REGISTER FOR YOUR FREE COPY OF AEROSPACE MANUFACTURING BY VISITING: WWW.AERO-MAG.COM 26 AEROSPACEMANUFACTURING | SEPTEMBER 2011


DESIGN I TEST & MEASUREMENT


Acquiring the data: NI’s FlexRIO card with digitiser


working with companies like QinetiQ to help them examine carbon fibre-based issues like ‘ply wrinkling’.” Along with its ANDSCAN mapping


and analysis software, QinetiQ is using FlawInspecta’s integral 3-axis position sensing hardware to analyse ply wrinkling and characterising ‘out of plane’ waviness. There are also issues with the residual strength of the composite material from which an NDT technician will need to decide whether to pass or fail it. Then there is the task of assessing problems like delamination, dis-bond and porosity. FlawInspecta can provide rapid data collection over the entire length of aircraft on components like wings, for example. The problems posed by the collection


and analysis of this type of inspection data are manifold and various constraints – such as high channel count and data rates – have prevented this approach until now. Not only does the technology need to see ‘inside’ the composite material plies and correctly interpret the image data relayed back, but the huge amount of number-crunching involved in acquiring this data can have serious repercussions in terms of additional production time – and ultimately cost. “Aircraft OEMs are looking to perform


100% NDT inspection of all their critical carbon fibre composite parts and this involves a huge amount of raw data collected for analysis,” confirms Lines. “This could potentially slow their aircraft production down so it’s a huge issue. It’s all very well collecting the data, and we


can provide the mechanisms for doing this rapidly so that production throughput of inspection on the aircraft isn’t delayed. However, the issue then becomes one of analysis and what the technician decides they must do with the data.” For conventional imaging, steering and focusing is achieved by applying differential delays in the excitations to each element and in the received signals from each element. The delays compensate for the varying path lengths between elements and focal point, to produce constructive interference at this point. DSL uses a technique it terms as


‘full raw data’ (FRD) acquisition and processing to investigate optimised steering and focusing of the composite material images. Rather than exciting a large group of elements to produce a transmit beam with well-defined focus, a much smaller group – typically just one element – is activated to produce a widely divergent sound field. Received signals from all elements are collected as usual, but rather than being delayed and combined to form the receive beam, they are stored for later processing. This is repeated for each element in turn on transmit to produce a data set of signals corresponding to all combinations of transmit and receive elements. DSL was faced with the challenge


of creating a flexible and scalable architecture for acquiring ultrasonic array data and processing it in real-time, whilst being mindful of the additional production time and processor-frying issues that the manipulation of such huge swathes of raw data this would involve. “We were always trying to push


the envelope to speed up the data acquisition process, so we migrated to using field programmable gate arrays (FPGAs),” Lines continues. “As soon as


“Aircraft OEMs are looking to perform 100% NDT inspection of all their critical carbon fibre composite parts.” Dave Lines: Chief engineer, Diagnostic Sonar


we realised that National Instruments’ (NI) acquisition systems – including its LabVIEW FPGA platform and development environment used in tandem with its FlexRIO 5752R series – was available, we knew it would be the best route to adopt. “We’re using the power and speed


of LabVIEW’s real-time imaging acquisition hardware and digitising products to acquire the full raw data into our FlawInspecta system. A FlexRIO 5752 32-channel digitiser adapter module performs the data acquisition as part of a flexible imaging development system for NDT applications. FlexRIO offers a different approach to a normal digitiser or oscilloscope because it provides far more flexibility for acquiring data for analysis and manipulation without compromising performance. Because it’s reconfigurable, we can pull in all the raw data using a conventional beamformer as you would normally do with any traditional system, or perform full raw data processing to provide dynamic focusing on transmit and receive. One benefit is that it allows the user to steer


Page 1  |  Page 2  |  Page 3  |  Page 4  |  Page 5  |  Page 6  |  Page 7  |  Page 8  |  Page 9  |  Page 10  |  Page 11  |  Page 12  |  Page 13  |  Page 14  |  Page 15  |  Page 16  |  Page 17  |  Page 18  |  Page 19  |  Page 20  |  Page 21  |  Page 22  |  Page 23  |  Page 24  |  Page 25  |  Page 26  |  Page 27  |  Page 28  |  Page 29  |  Page 30  |  Page 31  |  Page 32  |  Page 33  |  Page 34  |  Page 35  |  Page 36  |  Page 37  |  Page 38  |  Page 39  |  Page 40  |  Page 41  |  Page 42  |  Page 43  |  Page 44