Two-Dimensional Arrays for the Quantitative Characterisation of Complex Defects

Lead Research Organisation: University of Bristol
Department Name: Mechanical Engineering

Abstract

Recent years have seen a rapid increase in the interest in arrays for NDE. Their advantages include increased flexibility, as one array probe can undertake many inspections, increased speed of imaging and increased coverage from a given location. However, current NDE systems utilise mainly 1-Dimensional (1D) arrays and so are limited to obtaining a 2-Dimensional (2D) image. 2D arrays offer the potential to image in all three dimensions. This has clear benefits as real defects and engineering structures are three-dimensional / for example defects such as cracking and inclusions in welds are of arbitrary shape and can occur in arbitrary orientations. 2D arrays are able to 'view' a given defect form a range of angles leading to the possibility of obtaining characterisation detail far beyond what is currently achievable. However there are a number of obstacles currently stifling the application of 2D arrays to NDE. Firstly, how should 2D arrays be designed with a low enough number of elements to be practically viable? Secondly, how should the vast amount of data potentially obtainable be minimised and processed? Thirdly, given these practical limitations, what imaging and characterisation performance can be achieved? This project will address these issues by developing a modelling suite to optimise array design, investigating a range of data management and signal processing techniques to make the most efficient use of the data, incorporating recently developed piezoelectric and passive materials into the array design and optimising 2D array manufacture for NDE. This proposal is being submitted within the UK Research Centre in NDE to the targeted research programme, the funding for which is earmarked by EPSRC for industrially driven research.
 
Description 2D ultrasonic arrays enable volumetric imaging of the interior of engineering components, without the major health and safety issues associated with x-ray tomography. The challenge for 2D arrays is to efficiently exploit the relatively small number of independent channels (typically 64-128) available in commercial array controllers. Previous 2D arrays used regular "chessboard" element layouts but this leads to arrays with very small apertures as the element pitch is limited by the spatial Nyquist criterion necessary to avoid grating lobe artefacts. Small aperture arrays provide limited coverage and poor focusing ability. This project developed two new paradigms for 2D arrays: annular arrays for far-field operation using a minimal number of elements and random element distributions. The latter allows the aperture of a 2D array to be almost trebled in diameter to provide much higher resolution and coverage without introducing grating lobes. An array of this design was built and tested and the improvement in performance demonstrated.
Exploitation Route Array manufacturers can offer arrays of the new designs to their customers to provide improved performance. These arrays can be used with existing array controllers, but software needs to be written to display the 3D results. We have produced such software in our free demonstration package, BRAIN, which has enabled various collaborators to see the benefits.
Sectors Aerospace, Defence and Marine,Energy,Manufacturing, including Industrial Biotechology,Transport
 
Description We have implemented 3D imaging software for use with 2D arrays (of any design) in our free demonstration software, BRAIN. This has been presented via hands-on workshops to numerous end-users and equipment manufacturers, mainly drawn from the UK Research Centre in NDE community. We are aware of various companies exploiting our published work on random arrays to design their own devices.
Sector Aerospace, Defence and Marine,Energy,Manufacturing, including Industrial Biotechology,Transport
Impact Types Economic
 
Title BRAIN 
Description BRAIN is a flexible ultrasonic array data capture and imaging software suite for NDT applications, based around the concept of Full Matrix Capture (FMC) of array data with imaging performed in post-processing. New imaging tools can be readily added to the core. BRAIN is written in Matlab and can be run either from within Matlab or as a standalone Matlab application. 
Type Of Technology Software 
Year Produced 2010 
Open Source License? Yes  
Impact Numerous collaborating companies are known to use BRAIN for trialling new inspection and imaging algorithms. These include Rolls-Royce, BAE System in the UK, Tenaris in Argentina and potentially many others. New array imaging algorithms developed under various programmes are added to BRAIN as they reach maturity. 
URL https://sourceforge.net/projects/bristol-brain/