughput with acceptable scanning speeds.

Inspection design using 2D phased array, TFM and cueMAP software

A simulation suite, cueMAP, has been developed to facilitate the design of inspection processes and sparse 2D array configurations. At the core of cueMAP is a Total Focusing Method (TFM) imaging algorithm that enables computer assisted design of ultrasonic inspection scenarios, including the design of bespoke array configurations to match the inspection criteria. This in-house developed TFM code allows for interactive evaluation of image quality indicators of ultrasonic imaging performance when utilizing a 2D phased array working in FMC/TFM mode. The cueMAP software uses a series of TFM images to build a map of resolution, contrast and sensitivity of imaging performance of a simulated reflector, swept across the inspection volume. The software takes into account probe properties, wedge or water standoff, and effects of specimen curvature. In the validation process of this new software package, two 2D arrays have been evaluated on 304n stainless steel samples, typical of the primary circuit in nuclear plants. Thick section samples have been inspected using a 1MHz 2D matrix array. Due to the processing efficiency of the software, the data collected from these array configurations has been used to investigate the influence sub-aperture operation on inspection performance.

An annular array with fiber composite microstructure for far field NDT imaging applications

This paper describes the design and fabrication of a reduced element count annular array for far field NDT imaging applications, built with a random fiber piezoelectric composite microstructure. An annular array design is considered, spatially it offers axi-symmetric layout while reducing number of array elements, which could potentially result in a significant reduction in the cost and complexity of building an ultrasonic volumetric imaging system. Modelling and preliminary experimental results are presented to evaluate the feasibility of this approach.

A 2D Ultrasonic array design incorporating hexagonal-shaped elements and triangular-cut piezocomposite substructure for NDE applications

Contemporary 2D Ultrasonic arrays suffer from low SNR and limited steering capabilities. Yet, there is a great desire in the industry to increase the operational frequency, in order to enhance their volumetric imaging resolution. State-of-the art arrays use an orthogonal matrix of rectangular elements as this is a natural step forward from the conventional 1D array structure. The objective of this work is to evaluate properties of triangular, rather than rectangular ceramic pillars in a 1–3 connectivity piezoelectric composite for application in a hexagonal-element 2D array. A 3MHz prototype device exploiting new hexagonal substructure have been manufactured. Measured mechanical cross-coupling level is −21.9dB between neighbouring hexagonal elements, providing validation of simulation result. Corroboration between measured and FE modelled device behaviour is demonstrated.

Design of a 2D sparse array transducer for integration into an ergonomic transcranial ultrasound system

Transcranial Doppler Ultrasound (TCD) is a non-invasive approach that has been used in both diagnosis and therapy of stroke. However, current TCD devices are highly operator dependent and a 2D sparse array transducer can help reduce the operator dependency with its improved imaging and focusing capabilities. This paper compares the potential of three aperiodic sparse array configurations: random array; sunflower spiral array; and log spiral array for application to TCD.

A design methodology for 2D sparse NDE arrays using an efficient implementation of refracted-ray TFM

An algorithm has been developed that allows extremely efficient calculation of the total time of flight of an acoustic ray through two layer media, taking into account the effects of refraction through a 3D non-planar surface. The approach has been implemented on GP-GPU hardware, and embedded within the Total Focussing Method (TFM) imaging algorithm. This new software module supports arbitrary location of probe elements, array element directivity, arbitrary curved interface between two media, arbitrary transmit/receive sequences and any 1D/2D/3D image size for reconstructing the ultrasonic image from raw RF ultrasonic data. This allows calculation of the Point Spread Function of the probe at a range of points in its field of view, in a practical timeframe. Methodology, performance benchmarks, and possible applications are discussed.

Enhancing 2D phased array sensitivity and bandwidth using in-probe electronics

An in-probe electronics printed circuit board (PCB) has been designed and built to improve the electrical matching issue in 2D ultrasonic array design. Each array channel has a dedicated line driver and the design utilized has low power consumption and importantly, a small footprint. Thus, the design is compatible with NDE probes, in which 128 elements are typical. The in-probe PCB was evaluated using a piezoceramic element scaled to obtain a 1kΩ impedance. Connected to the line driver, but otherwise acoustically un-matched, un-backed, the pulse-echo response from this element was acquired. Experimental results show an approximate 50dB improvement in sensitivity and an enhancement in bandwidth from 14.4% to 22.5% when compared to the ceramic interfaced directly to a standard 2m coaxial cable.

HEXAGONAL ARRAY STRUCTURE FOR 2D NDE APPLICATIONS

This paper describes a combination of simulation and experimentation to evaluate the advantages offered by utilizing a hexagonal shaped array element in a 2D NDE array structure. The active material is a 1–3 connectivity piezoelectric composite structure incorporating triangular shaped pillars—each hexagonal array element comprising six triangular pillars. A combination of PZFlex, COMSOL and Matlab has been used to simulate the behavior of this device microstructure, for operation around 2.25 MHz, with unimodal behavior and low levels of mechanical cross‐coupling predicted. Furthermore, the application of hexagonal array elements enables the array aperture to increase by approximately 30%, compared to a conventional orthogonal array matrix and hence will provide enhanced volumetric coverage and SNR. Prototype array configurations demonstrate good corroboration of the theoretically predicted mechanical cross‐coupling between adjacent array elements (∼23 dB).